HYBRD_
Section: C Library Functions (3)Updated: March 8, 2002
Index Return to Main Contents
NAME
hybrd_, hybrd1_ - find a zero of a system of nonlinear functionSYNOPSIS
#include <minpack.h>
- void hybrd1_ ( void (*fcn)( int *n, double *x,
-
double *fvec,
int *iflag),
-
int *n,
double *x,
double *fvec,
- double *tol, int *info, double *wa,
- int *lwa);
- double *tol, int *info, double *wa,
-
int *n,
double *x,
double *fvec,
- void hybrd_ ( void (*fcn)( int * n, double *x,
-
double *fvec,
int *iflag),
-
int *n,
double *x,
double *fvec,
- double *xtol, int *maxfev, int *ml, int *mu,
- double *epsfcn, double *diag, int *mode, double *factor, int *nprint, int *info,
- int *nfev, double *fjac, int *ldfjac,
- double *r, int *lr, double *qtf,
- double *wa1, double *wa2, double *wa3, double *wa4);
- double *xtol, int *maxfev, int *ml, int *mu,
-
int *n,
double *x,
double *fvec,
DESCRIPTION
hybrd1_ serves the same function but has a simplified calling
sequence.
Language notes
hybrd_ and hybrd1_ are written in FORTRAN. If calling from C, keep these points in mind:- Name mangling.
- With g77 version 2.95 or 3.0, all the function names end in an underscore. This may change with future versions of g77.
- Compile with g77.
- Even if your program is all C code, you should link with g77 so it will pull in the FORTRAN libraries automatically. It's easiest just to use g77 to do all the compiling. (It handles C just fine.)
- Call by reference.
- All function parameters must be pointers.
- Column-major arrays.
-
Suppose a function returns an array with 5 rows and 3 columns in an
array z and in the call you have declared a leading dimension of
7. The FORTRAN and equivalent C references are:
z(1,1) z[0] z(2,1) z[1] z(5,1) z[4] z(1,2) z[7] z(1,3) z[14] z(i,j) z[(i-1) + (j-1)*7]
Parameters for both functions
fcn is the name of the user-supplied subroutine which calculates the functions. In FORTRAN, fcn must be declared in an external statement in the user calling program, and should be written as follows:
subroutine fcn(n,x,fvec,iflag) integer n,iflag double precision x(n),fvec(n) ---------- calculate the functions at x and return this vector in fvec. --------- return end
In C, fcn should be written as follows:
void fcn(int n, double *x, double *fvec, int *iflag)
{
/* calculate the functions at x and
return this vector in fvec. */
}
The value of iflag should not be changed by fcn unless the user wants to terminate execution of hybrd_. In this case set iflag to a negative integer.
n is a positive integer input variable set to the number of functions and variables.
x is an array of length n. On input x must contain an initial estimate of the solution vector. On output x contains the final estimate of the solution vector.
fvec is an output array of length n which contains
the functions evaluated at the output x.
Parameters for hybrd1_
tol is a nonnegative input variable. Termination occurs when the algorithm estimates that the relative error between x and the solution is at most tol.
info is an integer output variable. If the user has terminated execution, info is set to the (negative) value of iflag. See description of fcn. Otherwise, info is set as follows.
info = 0 improper input parameters.
info = 1 algorithm estimates that the relative error
between x and the solution is at most tol.
info = 2 number of calls to fcn has reached or exceeded
200*(n+1).
info = 3 tol is too small. No further improvement in
the approximate solution x is possible.
info = 4 iteration is not making good progress.
wa is a work array of length lwa.
lwa is a positive integer input variable not less than
(n*(3*n+13))/2.
Parameters for hybrd_
xtol is a nonnegative input variable. Termination occurs when the relative error between two consecutive iterates is at most xtol.
maxfev is a positive integer input variable. Termination occurs when the number of calls to fcn is at least maxfev by the end of an iteration.
ml is a nonnegative integer input variable which specifies the number of subdiagonals within the band of the jacobian matrix. If the Jacobian is not banded, set ml to at least n - 1.
mu is a nonnegative integer input variable which specifies the number of superdiagonals within the band of the jacobian matrix. If the jacobian is not banded, set mu to at least n - 1.
epsfcn is an input variable used in determining a suitable step length for the forward-difference approximation. This approximation assumes that the relative errors in the functions are of the order of epsfcn. If epsfcn is less than the machine precision, it is assumed that the relative errors in the functions are of the order of the machine precision.
diag is an array of length n. If mode = 1 (see below), diag is internally set. If mode = 2, diag must contain positive entries that serve as multiplicative scale factors for the variables.
mode is an integer input variable. If mode = 1, the variables will be scaled internally. If mode = 2, the scaling is specified by the input diag. Other values of mode are equivalent to mode = 1.
factor is a positive input variable used in determining the initial step bound. This bound is set to the product of factor and the euclidean norm of diag*x if nonzero, or else to factor itself. In most cases factor should lie in the interval (.1,100.). 100. Is a generally recommended value.
nprint is an integer input variable that enables controlled printing of iterates if it is positive. In this case, fcn is called with iflag = 0 at the beginning of the first iteration and every nprint iterations thereafter and immediately prior to return, with x and fvec available for printing. If nprint is not positive, no special calls of fcn with iflag = 0 are made.
info is an integer output variable. If the user has terminated execution, info is set to the (negative) value of iflag. See description of fcn. Otherwise, info is set as follows.
info = 0 improper input parameters.
info = 1 relative error between two consecutive iterates
is at most xtol.
info = 2 number of calls to fcn has reached or exceeded
maxfev.
info = 3 xtol is too small. No further improvement in
the approximate solution x is possible.
info = 4 iteration is not making good progress, as
measured by the improvement from the last
five jacobian evaluations.
info = 5 iteration is not making good progress, as
measured by the improvement from the last
ten iterations.
nfev is an integer output variable set to the number of calls to fcn.
fjac is an output n by n array which contains the orthogonal matrix q produced by the qr factorization of the final approximate jacobian.
ldfjac is a positive integer input variable not less than n which specifies the leading dimension of the array fjac.
r is an output array of length lr which contains the upper triangular matrix produced by the qr factorization of the final approximate Jacobian, stored rowwise.
lr is a positive integer input variable not less than (n*(n+1))/2.
qtf is an output array of length n which contains the vector (q transpose)*fvec.
wa1, wa2, wa3, and wa4 are work arrays of length n.
SEE ALSO
hybrj(3), hybrj1(3).AUTHORS
Burton S. Garbow, Kenneth E. Hillstrom, Jorge J. More.This manual page was written by Jim Van Zandt <jrv@debian.org>, for the Debian GNU/Linux system (but may be used by others).
Index
This document was created by man2html, using the manual pages.
Time: 10:19:50 GMT, April 20, 2007 cminpack-1.3.6/doc/hybrj1_.3 0000664 0000000 0000000 00000000022 13054046253 0015471 0 ustar 00root root 0000000 0000000 .so man3/hybrj_.3 cminpack-1.3.6/doc/hybrj_.3 0000664 0000000 0000000 00000021464 13054046253 0015425 0 ustar 00root root 0000000 0000000 .\" Hey, EMACS: -*- nroff -*- .\" First parameter, NAME, should be all caps .\" Second parameter, SECTION, should be 1-8, maybe w/ subsection .\" other parameters are allowed: see man(7), man(1) .TH HYBRJ_ 3 "March 8, 2002" Minpack .\" Please adjust this date whenever revising the manpage. .SH NAME hybrj_, hybrj1_ \- find a zero of a system of nonlinear function .SH SYNOPSIS .B #include
HYBRJ_
Section: C Library Functions (3)Updated: March 8, 2002
Index Return to Main Contents
NAME
hybrj_, hybrj1_ - find a zero of a system of nonlinear functionSYNOPSIS
#include <minpack.h>- void hybrj1_ (void (*fcn)(int *n, double *x, double *fvec, double *fjec, int *ldfjac, int *iflag),
-
int *n,
double *x,
double *fvec,
double *fjac,
- int *ldfjac,
- double *tol, int *info, double *wa, int *lwa);
- int *ldfjac,
- void hybrj_ (void (*fcn)(int *n, double *x, double *fvec, double *fjec, int *ldfjac, int *iflag),
-
int *n,
double *x,
double *fvec,
double *fjac,
- int *ldfjac,
- double *xtol, int *maxfev, double *diag, int *mode, double *factor, int *nprint, int *info, int *nfev,
- int *njev, double *r, int *lr, double *qtf,
- double *wa1, double *wa2, double *wa3, double *wa4);
- int *ldfjac,
DESCRIPTION
hybrj1_ serves the same function but has a simplified calling
sequence.
Language notes
hybrj_ and hybrj1_ are written in FORTRAN. If calling from C, keep these points in mind:- Name mangling.
- With g77 version 2.95 or 3.0, all the function names end in an underscore. This may change with future versions of g77.
- Compile with g77.
- Even if your program is all C code, you should link with g77 so it will pull in the FORTRAN libraries automatically. It's easiest just to use g77 to do all the compiling. (It handles C just fine.)
- Call by reference.
- All function parameters must be pointers.
- Column-major arrays.
-
Suppose a function returns an array with 5 rows and 3 columns in an
array z and in the call you have declared a leading dimension of
7. The FORTRAN and equivalent C references are:
z(1,1) z[0] z(2,1) z[1] z(5,1) z[4] z(1,2) z[7] z(1,3) z[14] z(i,j) z[(i-1) + (j-1)*7]
Parameters for both functions
fcn is the name of the user-supplied subroutine which calculates the functions. In FORTRAN, fcn must be declared in an external statement in the user calling program, and should be written as follows:
subroutine fcn(n,x,fvec,fjac,ldfjac,iflag) integer n,ldfjac,iflag double precision x(n),fvec(n),fjac(ldfjac,n) ---------- if iflag = 1 calculate the functions at x and return this vector in fvec. do not alter fjac. if iflag = 2 calculate the jacobian at x and return this matrix in fjac. do not alter fvec. --------- return end
In C, fcn should be written as follows:
void fcn(int n, double *x, double *fvec, double *fjac,
int *ldfjac, int *iflag)
{
/* if iflag = 1 calculate the functions at x and
return this vector in fvec. do not alter fjac.
if iflag = 2 calculate the jacobian at x and
return this matrix in fjac. do not alter fvec. */
}
The value of iflag should not be changed by fcn unless the user wants to terminate execution of hybrj_. In this case set iflag to a negative integer.
n is a positive integer input variable set to the number of functions and variables.
x is an array of length n. On input x must contain an initial estimate of the solution vector. On output x contains the final estimate of the solution vector.
fjac is an output n by n array which contains the orthogonal matrix q produced by the qr factorization of the final approximate jacobian.
ldfjac is a positive integer input variable not less than n which specifies the leading dimension of the array fjac.
fvec is an output array of length n which contains
the functions evaluated at the output x.
Parameters for hybrj1_
tol is a nonnegative input variable. Termination occurs when the algorithm estimates that the relative error between x and the solution is at most tol.
info is an integer output variable. If the user has terminated execution, info is set to the (negative) value of iflag. See description of fcn. Otherwise, info is set as follows.
info = 0 improper input parameters.
info = 1 algorithm estimates that the relative error
between x and the solution is at most tol.
info = 2 number of calls to fcn has reached or exceeded
200*(n+1).
info = 3 tol is too small. No further improvement in
the approximate solution x is possible.
info = 4 iteration is not making good progress.
wa is a work array of length lwa.
lwa is a positive integer input variable not less than
(n*(3*n+13))/2.
Parameters for hybrj_
xtol is a nonnegative input variable. Termination occurs when the relative error between two consecutive iterates is at most xtol.
maxfev is a positive integer input variable. Termination occurs when the number of calls to fcn is at least maxfev by the end of an iteration.
diag is an array of length n. If mode = 1 (see below), diag is internally set. If mode = 2, diag must contain positive entries that serve as multiplicative scale factors for the variables.
mode is an integer input variable. If mode = 1, the variables will be scaled internally. If mode = 2, the scaling is specified by the input diag. Other values of mode are equivalent to mode = 1.
factor is a positive input variable used in determining the initial step bound. This bound is set to the product of factor and the euclidean norm of diag*x if nonzero, or else to factor itself. In most cases factor should lie in the interval (.1,100.). 100. Is a generally recommended value.
nprint is an integer input variable that enables controlled printing of iterates if it is positive. In this case, fcn is called with iflag = 0 at the beginning of the first iteration and every nprint iterations thereafter and immediately prior to return, with x and fvec available for printing. If nprint is not positive, no special calls of fcn with iflag = 0 are made.
info is an integer output variable. If the user has terminated execution, info is set to the (negative) value of iflag. See description of fcn. Otherwise, info is set as follows.
info = 0 improper input parameters.
info = 1 relative error between two consecutive iterates
is at most xtol.
info = 2 number of calls to fcn has reached or exceeded
maxfev.
info = 3 xtol is too small. No further improvement in
the approximate solution x is possible.
info = 4 iteration is not making good progress, as
measured by the improvement from the last
five jacobian evaluations.
info = 5 iteration is not making good progress, as
measured by the improvement from the last
ten iterations.
nfev is an integer output variable set to the number of calls to fcn.
fjac is an output n by n array which contains the orthogonal matrix q produced by the qr factorization of the final approximate jacobian.
ldfjac is a positive integer input variable not less than n which specifies the leading dimension of the array fjac.
r is an output array of length lr which contains the upper triangular matrix produced by the qr factorization of the final approximate Jacobian, stored rowwise.
lr is a positive integer input variable not less than (n*(n+1))/2.
qtf is an output array of length n which contains the vector (q transpose)*fvec.
wa1, wa2, wa3, and wa4 are work arrays of length n.
SEE ALSO
hybrd(3), hybrd1(3).AUTHORS
Burton S. Garbow, Kenneth E. Hillstrom, Jorge J. More.This manual page was written by Jim Van Zandt <jrv@debian.org>, for the Debian GNU/Linux system (but may be used by others).
Index
This document was created by man2html, using the manual pages.
Time: 10:19:50 GMT, April 20, 2007 cminpack-1.3.6/doc/index.html 0000664 0000000 0000000 00000057265 13054046253 0016071 0 ustar 00root root 0000000 0000000
C/C++ Minpack
What is Minpack?
This is the official description of Minpack, from the original ReadMe file: Minpack includes software for solving nonlinear equations and nonlinear least squares problems. Five algorithmic paths each include a core subroutine and an easy-to-use driver. The algorithms proceed either from an analytic specification of the Jacobian matrix or directly from the problem functions. The paths include facilities for systems of equations with a banded Jacobian matrix, for least squares problems with a large amount of data, and for checking the consistency of the Jacobian matrix with the functions.
The original authors of the FORTRAN version are Jorge More', Burt Garbow, and Ken Hillstrom from Argonne National Laboratory, and the code can be obtained from Netlib.
Minpack is probably the best open-source implementation of the Levenberg-Marquardt algorithm (in fact, it is even better, since it adds to L-M automatic variables scaling). There is another open-source L-M implementation in C/C++, levmar by Manolis Lourakis, but unfortunately is is released under the GPL, which restricts its inclusion in commercial software. Minpack is licensed under a BSD-like license (available in the distribution).
What about CMinpack?
In July 2002 (before levmar), Manolis Lourakis (lourakis at ics forth gr) released a C version of Minpack, called CMinpack, obtained from the FORTRAN version using f2c and some limited manual editing. However, this version had several problems, which came from the FORTRAN version:
- All the function prototypes were following the original FORTRAN call conventions, so that all parameters are passed by reference (if a function needs an int parameter, you have to pass a pointer to this int).
- There were lots of static variables in the code, thus you could not optimize a function which required calling Minpack to be evaluated (a minimization-of-minimization problem for example): The Minpack code is not reentrant.
- If the function to be optimized has to use extra parameters or data (this is the case most of the time), the only way to access them was though global variables, which is very bad, especially if you want to use the same function with different data in different threads: The Minpack code is not MT-Safe.
- There was no C/C++ include file.
- Examples and tests were missing from the distribution, although there are some FORTRAN examples in the documentation.
Why is C/C++ Minpack better?
I took a dozen of hours to rework all these problems, and came out with a pure C version of Minpack, with has standard (ISO C99) parameters passing, is fully reentrant, multithread-safe, and has a full set of examples and tests:
- Input variables are now passed by value, output variables are passed by reference. The keyword "const" is used as much as possible for constant arrays. The return value of each function is now used to get the function status (it was obtained via the IFLAG or INFO parameter in Minpack).
- All non-const static variables were removed, and the code was tested after that. Luckily, Minpack didn't use the nastiest feature in FORTRAN: all local variables are static, so that a function can behave differently when you call it several times.
- The function to be minimized and all the Minpack functions now take an extra "void*" argument, which can be used to pass any pointer-to-struct or pointer-to-class, and you can put all you extra parameters and data in that struct. Just cast this pointer to the appropriate pointer type in your function, and there they are! There is no need for global variables anymore. Be careful if you access the same object from different threads, though (a solution is to protect this extra data with a mutex).
- The Debian project did a C include file for Minpack. It still needed some work (add consts and C++ compatibility), so I did this work, and used the include file for the FORTRAN version as the base for my C/C++ version.
- The Debian project also translated all the FORTRAN examples to C. I worked from these to produce examples which also call my C/C++ version of Minpack instead of the FORTRAN version. Also included in the distribution are reference output files produced by the test runs (for comparison).
If you use C/C++ Minpack for a publication, you should cite it as:
@misc{cminpack,
title={C/C++ Minpack},
author={Devernay, Fr{\'e}d{\'e}ric},
year={2007},
howpublished = "\url{http://devernay.free.fr/hacks/cminpack/}",
}
Distribution
The distribution contains:
- The CMinpack code, where static and global variables were removed (it is thus reentrant, but not MT-Safe).
- The C/C++ Minpack code (reentrant and MT-Safe).
- C and C++-compatible include files for Minpack or CMinpack (minpack.h) and C/C++ Minpack (cminpack.h), and Unix Makefiles.
- Full original documentation, translated to HTML, and all the examples, tests, and reference test results, so that you can check if the code runs properly on your machine before really using it.
- The extra covariance function "covar", with sample uses in the tlmder and tlmdir examples. Note that the result of covar has to be scaled by some factor, as shown in the source file examples/tlmderc.c (look for the documentation of the NAG function E04YCF for further explanations).
It is distributed under the original Minpack license (see the file CopyrightMINPACK.txt in the distribution).
Download
- cminpack-1.3.6.tar.gz (latest version)
- cminpack-1.3.5.tar.gz
- cminpack-1.3.4.tar.gz
- cminpack-1.3.3.tar.gz
- cminpack-1.3.2.tar.gz
- cminpack-1.3.1.tar.gz
- cminpack-1.2.2.tar.gz
- cminpack-1.2.1.tar.gz
- cminpack-1.2.0.tar.gz
- cminpack-1.1.5.tar.gz
- cminpack-1.1.4.tar.gz
- cminpack-1.1.3.tar.gz
- cminpack-1.1.1.tar.gz
- cminpack-1.0.4.tar.gz
- cminpack-1.0.3.tar.gz
- cminpack-1.0.2.tar.gz
- cminpack-1.0.1.tar.gz
GitHub repository: https://github.com/devernay/cminpack
Using CMinpack
The CMinpack calls have the same name as the FORTRAN functions, in lowercase (e.g. lmder(...)). See the links to the documentation below, or take a look at the simple examples in the examples directory of the distribution. The simple examples are named after the function they call: tlmder.c is the simple example for lmder.
If you want to use the single precision CMinpack, you should define __cminpack_float__ before including cminpack.h. __cminpack_half__ has to be defined for the half-precision version (and the code needs to be compiled with a C++ compiler).
The single-precision versions of the functions are prefixed by "s" (as in "slmder(...)"), and the half-precision are prefixed by "h".
CMinpack defines __cminpack_real__ as the floating point type, and the __cminpack_func__() macro can be used to call CMinpack functions independently of the precision used (as in the examples). However, you shouldn't use these macros in your own code, since your code is probably designed for a specific precision, and you should prefer calling directly slmder(...) or slmder(...).
Documentation
- The original documentation for MINPACK
- The Debian GNU/Linux manual pages for MINPACK
- MINPACK on Wikipedia
- B.S. Garbow, K.E. Hillstrom and J.J. Moré: Implementation Guide for Minpack-1. ANL-80-68 (July 1980)
- J.J. Moré, B.S. Garbow and K.E. Hillstrom: User Guide for Minpack-1. ANL-80-74 (August 1980) : Chapters 1-3, Chapter 4
- Documentation for the test functions (the fourteen nonlinear equations problems defined in
vecfcn.f/.candvecjac.f/.c, the eighteen nonlinear least squares problems defined inssqfcn.f/.candssqjac.f/.c, and the eighteen nonlinear unconstrained minimization problems defined inobjfcn.f,grdfcn.fandhesfcn.f) can be found in the following papers:- Moré, J. J., Garbow, B. S., & Hillstrom, K. E. (1981). Testing Unconstrained Optimization Software. ACM Transactions on Mathematical Software (TOMS), 7(1), 17-41. doi:10.1145/355934.355936
- Moré, J. J., Garbow, B. S., & Hillstrom, K. E. (1981). Algorithm 566: FORTRAN Subroutines for Testing Unconstrained Optimization Software [C5],[E4]. ACM Transactions on Mathematical Software (TOMS), 7(1), 136-140. doi:10.1145/355934.355943
- Averbukh, V. Z., Figueroa, S., & Schlick, T. (1992). HESFCN| A FORTRAN Package of Hessian Subroutines for Testing Nonlinear Optimization Software. New York University, New York, NY.
- Averbukh, V. Z., Figueroa, S., & Schlick, T. (1994). Remark on algorithm 566. ACM Transactions on Mathematical Software (TOMS), 20(3), 282-285. doi:10.1145/192115.192128
References
LMDER/LMDIF
- J.J. Moré, "The Levenberg-Marquardt Algorithm, Implementation and Theory", in Numerical Analysis, G.A. Watson, Editor, Lecture Notes in Mathematics 630, Springer-Verlag, 1977. doi:10.1007/BFb0067700
HYBRJ/HYBRD
- M. J. D. Powell, A Hybrid Method for Nonlinear Equations. Numerical Methods for Nonlinear Algebraic Equations, P. Rabinowitz, editor. Gordon and Breach, 1970.
Simulating box constraints
Note that box constraints can easily be simulated in C++ Minpack, using a change of variables in the function (that hint was found in the lmfit documentation).
For example, say you want xmin[j] < x[j] < xmax[j], just apply the following change of variable at the beginning of fcn on the variables vector, and also on the computed solution after the optimization was performed:
for (j = 0; j < 3; ++j) {
real xmiddle = (xmin[j]+xmax[j])/2.;
real xwidth = (xmax[j]-xmin[j])/2.;
real th = tanh((x[j]-xmiddle)/xwidth);
x[j] = xmiddle + th * xwidth;
jacfac[j] = 1. - th * th;
}
This change of variables preserves the variables scaling, and is almost the identity near the middle of the interval.
Of course, if you use lmder, lmder1, hybrj or hybrj1, the Jacobian must be also consistent with that new function, so the column of the original Jacobian corresponding to x1 must be multiplied by the derivative of the change of variable, i.e jacfac[j].
Similarly, each element of the covariance matrix must be multiplied by jacfac[i]*jacfac[j].
For examples on how to implement this in practice, see the portions of code delimited by "#ifdef BOX_CONSTRAINTS" in the following source files: tlmderc.c, thybrj.c, tchkderc.c.
Equivalence table with other libraries
The following table may be useful if you need to switch to or from another library.
| MINPACK | NAG | NPL | SLATEC | levmar | GSL |
|---|---|---|---|---|---|
| lmdif | E04FCF | LSQNDN | DNLS1 | dlevmar_dif | |
| lmdif1 | E04FYF | LSNDN1 | DNLS1E | dlevmar_dif | |
| lmder | E04GDF/E04GBF | LSQFDN | DNLS1 | dlevmar_der | gsl_multifit_fdfsolver_lmsder |
| lmder1 | E04GZF | LSFDN2 | DNLS1E | dlevmar_der | |
| lmstr | * | * | DNLS1 | ||
| hybrd | C05NCF | * | DNSQ | gsl_multiroot_fsolver_hybrids | |
| hybrd1 | C05NBF | * | DNSQE | ||
| hybrj | C05PCF | * | DNSQ | gsl_multiroot_fdfsolver_hybridsj | |
| hybrj1 | C05PBF | * | DNSQE | ||
| covar | E04YCF | * | DCOV | gsl_multifit_covar | |
| chkder | C05ZAF |
Other MINPACK implementations
- by John Burkardt: C++, FORTRAN77, FORTRAN90.
- by Steve Verrill: Java (documentation, problems).
- by Alan Miller: FORTRAN90.
- Quantlib has a C++ MINPACK hidden deep inside (C++, header, tutorial).
- GPL-licensed implementations of MINPACK algorithms in C are availaible from the GNU Scientific Library.
- Python library scipy, module
scipy.optimize.leastsq, - IDL, add-on MPFIT.
- R has the minpack.lm package.
- Eigen has an unsupported nonlinear optimization module based on cminpack.
- Ceres Solver is not derived from MINPACK, but is probably the best available alternative, with lots of features (New BSD License).
History
- 1.3.6 (24/02/2017): Fix FreeBSD build. CMake: install CMinpackConfig.cmake rather than FindCMinpack.cmake, and add option USE_BLAS to compile with blas.
- 1.3.5 (28/05/2016): Add support for compiling a long double version (Makefile only). CMake: static libraries now have the suffix
_s. - 1.3.4 (28/05/2014): Add FindCMinpack.cmake cmake module. If you use the cmake install, finding CMinpack from your
CMakeLists.txt(especially on Windows) is as easy asfind_package(CMinpack). - 1.3.3 (04/02/2014): Add documentation and examples abouts how to add box constraints to the variables. Continuous integration using Travis CI
- 1.3.2 (27/10/2013): Minor change in the CMake build: also set SOVERSION.
- 1.3.1 (02/10/2013): Fix CUDA examples compilation, and remove non-free files.
- 1.3.0 (09/06/2012): Optionally use LAPACK and CBLAS in lmpar, qrfac, and qrsolv. Added "make lapack" to build the LAPACK-based cminpack and "make checklapack" to test it (results of the test may depend on the underlying LAPACK and BLAS implementations). On 64-bits architectures, the preprocessor symbol __LP64__ must be defined (see cminpackP.h) if the LAPACK library uses the LP64 interface (i.e. 32-bits integer, vhereas the ILP interface uses 64 bits integers).
- 1.2.2 (16/05/2012): Update Makefiles and documentation (see "Using CMinpack" above) for easier building and testing.
- 1.2.1 (15/05/2012): The library can now be built as double, float or half versions. Standard tests in the "examples" directory can now be lauched using "make check" (to run common tests, including against the float version), "make checkhalf" (to test the half version) and "make checkfail" (to run all the tests, even those that fail).
- 1.2.0 (14/05/2012): Added original FORTRAN sources for better testing (type "make" in directory fortran, then "make" in examples and follow the instructions). Added driver tests lmsdrv, chkdrv, hyjdrv, hybdrv. Typing "make alltest" in the examples directory will run all possible test combinations (make sure you have gfortran installed).
- 1.1.5 (04/05/2012): cminpack now works in CUDA, thanks to Jordi Bataller Mascarell, type "make" in the "cuda" subdir (be careful, though: this is a straightforward port from C, and each problem is solved using a single thread). cminpack can now also be compiled with single-precision floating point computation (define __cminpack_real__ to float when compiling and using the library). Fix cmake support for CMINPACK_LIB_INSTALL_DIR. Update the reference files for tests.
- 1.1.4 (30/10/2011): Translated all the Levenberg-Marquardt code (lmder, lmdif, lmstr, lmder1, lmdif1, lmstr1, lmpar, qrfac, qrsolv, fdjac2, chkder) to use C-style indices.
- 1.1.3 (16/03/2011): Minor fix: Change non-standard strnstr() to strstr() in genf77tests.c.
- 1.1.2 (07/01/2011): Fix Windows DLL building (David Graeff) and document covar in cminpack.h.
- 1.1.1 (04/12/2010): Complete rewrite of the C functions (without trailing underscore in the function name). Using the original FORTRAN code, the original algorithms structure was recovered, and many goto's were converted to if...then...else. The code should now be both more readable and easier to optimize, both for humans and for compilers. Added lmddrv and lmfdrv test drivers, which test a lot of difficult functions (these functions are explained in Testing Unconstrained Optimization Software by Moré et al.). Also added the pkg-config files to the cmake build, as well as an "uninstall" target, contributed by Geoffrey Biggs.
- 1.0.4 (18/10/2010): Support for shared library building using CMake, thanks to Goeffrey Biggs from AIST and Radu Bogdan Rusu from Willow Garage. Shared libraries can be enabled using cmake options, as in:
cmake -DUSE_FPIC=ON -DSHARED_LIBS=ON -DBUILD_EXAMPLES=OFF path_to_sources - 1.0.3 (18/03/2010): Added CMake support. XCode build is now Universal (i386+ppc). Added tfdjac2_ and tfdjac2c examples, which test the accuracy of a finite-differences approximation of the Jacobian. Bug fix in tlmstr1 (signaled by Thomas Capricelli).
- 1.0.2 (27/02/2009): Added Xcode and Visual Studio project files
- 1.0.1 (17/12/2007): bug fix in covar() and covar_(), the computation of tolr caused a segfault (signaled by Timo Hartmann).
- 1.0.0 (24/04/2007): Initial revision.
Future work
There is now a very powerful alternative to MINPACK, which is the Ceres Solver. You may want to consider using Ceres for any new project.
The main feature that's missing on cminpack is the possibility to add constraints on variables. Simple boundary constraints should be enough, as implemented in ALGLIB or MPFIT.
levmar also has linear constraints, but they shouldn't be necessary since linear constraints can be changed to box constraints by a simple change of variables. If you really need nonlinear constraints, and no reparameterization of variables (which may be able to linearize these constraints), you should consider using NLopt instead of cminpack.
Please contact me for any suggestion or request.
Frédéric Devernay 
LMDER_
Section: C Library Functions (3)Updated: March 8, 2002
Index Return to Main Contents
NAME
lmder_, lmder1_ - minimize the sum of squares of m nonlinear functions, with user supplied JacobianSYNOPSIS
include <minpack.h>- void lmder1_ ( void (*fcn) (int *m, int *n, double *x, double *fvec, double *fjac,
-
int *ldfjac,
int *iflag),
-
int *m,
int * n,
double *x,
double *fvec,
double *fjac,
int *ldfjac,
- double *tol, int *info, int *iwa, double *wa, int *lwa);
-
int *m,
int * n,
double *x,
double *fvec,
double *fjac,
int *ldfjac,
- void lmder_ ( void (*fcn)( int *m, int *n, double *x, double *fvec, double *fjac,
-
int *ldfjac,
int *iflag),
-
int *m,
int *n,
double *x,
double *fvec,
double *fjac,
int *ldfjac,
- double *ftol, double *xtol, double *gtol, int *maxfev, double *diag, int *mode,
- double *factor, int *nprint, int *info,
- int *nfev, int *njev, int *ipvt,
- double *qtf, double *wa1, double *wa2, double *wa3, double *wa4 );
- double *ftol, double *xtol, double *gtol, int *maxfev, double *diag, int *mode,
-
int *m,
int *n,
double *x,
double *fvec,
double *fjac,
int *ldfjac,
DESCRIPTION
lmder1_ performs the same function as lmder_ but has a simplified calling sequence.
lmstr and lmstr1 also perform the same function but use
minimal storage.
Language notes
These functions are written in FORTRAN. If calling from C, keep these points in mind:- Name mangling.
- With g77 version 2.95 or 3.0, all the function names end in an underscore. This may change with future versions of g77.
- Compile with g77.
- Even if your program is all C code, you should link with g77 so it will pull in the FORTRAN libraries automatically. It's easiest just to use g77 to do all the compiling. (It handles C just fine.)
- Call by reference.
- All function parameters must be pointers.
- Column-major arrays.
-
Suppose a function returns an array with 5 rows and 3 columns in an
array z and in the call you have declared a leading dimension of
7. The FORTRAN and equivalent C references are:
z(1,1) z[0] z(2,1) z[1] z(5,1) z[4] z(1,2) z[7] z(1,3) z[14] z(i,j) z[(i-1) + (j-1)*7]
User-supplied Function
fcn is the name of the user-supplied subroutine which calculates the functions. In FORTRAN, fcn must be declared in an external statement in the user calling program, and should be written as follows:
subroutine fcn(m,n,x,fvec,fjac,ldfjac,iflag) integer m,n,iflag double precision x(n),fvec(m),fjac(ldfjac,n) ---------- if iflag = 1 calculate the functions at x and return this vector in fvec. do not alter fjac. if iflag = 2 calculate the jacobian at x and return this matrix in fjac. do not alter fvec. ---------- return end
In C, fcn should be written as follows:
void fcn(int m, int n, double *x, double *fvec, double *fjac,
int *ldfjac, int *iflag)
{
/* if iflag = 1 calculate the functions at x and return this
vector in fvec[0] through fvec[m-1]. do not alter fjac.
if iflag = 2 calculate the jacobian at x and return this
matrix in fjac. do not alter fvec. */
}
The value of iflag should not be changed by fcn unless the
user wants to terminate execution of lmder_ (or lmder1_). In
this case set iflag to a negative integer.
Parameters for both lmder_ and lmder1_
m is a positive integer input variable set to the number of functions.
n is a positive integer input variable set to the number of variables. n must not exceed m.
x is an array of length n. On input x must contain an initial estimate of the solution vector. On output x contains the final estimate of the solution vector.
fvec is an output array of length m which contains the functions evaluated at the output x.
fjac is an output m by n array. The upper n by n submatrix of fjac contains an upper triangular matrix r with diagonal elements of nonincreasing magnitude such that
t t t
p *(jac *jac)*p = r *r,
where p is a permutation matrix and jac is the final calculated Jacobian. column j of p is column ipvt(j) (see below) of the identity matrix. The lower trapezoidal part of fjac contains information generated during the computation of r.
ldfjac is a positive integer input variable not less than
m which specifies the leading dimension of the array
fjac.
Parameters for lmder1_
tol is a nonnegative input variable. Termination occurs when the algorithm estimates either that the relative error in the sum of squares is at most tol or that the relative error between x and the solution is at most tol.
info is an integer output variable. if the user has terminated execution, info is set to the (negative) value of iflag. see description of fcn. otherwise, info is set as follows.
info = 0 improper input parameters.
info = 1 algorithm estimates that the relative error
in the sum of squares is at most tol.
info = 2 algorithm estimates that the relative error
between x and the solution is at most tol.
info = 3 conditions for info = 1 and info = 2 both hold.
info = 4 fvec is orthogonal to the columns of the
Jacobian to machine precision.
info = 5 number of calls to fcn has reached or
exceeded 200*(n+1).
info = 6 tol is too small. no further reduction in
the sum of squares is possible.
info = 7 tol is too small. no further improvement in
the approximate solution x is possible.
iwa is an integer work array of length n.
wa is a work array of length lwa.
lwa is an integer input variable not less than m*n +
5*n + m for lmder1_.
Parameters for lmder_
ftol is a nonnegative input variable. Termination occurs when both the actual and predicted relative reductions in the sum of squares are at most ftol. Therefore, ftol measures the relative error desired in the sum of squares.
xtol is a nonnegative input variable. Termination occurs when the relative error between two consecutive iterates is at most xtol. Therefore, xtol measures the relative error desired in the approximate solution.
gtol is a nonnegative input variable. Termination occurs when the cosine of the angle between fvec and any column of the Jacobian is at most gtol in absolute value. Therefore, gtol measures the orthogonality desired between the function vector and the columns of the Jacobian.
maxfev is a positive integer input variable. Termination occurs when the number of calls to fcn is at least maxfev by the end of an iteration.
diag is an array of length n. If mode = 1 (see below), diag is internally set. If mode = 2, diag must contain positive entries that serve as multiplicative scale factors for the variables.
mode is an integer input variable. If mode = 1, the variables will be scaled internally. If mode = 2, the scaling is specified by the input diag. Other values of mode are equivalent to mode = 1.
factor is a positive input variable used in determining the initial step bound. This bound is set to the product of factor and the euclidean norm of diag*x if the latter is nonzero, or else to factor itself. In most cases factor should lie in the interval (.1,100.). 100. is a generally recommended value.
nprint is an integer input variable that enables controlled printing of iterates if it is positive. In this case, fcn is called with iflag = 0 at the beginning of the first iteration and every nprint iterations thereafter and immediately prior to return, with x and fvec available for printing. If nprint is not positive, no special calls of fcn with iflag = 0 are made.
info is an integer output variable. If the user has terminated execution, info is set to the (negative) value of iflag. See description of fcn. Otherwise, info is set as follows.
info = 0 improper input parameters.
info = 1 both actual and predicted relative reductions
in the sum of squares are at most ftol.
info = 2 relative error between two consecutive iterates
is at most xtol.
info = 3 conditions for info = 1 and info = 2 both hold.
info = 4 the cosine of the angle between fvec and any
column of the Jacobian is at most gtol in absolute value.
info = 5 number of calls to fcn has reached or
exceeded maxfev.
info = 6 ftol is too small. No further reduction in
the sum of squares is possible.
info = 7 xtol is too small. No further improvement in
the approximate solution x is possible.
info = 8 gtol is too small. fvec is orthogonal to
the columns of the Jacobian to machine precision.
nfev is an integer output variable set to the number of calls to fcn with iflag = 1.
njev is an integer output variable set to the number of calls to fcn with iflag = 2.
ipvt is an integer output array of length n. ipvt defines a permutation matrix p such that jac*p = q*r, where jac is the final calculated Jacobian, q is orthogonal (not stored), and r is upper triangular with diagonal elements of nonincreasing magnitude. Column j of p is column ipvt(j) of the identity matrix.
qtf is an output array of length n which contains the first n elements of the vector (q transpose)*fvec.
wa1, wa2, and wa3 are work arrays of length n.
wa4 is a work array of length m.
SEE ALSO
lmdif(3), lmdif1(3), lmstr(3), lmstr1(3).AUTHORS
Jorge More', Burt Garbow, and Ken Hillstrom at Argonne National Laboratory. This manual page was written by Jim Van Zandt <jrv@debian.org>, for the Debian GNU/Linux system (but may be used by others).
Index
This document was created by man2html, using the manual pages.
Time: 10:19:50 GMT, April 20, 2007 cminpack-1.3.6/doc/lmdif1_.3 0000664 0000000 0000000 00000000022 13054046253 0015446 0 ustar 00root root 0000000 0000000 .so man3/lmdif_.3 cminpack-1.3.6/doc/lmdif_.3 0000664 0000000 0000000 00000025271 13054046253 0015402 0 ustar 00root root 0000000 0000000 .\" Hey, EMACS: -*- nroff -*- .TH LMDIF_ 3 "March 8, 2002" Minpack .\" Please adjust this date whenever revising the manpage. .SH NAME lmdif_, lmdif1_ \- minimize the sum of squares of m nonlinear functions .SH SYNOPSIS .B include
LMDIF_
Section: C Library Functions (3)Updated: March 8, 2002
Index Return to Main Contents
NAME
lmdif_, lmdif1_ - minimize the sum of squares of m nonlinear functionsSYNOPSIS
include <minpack.h>- void lmdif1_ ( void (*fcn)(int *m, int *n, double *x, double *fvec, int *iflag),
-
int *m,
int * n,
double *x,
double *fvec,
- double *tol, int *info, int *iwa, double *wa, int *lwa);
- void lmdif_ ( void (*fcn)(int *m, int *n, double *x, double *fvec, int *iflag),
-
int *m,
int *n,
double *x,
double *fvec,
- double *ftol, double *xtol, double *gtol, int *maxfev, double *epsfcn, double *diag, int *mode, double *factor, int *nprint, int *info, int *nfev, double *fjac,
- int *ldfjac, int *ipvt, double *qtf,
- double *wa1, double *wa2, double *wa3, double *wa4 );
- double *ftol, double *xtol, double *gtol, int *maxfev, double *epsfcn, double *diag, int *mode, double *factor, int *nprint, int *info, int *nfev, double *fjac,
DESCRIPTION
lmdif1_ serves the same purpose but has a simplified calling
sequence.
Language notes
These functions are written in FORTRAN. If calling from C, keep these points in mind:- Name mangling.
- With g77 version 2.95 or 3.0, all the function names end in an underscore. This may change with future versions of g77.
- Compile with g77.
- Even if your program is all C code, you should link with g77 so it will pull in the FORTRAN libraries automatically. It's easiest just to use g77 to do all the compiling. (It handles C just fine.)
- Call by reference.
- All function parameters must be pointers.
- Column-major arrays.
-
Suppose a function returns an array with 5 rows and 3 columns in an
array z and in the call you have declared a leading dimension of
7. The FORTRAN and equivalent C references are:
z(1,1) z[0] z(2,1) z[1] z(5,1) z[4] z(1,2) z[7] z(1,3) z[14] z(i,j) z[(i-1) + (j-1)*7]
fcn is the name of the user-supplied subroutine which calculates the functions. In FORTRAN, fcn must be declared in an external statement in the user calling program, and should be written as follows:subroutine fcn(m,n,x,fvec,iflag) integer m,n,iflag double precision x(n),fvec(m) ---------- calculate the functions at x and return this vector in fvec. ---------- return end
In C, fcn should be written as follows:
void fcn(int m, int n, double *x, double *fvec, int *iflag) { /* calculate the functions at x and return the values in fvec[0] through fvec[m-1] */ }The value of iflag should not be changed by fcn unless the user wants to terminate execution of lmdif_ (or lmdif1_). In this case set iflag to a negative integer.
Parameters for both lmdif_ and lmdif1_
m is a positive integer input variable set to the number of functions.
n is a positive integer input variable set to the number of variables. n must not exceed m.
x is an array of length n. On input x must contain an initial estimate of the solution vector. On output x contains the final estimate of the solution vector.
fvec is an output array of length m which contains
the functions evaluated at the output x.
Parameters for lmdif1_
tol is a nonnegative input variable. Termination occurs when the algorithm estimates either that the relative error in the sum of squares is at most tol or that the relative error between x and the solution is at most tol.
info is an integer output variable. if the user has terminated execution, info is set to the (negative) value of iflag. see description of fcn. otherwise, info is set as follows.
info = 0 improper input parameters.
info = 1 algorithm estimates that the relative error
in the sum of squares is at most tol.
info = 2 algorithm estimates that the relative error
between x and the solution is at most tol.
info = 3 conditions for info = 1 and info = 2 both hold.
info = 4 fvec is orthogonal to the columns of the
Jacobian to machine precision.
info = 5 number of calls to fcn has reached or
exceeded 200*(n+1).
info = 6 tol is too small. no further reduction in
the sum of squares is possible.
info = 7 tol is too small. no further improvement in
the approximate solution x is possible.
iwa is an integer work array of length n.
wa is a work array of length lwa.
lwa is an integer input variable not less than m*n +
5*n + m.
Parameters for lmdif_
ftol is a nonnegative input variable. Termination occurs when both the actual and predicted relative reductions in the sum of squares are at most ftol. Therefore, ftol measures the relative error desired in the sum of squares.
xtol is a nonnegative input variable. Termination occurs when the relative error between two consecutive iterates is at most xtol. Therefore, xtol measures the relative error desired in the approximate solution.
gtol is a nonnegative input variable. Termination occurs when the cosine of the angle between fvec and any column of the Jacobian is at most gtol in absolute value. Therefore, gtol measures the orthogonality desired between the function vector and the columns of the Jacobian.
maxfev is a positive integer input variable. Termination occurs when the number of calls to fcn is at least maxfev by the end of an iteration.
epsfcn is an input variable used in determining a suitable step length for the forward-difference approximation. This approximation assumes that the relative errors in the functions are of the order of epsfcn. If epsfcn is less than the machine precision, it is assumed that the relative errors in the functions are of the order of the machine precision.
diag is an array of length n. If mode = 1 (see below), diag is internally set. If mode = 2, diag must contain positive entries that serve as multiplicative scale factors for the variables.
mode is an integer input variable. If mode = 1, the variables will be scaled internally. If mode = 2, the scaling is specified by the input diag. Other values of mode are equivalent to mode = 1.
factor is a positive input variable used in determining the initial step bound. This bound is set to the product of factor and the euclidean norm of diag*x if the latter is nonzero, or else to factor itself. In most cases factor should lie in the interval (.1,100.). 100. is a generally recommended value.
nprint is an integer input variable that enables controlled printing of iterates if it is positive. In this case, fcn is called with iflag = 0 at the beginning of the first iteration and every nprint iterations thereafter and immediately prior to return, with x and fvec available for printing. If nprint is not positive, no special calls of fcn with iflag = 0 are made.
info is an integer output variable. If the user has terminated execution, info is set to the (negative) value of iflag. See description of fcn. Otherwise, info is set as follows.
info = 0 improper input parameters.
info = 1 both actual and predicted relative reductions
in the sum of squares are at most ftol.
info = 2 relative error between two consecutive iterates
is at most xtol.
info = 3 conditions for info = 1 and info = 2 both hold.
info = 4 the cosine of the angle between fvec and any
column of the Jacobian is at most gtol in absolute value.
info = 5 number of calls to fcn has reached or
exceeded maxfev.
info = 6 ftol is too small. No further reduction in
the sum of squares is possible.
info = 7 xtol is too small. No further improvement in
the approximate solution x is possible.
info = 8 gtol is too small. fvec is orthogonal to
the columns of the Jacobian to machine precision.
nfev is an integer output variable set to the number of calls to fcn.
fjac is an output m by n array. The upper n by n submatrix of fjac contains an upper triangular matrix r with diagonal elements of nonincreasing magnitude such that
t t t
p *(jac *jac)*p = r *r,
where p is a permutation matrix and jac is the final calculated Jacobian. column j of p is column ipvt(j) (see below) of the identity matrix. The lower trapezoidal part of fjac contains information generated during the computation of r.
ldfjac is a positive integer input variable not less than m which specifies the leading dimension of the array fjac.
ipvt is an integer output array of length n. ipvt defines a permutation matrix p such that jac*p = q*r, where jac is the final calculated Jacobian, q is orthogonal (not stored), and r is upper triangular with diagonal elements of nonincreasing magnitude. Column j of p is column ipvt(j) of the identity matrix.
qtf is an output array of length n which contains the first n elements of the vector (q transpose)*fvec.
wa1, wa2, and wa3 are work arrays of length n.
wa4 is a work array of length m.
SEE ALSO
lmder(3), lmder1(3), lmstr(3), lmstr1(3).AUTHORS
Jorge More', Burt Garbow, and Ken Hillstrom at Argonne National Laboratory. This manual page was written by Jim Van Zandt <jrv@debian.org>, for the Debian GNU/Linux system (but may be used by others).
Index
This document was created by man2html, using the manual pages.
Time: 10:19:50 GMT, April 20, 2007 cminpack-1.3.6/doc/lmstr1_.3 0000664 0000000 0000000 00000000022 13054046253 0015514 0 ustar 00root root 0000000 0000000 .so man3/lmstr_.3 cminpack-1.3.6/doc/lmstr_.3 0000664 0000000 0000000 00000026530 13054046253 0015447 0 ustar 00root root 0000000 0000000 .\" Hey, EMACS: -*- nroff -*- .TH LMSTR_ 3 "March 8, 2002" Minpack .\" Please adjust this date whenever revising the manpage. .SH NAME lmstr_, lmstr1_ \- minimize the sum of squares of m nonlinear functions, with user supplied Jacobian and minimal storage .SH SYNOPSIS .B include
LMSTR_
Section: C Library Functions (3)Updated: March 8, 2002
Index Return to Main Contents
NAME
lmstr_, lmstr1_ - minimize the sum of squares of m nonlinear functions, with user supplied Jacobian and minimal storageSYNOPSIS
include <minpack.h>- void lmstr1_ ( void (*fcn) (int *m, int *n, double *x, double *fvec, double *fjrow, int *iflag),
-
int *m,
int * n,
double *x,
double *fvec,
double *fjac,
int *ldfjac,
- double *tol, int *info, int *iwa,
- double *wa, int *kwa);
- double *tol, int *info, int *iwa,
- void lmstr_ ( void (*fcn)( int *m, int *n, double *x, double *fvec, double *fjrow, int *iflag),
-
int *m,
int *n,
double *x,
double *fvec,
double *fjac,
int *ldfjac,
- double *ftol, double *xtol, double *gtol,
- int *maxfev, double *diag, int *mode, double *factor,
- int *nprint, int *info, int *nfev, int *njev,
- int *ipvt, double *qtf,
- double *wa1, double *wa2, double *wa3, double *wa4 );
- double *ftol, double *xtol, double *gtol,
DESCRIPTION
lmstr1_ performs the same function but has a simplified calling sequence.
lmder(3) and lmder1(3) perform the same function but do
not attempt to minimize storage.
Language notes
These functions are written in FORTRAN. If calling from C, keep these points in mind:- Name mangling.
- With g77 version 2.95 or 3.0, all the function names end in an underscore. This may change with future versions of g77.
- Compile with g77.
- Even if your program is all C code, you should link with g77 so it will pull in the FORTRAN libraries automatically. It's easiest just to use g77 to do all the compiling. (It handles C just fine.)
- Call by reference.
- All function parameters must be pointers.
- Column-major arrays.
-
Suppose a function returns an array with 5 rows and 3 columns in an
array z and in the call you have declared a leading dimension of
7. The FORTRAN and equivalent C references are:
z(1,1) z[0] z(2,1) z[1] z(5,1) z[4] z(1,2) z[7] z(1,3) z[14] z(i,j) z[(i-1) + (j-1)*7]
User-supplied Function
fcn is the name of the user-supplied subroutine which calculates the functions. In FORTRAN, fcn must be declared in an external statement in the user calling program, and should be written as follows:
subroutine fcn(m,n,x,fvec,fjrow,iflag) integer m,n,iflag double precision x(n),fvec(m),fjrow(n) ---------- if iflag = 1 calculate the functions at x and return this vector in fvec. Do not alter fjac. if iflag = i calculate row (i-1) of the Jacobian at x and return this vector in fjrow. ---------- return end
In C, fcn should be written as follows:
void fcn(int m, int n, double *x, double *fvec, double *fjrow,
int *iflag)
{
/* If iflag = 1 calculate the functions at x and return the
values in fvec[0] through fvec[m-1]. Do not alter fjac.
If iflag = i calculate row (i-1) of the Jacobian
at x and return the vector in fjrow. */
}
iflag is an input integer which specifies whether a function
value or Jacobian row is to be calculated.
The value of iflag should not be changed by fcn unless the
user wants to terminate execution of lmstr_ (or lmstr1_). In
this case set iflag to a negative integer.
Parameters for both lmstr_ and lmstr1_
m is a positive integer input variable set to the number of functions.
n is a positive integer input variable set to the number of variables. n must not exceed m.
x is an array of length n. On input x must contain an initial estimate of the solution vector. On output x contains the final estimate of the solution vector.
fvec is an output array of length m which contains the functions evaluated at the output x.
fjrow is an output array of length n which is set to one row of the Jacobian evaluated at x.
fjac is an output m by n array. The upper n by n submatrix of fjac contains an upper triangular matrix r with diagonal elements of nonincreasing magnitude such that
t t t
p *(jac *jac)*p = r *r,
where p is a permutation matrix and jac is the final calculated Jacobian. Column j of p is column ipvt(j) (see below) of the identity matrix. The lower trapezoidal part of fjac contains information generated during the computation of r.
ldfjac is a positive integer input variable not less than
m which specifies the leading dimension of the array
fjac.
Parameters for lmstr1_
tol is a nonnegative input variable. Termination occurs when the algorithm estimates either that the relative error in the sum of squares is at most tol or that the relative error between x and the solution is at most tol.
info is an integer output variable. if the user has terminated execution, info is set to the (negative) value of iflag. see description of fcn. otherwise, info is set as follows.
info = 0 improper input parameters.
info = 1 algorithm estimates that the relative error
in the sum of squares is at most tol.
info = 2 algorithm estimates that the relative error
between x and the solution is at most tol.
info = 3 conditions for info = 1 and info = 2 both hold.
info = 4 fvec is orthogonal to the columns of the
Jacobian to machine precision.
info = 5 number of calls to fcn has reached or
exceeded 100*(n+1).
info = 6 tol is too small. no further reduction in
the sum of squares is possible.
info = 7 tol is too small. no further improvement in
the approximate solution x is possible.
wa is a work array of length lwa.
lwa is an integer input variable not less than m*n +
5*n + m for lmder1, or 5*n+m for lmstr1_.
Parameters for lmstr_
ftol is a nonnegative input variable. Termination occurs when both the actual and predicted relative reductions in the sum of squares are at most ftol. Therefore, ftol measures the relative error desired in the sum of squares.
xtol is a nonnegative input variable. Termination occurs when the relative error between two consecutive iterates is at most xtol. Therefore, xtol measures the relative error desired in the approximate solution.
gtol is a nonnegative input variable. Termination occurs when the cosine of the angle between fvec and any column of the Jacobian is at most gtol in absolute value. Therefore, gtol measures the orthogonality desired between the function vector and the columns of the Jacobian.
maxfev is a positive integer input variable. Termination occurs when the number of calls to fcn is at least maxfev by the end of an iteration.
diag is an array of length n. If mode = 1 (see below), diag is internally set. If mode = 2, diag must contain positive entries that serve as multiplicative scale factors for the variables.
mode is an integer input variable. If mode = 1, the variables will be scaled internally. If mode = 2, the scaling is specified by the input diag. Other values of mode are equivalent to mode = 1.
factor is a positive input variable used in determining the initial step bound. This bound is set to the product of factor and the euclidean norm of diag*x if the latter is nonzero, or else to factor itself. In most cases factor should lie in the interval (.1,100.). 100. is a generally recommended value.
nprint is an integer input variable that enables controlled printing of iterates if it is positive. In this case, fcn is called with iflag = 0 at the beginning of the first iteration and every nprint iterations thereafter and immediately prior to return, with x and fvec available for printing. If nprint is not positive, no special calls of fcn with iflag = 0 are made.
info is an integer output variable. If the user has terminated execution, info is set to the (negative) value of iflag. See description of fcn. Otherwise, info is set as follows.
info = 0 improper input parameters.
info = 1 both actual and predicted relative reductions
in the sum of squares are at most ftol.
info = 2 relative error between two consecutive iterates
is at most xtol.
info = 3 conditions for info = 1 and info = 2 both hold.
info = 4 the cosine of the angle between fvec and any
column of the Jacobian is at most gtol in absolute value.
info = 5 number of calls to fcn has reached or
exceeded maxfev.
info = 6 ftol is too small. No further reduction in
the sum of squares is possible.
info = 7 xtol is too small. No further improvement in
the approximate solution x is possible.
info = 8 gtol is too small. fvec is orthogonal to
the columns of the Jacobian to machine precision.
nfev is an integer output variable set to the number of calls to fcn with iflag = 1.
njev is an integer output variable set to the number of calls to fcn with iflag = 2.
ipvt is an integer output array of length n. ipvt defines a permutation matrix p such that jac*p = q*r, where jac is the final calculated Jacobian, q is orthogonal (not stored), and r is upper triangular with diagonal elements of nonincreasing magnitude. Column j of p is column ipvt(j) of the identity matrix.
qtf is an output array of length n which contains the first n elements of the vector (q transpose)*fvec.
wa1, wa2, and wa3 are work arrays of length n.
wa4 is a work array of length m.
SEE ALSO
lmdif(3), lmdif1(3), lmder(3), lmder1(3).AUTHORS
Jorge More', Burt Garbow, and Ken Hillstrom at Argonne National Laboratory. This manual page was written by Jim Van Zandt <jrv@debian.org>, for the Debian GNU/Linux system (but may be used by others).
Index
This document was created by man2html, using the manual pages.
Time: 10:19:50 GMT, April 20, 2007 cminpack-1.3.6/doc/man.html 0000664 0000000 0000000 00000002062 13054046253 0015516 0 ustar 00root root 0000000 0000000
MINPACK
Function Index
- hybrd_, hybrd1_ - find a zero of a system of nonlinear function
- hybrj_, hybrj1_ - find a zero of a system of nonlinear function
- lmder_, lmder1_ - minimize the sum of squares of m nonlinear functions, with user supplied Jacobian
- lmdif_, lmdif1_ - minimize the sum of squares of m nonlinear functions
- lmstr_, lmstr1_ - minimize the sum of squares of m nonlinear functions, with user supplied Jacobian and minimal storage
AUTHORS
Jorge More', Burt Garbow, and Ken Hillstrom at Argonne National Laboratory. These manual pages were written by Jim Van Zandt <jrv@debian.org>, for the Debian GNU/Linux system (but may be used by others).
This document was created by man2html. cminpack-1.3.6/doc/minpack-documentation.txt 0000664 0000000 0000000 00000507022 13054046253 0021115 0 ustar 00root root 0000000 0000000 Page Documentation for MINPACK subroutine HYBRD1 Double precision version Argonne National Laboratory Burton S. Garbow, Kenneth E. Hillstrom, Jorge J. More March 1980 1. Purpose. The purpose of HYBRD1 is to find a zero of a system of N non- linear functions in N variables by a modification of the Powell hybrid method. This is done by using the more general nonlinear equation solver HYBRD. The user must provide a subroutine which calculates the functions. The Jacobian is then calculated by a forward-difference approximation. 2. Subroutine and type statements. SUBROUTINE HYBRD1(FCN,N,X,FVEC,TOL,INFO,WA,LWA) INTEGER N,INFO,LWA DOUBLE PRECISION TOL DOUBLE PRECISION X(N),FVEC(N),WA(LWA) EXTERNAL FCN 3. Parameters. Parameters designated as input parameters must be specified on entry to HYBRD1 and are not changed on exit, while parameters designated as output parameters need not be specified on entry and are set to appropriate values on exit from HYBRD1. FCN is the name of the user-supplied subroutine which calculate the functions. FCN must be declared in an EXTERNAL statement in the user calling program, and should be written as follows SUBROUTINE FCN(N,X,FVEC,IFLAG) INTEGER N,IFLAG DOUBLE PRECISION X(N),FVEC(N) ---------- CALCULATE THE FUNCTIONS AT X AND RETURN THIS VECTOR IN FVEC. ---------- RETURN END The value of IFLAG should not be changed by FCN unless the user wants to terminate execution of HYBRD1. In this case set IFLAG to a negative integer. Page N is a positive integer input variable set to the number of functions and variables. X is an array of length N. On input X must contain an initial estimate of the solution vector. On output X contains the final estimate of the solution vector. FVEC is an output array of length N which contains the function evaluated at the output X. TOL is a nonnegative input variable. Termination occurs when the algorithm estimates that the relative error between X and the solution is at most TOL. Section 4 contains more details about TOL. INFO is an integer output variable. If the user has terminated execution, INFO is set to the (negative) value of IFLAG. See description of FCN. Otherwise, INFO is set as follows. INFO = 0 Improper input parameters. INFO = 1 Algorithm estimates that the relative error between X and the solution is at most TOL. INFO = 2 Number of calls to FCN has reached or exceeded 200*(N+1). INFO = 3 TOL is too small. No further improvement in the approximate solution X is possible. INFO = 4 Iteration is not making good progress. Sections 4 and 5 contain more details about INFO. WA is a work array of length LWA. LWA is a positive integer input variable not less than (N*(3*N+13))/2. 4. Successful completion. The accuracy of HYBRD1 is controlled by the convergence parame- ter TOL. This parameter is used in a test which makes a compar- ison between the approximation X and a solution XSOL. HYBRD1 terminates when the test is satisfied. If TOL is less than the machine precision (as defined by the MINPACK function DPMPAR(1)), then HYBRD1 only attempts to satisfy the test defined by the machine precision. Further progress is not usu- ally possible. Unless high precision solutions are required, the recommended value for TOL is the square root of the machine precision. The test assumes that the functions are reasonably well behaved Page If this condition is not satisfied, then HYBRD1 may incorrectly indicate convergence. The validity of the answer can be checked, for example, by rerunning HYBRD1 with a tighter toler- ance. Convergence test. If ENORM(Z) denotes the Euclidean norm of a vector Z, then this test attempts to guarantee that ENORM(X-XSOL) .LE. TOL*ENORM(XSOL). If this condition is satisfied with TOL = 10**(-K), then the larger components of X have K significant decimal digits and INFO is set to 1. There is a danger that the smaller compo- nents of X may have large relative errors, but the fast rate of convergence of HYBRD1 usually avoids this possibility. 5. Unsuccessful completion. Unsuccessful termination of HYBRD1 can be due to improper input parameters, arithmetic interrupts, an excessive number of func- tion evaluations, errors in the functions, or lack of good prog ress. Improper input parameters. INFO is set to 0 if N .LE. 0, or TOL .LT. 0.D0, or LWA .LT. (N*(3*N+13))/2. Arithmetic interrupts. If these interrupts occur in the FCN subroutine during an early stage of the computation, they may be caused by an unacceptable choice of X by HYBRD1. In this case, it may be possible to remedy the situation by not evalu- ating the functions here, but instead setting the components of FVEC to numbers that exceed those in the initial FVEC, thereby indirectly reducing the step length. The step length can be more directly controlled by using instead HYBRD, which includes in its calling sequence the step-length- governing parameter FACTOR. Excessive number of function evaluations. If the number of calls to FCN reaches 200*(N+1), then this indicates that the routine is converging very slowly as measured by the progress of FVEC, and INFO is set to 2. This situation should be unu- sual because, as indicated below, lack of good progress is usually diagnosed earlier by HYBRD1, causing termination with INFO = 4. Errors in the functions. The choice of step length in the for- ward-difference approximation to the Jacobian assumes that th relative errors in the functions are of the order of the machine precision. If this is not the case, HYBRD1 may fail (usually with INFO = 4). The user should then use HYBRD instead, or one of the programs which require the analytic Jacobian (HYBRJ1 and HYBRJ). Page Lack of good progress. HYBRD1 searches for a zero of the system by minimizing the sum of the squares of the functions. In so doing, it can become trapped in a region where the minimum does not correspond to a zero of the system and, in this situ- ation, the iteration eventually fails to make good progress. In particular, this will happen if the system does not have a zero. If the system has a zero, rerunning HYBRD1 from a dif- ferent starting point may be helpful. 6. Characteristics of the algorithm. HYBRD1 is a modification of the Powell hybrid method. Two of its main characteristics involve the choice of the correction a a convex combination of the Newton and scaled gradient direc- tions, and the updating of the Jacobian by the rank-1 method of Broyden. The choice of the correction guarantees (under reason able conditions) global convergence for starting points far fro the solution and a fast rate of convergence. The Jacobian is approximated by forward differences at the starting point, but forward differences are not used again until the rank-1 method fails to produce satisfactory progress. Timing. The time required by HYBRD1 to solve a given problem depends on N, the behavior of the functions, the accuracy requested, and the starting point. The number of arithmetic operations needed by HYBRD1 is about 11.5*(N**2) to process each call to FCN. Unless FCN can be evaluated quickly, the timing of HYBRD1 will be strongly influenced by the time spent in FCN. Storage. HYBRD1 requires (3*N**2 + 17*N)/2 double precision storage locations, in addition to the storage required by the program. There are no internally declared storage arrays. 7. Subprograms required. USER-supplied ...... FCN MINPACK-supplied ... DOGLEG,DPMPAR,ENORM,FDJAC1,HYBRD, QFORM,QRFAC,R1MPYQ,R1UPDT FORTRAN-supplied ... DABS,DMAX1,DMIN1,DSQRT,MIN0,MOD 8. References. M. J. D. Powell, A Hybrid Method for Nonlinear Equations. Numerical Methods for Nonlinear Algebraic Equations, P. Rabinowitz, editor. Gordon and Breach, 1970. 9. Example. Page The problem is to determine the values of x(1), x(2), ..., x(9) which solve the system of tridiagonal equations (3-2*x(1))*x(1) -2*x(2) = -1 -x(i-1) + (3-2*x(i))*x(i) -2*x(i+1) = -1, i=2-8 -x(8) + (3-2*x(9))*x(9) = -1 C ********** C C DRIVER FOR HYBRD1 EXAMPLE. C DOUBLE PRECISION VERSION C C ********** INTEGER J,N,INFO,LWA,NWRITE DOUBLE PRECISION TOL,FNORM DOUBLE PRECISION X(9),FVEC(9),WA(180) DOUBLE PRECISION ENORM,DPMPAR EXTERNAL FCN C C LOGICAL OUTPUT UNIT IS ASSUMED TO BE NUMBER 6. C DATA NWRITE /6/ C N = 9 C C THE FOLLOWING STARTING VALUES PROVIDE A ROUGH SOLUTION. C DO 10 J = 1, 9 X(J) = -1.D0 10 CONTINUE C LWA = 180 C C SET TOL TO THE SQUARE ROOT OF THE MACHINE PRECISION. C UNLESS HIGH PRECISION SOLUTIONS ARE REQUIRED, C THIS IS THE RECOMMENDED SETTING. C TOL = DSQRT(DPMPAR(1)) C CALL HYBRD1(FCN,N,X,FVEC,TOL,INFO,WA,LWA) FNORM = ENORM(N,FVEC) WRITE (NWRITE,1000) FNORM,INFO,(X(J),J=1,N) STOP 1000 FORMAT (5X,31H FINAL L2 NORM OF THE RESIDUALS,D15.7 // * 5X,15H EXIT PARAMETER,16X,I10 // * 5X,27H FINAL APPROXIMATE SOLUTION // (5X,3D15.7)) C C LAST CARD OF DRIVER FOR HYBRD1 EXAMPLE. C END SUBROUTINE FCN(N,X,FVEC,IFLAG) INTEGER N,IFLAG DOUBLE PRECISION X(N),FVEC(N) C Page C SUBROUTINE FCN FOR HYBRD1 EXAMPLE. C INTEGER K DOUBLE PRECISION ONE,TEMP,TEMP1,TEMP2,THREE,TWO,ZERO DATA ZERO,ONE,TWO,THREE /0.D0,1.D0,2.D0,3.D0/ C DO 10 K = 1, N TEMP = (THREE - TWO*X(K))*X(K) TEMP1 = ZERO IF (K .NE. 1) TEMP1 = X(K-1) TEMP2 = ZERO IF (K .NE. N) TEMP2 = X(K+1) FVEC(K) = TEMP - TEMP1 - TWO*TEMP2 + ONE 10 CONTINUE RETURN C C LAST CARD OF SUBROUTINE FCN. C END Results obtained with different compilers or machines may be slightly different. FINAL L2 NORM OF THE RESIDUALS 0.1192636D-07 EXIT PARAMETER 1 FINAL APPROXIMATE SOLUTION -0.5706545D+00 -0.6816283D+00 -0.7017325D+00 -0.7042129D+00 -0.7013690D+00 -0.6918656D+00 -0.6657920D+00 -0.5960342D+00 -0.4164121D+00 Page Documentation for MINPACK subroutine HYBRD Double precision version Argonne National Laboratory Burton S. Garbow, Kenneth E. Hillstrom, Jorge J. More March 1980 1. Purpose. The purpose of HYBRD is to find a zero of a system of N non- linear functions in N variables by a modification of the Powell hybrid method. The user must provide a subroutine which calcu- lates the functions. The Jacobian is then calculated by a for- ward-difference approximation. 2. Subroutine and type statements. SUBROUTINE HYBRD(FCN,N,X,FVEC,XTOL,MAXFEV,ML,MU,EPSFCN,DIAG, * MODE,FACTOR,NPRINT,INFO,NFEV,FJAC,LDFJAC, * R,LR,QTF,WA1,WA2,WA3,WA4) INTEGER N,MAXFEV,ML,MU,MODE,NPRINT,INFO,NFEV,LDFJAC,LR DOUBLE PRECISION XTOL,EPSFCN,FACTOR DOUBLE PRECISION X(N),FVEC(N),DIAG(N),FJAC(LDFJAC,N),R(LR),QTF( * WA1(N),WA2(N),WA3(N),WA4(N) EXTERNAL FCN 3. Parameters. Parameters designated as input parameters must be specified on entry to HYBRD and are not changed on exit, while parameters designated as output parameters need not be specified on entry and are set to appropriate values on exit from HYBRD. FCN is the name of the user-supplied subroutine which calculate the functions. FCN must be declared in an EXTERNAL statement in the user calling program, and should be written as follows SUBROUTINE FCN(N,X,FVEC,IFLAG) INTEGER N,IFLAG DOUBLE PRECISION X(N),FVEC(N) ---------- CALCULATE THE FUNCTIONS AT X AND RETURN THIS VECTOR IN FVEC. ---------- RETURN END The value of IFLAG should not be changed by FCN unless the Page user wants to terminate execution of HYBRD. In this case set IFLAG to a negative integer. N is a positive integer input variable set to the number of functions and variables. X is an array of length N. On input X must contain an initial estimate of the solution vector. On output X contains the final estimate of the solution vector. FVEC is an output array of length N which contains the function evaluated at the output X. XTOL is a nonnegative input variable. Termination occurs when the relative error between two consecutive iterates is at most XTOL. Therefore, XTOL measures the relative error desired in the approximate solution. Section 4 contains more details about XTOL. MAXFEV is a positive integer input variable. Termination occur when the number of calls to FCN is at least MAXFEV by the end of an iteration. ML is a nonnegative integer input variable which specifies the number of subdiagonals within the band of the Jacobian matrix If the Jacobian is not banded, set ML to at least N - 1. MU is a nonnegative integer input variable which specifies the number of superdiagonals within the band of the Jacobian matrix. If the Jacobian is not banded, set MU to at least N - 1. EPSFCN is an input variable used in determining a suitable step for the forward-difference approximation. This approximation assumes that the relative errors in the functions are of the order of EPSFCN. If EPSFCN is less than the machine preci- sion, it is assumed that the relative errors in the functions are of the order of the machine precision. DIAG is an array of length N. If MODE = 1 (see below), DIAG is internally set. If MODE = 2, DIAG must contain positive entries that serve as multiplicative scale factors for the variables. MODE is an integer input variable. If MODE = 1, the variables will be scaled internally. If MODE = 2, the scaling is speci- fied by the input DIAG. Other values of MODE are equivalent to MODE = 1. FACTOR is a positive input variable used in determining the ini- tial step bound. This bound is set to the product of FACTOR and the Euclidean norm of DIAG*X if nonzero, or else to FACTO itself. In most cases FACTOR should lie in the interval (.1,100.). 100. is a generally recommended value. Page NPRINT is an integer input variable that enables controlled printing of iterates if it is positive. In this case, FCN is called with IFLAG = 0 at the beginning of the first iteration and every NPRINT iterations thereafter and immediately prior to return, with X and FVEC available for printing. If NPRINT is not positive, no special calls of FCN with IFLAG = 0 are made. INFO is an integer output variable. If the user has terminated execution, INFO is set to the (negative) value of IFLAG. See description of FCN. Otherwise, INFO is set as follows. INFO = 0 Improper input parameters. INFO = 1 Relative error between two consecutive iterates is at most XTOL. INFO = 2 Number of calls to FCN has reached or exceeded MAXFEV. INFO = 3 XTOL is too small. No further improvement in the approximate solution X is possible. INFO = 4 Iteration is not making good progress, as measured by the improvement from the last five Jacobian eval- uations. INFO = 5 Iteration is not making good progress, as measured by the improvement from the last ten iterations. Sections 4 and 5 contain more details about INFO. NFEV is an integer output variable set to the number of calls t FCN. FJAC is an output N by N array which contains the orthogonal matrix Q produced by the QR factorization of the final approx- imate Jacobian. LDFJAC is a positive integer input variable not less than N which specifies the leading dimension of the array FJAC. R is an output array of length LR which contains the upper triangular matrix produced by the QR factorization of the final approximate Jacobian, stored rowwise. LR is a positive integer input variable not less than (N*(N+1))/2. QTF is an output array of length N which contains the vector (Q transpose)*FVEC. WA1, WA2, WA3, and WA4 are work arrays of length N. Page 4. Successful completion. The accuracy of HYBRD is controlled by the convergence parameter XTOL. This parameter is used in a test which makes a comparison between the approximation X and a solution XSOL. HYBRD termi- nates when the test is satisfied. If the convergence parameter is less than the machine precision (as defined by the MINPACK function DPMPAR(1)), then HYBRD only attempts to satisfy the test defined by the machine precision. Further progress is not usually possible. The test assumes that the functions are reasonably well behaved If this condition is not satisfied, then HYBRD may incorrectly indicate convergence. The validity of the answer can be checked, for example, by rerunning HYBRD with a tighter toler- ance. Convergence test. If ENORM(Z) denotes the Euclidean norm of a vector Z and D is the diagonal matrix whose entries are defined by the array DIAG, then this test attempts to guaran- tee that ENORM(D*(X-XSOL)) .LE. XTOL*ENORM(D*XSOL). If this condition is satisfied with XTOL = 10**(-K), then the larger components of D*X have K significant decimal digits an INFO is set to 1. There is a danger that the smaller compo- nents of D*X may have large relative errors, but the fast rat of convergence of HYBRD usually avoids this possibility. Unless high precision solutions are required, the recommended value for XTOL is the square root of the machine precision. 5. Unsuccessful completion. Unsuccessful termination of HYBRD can be due to improper input parameters, arithmetic interrupts, an excessive number of func- tion evaluations, or lack of good progress. Improper input parameters. INFO is set to 0 if N .LE. 0, or XTOL .LT. 0.D0, or MAXFEV .LE. 0, or ML .LT. 0, or MU .LT. 0, or FACTOR .LE. 0.D0, or LDFJAC .LT. N, or LR .LT. (N*(N+1))/2 Arithmetic interrupts. If these interrupts occur in the FCN subroutine during an early stage of the computation, they may be caused by an unacceptable choice of X by HYBRD. In this case, it may be possible to remedy the situation by rerunning HYBRD with a smaller value of FACTOR. Excessive number of function evaluations. A reasonable value for MAXFEV is 200*(N+1). If the number of calls to FCN reaches MAXFEV, then this indicates that the routine is con- verging very slowly as measured by the progress of FVEC, and Page INFO is set to 2. This situation should be unusual because, as indicated below, lack of good progress is usually diagnose earlier by HYBRD, causing termination with INFO = 4 or INFO = 5. Lack of good progress. HYBRD searches for a zero of the system by minimizing the sum of the squares of the functions. In so doing, it can become trapped in a region where the minimum does not correspond to a zero of the system and, in this situ- ation, the iteration eventually fails to make good progress. In particular, this will happen if the system does not have a zero. If the system has a zero, rerunning HYBRD from a dif- ferent starting point may be helpful. 6. Characteristics of the algorithm. HYBRD is a modification of the Powell hybrid method. Two of it main characteristics involve the choice of the correction as a convex combination of the Newton and scaled gradient directions and the updating of the Jacobian by the rank-1 method of Broy- den. The choice of the correction guarantees (under reasonable conditions) global convergence for starting points far from the solution and a fast rate of convergence. The Jacobian is approximated by forward differences at the starting point, but forward differences are not used again until the rank-1 method fails to produce satisfactory progress. Timing. The time required by HYBRD to solve a given problem depends on N, the behavior of the functions, the accuracy requested, and the starting point. The number of arithmetic operations needed by HYBRD is about 11.5*(N**2) to process each call to FCN. Unless FCN can be evaluated quickly, the timing of HYBRD will be strongly influenced by the time spent in FCN. Storage. HYBRD requires (3*N**2 + 17*N)/2 double precision storage locations, in addition to the storage required by the program. There are no internally declared storage arrays. 7. Subprograms required. USER-supplied ...... FCN MINPACK-supplied ... DOGLEG,DPMPAR,ENORM,FDJAC1, QFORM,QRFAC,R1MPYQ,R1UPDT FORTRAN-supplied ... DABS,DMAX1,DMIN1,DSQRT,MIN0,MOD 8. References. M. J. D. Powell, A Hybrid Method for Nonlinear Equations. Page Numerical Methods for Nonlinear Algebraic Equations, P. Rabinowitz, editor. Gordon and Breach, 1970. 9. Example. The problem is to determine the values of x(1), x(2), ..., x(9) which solve the system of tridiagonal equations (3-2*x(1))*x(1) -2*x(2) = -1 -x(i-1) + (3-2*x(i))*x(i) -2*x(i+1) = -1, i=2-8 -x(8) + (3-2*x(9))*x(9) = -1 C ********** C C DRIVER FOR HYBRD EXAMPLE. C DOUBLE PRECISION VERSION C C ********** INTEGER J,N,MAXFEV,ML,MU,MODE,NPRINT,INFO,NFEV,LDFJAC,LR,NWRITE DOUBLE PRECISION XTOL,EPSFCN,FACTOR,FNORM DOUBLE PRECISION X(9),FVEC(9),DIAG(9),FJAC(9,9),R(45),QTF(9), * WA1(9),WA2(9),WA3(9),WA4(9) DOUBLE PRECISION ENORM,DPMPAR EXTERNAL FCN C C LOGICAL OUTPUT UNIT IS ASSUMED TO BE NUMBER 6. C DATA NWRITE /6/ C N = 9 C C THE FOLLOWING STARTING VALUES PROVIDE A ROUGH SOLUTION. C DO 10 J = 1, 9 X(J) = -1.D0 10 CONTINUE C LDFJAC = 9 LR = 45 C C SET XTOL TO THE SQUARE ROOT OF THE MACHINE PRECISION. C UNLESS HIGH PRECISION SOLUTIONS ARE REQUIRED, C THIS IS THE RECOMMENDED SETTING. C XTOL = DSQRT(DPMPAR(1)) C MAXFEV = 2000 ML = 1 MU = 1 EPSFCN = 0.D0 MODE = 2 DO 20 J = 1, 9 DIAG(J) = 1.D0 Page 20 CONTINUE FACTOR = 1.D2 NPRINT = 0 C CALL HYBRD(FCN,N,X,FVEC,XTOL,MAXFEV,ML,MU,EPSFCN,DIAG, * MODE,FACTOR,NPRINT,INFO,NFEV,FJAC,LDFJAC, * R,LR,QTF,WA1,WA2,WA3,WA4) FNORM = ENORM(N,FVEC) WRITE (NWRITE,1000) FNORM,NFEV,INFO,(X(J),J=1,N) STOP 1000 FORMAT (5X,31H FINAL L2 NORM OF THE RESIDUALS,D15.7 // * 5X,31H NUMBER OF FUNCTION EVALUATIONS,I10 // * 5X,15H EXIT PARAMETER,16X,I10 // * 5X,27H FINAL APPROXIMATE SOLUTION // (5X,3D15.7)) C C LAST CARD OF DRIVER FOR HYBRD EXAMPLE. C END SUBROUTINE FCN(N,X,FVEC,IFLAG) INTEGER N,IFLAG DOUBLE PRECISION X(N),FVEC(N) C C SUBROUTINE FCN FOR HYBRD EXAMPLE. C INTEGER K DOUBLE PRECISION ONE,TEMP,TEMP1,TEMP2,THREE,TWO,ZERO DATA ZERO,ONE,TWO,THREE /0.D0,1.D0,2.D0,3.D0/ C IF (IFLAG .NE. 0) GO TO 5 C C INSERT PRINT STATEMENTS HERE WHEN NPRINT IS POSITIVE. C RETURN 5 CONTINUE DO 10 K = 1, N TEMP = (THREE - TWO*X(K))*X(K) TEMP1 = ZERO IF (K .NE. 1) TEMP1 = X(K-1) TEMP2 = ZERO IF (K .NE. N) TEMP2 = X(K+1) FVEC(K) = TEMP - TEMP1 - TWO*TEMP2 + ONE 10 CONTINUE RETURN C C LAST CARD OF SUBROUTINE FCN. C END Results obtained with different compilers or machines may be slightly different. FINAL L2 NORM OF THE RESIDUALS 0.1192636D-07 NUMBER OF FUNCTION EVALUATIONS 14 Page EXIT PARAMETER 1 FINAL APPROXIMATE SOLUTION -0.5706545D+00 -0.6816283D+00 -0.7017325D+00 -0.7042129D+00 -0.7013690D+00 -0.6918656D+00 -0.6657920D+00 -0.5960342D+00 -0.4164121D+00 Page Documentation for MINPACK subroutine HYBRJ1 Double precision version Argonne National Laboratory Burton S. Garbow, Kenneth E. Hillstrom, Jorge J. More March 1980 1. Purpose. The purpose of HYBRJ1 is to find a zero of a system of N non- linear functions in N variables by a modification of the Powell hybrid method. This is done by using the more general nonlinear equation solver HYBRJ. The user must provide a subroutine which calculates the functions and the Jacobian. 2. Subroutine and type statements. SUBROUTINE HYBRJ1(FCN,N,X,FVEC,FJAC,LDFJAC,TOL,INFO,WA,LWA) INTEGER N,LDFJAC,INFO,LWA DOUBLE PRECISION TOL DOUBLE PRECISION X(N),FVEC(N),FJAC(LDFJAC,N),WA(LWA) EXTERNAL FCN 3. Parameters. Parameters designated as input parameters must be specified on entry to HYBRJ1 and are not changed on exit, while parameters designated as output parameters need not be specified on entry and are set to appropriate values on exit from HYBRJ1. FCN is the name of the user-supplied subroutine which calculate the functions and the Jacobian. FCN must be declared in an EXTERNAL statement in the user calling program, and should be written as follows. SUBROUTINE FCN(N,X,FVEC,FJAC,LDFJAC,IFLAG) INTEGER N,LDFJAC,IFLAG DOUBLE PRECISION X(N),FVEC(N),FJAC(LDFJAC,N) ---------- IF IFLAG = 1 CALCULATE THE FUNCTIONS AT X AND RETURN THIS VECTOR IN FVEC. DO NOT ALTER FJAC. IF IFLAG = 2 CALCULATE THE JACOBIAN AT X AND RETURN THIS MATRIX IN FJAC. DO NOT ALTER FVEC. ---------- RETURN END The value of IFLAG should not be changed by FCN unless the Page user wants to terminate execution of HYBRJ1. In this case set IFLAG to a negative integer. N is a positive integer input variable set to the number of functions and variables. X is an array of length N. On input X must contain an initial estimate of the solution vector. On output X contains the final estimate of the solution vector. FVEC is an output array of length N which contains the function evaluated at the output X. FJAC is an output N by N array which contains the orthogonal matrix Q produced by the QR factorization of the final approx- imate Jacobian. Section 6 contains more details about the approximation to the Jacobian. LDFJAC is a positive integer input variable not less than N which specifies the leading dimension of the array FJAC. TOL is a nonnegative input variable. Termination occurs when the algorithm estimates that the relative error between X and the solution is at most TOL. Section 4 contains more details about TOL. INFO is an integer output variable. If the user has terminated execution, INFO is set to the (negative) value of IFLAG. See description of FCN. Otherwise, INFO is set as follows. INFO = 0 Improper input parameters. INFO = 1 Algorithm estimates that the relative error between X and the solution is at most TOL. INFO = 2 Number of calls to FCN with IFLAG = 1 has reached 100*(N+1). INFO = 3 TOL is too small. No further improvement in the approximate solution X is possible. INFO = 4 Iteration is not making good progress. Sections 4 and 5 contain more details about INFO. WA is a work array of length LWA. LWA is a positive integer input variable not less than (N*(N+13))/2. 4. Successful completion. The accuracy of HYBRJ1 is controlled by the convergence Page parameter TOL. This parameter is used in a test which makes a comparison between the approximation X and a solution XSOL. HYBRJ1 terminates when the test is satisfied. If TOL is less than the machine precision (as defined by the MINPACK function DPMPAR(1)), then HYBRJ1 only attempts to satisfy the test defined by the machine precision. Further progress is not usu- ally possible. Unless high precision solutions are required, the recommended value for TOL is the square root of the machine precision. The test assumes that the functions and the Jacobian are coded consistently, and that the functions are reasonably well behaved. If these conditions are not satisfied, then HYBRJ1 ma incorrectly indicate convergence. The coding of the Jacobian can be checked by the MINPACK subroutine CHKDER. If the Jaco- bian is coded correctly, then the validity of the answer can be checked, for example, by rerunning HYBRJ1 with a tighter toler- ance. Convergence test. If ENORM(Z) denotes the Euclidean norm of a vector Z, then this test attempts to guarantee that ENORM(X-XSOL) .LE. TOL*ENORM(XSOL). If this condition is satisfied with TOL = 10**(-K), then the larger components of X have K significant decimal digits and INFO is set to 1. There is a danger that the smaller compo- nents of X may have large relative errors, but the fast rate of convergence of HYBRJ1 usually avoids this possibility. 5. Unsuccessful completion. Unsuccessful termination of HYBRJ1 can be due to improper input parameters, arithmetic interrupts, an excessive number of func- tion evaluations, or lack of good progress. Improper input parameters. INFO is set to 0 if N .LE. 0, or LDFJAC .LT. N, or TOL .LT. 0.D0, or LWA .LT. (N*(N+13))/2. Arithmetic interrupts. If these interrupts occur in the FCN subroutine during an early stage of the computation, they may be caused by an unacceptable choice of X by HYBRJ1. In this case, it may be possible to remedy the situation by not evalu ating the functions here, but instead setting the components of FVEC to numbers that exceed those in the initial FVEC, thereby indirectly reducing the step length. The step length can be more directly controlled by using instead HYBRJ, which includes in its calling sequence the step-length- governing parameter FACTOR. Excessive number of function evaluations. If the number of calls to FCN with IFLAG = 1 reaches 100*(N+1), then this indi- cates that the routine is converging very slowly as measured Page by the progress of FVEC, and INFO is set to 2. This situation should be unusual because, as indicated below, lack of good progress is usually diagnosed earlier by HYBRJ1, causing ter- mination with INFO = 4. Lack of good progress. HYBRJ1 searches for a zero of the system by minimizing the sum of the squares of the functions. In so doing, it can become trapped in a region where the minimum does not correspond to a zero of the system and, in this situ- ation, the iteration eventually fails to make good progress. In particular, this will happen if the system does not have a zero. If the system has a zero, rerunning HYBRJ1 from a dif- ferent starting point may be helpful. 6. Characteristics of the algorithm. HYBRJ1 is a modification of the Powell hybrid method. Two of its main characteristics involve the choice of the correction a a convex combination of the Newton and scaled gradient direc- tions, and the updating of the Jacobian by the rank-1 method of Broyden. The choice of the correction guarantees (under reason able conditions) global convergence for starting points far fro the solution and a fast rate of convergence. The Jacobian is calculated at the starting point, but it is not recalculated until the rank-1 method fails to produce satisfactory progress. Timing. The time required by HYBRJ1 to solve a given problem depends on N, the behavior of the functions, the accuracy requested, and the starting point. The number of arithmetic operations needed by HYBRJ1 is about 11.5*(N**2) to process each evaluation of the functions (call to FCN with IFLAG = 1) and 1.3*(N**3) to process each evaluation of the Jacobian (call to FCN with IFLAG = 2). Unless FCN can be evaluated quickly, the timing of HYBRJ1 will be strongly influenced by the time spent in FCN. Storage. HYBRJ1 requires (3*N**2 + 17*N)/2 double precision storage locations, in addition to the storage required by the program. There are no internally declared storage arrays. 7. Subprograms required. USER-supplied ...... FCN MINPACK-supplied ... DOGLEG,DPMPAR,ENORM,HYBRJ, QFORM,QRFAC,R1MPYQ,R1UPDT FORTRAN-supplied ... DABS,DMAX1,DMIN1,DSQRT,MIN0,MOD 8. References. Page M. J. D. Powell, A Hybrid Method for Nonlinear Equations. Numerical Methods for Nonlinear Algebraic Equations, P. Rabinowitz, editor. Gordon and Breach, 1970. 9. Example. The problem is to determine the values of x(1), x(2), ..., x(9) which solve the system of tridiagonal equations (3-2*x(1))*x(1) -2*x(2) = -1 -x(i-1) + (3-2*x(i))*x(i) -2*x(i+1) = -1, i=2-8 -x(8) + (3-2*x(9))*x(9) = -1 C ********** C C DRIVER FOR HYBRJ1 EXAMPLE. C DOUBLE PRECISION VERSION C C ********** INTEGER J,N,LDFJAC,INFO,LWA,NWRITE DOUBLE PRECISION TOL,FNORM DOUBLE PRECISION X(9),FVEC(9),FJAC(9,9),WA(99) DOUBLE PRECISION ENORM,DPMPAR EXTERNAL FCN C C LOGICAL OUTPUT UNIT IS ASSUMED TO BE NUMBER 6. C DATA NWRITE /6/ C N = 9 C C THE FOLLOWING STARTING VALUES PROVIDE A ROUGH SOLUTION. C DO 10 J = 1, 9 X(J) = -1.D0 10 CONTINUE C LDFJAC = 9 LWA = 99 C C SET TOL TO THE SQUARE ROOT OF THE MACHINE PRECISION. C UNLESS HIGH PRECISION SOLUTIONS ARE REQUIRED, C THIS IS THE RECOMMENDED SETTING. C TOL = DSQRT(DPMPAR(1)) C CALL HYBRJ1(FCN,N,X,FVEC,FJAC,LDFJAC,TOL,INFO,WA,LWA) FNORM = ENORM(N,FVEC) WRITE (NWRITE,1000) FNORM,INFO,(X(J),J=1,N) STOP 1000 FORMAT (5X,31H FINAL L2 NORM OF THE RESIDUALS,D15.7 // * 5X,15H EXIT PARAMETER,16X,I10 // * 5X,27H FINAL APPROXIMATE SOLUTION // (5X,3D15.7)) Page C C LAST CARD OF DRIVER FOR HYBRJ1 EXAMPLE. C END SUBROUTINE FCN(N,X,FVEC,FJAC,LDFJAC,IFLAG) INTEGER N,LDFJAC,IFLAG DOUBLE PRECISION X(N),FVEC(N),FJAC(LDFJAC,N) C C SUBROUTINE FCN FOR HYBRJ1 EXAMPLE. C INTEGER J,K DOUBLE PRECISION ONE,TEMP,TEMP1,TEMP2,THREE,TWO,ZERO DATA ZERO,ONE,TWO,THREE,FOUR /0.D0,1.D0,2.D0,3.D0,4.D0/ C IF (IFLAG .EQ. 2) GO TO 20 DO 10 K = 1, N TEMP = (THREE - TWO*X(K))*X(K) TEMP1 = ZERO IF (K .NE. 1) TEMP1 = X(K-1) TEMP2 = ZERO IF (K .NE. N) TEMP2 = X(K+1) FVEC(K) = TEMP - TEMP1 - TWO*TEMP2 + ONE 10 CONTINUE GO TO 50 20 CONTINUE DO 40 K = 1, N DO 30 J = 1, N FJAC(K,J) = ZERO 30 CONTINUE FJAC(K,K) = THREE - FOUR*X(K) IF (K .NE. 1) FJAC(K,K-1) = -ONE IF (K .NE. N) FJAC(K,K+1) = -TWO 40 CONTINUE 50 CONTINUE RETURN C C LAST CARD OF SUBROUTINE FCN. C END Results obtained with different compilers or machines may be slightly different. FINAL L2 NORM OF THE RESIDUALS 0.1192636D-07 EXIT PARAMETER 1 FINAL APPROXIMATE SOLUTION -0.5706545D+00 -0.6816283D+00 -0.7017325D+00 -0.7042129D+00 -0.7013690D+00 -0.6918656D+00 -0.6657920D+00 -0.5960342D+00 -0.4164121D+00 Page Documentation for MINPACK subroutine HYBRJ Double precision version Argonne National Laboratory Burton S. Garbow, Kenneth E. Hillstrom, Jorge J. More March 1980 1. Purpose. The purpose of HYBRJ is to find a zero of a system of N non- linear functions in N variables by a modification of the Powell hybrid method. The user must provide a subroutine which calcu- lates the functions and the Jacobian. 2. Subroutine and type statements. SUBROUTINE HYBRJ(FCN,N,X,FVEC,FJAC,LDFJAC,XTOL,MAXFEV,DIAG, * MODE,FACTOR,NPRINT,INFO,NFEV,NJEV,R,LR,QTF, * WA1,WA2,WA3,WA4) INTEGER N,LDFJAC,MAXFEV,MODE,NPRINT,INFO,NFEV,NJEV,LR DOUBLE PRECISION XTOL,FACTOR DOUBLE PRECISION X(N),FVEC(N),FJAC(LDFJAC,N),DIAG(N),R(LR),QTF( * WA1(N),WA2(N),WA3(N),WA4(N) 3. Parameters. Parameters designated as input parameters must be specified on entry to HYBRJ and are not changed on exit, while parameters designated as output parameters need not be specified on entry and are set to appropriate values on exit from HYBRJ. FCN is the name of the user-supplied subroutine which calculate the functions and the Jacobian. FCN must be declared in an EXTERNAL statement in the user calling program, and should be written as follows. SUBROUTINE FCN(N,X,FVEC,FJAC,LDFJAC,IFLAG) INTEGER N,LDFJAC,IFLAG DOUBLE PRECISION X(N),FVEC(N),FJAC(LDFJAC,N) ---------- IF IFLAG = 1 CALCULATE THE FUNCTIONS AT X AND RETURN THIS VECTOR IN FVEC. DO NOT ALTER FJAC. IF IFLAG = 2 CALCULATE THE JACOBIAN AT X AND RETURN THIS MATRIX IN FJAC. DO NOT ALTER FVEC. ---------- RETURN END Page The value of IFLAG should not be changed by FCN unless the user wants to terminate execution of HYBRJ. In this case set IFLAG to a negative integer. N is a positive integer input variable set to the number of functions and variables. X is an array of length N. On input X must contain an initial estimate of the solution vector. On output X contains the final estimate of the solution vector. FVEC is an output array of length N which contains the function evaluated at the output X. FJAC is an output N by N array which contains the orthogonal matrix Q produced by the QR factorization of the final approx- imate Jacobian. Section 6 contains more details about the approximation to the Jacobian. LDFJAC is a positive integer input variable not less than N which specifies the leading dimension of the array FJAC. XTOL is a nonnegative input variable. Termination occurs when the relative error between two consecutive iterates is at most XTOL. Therefore, XTOL measures the relative error desired in the approximate solution. Section 4 contains more details about XTOL. MAXFEV is a positive integer input variable. Termination occur when the number of calls to FCN with IFLAG = 1 has reached MAXFEV. DIAG is an array of length N. If MODE = 1 (see below), DIAG is internally set. If MODE = 2, DIAG must contain positive entries that serve as multiplicative scale factors for the variables. MODE is an integer input variable. If MODE = 1, the variables will be scaled internally. If MODE = 2, the scaling is speci- fied by the input DIAG. Other values of MODE are equivalent to MODE = 1. FACTOR is a positive input variable used in determining the ini- tial step bound. This bound is set to the product of FACTOR and the Euclidean norm of DIAG*X if nonzero, or else to FACTO itself. In most cases FACTOR should lie in the interval (.1,100.). 100. is a generally recommended value. NPRINT is an integer input variable that enables controlled printing of iterates if it is positive. In this case, FCN is called with IFLAG = 0 at the beginning of the first iteration and every NPRINT iterations thereafter and immediately prior to return, with X and FVEC available for printing. FVEC and FJAC should not be altered. If NPRINT is not positive, no Page special calls of FCN with IFLAG = 0 are made. INFO is an integer output variable. If the user has terminated execution, INFO is set to the (negative) value of IFLAG. See description of FCN. Otherwise, INFO is set as follows. INFO = 0 Improper input parameters. INFO = 1 Relative error between two consecutive iterates is at most XTOL. INFO = 2 Number of calls to FCN with IFLAG = 1 has reached MAXFEV. INFO = 3 XTOL is too small. No further improvement in the approximate solution X is possible. INFO = 4 Iteration is not making good progress, as measured by the improvement from the last five Jacobian eval- uations. INFO = 5 Iteration is not making good progress, as measured by the improvement from the last ten iterations. Sections 4 and 5 contain more details about INFO. NFEV is an integer output variable set to the number of calls t FCN with IFLAG = 1. NJEV is an integer output variable set to the number of calls t FCN with IFLAG = 2. R is an output array of length LR which contains the upper triangular matrix produced by the QR factorization of the final approximate Jacobian, stored rowwise. LR is a positive integer input variable not less than (N*(N+1))/2. QTF is an output array of length N which contains the vector (Q transpose)*FVEC. WA1, WA2, WA3, and WA4 are work arrays of length N. 4. Successful completion. The accuracy of HYBRJ is controlled by the convergence parameter XTOL. This parameter is used in a test which makes a comparison between the approximation X and a solution XSOL. HYBRJ termi- nates when the test is satisfied. If the convergence parameter is less than the machine precision (as defined by the MINPACK function DPMPAR(1)), then HYBRJ only attempts to satisfy the test defined by the machine precision. Further progress is not Page usually possible. The test assumes that the functions and the Jacobian are coded consistently, and that the functions are reasonably well behaved. If these conditions are not satisfied, then HYBRJ may incorrectly indicate convergence. The coding of the Jacobian can be checked by the MINPACK subroutine CHKDER. If the Jaco- bian is coded correctly, then the validity of the answer can be checked, for example, by rerunning HYBRJ with a tighter toler- ance. Convergence test. If ENORM(Z) denotes the Euclidean norm of a vector Z and D is the diagonal matrix whose entries are defined by the array DIAG, then this test attempts to guaran- tee that ENORM(D*(X-XSOL)) .LE. XTOL*ENORM(D*XSOL). If this condition is satisfied with XTOL = 10**(-K), then the larger components of D*X have K significant decimal digits an INFO is set to 1. There is a danger that the smaller compo- nents of D*X may have large relative errors, but the fast rat of convergence of HYBRJ usually avoids this possibility. Unless high precision solutions are required, the recommended value for XTOL is the square root of the machine precision. 5. Unsuccessful completion. Unsuccessful termination of HYBRJ can be due to improper input parameters, arithmetic interrupts, an excessive number of func- tion evaluations, or lack of good progress. Improper input parameters. INFO is set to 0 if N .LE. 0, or LDFJAC .LT. N, or XTOL .LT. 0.D0, or MAXFEV .LE. 0, or FACTOR .LE. 0.D0, or LR .LT. (N*(N+1))/2. Arithmetic interrupts. If these interrupts occur in the FCN subroutine during an early stage of the computation, they may be caused by an unacceptable choice of X by HYBRJ. In this case, it may be possible to remedy the situation by rerunning HYBRJ with a smaller value of FACTOR. Excessive number of function evaluations. A reasonable value for MAXFEV is 100*(N+1). If the number of calls to FCN with IFLAG = 1 reaches MAXFEV, then this indicates that the routine is converging very slowly as measured by the progress of FVEC and INFO is set to 2. This situation should be unusual because, as indicated below, lack of good progress is usually diagnosed earlier by HYBRJ, causing termination with INFO = 4 or INFO = 5. Lack of good progress. HYBRJ searches for a zero of the system by minimizing the sum of the squares of the functions. In so Page doing, it can become trapped in a region where the minimum does not correspond to a zero of the system and, in this situ- ation, the iteration eventually fails to make good progress. In particular, this will happen if the system does not have a zero. If the system has a zero, rerunning HYBRJ from a dif- ferent starting point may be helpful. 6. Characteristics of the algorithm. HYBRJ is a modification of the Powell hybrid method. Two of it main characteristics involve the choice of the correction as a convex combination of the Newton and scaled gradient directions and the updating of the Jacobian by the rank-1 method of Broy- den. The choice of the correction guarantees (under reasonable conditions) global convergence for starting points far from the solution and a fast rate of convergence. The Jacobian is calcu lated at the starting point, but it is not recalculated until the rank-1 method fails to produce satisfactory progress. Timing. The time required by HYBRJ to solve a given problem depends on N, the behavior of the functions, the accuracy requested, and the starting point. The number of arithmetic operations needed by HYBRJ is about 11.5*(N**2) to process each evaluation of the functions (call to FCN with IFLAG = 1) and 1.3*(N**3) to process each evaluation of the Jacobian (call to FCN with IFLAG = 2). Unless FCN can be evaluated quickly, the timing of HYBRJ will be strongly influenced by the time spent in FCN. Storage. HYBRJ requires (3*N**2 + 17*N)/2 double precision storage locations, in addition to the storage required by the program. There are no internally declared storage arrays. 7. Subprograms required. USER-supplied ...... FCN MINPACK-supplied ... DOGLEG,DPMPAR,ENORM, QFORM,QRFAC,R1MPYQ,R1UPDT FORTRAN-supplied ... DABS,DMAX1,DMIN1,DSQRT,MIN0,MOD 8. References. M. J. D. Powell, A Hybrid Method for Nonlinear Equations. Numerical Methods for Nonlinear Algebraic Equations, P. Rabinowitz, editor. Gordon and Breach, 1970. 9. Example. Page The problem is to determine the values of x(1), x(2), ..., x(9) which solve the system of tridiagonal equations (3-2*x(1))*x(1) -2*x(2) = -1 -x(i-1) + (3-2*x(i))*x(i) -2*x(i+1) = -1, i=2-8 -x(8) + (3-2*x(9))*x(9) = -1 C ********** C C DRIVER FOR HYBRJ EXAMPLE. C DOUBLE PRECISION VERSION C C ********** INTEGER J,N,LDFJAC,MAXFEV,MODE,NPRINT,INFO,NFEV,NJEV,LR,NWRITE DOUBLE PRECISION XTOL,FACTOR,FNORM DOUBLE PRECISION X(9),FVEC(9),FJAC(9,9),DIAG(9),R(45),QTF(9), * WA1(9),WA2(9),WA3(9),WA4(9) DOUBLE PRECISION ENORM,DPMPAR EXTERNAL FCN C C LOGICAL OUTPUT UNIT IS ASSUMED TO BE NUMBER 6. C DATA NWRITE /6/ C N = 9 C C THE FOLLOWING STARTING VALUES PROVIDE A ROUGH SOLUTION. C DO 10 J = 1, 9 X(J) = -1.D0 10 CONTINUE C LDFJAC = 9 LR = 45 C C SET XTOL TO THE SQUARE ROOT OF THE MACHINE PRECISION. C UNLESS HIGH PRECISION SOLUTIONS ARE REQUIRED, C THIS IS THE RECOMMENDED SETTING. C XTOL = DSQRT(DPMPAR(1)) C MAXFEV = 1000 MODE = 2 DO 20 J = 1, 9 DIAG(J) = 1.D0 20 CONTINUE FACTOR = 1.D2 NPRINT = 0 C CALL HYBRJ(FCN,N,X,FVEC,FJAC,LDFJAC,XTOL,MAXFEV,DIAG, * MODE,FACTOR,NPRINT,INFO,NFEV,NJEV,R,LR,QTF, * WA1,WA2,WA3,WA4) FNORM = ENORM(N,FVEC) WRITE (NWRITE,1000) FNORM,NFEV,NJEV,INFO,(X(J),J=1,N) Page STOP 1000 FORMAT (5X,31H FINAL L2 NORM OF THE RESIDUALS,D15.7 // * 5X,31H NUMBER OF FUNCTION EVALUATIONS,I10 // * 5X,31H NUMBER OF JACOBIAN EVALUATIONS,I10 // * 5X,15H EXIT PARAMETER,16X,I10 // * 5X,27H FINAL APPROXIMATE SOLUTION // (5X,3D15.7)) C C LAST CARD OF DRIVER FOR HYBRJ EXAMPLE. C END SUBROUTINE FCN(N,X,FVEC,FJAC,LDFJAC,IFLAG) INTEGER N,LDFJAC,IFLAG DOUBLE PRECISION X(N),FVEC(N),FJAC(LDFJAC,N) C C SUBROUTINE FCN FOR HYBRJ EXAMPLE. C INTEGER J,K DOUBLE PRECISION ONE,TEMP,TEMP1,TEMP2,THREE,TWO,ZERO DATA ZERO,ONE,TWO,THREE,FOUR /0.D0,1.D0,2.D0,3.D0,4.D0/ C IF (IFLAG .NE. 0) GO TO 5 C C INSERT PRINT STATEMENTS HERE WHEN NPRINT IS POSITIVE. C RETURN 5 CONTINUE IF (IFLAG .EQ. 2) GO TO 20 DO 10 K = 1, N TEMP = (THREE - TWO*X(K))*X(K) TEMP1 = ZERO IF (K .NE. 1) TEMP1 = X(K-1) TEMP2 = ZERO IF (K .NE. N) TEMP2 = X(K+1) FVEC(K) = TEMP - TEMP1 - TWO*TEMP2 + ONE 10 CONTINUE GO TO 50 20 CONTINUE DO 40 K = 1, N DO 30 J = 1, N FJAC(K,J) = ZERO 30 CONTINUE FJAC(K,K) = THREE - FOUR*X(K) IF (K .NE. 1) FJAC(K,K-1) = -ONE IF (K .NE. N) FJAC(K,K+1) = -TWO 40 CONTINUE 50 CONTINUE RETURN C C LAST CARD OF SUBROUTINE FCN. C END Results obtained with different compilers or machines may be slightly different. Page FINAL L2 NORM OF THE RESIDUALS 0.1192636D-07 NUMBER OF FUNCTION EVALUATIONS 11 NUMBER OF JACOBIAN EVALUATIONS 1 EXIT PARAMETER 1 FINAL APPROXIMATE SOLUTION -0.5706545D+00 -0.6816283D+00 -0.7017325D+00 -0.7042129D+00 -0.7013690D+00 -0.6918656D+00 -0.6657920D+00 -0.5960342D+00 -0.4164121D+00 Page Documentation for MINPACK subroutine LMDER1 Double precision version Argonne National Laboratory Burton S. Garbow, Kenneth E. Hillstrom, Jorge J. More March 1980 1. Purpose. The purpose of LMDER1 is to minimize the sum of the squares of nonlinear functions in N variables by a modification of the Levenberg-Marquardt algorithm. This is done by using the more general least-squares solver LMDER. The user must provide a subroutine which calculates the functions and the Jacobian. 2. Subroutine and type statements. SUBROUTINE LMDER1(FCN,M,N,X,FVEC,FJAC,LDFJAC,TOL, * INFO,IPVT,WA,LWA) INTEGER M,N,LDFJAC,INFO,LWA INTEGER IPVT(N) DOUBLE PRECISION TOL DOUBLE PRECISION X(N),FVEC(M),FJAC(LDFJAC,N),WA(LWA) EXTERNAL FCN 3. Parameters. Parameters designated as input parameters must be specified on entry to LMDER1 and are not changed on exit, while parameters designated as output parameters need not be specified on entry and are set to appropriate values on exit from LMDER1. FCN is the name of the user-supplied subroutine which calculate the functions and the Jacobian. FCN must be declared in an EXTERNAL statement in the user calling program, and should be written as follows. SUBROUTINE FCN(M,N,X,FVEC,FJAC,LDFJAC,IFLAG) INTEGER M,N,LDFJAC,IFLAG DOUBLE PRECISION X(N),FVEC(M),FJAC(LDFJAC,N) ---------- IF IFLAG = 1 CALCULATE THE FUNCTIONS AT X AND RETURN THIS VECTOR IN FVEC. DO NOT ALTER FJAC. IF IFLAG = 2 CALCULATE THE JACOBIAN AT X AND RETURN THIS MATRIX IN FJAC. DO NOT ALTER FVEC. ---------- RETURN END Page The value of IFLAG should not be changed by FCN unless the user wants to terminate execution of LMDER1. In this case set IFLAG to a negative integer. M is a positive integer input variable set to the number of functions. N is a positive integer input variable set to the number of variables. N must not exceed M. X is an array of length N. On input X must contain an initial estimate of the solution vector. On output X contains the final estimate of the solution vector. FVEC is an output array of length M which contains the function evaluated at the output X. FJAC is an output M by N array. The upper N by N submatrix of FJAC contains an upper triangular matrix R with diagonal ele- ments of nonincreasing magnitude such that T T T P *(JAC *JAC)*P = R *R, where P is a permutation matrix and JAC is the final calcu- lated Jacobian. Column j of P is column IPVT(j) (see below) of the identity matrix. The lower trapezoidal part of FJAC contains information generated during the computation of R. LDFJAC is a positive integer input variable not less than M which specifies the leading dimension of the array FJAC. TOL is a nonnegative input variable. Termination occurs when the algorithm estimates either that the relative error in the sum of squares is at most TOL or that the relative error between X and the solution is at most TOL. Section 4 contain more details about TOL. INFO is an integer output variable. If the user has terminated execution, INFO is set to the (negative) value of IFLAG. See description of FCN. Otherwise, INFO is set as follows. INFO = 0 Improper input parameters. INFO = 1 Algorithm estimates that the relative error in the sum of squares is at most TOL. INFO = 2 Algorithm estimates that the relative error between X and the solution is at most TOL. INFO = 3 Conditions for INFO = 1 and INFO = 2 both hold. INFO = 4 FVEC is orthogonal to the columns of the Jacobian t machine precision. Page INFO = 5 Number of calls to FCN with IFLAG = 1 has reached 100*(N+1). INFO = 6 TOL is too small. No further reduction in the sum of squares is possible. INFO = 7 TOL is too small. No further improvement in the approximate solution X is possible. Sections 4 and 5 contain more details about INFO. IPVT is an integer output array of length N. IPVT defines a permutation matrix P such that JAC*P = Q*R, where JAC is the final calculated Jacobian, Q is orthogonal (not stored), and is upper triangular with diagonal elements of nonincreasing magnitude. Column j of P is column IPVT(j) of the identity matrix. WA is a work array of length LWA. LWA is a positive integer input variable not less than 5*N+M. 4. Successful completion. The accuracy of LMDER1 is controlled by the convergence parame- ter TOL. This parameter is used in tests which make three type of comparisons between the approximation X and a solution XSOL. LMDER1 terminates when any of the tests is satisfied. If TOL i less than the machine precision (as defined by the MINPACK func- tion DPMPAR(1)), then LMDER1 only attempts to satisfy the test defined by the machine precision. Further progress is not usu- ally possible. Unless high precision solutions are required, the recommended value for TOL is the square root of the machine precision. The tests assume that the functions and the Jacobian are coded consistently, and that the functions are reasonably well behaved. If these conditions are not satisfied, then LMDER1 ma incorrectly indicate convergence. The coding of the Jacobian can be checked by the MINPACK subroutine CHKDER. If the Jaco- bian is coded correctly, then the validity of the answer can be checked, for example, by rerunning LMDER1 with a tighter toler- ance. First convergence test. If ENORM(Z) denotes the Euclidean norm of a vector Z, then this test attempts to guarantee that ENORM(FVEC) .LE. (1+TOL)*ENORM(FVECS), where FVECS denotes the functions evaluated at XSOL. If this condition is satisfied with TOL = 10**(-K), then the final residual norm ENORM(FVEC) has K significant decimal digits an INFO is set to 1 (or to 3 if the second test is also Page satisfied). Second convergence test. If D is a diagonal matrix (implicitly generated by LMDER1) whose entries contain scale factors for the variables, then this test attempts to guarantee that ENORM(D*(X-XSOL)) .LE. TOL*ENORM(D*XSOL). If this condition is satisfied with TOL = 10**(-K), then the larger components of D*X have K significant decimal digits an INFO is set to 2 (or to 3 if the first test is also satis- fied). There is a danger that the smaller components of D*X may have large relative errors, but the choice of D is such that the accuracy of the components of X is usually related t their sensitivity. Third convergence test. This test is satisfied when FVEC is orthogonal to the columns of the Jacobian to machine preci- sion. There is no clear relationship between this test and the accuracy of LMDER1, and furthermore, the test is equally well satisfied at other critical points, namely maximizers an saddle points. Therefore, termination caused by this test (INFO = 4) should be examined carefully. 5. Unsuccessful completion. Unsuccessful termination of LMDER1 can be due to improper input parameters, arithmetic interrupts, or an excessive number of function evaluations. Improper input parameters. INFO is set to 0 if N .LE. 0, or M .LT. N, or LDFJAC .LT. M, or TOL .LT. 0.D0, or LWA .LT. 5*N+M. Arithmetic interrupts. If these interrupts occur in the FCN subroutine during an early stage of the computation, they may be caused by an unacceptable choice of X by LMDER1. In this case, it may be possible to remedy the situation by not evalu- ating the functions here, but instead setting the components of FVEC to numbers that exceed those in the initial FVEC, thereby indirectly reducing the step length. The step length can be more directly controlled by using instead LMDER, which includes in its calling sequence the step-length- governing parameter FACTOR. Excessive number of function evaluations. If the number of calls to FCN with IFLAG = 1 reaches 100*(N+1), then this indi- cates that the routine is converging very slowly as measured by the progress of FVEC, and INFO is set to 5. In this case, it may be helpful to restart LMDER1, thereby forcing it to disregard old (and possibly harmful) information. Page 6. Characteristics of the algorithm. LMDER1 is a modification of the Levenberg-Marquardt algorithm. Two of its main characteristics involve the proper use of implicitly scaled variables and an optimal choice for the cor- rection. The use of implicitly scaled variables achieves scale invariance of LMDER1 and limits the size of the correction in any direction where the functions are changing rapidly. The optimal choice of the correction guarantees (under reasonable conditions) global convergence from starting points far from th solution and a fast rate of convergence for problems with small residuals. Timing. The time required by LMDER1 to solve a given problem depends on M and N, the behavior of the functions, the accu- racy requested, and the starting point. The number of arith- metic operations needed by LMDER1 is about N**3 to process each evaluation of the functions (call to FCN with IFLAG = 1) and M*(N**2) to process each evaluation of the Jacobian (call to FCN with IFLAG = 2). Unless FCN can be evaluated quickly, the timing of LMDER1 will be strongly influenced by the time spent in FCN. Storage. LMDER1 requires M*N + 2*M + 6*N double precision sto- rage locations and N integer storage locations, in addition t the storage required by the program. There are no internally declared storage arrays. 7. Subprograms required. USER-supplied ...... FCN MINPACK-supplied ... DPMPAR,ENORM,LMDER,LMPAR,QRFAC,QRSOLV FORTRAN-supplied ... DABS,DMAX1,DMIN1,DSQRT,MOD 8. References. Jorge J. More, The Levenberg-Marquardt Algorithm, Implementation and Theory. Numerical Analysis, G. A. Watson, editor. Lecture Notes in Mathematics 630, Springer-Verlag, 1977. 9. Example. The problem is to determine the values of x(1), x(2), and x(3) which provide the best fit (in the least squares sense) of x(1) + u(i)/(v(i)*x(2) + w(i)*x(3)), i = 1, 15 to the data Page y = (0.14,0.18,0.22,0.25,0.29,0.32,0.35,0.39, 0.37,0.58,0.73,0.96,1.34,2.10,4.39), where u(i) = i, v(i) = 16 - i, and w(i) = min(u(i),v(i)). The i-th component of FVEC is thus defined by y(i) - (x(1) + u(i)/(v(i)*x(2) + w(i)*x(3))). C ********** C C DRIVER FOR LMDER1 EXAMPLE. C DOUBLE PRECISION VERSION C C ********** INTEGER J,M,N,LDFJAC,INFO,LWA,NWRITE INTEGER IPVT(3) DOUBLE PRECISION TOL,FNORM DOUBLE PRECISION X(3),FVEC(15),FJAC(15,3),WA(30) DOUBLE PRECISION ENORM,DPMPAR EXTERNAL FCN C C LOGICAL OUTPUT UNIT IS ASSUMED TO BE NUMBER 6. C DATA NWRITE /6/ C M = 15 N = 3 C C THE FOLLOWING STARTING VALUES PROVIDE A ROUGH FIT. C X(1) = 1.D0 X(2) = 1.D0 X(3) = 1.D0 C LDFJAC = 15 LWA = 30 C C SET TOL TO THE SQUARE ROOT OF THE MACHINE PRECISION. C UNLESS HIGH PRECISION SOLUTIONS ARE REQUIRED, C THIS IS THE RECOMMENDED SETTING. C TOL = DSQRT(DPMPAR(1)) C CALL LMDER1(FCN,M,N,X,FVEC,FJAC,LDFJAC,TOL, * INFO,IPVT,WA,LWA) FNORM = ENORM(M,FVEC) WRITE (NWRITE,1000) FNORM,INFO,(X(J),J=1,N) STOP 1000 FORMAT (5X,31H FINAL L2 NORM OF THE RESIDUALS,D15.7 // * 5X,15H EXIT PARAMETER,16X,I10 // * 5X,27H FINAL APPROXIMATE SOLUTION // 5X,3D15.7) C C LAST CARD OF DRIVER FOR LMDER1 EXAMPLE. C Page END SUBROUTINE FCN(M,N,X,FVEC,FJAC,LDFJAC,IFLAG) INTEGER M,N,LDFJAC,IFLAG DOUBLE PRECISION X(N),FVEC(M),FJAC(LDFJAC,N) C C SUBROUTINE FCN FOR LMDER1 EXAMPLE. C INTEGER I DOUBLE PRECISION TMP1,TMP2,TMP3,TMP4 DOUBLE PRECISION Y(15) DATA Y(1),Y(2),Y(3),Y(4),Y(5),Y(6),Y(7),Y(8), * Y(9),Y(10),Y(11),Y(12),Y(13),Y(14),Y(15) * /1.4D-1,1.8D-1,2.2D-1,2.5D-1,2.9D-1,3.2D-1,3.5D-1,3.9D-1, * 3.7D-1,5.8D-1,7.3D-1,9.6D-1,1.34D0,2.1D0,4.39D0/ C IF (IFLAG .EQ. 2) GO TO 20 DO 10 I = 1, 15 TMP1 = I TMP2 = 16 - I TMP3 = TMP1 IF (I .GT. 8) TMP3 = TMP2 FVEC(I) = Y(I) - (X(1) + TMP1/(X(2)*TMP2 + X(3)*TMP3)) 10 CONTINUE GO TO 40 20 CONTINUE DO 30 I = 1, 15 TMP1 = I TMP2 = 16 - I TMP3 = TMP1 IF (I .GT. 8) TMP3 = TMP2 TMP4 = (X(2)*TMP2 + X(3)*TMP3)**2 FJAC(I,1) = -1.D0 FJAC(I,2) = TMP1*TMP2/TMP4 FJAC(I,3) = TMP1*TMP3/TMP4 30 CONTINUE 40 CONTINUE RETURN C C LAST CARD OF SUBROUTINE FCN. C END Results obtained with different compilers or machines may be slightly different. FINAL L2 NORM OF THE RESIDUALS 0.9063596D-01 EXIT PARAMETER 1 FINAL APPROXIMATE SOLUTION 0.8241058D-01 0.1133037D+01 0.2343695D+01 Page Documentation for MINPACK subroutine LMDER Double precision version Argonne National Laboratory Burton S. Garbow, Kenneth E. Hillstrom, Jorge J. More March 1980 1. Purpose. The purpose of LMDER is to minimize the sum of the squares of M nonlinear functions in N variables by a modification of the Levenberg-Marquardt algorithm. The user must provide a subrou- tine which calculates the functions and the Jacobian. 2. Subroutine and type statements. SUBROUTINE LMDER(FCN,M,N,X,FVEC,FJAC,LDFJAC,FTOL,XTOL,GTOL, * MAXFEV,DIAG,MODE,FACTOR,NPRINT,INFO,NFEV,NJEV, * IPVT,QTF,WA1,WA2,WA3,WA4) INTEGER M,N,LDFJAC,MAXFEV,MODE,NPRINT,INFO,NFEV,NJEV INTEGER IPVT(N) DOUBLE PRECISION FTOL,XTOL,GTOL,FACTOR DOUBLE PRECISION X(N),FVEC(M),FJAC(LDFJAC,N),DIAG(N),QTF(N), * WA1(N),WA2(N),WA3(N),WA4(M) 3. Parameters. Parameters designated as input parameters must be specified on entry to LMDER and are not changed on exit, while parameters designated as output parameters need not be specified on entry and are set to appropriate values on exit from LMDER. FCN is the name of the user-supplied subroutine which calculate the functions and the Jacobian. FCN must be declared in an EXTERNAL statement in the user calling program, and should be written as follows. SUBROUTINE FCN(M,N,X,FVEC,FJAC,LDFJAC,IFLAG) INTEGER M,N,LDFJAC,IFLAG DOUBLE PRECISION X(N),FVEC(M),FJAC(LDFJAC,N) ---------- IF IFLAG = 1 CALCULATE THE FUNCTIONS AT X AND RETURN THIS VECTOR IN FVEC. DO NOT ALTER FJAC. IF IFLAG = 2 CALCULATE THE JACOBIAN AT X AND RETURN THIS MATRIX IN FJAC. DO NOT ALTER FVEC. ---------- RETURN END Page The value of IFLAG should not be changed by FCN unless the user wants to terminate execution of LMDER. In this case set IFLAG to a negative integer. M is a positive integer input variable set to the number of functions. N is a positive integer input variable set to the number of variables. N must not exceed M. X is an array of length N. On input X must contain an initial estimate of the solution vector. On output X contains the final estimate of the solution vector. FVEC is an output array of length M which contains the function evaluated at the output X. FJAC is an output M by N array. The upper N by N submatrix of FJAC contains an upper triangular matrix R with diagonal ele- ments of nonincreasing magnitude such that T T T P *(JAC *JAC)*P = R *R, where P is a permutation matrix and JAC is the final calcu- lated Jacobian. Column j of P is column IPVT(j) (see below) of the identity matrix. The lower trapezoidal part of FJAC contains information generated during the computation of R. LDFJAC is a positive integer input variable not less than M which specifies the leading dimension of the array FJAC. FTOL is a nonnegative input variable. Termination occurs when both the actual and predicted relative reductions in the sum of squares are at most FTOL. Therefore, FTOL measures the relative error desired in the sum of squares. Section 4 con- tains more details about FTOL. XTOL is a nonnegative input variable. Termination occurs when the relative error between two consecutive iterates is at most XTOL. Therefore, XTOL measures the relative error desired in the approximate solution. Section 4 contains more details about XTOL. GTOL is a nonnegative input variable. Termination occurs when the cosine of the angle between FVEC and any column of the Jacobian is at most GTOL in absolute value. Therefore, GTOL measures the orthogonality desired between the function vector and the columns of the Jacobian. Section 4 contains more details about GTOL. MAXFEV is a positive integer input variable. Termination occur when the number of calls to FCN with IFLAG = 1 has reached MAXFEV. Page DIAG is an array of length N. If MODE = 1 (see below), DIAG is internally set. If MODE = 2, DIAG must contain positive entries that serve as multiplicative scale factors for the variables. MODE is an integer input variable. If MODE = 1, the variables will be scaled internally. If MODE = 2, the scaling is speci- fied by the input DIAG. Other values of MODE are equivalent to MODE = 1. FACTOR is a positive input variable used in determining the ini- tial step bound. This bound is set to the product of FACTOR and the Euclidean norm of DIAG*X if nonzero, or else to FACTO itself. In most cases FACTOR should lie in the interval (.1,100.). 100. is a generally recommended value. NPRINT is an integer input variable that enables controlled printing of iterates if it is positive. In this case, FCN is called with IFLAG = 0 at the beginning of the first iteration and every NPRINT iterations thereafter and immediately prior to return, with X, FVEC, and FJAC available for printing. FVEC and FJAC should not be altered. If NPRINT is not posi- tive, no special calls of FCN with IFLAG = 0 are made. INFO is an integer output variable. If the user has terminated execution, INFO is set to the (negative) value of IFLAG. See description of FCN. Otherwise, INFO is set as follows. INFO = 0 Improper input parameters. INFO = 1 Both actual and predicted relative reductions in th sum of squares are at most FTOL. INFO = 2 Relative error between two consecutive iterates is at most XTOL. INFO = 3 Conditions for INFO = 1 and INFO = 2 both hold. INFO = 4 The cosine of the angle between FVEC and any column of the Jacobian is at most GTOL in absolute value. INFO = 5 Number of calls to FCN with IFLAG = 1 has reached MAXFEV. INFO = 6 FTOL is too small. No further reduction in the sum of squares is possible. INFO = 7 XTOL is too small. No further improvement in the approximate solution X is possible. INFO = 8 GTOL is too small. FVEC is orthogonal to the columns of the Jacobian to machine precision. Sections 4 and 5 contain more details about INFO. Page NFEV is an integer output variable set to the number of calls t FCN with IFLAG = 1. NJEV is an integer output variable set to the number of calls t FCN with IFLAG = 2. IPVT is an integer output array of length N. IPVT defines a permutation matrix P such that JAC*P = Q*R, where JAC is the final calculated Jacobian, Q is orthogonal (not stored), and is upper triangular with diagonal elements of nonincreasing magnitude. Column j of P is column IPVT(j) of the identity matrix. QTF is an output array of length N which contains the first N elements of the vector (Q transpose)*FVEC. WA1, WA2, and WA3 are work arrays of length N. WA4 is a work array of length M. 4. Successful completion. The accuracy of LMDER is controlled by the convergence parame- ters FTOL, XTOL, and GTOL. These parameters are used in tests which make three types of comparisons between the approximation X and a solution XSOL. LMDER terminates when any of the tests is satisfied. If any of the convergence parameters is less than the machine precision (as defined by the MINPACK function DPMPAR(1)), then LMDER only attempts to satisfy the test define by the machine precision. Further progress is not usually pos- sible. The tests assume that the functions and the Jacobian are coded consistently, and that the functions are reasonably well behaved. If these conditions are not satisfied, then LMDER may incorrectly indicate convergence. The coding of the Jacobian can be checked by the MINPACK subroutine CHKDER. If the Jaco- bian is coded correctly, then the validity of the answer can be checked, for example, by rerunning LMDER with tighter toler- ances. First convergence test. If ENORM(Z) denotes the Euclidean norm of a vector Z, then this test attempts to guarantee that ENORM(FVEC) .LE. (1+FTOL)*ENORM(FVECS), where FVECS denotes the functions evaluated at XSOL. If this condition is satisfied with FTOL = 10**(-K), then the final residual norm ENORM(FVEC) has K significant decimal digits an INFO is set to 1 (or to 3 if the second test is also satis- fied). Unless high precision solutions are required, the recommended value for FTOL is the square root of the machine precision. Page Second convergence test. If D is the diagonal matrix whose entries are defined by the array DIAG, then this test attempt to guarantee that ENORM(D*(X-XSOL)) .LE. XTOL*ENORM(D*XSOL). If this condition is satisfied with XTOL = 10**(-K), then the larger components of D*X have K significant decimal digits an INFO is set to 2 (or to 3 if the first test is also satis- fied). There is a danger that the smaller components of D*X may have large relative errors, but if MODE = 1, then the accuracy of the components of X is usually related to their sensitivity. Unless high precision solutions are required, the recommended value for XTOL is the square root of the machine precision. Third convergence test. This test is satisfied when the cosine of the angle between FVEC and any column of the Jacobian at X is at most GTOL in absolute value. There is no clear rela- tionship between this test and the accuracy of LMDER, and furthermore, the test is equally well satisfied at other crit- ical points, namely maximizers and saddle points. Therefore, termination caused by this test (INFO = 4) should be examined carefully. The recommended value for GTOL is zero. 5. Unsuccessful completion. Unsuccessful termination of LMDER can be due to improper input parameters, arithmetic interrupts, or an excessive number of function evaluations. Improper input parameters. INFO is set to 0 if N .LE. 0, or M .LT. N, or LDFJAC .LT. M, or FTOL .LT. 0.D0, or XTOL .LT. 0.D0, or GTOL .LT. 0.D0, or MAXFEV .LE. 0, or FACTOR .LE. 0.D0. Arithmetic interrupts. If these interrupts occur in the FCN subroutine during an early stage of the computation, they may be caused by an unacceptable choice of X by LMDER. In this case, it may be possible to remedy the situation by rerunning LMDER with a smaller value of FACTOR. Excessive number of function evaluations. A reasonable value for MAXFEV is 100*(N+1). If the number of calls to FCN with IFLAG = 1 reaches MAXFEV, then this indicates that the routine is converging very slowly as measured by the progress of FVEC and INFO is set to 5. In this case, it may be helpful to restart LMDER with MODE set to 1. 6. Characteristics of the algorithm. LMDER is a modification of the Levenberg-Marquardt algorithm. Page Two of its main characteristics involve the proper use of implicitly scaled variables (if MODE = 1) and an optimal choice for the correction. The use of implicitly scaled variables achieves scale invariance of LMDER and limits the size of the correction in any direction where the functions are changing rapidly. The optimal choice of the correction guarantees (under reasonable conditions) global convergence from starting points far from the solution and a fast rate of convergence for prob- lems with small residuals. Timing. The time required by LMDER to solve a given problem depends on M and N, the behavior of the functions, the accu- racy requested, and the starting point. The number of arith- metic operations needed by LMDER is about N**3 to process each evaluation of the functions (call to FCN with IFLAG = 1) and M*(N**2) to process each evaluation of the Jacobian (call to FCN with IFLAG = 2). Unless FCN can be evaluated quickly, th timing of LMDER will be strongly influenced by the time spent in FCN. Storage. LMDER requires M*N + 2*M + 6*N double precision sto- rage locations and N integer storage locations, in addition t the storage required by the program. There are no internally declared storage arrays. 7. Subprograms required. USER-supplied ...... FCN MINPACK-supplied ... DPMPAR,ENORM,LMPAR,QRFAC,QRSOLV FORTRAN-supplied ... DABS,DMAX1,DMIN1,DSQRT,MOD 8. References. Jorge J. More, The Levenberg-Marquardt Algorithm, Implementation and Theory. Numerical Analysis, G. A. Watson, editor. Lecture Notes in Mathematics 630, Springer-Verlag, 1977. 9. Example. The problem is to determine the values of x(1), x(2), and x(3) which provide the best fit (in the least squares sense) of x(1) + u(i)/(v(i)*x(2) + w(i)*x(3)), i = 1, 15 to the data y = (0.14,0.18,0.22,0.25,0.29,0.32,0.35,0.39, 0.37,0.58,0.73,0.96,1.34,2.10,4.39), Page where u(i) = i, v(i) = 16 - i, and w(i) = min(u(i),v(i)). The i-th component of FVEC is thus defined by y(i) - (x(1) + u(i)/(v(i)*x(2) + w(i)*x(3))). C ********** C C DRIVER FOR LMDER EXAMPLE. C DOUBLE PRECISION VERSION C C ********** INTEGER J,M,N,LDFJAC,MAXFEV,MODE,NPRINT,INFO,NFEV,NJEV,NWRITE INTEGER IPVT(3) DOUBLE PRECISION FTOL,XTOL,GTOL,FACTOR,FNORM DOUBLE PRECISION X(3),FVEC(15),FJAC(15,3),DIAG(3),QTF(3), * WA1(3),WA2(3),WA3(3),WA4(15) DOUBLE PRECISION ENORM,DPMPAR EXTERNAL FCN C C LOGICAL OUTPUT UNIT IS ASSUMED TO BE NUMBER 6. C DATA NWRITE /6/ C M = 15 N = 3 C C THE FOLLOWING STARTING VALUES PROVIDE A ROUGH FIT. C X(1) = 1.D0 X(2) = 1.D0 X(3) = 1.D0 C LDFJAC = 15 C C SET FTOL AND XTOL TO THE SQUARE ROOT OF THE MACHINE PRECISION C AND GTOL TO ZERO. UNLESS HIGH PRECISION SOLUTIONS ARE C REQUIRED, THESE ARE THE RECOMMENDED SETTINGS. C FTOL = DSQRT(DPMPAR(1)) XTOL = DSQRT(DPMPAR(1)) GTOL = 0.D0 C MAXFEV = 400 MODE = 1 FACTOR = 1.D2 NPRINT = 0 C CALL LMDER(FCN,M,N,X,FVEC,FJAC,LDFJAC,FTOL,XTOL,GTOL, * MAXFEV,DIAG,MODE,FACTOR,NPRINT,INFO,NFEV,NJEV, * IPVT,QTF,WA1,WA2,WA3,WA4) FNORM = ENORM(M,FVEC) WRITE (NWRITE,1000) FNORM,NFEV,NJEV,INFO,(X(J),J=1,N) STOP 1000 FORMAT (5X,31H FINAL L2 NORM OF THE RESIDUALS,D15.7 // Page * 5X,31H NUMBER OF FUNCTION EVALUATIONS,I10 // * 5X,31H NUMBER OF JACOBIAN EVALUATIONS,I10 // * 5X,15H EXIT PARAMETER,16X,I10 // * 5X,27H FINAL APPROXIMATE SOLUTION // 5X,3D15.7) C C LAST CARD OF DRIVER FOR LMDER EXAMPLE. C END SUBROUTINE FCN(M,N,X,FVEC,FJAC,LDFJAC,IFLAG) INTEGER M,N,LDFJAC,IFLAG DOUBLE PRECISION X(N),FVEC(M),FJAC(LDFJAC,N) C C SUBROUTINE FCN FOR LMDER EXAMPLE. C INTEGER I DOUBLE PRECISION TMP1,TMP2,TMP3,TMP4 DOUBLE PRECISION Y(15) DATA Y(1),Y(2),Y(3),Y(4),Y(5),Y(6),Y(7),Y(8), * Y(9),Y(10),Y(11),Y(12),Y(13),Y(14),Y(15) * /1.4D-1,1.8D-1,2.2D-1,2.5D-1,2.9D-1,3.2D-1,3.5D-1,3.9D-1, * 3.7D-1,5.8D-1,7.3D-1,9.6D-1,1.34D0,2.1D0,4.39D0/ C IF (IFLAG .NE. 0) GO TO 5 C C INSERT PRINT STATEMENTS HERE WHEN NPRINT IS POSITIVE. C RETURN 5 CONTINUE IF (IFLAG .EQ. 2) GO TO 20 DO 10 I = 1, 15 TMP1 = I TMP2 = 16 - I TMP3 = TMP1 IF (I .GT. 8) TMP3 = TMP2 FVEC(I) = Y(I) - (X(1) + TMP1/(X(2)*TMP2 + X(3)*TMP3)) 10 CONTINUE GO TO 40 20 CONTINUE DO 30 I = 1, 15 TMP1 = I TMP2 = 16 - I TMP3 = TMP1 IF (I .GT. 8) TMP3 = TMP2 TMP4 = (X(2)*TMP2 + X(3)*TMP3)**2 FJAC(I,1) = -1.D0 FJAC(I,2) = TMP1*TMP2/TMP4 FJAC(I,3) = TMP1*TMP3/TMP4 30 CONTINUE 40 CONTINUE RETURN C C LAST CARD OF SUBROUTINE FCN. C END Page Results obtained with different compilers or machines may be slightly different. FINAL L2 NORM OF THE RESIDUALS 0.9063596D-01 NUMBER OF FUNCTION EVALUATIONS 6 NUMBER OF JACOBIAN EVALUATIONS 5 EXIT PARAMETER 1 FINAL APPROXIMATE SOLUTION 0.8241058D-01 0.1133037D+01 0.2343695D+01 Page Documentation for MINPACK subroutine LMSTR1 Double precision version Argonne National Laboratory Burton S. Garbow, Kenneth E. Hillstrom, Jorge J. More March 1980 1. Purpose. The purpose of LMSTR1 is to minimize the sum of the squares of nonlinear functions in N variables by a modification of the Levenberg-Marquardt algorithm which uses minimal storage. This is done by using the more general least-squares solver LMSTR. The user must provide a subroutine which calculates the func- tions and the rows of the Jacobian. 2. Subroutine and type statements. SUBROUTINE LMSTR1(FCN,M,N,X,FVEC,FJAC,LDFJAC,TOL, * INFO,IPVT,WA,LWA) INTEGER M,N,LDFJAC,INFO,LWA INTEGER IPVT(N) DOUBLE PRECISION TOL DOUBLE PRECISION X(N),FVEC(M),FJAC(LDFJAC,N),WA(LWA) EXTERNAL FCN 3. Parameters. Parameters designated as input parameters must be specified on entry to LMSTR1 and are not changed on exit, while parameters designated as output parameters need not be specified on entry and are set to appropriate values on exit from LMSTR1. FCN is the name of the user-supplied subroutine which calculate the functions and the rows of the Jacobian. FCN must be declared in an EXTERNAL statement in the user calling program and should be written as follows. SUBROUTINE FCN(M,N,X,FVEC,FJROW,IFLAG) INTEGER M,N,IFLAG DOUBLE PRECISION X(N),FVEC(M),FJROW(N) ---------- IF IFLAG = 1 CALCULATE THE FUNCTIONS AT X AND RETURN THIS VECTOR IN FVEC. IF IFLAG = I CALCULATE THE (I-1)-ST ROW OF THE JACOBIAN AT X AND RETURN THIS VECTOR IN FJROW. ---------- RETURN Page END The value of IFLAG should not be changed by FCN unless the user wants to terminate execution of LMSTR1. In this case set IFLAG to a negative integer. M is a positive integer input variable set to the number of functions. N is a positive integer input variable set to the number of variables. N must not exceed M. X is an array of length N. On input X must contain an initial estimate of the solution vector. On output X contains the final estimate of the solution vector. FVEC is an output array of length M which contains the function evaluated at the output X. FJAC is an output N by N array. The upper triangle of FJAC con tains an upper triangular matrix R such that T T T P *(JAC *JAC)*P = R *R, where P is a permutation matrix and JAC is the final calcu- lated Jacobian. Column j of P is column IPVT(j) (see below) of the identity matrix. The lower triangular part of FJAC contains information generated during the computation of R. LDFJAC is a positive integer input variable not less than N which specifies the leading dimension of the array FJAC. TOL is a nonnegative input variable. Termination occurs when the algorithm estimates either that the relative error in the sum of squares is at most TOL or that the relative error between X and the solution is at most TOL. Section 4 contain more details about TOL. INFO is an integer output variable. If the user has terminated execution, INFO is set to the (negative) value of IFLAG. See description of FCN. Otherwise, INFO is set as follows. INFO = 0 Improper input parameters. INFO = 1 Algorithm estimates that the relative error in the sum of squares is at most TOL. INFO = 2 Algorithm estimates that the relative error between X and the solution is at most TOL. INFO = 3 Conditions for INFO = 1 and INFO = 2 both hold. INFO = 4 FVEC is orthogonal to the columns of the Jacobian t Page machine precision. INFO = 5 Number of calls to FCN with IFLAG = 1 has reached 100*(N+1). INFO = 6 TOL is too small. No further reduction in the sum of squares is possible. INFO = 7 TOL is too small. No further improvement in the approximate solution X is possible. Sections 4 and 5 contain more details about INFO. IPVT is an integer output array of length N. IPVT defines a permutation matrix P such that JAC*P = Q*R, where JAC is the final calculated Jacobian, Q is orthogonal (not stored), and is upper triangular. Column j of P is column IPVT(j) of the identity matrix. WA is a work array of length LWA. LWA is a positive integer input variable not less than 5*N+M. 4. Successful completion. The accuracy of LMSTR1 is controlled by the convergence parame- ter TOL. This parameter is used in tests which make three type of comparisons between the approximation X and a solution XSOL. LMSTR1 terminates when any of the tests is satisfied. If TOL i less than the machine precision (as defined by the MINPACK func- tion DPMPAR(1)), then LMSTR1 only attempts to satisfy the test defined by the machine precision. Further progress is not usu- ally possible. Unless high precision solutions are required, the recommended value for TOL is the square root of the machine precision. The tests assume that the functions and the Jacobian are coded consistently, and that the functions are reasonably well behaved. If these conditions are not satisfied, then LMSTR1 ma incorrectly indicate convergence. The coding of the Jacobian can be checked by the MINPACK subroutine CHKDER. If the Jaco- bian is coded correctly, then the validity of the answer can be checked, for example, by rerunning LMSTR1 with a tighter toler- ance. First convergence test. If ENORM(Z) denotes the Euclidean norm of a vector Z, then this test attempts to guarantee that ENORM(FVEC) .LE. (1+TOL)*ENORM(FVECS), where FVECS denotes the functions evaluated at XSOL. If this condition is satisfied with TOL = 10**(-K), then the final residual norm ENORM(FVEC) has K significant decimal digits an Page INFO is set to 1 (or to 3 if the second test is also satis- fied). Second convergence test. If D is a diagonal matrix (implicitly generated by LMSTR1) whose entries contain scale factors for the variables, then this test attempts to guarantee that ENORM(D*(X-XSOL)) .LE. TOL*ENORM(D*XSOL). If this condition is satisfied with TOL = 10**(-K), then the larger components of D*X have K significant decimal digits an INFO is set to 2 (or to 3 if the first test is also satis- fied). There is a danger that the smaller components of D*X may have large relative errors, but the choice of D is such that the accuracy of the components of X is usually related t their sensitivity. Third convergence test. This test is satisfied when FVEC is orthogonal to the columns of the Jacobian to machine preci- sion. There is no clear relationship between this test and the accuracy of LMSTR1, and furthermore, the test is equally well satisfied at other critical points, namely maximizers an saddle points. Therefore, termination caused by this test (INFO = 4) should be examined carefully. 5. Unsuccessful completion. Unsuccessful termination of LMSTR1 can be due to improper input parameters, arithmetic interrupts, or an excessive number of function evaluations. Improper input parameters. INFO is set to 0 if N .LE. 0, or M .LT. N, or LDFJAC .LT. N, or TOL .LT. 0.D0, or LWA .LT. 5*N+M. Arithmetic interrupts. If these interrupts occur in the FCN subroutine during an early stage of the computation, they may be caused by an unacceptable choice of X by LMSTR1. In this case, it may be possible to remedy the situation by not evalu- ating the functions here, but instead setting the components of FVEC to numbers that exceed those in the initial FVEC, thereby indirectly reducing the step length. The step length can be more directly controlled by using instead LMSTR, which includes in its calling sequence the step-length- governing parameter FACTOR. Excessive number of function evaluations. If the number of calls to FCN with IFLAG = 1 reaches 100*(N+1), then this indi- cates that the routine is converging very slowly as measured by the progress of FVEC, and INFO is set to 5. In this case, it may be helpful to restart LMSTR1, thereby forcing it to disregard old (and possibly harmful) information. Page 6. Characteristics of the algorithm. LMSTR1 is a modification of the Levenberg-Marquardt algorithm. Two of its main characteristics involve the proper use of implicitly scaled variables and an optimal choice for the cor- rection. The use of implicitly scaled variables achieves scale invariance of LMSTR1 and limits the size of the correction in any direction where the functions are changing rapidly. The optimal choice of the correction guarantees (under reasonable conditions) global convergence from starting points far from th solution and a fast rate of convergence for problems with small residuals. Timing. The time required by LMSTR1 to solve a given problem depends on M and N, the behavior of the functions, the accu- racy requested, and the starting point. The number of arith- metic operations needed by LMSTR1 is about N**3 to process each evaluation of the functions (call to FCN with IFLAG = 1) and 1.5*(N**2) to process each row of the Jacobian (call to FCN with IFLAG .GE. 2). Unless FCN can be evaluated quickly, the timing of LMSTR1 will be strongly influenced by the time spent in FCN. Storage. LMSTR1 requires N**2 + 2*M + 6*N double precision sto- rage locations and N integer storage locations, in addition t the storage required by the program. There are no internally declared storage arrays. 7. Subprograms required. USER-supplied ...... FCN MINPACK-supplied ... DPMPAR,ENORM,LMSTR,LMPAR,QRFAC,QRSOLV, RWUPDT FORTRAN-supplied ... DABS,DMAX1,DMIN1,DSQRT,MOD 8. References. Jorge J. More, The Levenberg-Marquardt Algorithm, Implementation and Theory. Numerical Analysis, G. A. Watson, editor. Lecture Notes in Mathematics 630, Springer-Verlag, 1977. 9. Example. The problem is to determine the values of x(1), x(2), and x(3) which provide the best fit (in the least squares sense) of x(1) + u(i)/(v(i)*x(2) + w(i)*x(3)), i = 1, 15 Page to the data y = (0.14,0.18,0.22,0.25,0.29,0.32,0.35,0.39, 0.37,0.58,0.73,0.96,1.34,2.10,4.39), where u(i) = i, v(i) = 16 - i, and w(i) = min(u(i),v(i)). The i-th component of FVEC is thus defined by y(i) - (x(1) + u(i)/(v(i)*x(2) + w(i)*x(3))). C ********** C C DRIVER FOR LMSTR1 EXAMPLE. C DOUBLE PRECISION VERSION C C ********** INTEGER J,M,N,LDFJAC,INFO,LWA,NWRITE INTEGER IPVT(3) DOUBLE PRECISION TOL,FNORM DOUBLE PRECISION X(3),FVEC(15),FJAC(3,3),WA(30) DOUBLE PRECISION ENORM,DPMPAR EXTERNAL FCN C C LOGICAL OUTPUT UNIT IS ASSUMED TO BE NUMBER 6. C DATA NWRITE /6/ C M = 15 N = 3 C C THE FOLLOWING STARTING VALUES PROVIDE A ROUGH FIT. C X(1) = 1.D0 X(2) = 1.D0 X(3) = 1.D0 C LDFJAC = 3 LWA = 30 C C SET TOL TO THE SQUARE ROOT OF THE MACHINE PRECISION. C UNLESS HIGH PRECISION SOLUTIONS ARE REQUIRED, C THIS IS THE RECOMMENDED SETTING. C TOL = DSQRT(DPMPAR(1)) C CALL LMSTR1(FCN,M,N,X,FVEC,FJAC,LDFJAC,TOL, * INFO,IPVT,WA,LWA) FNORM = ENORM(M,FVEC) WRITE (NWRITE,1000) FNORM,INFO,(X(J),J=1,N) STOP 1000 FORMAT (5X,31H FINAL L2 NORM OF THE RESIDUALS,D15.7 // * 5X,15H EXIT PARAMETER,16X,I10 // * 5X,27H FINAL APPROXIMATE SOLUTION // 5X,3D15.7) C Page C LAST CARD OF DRIVER FOR LMSTR1 EXAMPLE. C END SUBROUTINE FCN(M,N,X,FVEC,FJROW,IFLAG) INTEGER M,N,IFLAG DOUBLE PRECISION X(N),FVEC(M),FJROW(N) C C SUBROUTINE FCN FOR LMSTR1 EXAMPLE. C INTEGER I DOUBLE PRECISION TMP1,TMP2,TMP3,TMP4 DOUBLE PRECISION Y(15) DATA Y(1),Y(2),Y(3),Y(4),Y(5),Y(6),Y(7),Y(8), * Y(9),Y(10),Y(11),Y(12),Y(13),Y(14),Y(15) * /1.4D-1,1.8D-1,2.2D-1,2.5D-1,2.9D-1,3.2D-1,3.5D-1,3.9D-1, * 3.7D-1,5.8D-1,7.3D-1,9.6D-1,1.34D0,2.1D0,4.39D0/ C IF (IFLAG .GE. 2) GO TO 20 DO 10 I = 1, 15 TMP1 = I TMP2 = 16 - I TMP3 = TMP1 IF (I .GT. 8) TMP3 = TMP2 FVEC(I) = Y(I) - (X(1) + TMP1/(X(2)*TMP2 + X(3)*TMP3)) 10 CONTINUE GO TO 40 20 CONTINUE I = IFLAG - 1 TMP1 = I TMP2 = 16 - I TMP3 = TMP1 IF (I .GT. 8) TMP3 = TMP2 TMP4 = (X(2)*TMP2 + X(3)*TMP3)**2 FJROW(1) = -1.D0 FJROW(2) = TMP1*TMP2/TMP4 FJROW(3) = TMP1*TMP3/TMP4 30 CONTINUE 40 CONTINUE RETURN C C LAST CARD OF SUBROUTINE FCN. C END Results obtained with different compilers or machines may be slightly different. FINAL L2 NORM OF THE RESIDUALS 0.9063596D-01 EXIT PARAMETER 1 FINAL APPROXIMATE SOLUTION 0.8241058D-01 0.1133037D+01 0.2343695D+01 Page Documentation for MINPACK subroutine LMSTR Double precision version Argonne National Laboratory Burton S. Garbow, Kenneth E. Hillstrom, Jorge J. More March 1980 1. Purpose. The purpose of LMSTR is to minimize the sum of the squares of M nonlinear functions in N variables by a modification of the Levenberg-Marquardt algorithm which uses minimal storage. The user must provide a subroutine which calculates the functions and the rows of the Jacobian. 2. Subroutine and type statements. SUBROUTINE LMSTR(FCN,M,N,X,FVEC,FJAC,LDFJAC,FTOL,XTOL,GTOL, * MAXFEV,DIAG,MODE,FACTOR,NPRINT,INFO,NFEV,NJEV, * IPVT,QTF,WA1,WA2,WA3,WA4) INTEGER M,N,LDFJAC,MAXFEV,MODE,NPRINT,INFO,NFEV,NJEV INTEGER IPVT(N) DOUBLE PRECISION FTOL,XTOL,GTOL,FACTOR DOUBLE PRECISION X(N),FVEC(M),FJAC(LDFJAC,N),DIAG(N),QTF(N), * WA1(N),WA2(N),WA3(N),WA4(M) 3. Parameters. Parameters designated as input parameters must be specified on entry to LMSTR and are not changed on exit, while parameters designated as output parameters need not be specified on entry and are set to appropriate values on exit from LMSTR. FCN is the name of the user-supplied subroutine which calculate the functions and the rows of the Jacobian. FCN must be declared in an EXTERNAL statement in the user calling program and should be written as follows. SUBROUTINE FCN(M,N,X,FVEC,FJROW,IFLAG) INTEGER M,N,IFLAG DOUBLE PRECISION X(N),FVEC(M),FJROW(N) ---------- IF IFLAG = 1 CALCULATE THE FUNCTIONS AT X AND RETURN THIS VECTOR IN FVEC. IF IFLAG = I CALCULATE THE (I-1)-ST ROW OF THE JACOBIAN AT X AND RETURN THIS VECTOR IN FJROW. ---------- RETURN Page END The value of IFLAG should not be changed by FCN unless the user wants to terminate execution of LMSTR. In this case set IFLAG to a negative integer. M is a positive integer input variable set to the number of functions. N is a positive integer input variable set to the number of variables. N must not exceed M. X is an array of length N. On input X must contain an initial estimate of the solution vector. On output X contains the final estimate of the solution vector. FVEC is an output array of length M which contains the function evaluated at the output X. FJAC is an output N by N array. The upper triangle of FJAC con tains an upper triangular matrix R such that T T T P *(JAC *JAC)*P = R *R, where P is a permutation matrix and JAC is the final calcu- lated Jacobian. Column j of P is column IPVT(j) (see below) of the identity matrix. The lower triangular part of FJAC contains information generated during the computation of R. LDFJAC is a positive integer input variable not less than N which specifies the leading dimension of the array FJAC. FTOL is a nonnegative input variable. Termination occurs when both the actual and predicted relative reductions in the sum of squares are at most FTOL. Therefore, FTOL measures the relative error desired in the sum of squares. Section 4 con- tains more details about FTOL. XTOL is a nonnegative input variable. Termination occurs when the relative error between two consecutive iterates is at most XTOL. Therefore, XTOL measures the relative error desired in the approximate solution. Section 4 contains more details about XTOL. GTOL is a nonnegative input variable. Termination occurs when the cosine of the angle between FVEC and any column of the Jacobian is at most GTOL in absolute value. Therefore, GTOL measures the orthogonality desired between the function vector and the columns of the Jacobian. Section 4 contains more details about GTOL. MAXFEV is a positive integer input variable. Termination occur when the number of calls to FCN with IFLAG = 1 has reached Page MAXFEV. DIAG is an array of length N. If MODE = 1 (see below), DIAG is internally set. If MODE = 2, DIAG must contain positive entries that serve as multiplicative scale factors for the variables. MODE is an integer input variable. If MODE = 1, the variables will be scaled internally. If MODE = 2, the scaling is speci- fied by the input DIAG. Other values of MODE are equivalent to MODE = 1. FACTOR is a positive input variable used in determining the ini- tial step bound. This bound is set to the product of FACTOR and the Euclidean norm of DIAG*X if nonzero, or else to FACTO itself. In most cases FACTOR should lie in the interval (.1,100.). 100. is a generally recommended value. NPRINT is an integer input variable that enables controlled printing of iterates if it is positive. In this case, FCN is called with IFLAG = 0 at the beginning of the first iteration and every NPRINT iterations thereafter and immediately prior to return, with X and FVEC available for printing. If NPRINT is not positive, no special calls of FCN with IFLAG = 0 are made. INFO is an integer output variable. If the user has terminated execution, INFO is set to the (negative) value of IFLAG. See description of FCN. Otherwise, INFO is set as follows. INFO = 0 Improper input parameters. INFO = 1 Both actual and predicted relative reductions in th sum of squares are at most FTOL. INFO = 2 Relative error between two consecutive iterates is at most XTOL. INFO = 3 Conditions for INFO = 1 and INFO = 2 both hold. INFO = 4 The cosine of the angle between FVEC and any column of the Jacobian is at most GTOL in absolute value. INFO = 5 Number of calls to FCN with IFLAG = 1 has reached MAXFEV. INFO = 6 FTOL is too small. No further reduction in the sum of squares is possible. INFO = 7 XTOL is too small. No further improvement in the approximate solution X is possible. INFO = 8 GTOL is too small. FVEC is orthogonal to the columns of the Jacobian to machine precision. Page Sections 4 and 5 contain more details about INFO. NFEV is an integer output variable set to the number of calls t FCN with IFLAG = 1. NJEV is an integer output variable set to the number of calls t FCN with IFLAG = 2. IPVT is an integer output array of length N. IPVT defines a permutation matrix P such that JAC*P = Q*R, where JAC is the final calculated Jacobian, Q is orthogonal (not stored), and is upper triangular. Column j of P is column IPVT(j) of the identity matrix. QTF is an output array of length N which contains the first N elements of the vector (Q transpose)*FVEC. WA1, WA2, and WA3 are work arrays of length N. WA4 is a work array of length M. 4. Successful completion. The accuracy of LMSTR is controlled by the convergence parame- ters FTOL, XTOL, and GTOL. These parameters are used in tests which make three types of comparisons between the approximation X and a solution XSOL. LMSTR terminates when any of the tests is satisfied. If any of the convergence parameters is less than the machine precision (as defined by the MINPACK function DPMPAR(1)), then LMSTR only attempts to satisfy the test define by the machine precision. Further progress is not usually pos- sible. The tests assume that the functions and the Jacobian are coded consistently, and that the functions are reasonably well behaved. If these conditions are not satisfied, then LMSTR may incorrectly indicate convergence. The coding of the Jacobian can be checked by the MINPACK subroutine CHKDER. If the Jaco- bian is coded correctly, then the validity of the answer can be checked, for example, by rerunning LMSTR with tighter toler- ances. First convergence test. If ENORM(Z) denotes the Euclidean norm of a vector Z, then this test attempts to guarantee that ENORM(FVEC) .LE. (1+FTOL)*ENORM(FVECS), where FVECS denotes the functions evaluated at XSOL. If this condition is satisfied with FTOL = 10**(-K), then the final residual norm ENORM(FVEC) has K significant decimal digits an INFO is set to 1 (or to 3 if the second test is also satis- fied). Unless high precision solutions are required, the recommended value for FTOL is the square root of the machine Page precision. Second convergence test. If D is the diagonal matrix whose entries are defined by the array DIAG, then this test attempt to guarantee that ENORM(D*(X-XSOL)) .LE. XTOL*ENORM(D*XSOL). If this condition is satisfied with XTOL = 10**(-K), then the larger components of D*X have K significant decimal digits an INFO is set to 2 (or to 3 if the first test is also satis- fied). There is a danger that the smaller components of D*X may have large relative errors, but if MODE = 1, then the accuracy of the components of X is usually related to their sensitivity. Unless high precision solutions are required, the recommended value for XTOL is the square root of the machine precision. Third convergence test. This test is satisfied when the cosine of the angle between FVEC and any column of the Jacobian at X is at most GTOL in absolute value. There is no clear rela- tionship between this test and the accuracy of LMSTR, and furthermore, the test is equally well satisfied at other crit- ical points, namely maximizers and saddle points. Therefore, termination caused by this test (INFO = 4) should be examined carefully. The recommended value for GTOL is zero. 5. Unsuccessful completion. Unsuccessful termination of LMSTR can be due to improper input parameters, arithmetic interrupts, or an excessive number of function evaluations. Improper input parameters. INFO is set to 0 if N .LE. 0, or M .LT. N, or LDFJAC .LT. N, or FTOL .LT. 0.D0, or XTOL .LT. 0.D0, or GTOL .LT. 0.D0, or MAXFEV .LE. 0, or FACTOR .LE. 0.D0. Arithmetic interrupts. If these interrupts occur in the FCN subroutine during an early stage of the computation, they may be caused by an unacceptable choice of X by LMSTR. In this case, it may be possible to remedy the situation by rerunning LMSTR with a smaller value of FACTOR. Excessive number of function evaluations. A reasonable value for MAXFEV is 100*(N+1). If the number of calls to FCN with IFLAG = 1 reaches MAXFEV, then this indicates that the routine is converging very slowly as measured by the progress of FVEC and INFO is set to 5. In this case, it may be helpful to restart LMSTR with MODE set to 1. 6. Characteristics of the algorithm. Page LMSTR is a modification of the Levenberg-Marquardt algorithm. Two of its main characteristics involve the proper use of implicitly scaled variables (if MODE = 1) and an optimal choice for the correction. The use of implicitly scaled variables achieves scale invariance of LMSTR and limits the size of the correction in any direction where the functions are changing rapidly. The optimal choice of the correction guarantees (under reasonable conditions) global convergence from starting points far from the solution and a fast rate of convergence for prob- lems with small residuals. Timing. The time required by LMSTR to solve a given problem depends on M and N, the behavior of the functions, the accu- racy requested, and the starting point. The number of arith- metic operations needed by LMSTR is about N**3 to process each evaluation of the functions (call to FCN with IFLAG = 1) and 1.5*(N**2) to process each row of the Jacobian (call to FCN with IFLAG .GE. 2). Unless FCN can be evaluated quickly, the timing of LMSTR will be strongly influenced by the time spent in FCN. Storage. LMSTR requires N**2 + 2*M + 6*N double precision sto- rage locations and N integer storage locations, in addition t the storage required by the program. There are no internally declared storage arrays. 7. Subprograms required. USER-supplied ...... FCN MINPACK-supplied ... DPMPAR,ENORM,LMPAR,QRFAC,QRSOLV,RWUPDT FORTRAN-supplied ... DABS,DMAX1,DMIN1,DSQRT,MOD 8. References. Jorge J. More, The Levenberg-Marquardt Algorithm, Implementation and Theory. Numerical Analysis, G. A. Watson, editor. Lecture Notes in Mathematics 630, Springer-Verlag, 1977. 9. Example. The problem is to determine the values of x(1), x(2), and x(3) which provide the best fit (in the least squares sense) of x(1) + u(i)/(v(i)*x(2) + w(i)*x(3)), i = 1, 15 to the data y = (0.14,0.18,0.22,0.25,0.29,0.32,0.35,0.39, 0.37,0.58,0.73,0.96,1.34,2.10,4.39), Page where u(i) = i, v(i) = 16 - i, and w(i) = min(u(i),v(i)). The i-th component of FVEC is thus defined by y(i) - (x(1) + u(i)/(v(i)*x(2) + w(i)*x(3))). C ********** C C DRIVER FOR LMSTR EXAMPLE. C DOUBLE PRECISION VERSION C C ********** INTEGER J,M,N,LDFJAC,MAXFEV,MODE,NPRINT,INFO,NFEV,NJEV,NWRITE INTEGER IPVT(3) DOUBLE PRECISION FTOL,XTOL,GTOL,FACTOR,FNORM DOUBLE PRECISION X(3),FVEC(15),FJAC(3,3),DIAG(3),QTF(3), * WA1(3),WA2(3),WA3(3),WA4(15) DOUBLE PRECISION ENORM,DPMPAR EXTERNAL FCN C C LOGICAL OUTPUT UNIT IS ASSUMED TO BE NUMBER 6. C DATA NWRITE /6/ C M = 15 N = 3 C C THE FOLLOWING STARTING VALUES PROVIDE A ROUGH FIT. C X(1) = 1.D0 X(2) = 1.D0 X(3) = 1.D0 C LDFJAC = 3 C C SET FTOL AND XTOL TO THE SQUARE ROOT OF THE MACHINE PRECISION C AND GTOL TO ZERO. UNLESS HIGH PRECISION SOLUTIONS ARE C REQUIRED, THESE ARE THE RECOMMENDED SETTINGS. C FTOL = DSQRT(DPMPAR(1)) XTOL = DSQRT(DPMPAR(1)) GTOL = 0.D0 C MAXFEV = 400 MODE = 1 FACTOR = 1.D2 NPRINT = 0 C CALL LMSTR(FCN,M,N,X,FVEC,FJAC,LDFJAC,FTOL,XTOL,GTOL, * MAXFEV,DIAG,MODE,FACTOR,NPRINT,INFO,NFEV,NJEV, * IPVT,QTF,WA1,WA2,WA3,WA4) FNORM = ENORM(M,FVEC) WRITE (NWRITE,1000) FNORM,NFEV,NJEV,INFO,(X(J),J=1,N) STOP 1000 FORMAT (5X,31H FINAL L2 NORM OF THE RESIDUALS,D15.7 // Page * 5X,31H NUMBER OF FUNCTION EVALUATIONS,I10 // * 5X,31H NUMBER OF JACOBIAN EVALUATIONS,I10 // * 5X,15H EXIT PARAMETER,16X,I10 // * 5X,27H FINAL APPROXIMATE SOLUTION // 5X,3D15.7) C C LAST CARD OF DRIVER FOR LMSTR EXAMPLE. C END SUBROUTINE FCN(M,N,X,FVEC,FJROW,IFLAG) INTEGER M,N,IFLAG DOUBLE PRECISION X(N),FVEC(M),FJROW(N) C C SUBROUTINE FCN FOR LMSTR EXAMPLE. C INTEGER I DOUBLE PRECISION TMP1,TMP2,TMP3,TMP4 DOUBLE PRECISION Y(15) DATA Y(1),Y(2),Y(3),Y(4),Y(5),Y(6),Y(7),Y(8), * Y(9),Y(10),Y(11),Y(12),Y(13),Y(14),Y(15) * /1.4D-1,1.8D-1,2.2D-1,2.5D-1,2.9D-1,3.2D-1,3.5D-1,3.9D-1, * 3.7D-1,5.8D-1,7.3D-1,9.6D-1,1.34D0,2.1D0,4.39D0/ C IF (IFLAG .NE. 0) GO TO 5 C C INSERT PRINT STATEMENTS HERE WHEN NPRINT IS POSITIVE. C RETURN 5 CONTINUE IF (IFLAG .GE. 2) GO TO 20 DO 10 I = 1, 15 TMP1 = I TMP2 = 16 - I TMP3 = TMP1 IF (I .GT. 8) TMP3 = TMP2 FVEC(I) = Y(I) - (X(1) + TMP1/(X(2)*TMP2 + X(3)*TMP3)) 10 CONTINUE GO TO 40 20 CONTINUE I = IFLAG - 1 TMP1 = I TMP2 = 16 - I TMP3 = TMP1 IF (I .GT. 8) TMP3 = TMP2 TMP4 = (X(2)*TMP2 + X(3)*TMP3)**2 FJROW(1) = -1.D0 FJROW(2) = TMP1*TMP2/TMP4 FJROW(3) = TMP1*TMP3/TMP4 30 CONTINUE 40 CONTINUE RETURN C C LAST CARD OF SUBROUTINE FCN. C END Page Results obtained with different compilers or machines may be slightly different. FINAL L2 NORM OF THE RESIDUALS 0.9063596D-01 NUMBER OF FUNCTION EVALUATIONS 6 NUMBER OF JACOBIAN EVALUATIONS 5 EXIT PARAMETER 1 FINAL APPROXIMATE SOLUTION 0.8241058D-01 0.1133037D+01 0.2343695D+01 Page Documentation for MINPACK subroutine LMDIF1 Double precision version Argonne National Laboratory Burton S. Garbow, Kenneth E. Hillstrom, Jorge J. More March 1980 1. Purpose. The purpose of LMDIF1 is to minimize the sum of the squares of nonlinear functions in N variables by a modification of the Levenberg-Marquardt algorithm. This is done by using the more general least-squares solver LMDIF. The user must provide a subroutine which calculates the functions. The Jacobian is the calculated by a forward-difference approximation. 2. Subroutine and type statements. SUBROUTINE LMDIF1(FCN,M,N,X,FVEC,TOL,INFO,IWA,WA,LWA) INTEGER M,N,INFO,LWA INTEGER IWA(N) DOUBLE PRECISION TOL DOUBLE PRECISION X(N),FVEC(M),WA(LWA) EXTERNAL FCN 3. Parameters. Parameters designated as input parameters must be specified on entry to LMDIF1 and are not changed on exit, while parameters designated as output parameters need not be specified on entry and are set to appropriate values on exit from LMDIF1. FCN is the name of the user-supplied subroutine which calculate the functions. FCN must be declared in an EXTERNAL statement in the user calling program, and should be written as follows SUBROUTINE FCN(M,N,X,FVEC,IFLAG) INTEGER M,N,IFLAG DOUBLE PRECISION X(N),FVEC(M) ---------- CALCULATE THE FUNCTIONS AT X AND RETURN THIS VECTOR IN FVEC. ---------- RETURN END The value of IFLAG should not be changed by FCN unless the user wants to terminate execution of LMDIF1. In this case set Page IFLAG to a negative integer. M is a positive integer input variable set to the number of functions. N is a positive integer input variable set to the number of variables. N must not exceed M. X is an array of length N. On input X must contain an initial estimate of the solution vector. On output X contains the final estimate of the solution vector. FVEC is an output array of length M which contains the function evaluated at the output X. TOL is a nonnegative input variable. Termination occurs when the algorithm estimates either that the relative error in the sum of squares is at most TOL or that the relative error between X and the solution is at most TOL. Section 4 contain more details about TOL. INFO is an integer output variable. If the user has terminated execution, INFO is set to the (negative) value of IFLAG. See description of FCN. Otherwise, INFO is set as follows. INFO = 0 Improper input parameters. INFO = 1 Algorithm estimates that the relative error in the sum of squares is at most TOL. INFO = 2 Algorithm estimates that the relative error between X and the solution is at most TOL. INFO = 3 Conditions for INFO = 1 and INFO = 2 both hold. INFO = 4 FVEC is orthogonal to the columns of the Jacobian t machine precision. INFO = 5 Number of calls to FCN has reached or exceeded 200*(N+1). INFO = 6 TOL is too small. No further reduction in the sum of squares is possible. INFO = 7 TOL is too small. No further improvement in the approximate solution X is possible. Sections 4 and 5 contain more details about INFO. IWA is an integer work array of length N. WA is a work array of length LWA. LWA is a positive integer input variable not less than Page M*N+5*N+M. 4. Successful completion. The accuracy of LMDIF1 is controlled by the convergence parame- ter TOL. This parameter is used in tests which make three type of comparisons between the approximation X and a solution XSOL. LMDIF1 terminates when any of the tests is satisfied. If TOL i less than the machine precision (as defined by the MINPACK func- tion DPMPAR(1)), then LMDIF1 only attempts to satisfy the test defined by the machine precision. Further progress is not usu- ally possible. Unless high precision solutions are required, the recommended value for TOL is the square root of the machine precision. The tests assume that the functions are reasonably well behaved If this condition is not satisfied, then LMDIF1 may incorrectly indicate convergence. The validity of the answer can be checked, for example, by rerunning LMDIF1 with a tighter toler- ance. First convergence test. If ENORM(Z) denotes the Euclidean norm of a vector Z, then this test attempts to guarantee that ENORM(FVEC) .LE. (1+TOL)*ENORM(FVECS), where FVECS denotes the functions evaluated at XSOL. If this condition is satisfied with TOL = 10**(-K), then the final residual norm ENORM(FVEC) has K significant decimal digits an INFO is set to 1 (or to 3 if the second test is also satis- fied). Second convergence test. If D is a diagonal matrix (implicitly generated by LMDIF1) whose entries contain scale factors for the variables, then this test attempts to guarantee that ENORM(D*(X-XSOL)) .LE. TOL*ENORM(D*XSOL). If this condition is satisfied with TOL = 10**(-K), then the larger components of D*X have K significant decimal digits an INFO is set to 2 (or to 3 if the first test is also satis- fied). There is a danger that the smaller components of D*X may have large relative errors, but the choice of D is such that the accuracy of the components of X is usually related t their sensitivity. Third convergence test. This test is satisfied when FVEC is orthogonal to the columns of the Jacobian to machine preci- sion. There is no clear relationship between this test and the accuracy of LMDIF1, and furthermore, the test is equally well satisfied at other critical points, namely maximizers an saddle points. Also, errors in the functions (see below) may result in the test being satisfied at a point not close to th Page minimum. Therefore, termination caused by this test (INFO = 4) should be examined carefully. 5. Unsuccessful completion. Unsuccessful termination of LMDIF1 can be due to improper input parameters, arithmetic interrupts, an excessive number of func- tion evaluations, or errors in the functions. Improper input parameters. INFO is set to 0 if N .LE. 0, or M .LT. N, or TOL .LT. 0.D0, or LWA .LT. M*N+5*N+M. Arithmetic interrupts. If these interrupts occur in the FCN subroutine during an early stage of the computation, they may be caused by an unacceptable choice of X by LMDIF1. In this case, it may be possible to remedy the situation by not evalu- ating the functions here, but instead setting the components of FVEC to numbers that exceed those in the initial FVEC, thereby indirectly reducing the step length. The step length can be more directly controlled by using instead LMDIF, which includes in its calling sequence the step-length-governing parameter FACTOR. Excessive number of function evaluations. If the number of calls to FCN reaches 200*(N+1), then this indicates that the routine is converging very slowly as measured by the progress of FVEC, and INFO is set to 5. In this case, it may be help- ful to restart LMDIF1, thereby forcing it to disregard old (and possibly harmful) information. Errors in the functions. The choice of step length in the for- ward-difference approximation to the Jacobian assumes that th relative errors in the functions are of the order of the machine precision. If this is not the case, LMDIF1 may fail (usually with INFO = 4). The user should then use LMDIF instead, or one of the programs which require the analytic Jacobian (LMDER1 and LMDER). 6. Characteristics of the algorithm. LMDIF1 is a modification of the Levenberg-Marquardt algorithm. Two of its main characteristics involve the proper use of implicitly scaled variables and an optimal choice for the cor- rection. The use of implicitly scaled variables achieves scale invariance of LMDIF1 and limits the size of the correction in any direction where the functions are changing rapidly. The optimal choice of the correction guarantees (under reasonable conditions) global convergence from starting points far from th solution and a fast rate of convergence for problems with small residuals. Timing. The time required by LMDIF1 to solve a given problem Page depends on M and N, the behavior of the functions, the accu- racy requested, and the starting point. The number of arith- metic operations needed by LMDIF1 is about N**3 to process each evaluation of the functions (one call to FCN) and M*(N**2) to process each approximation to the Jacobian (N calls to FCN). Unless FCN can be evaluated quickly, the tim- ing of LMDIF1 will be strongly influenced by the time spent i FCN. Storage. LMDIF1 requires M*N + 2*M + 6*N double precision sto- rage locations and N integer storage locations, in addition t the storage required by the program. There are no internally declared storage arrays. 7. Subprograms required. USER-supplied ...... FCN MINPACK-supplied ... DPMPAR,ENORM,FDJAC2,LMDIF,LMPAR, QRFAC,QRSOLV FORTRAN-supplied ... DABS,DMAX1,DMIN1,DSQRT,MOD 8. References. Jorge J. More, The Levenberg-Marquardt Algorithm, Implementation and Theory. Numerical Analysis, G. A. Watson, editor. Lecture Notes in Mathematics 630, Springer-Verlag, 1977. 9. Example. The problem is to determine the values of x(1), x(2), and x(3) which provide the best fit (in the least squares sense) of x(1) + u(i)/(v(i)*x(2) + w(i)*x(3)), i = 1, 15 to the data y = (0.14,0.18,0.22,0.25,0.29,0.32,0.35,0.39, 0.37,0.58,0.73,0.96,1.34,2.10,4.39), where u(i) = i, v(i) = 16 - i, and w(i) = min(u(i),v(i)). The i-th component of FVEC is thus defined by y(i) - (x(1) + u(i)/(v(i)*x(2) + w(i)*x(3))). C ********** C C DRIVER FOR LMDIF1 EXAMPLE. C DOUBLE PRECISION VERSION C Page C ********** INTEGER J,M,N,INFO,LWA,NWRITE INTEGER IWA(3) DOUBLE PRECISION TOL,FNORM DOUBLE PRECISION X(3),FVEC(15),WA(75) DOUBLE PRECISION ENORM,DPMPAR EXTERNAL FCN C C LOGICAL OUTPUT UNIT IS ASSUMED TO BE NUMBER 6. C DATA NWRITE /6/ C M = 15 N = 3 C C THE FOLLOWING STARTING VALUES PROVIDE A ROUGH FIT. C X(1) = 1.D0 X(2) = 1.D0 X(3) = 1.D0 C LWA = 75 C C SET TOL TO THE SQUARE ROOT OF THE MACHINE PRECISION. C UNLESS HIGH PRECISION SOLUTIONS ARE REQUIRED, C THIS IS THE RECOMMENDED SETTING. C TOL = DSQRT(DPMPAR(1)) C CALL LMDIF1(FCN,M,N,X,FVEC,TOL,INFO,IWA,WA,LWA) FNORM = ENORM(M,FVEC) WRITE (NWRITE,1000) FNORM,INFO,(X(J),J=1,N) STOP 1000 FORMAT (5X,31H FINAL L2 NORM OF THE RESIDUALS,D15.7 // * 5X,15H EXIT PARAMETER,16X,I10 // * 5X,27H FINAL APPROXIMATE SOLUTION // 5X,3D15.7) C C LAST CARD OF DRIVER FOR LMDIF1 EXAMPLE. C END SUBROUTINE FCN(M,N,X,FVEC,IFLAG) INTEGER M,N,IFLAG DOUBLE PRECISION X(N),FVEC(M) C C SUBROUTINE FCN FOR LMDIF1 EXAMPLE. C INTEGER I DOUBLE PRECISION TMP1,TMP2,TMP3 DOUBLE PRECISION Y(15) DATA Y(1),Y(2),Y(3),Y(4),Y(5),Y(6),Y(7),Y(8), * Y(9),Y(10),Y(11),Y(12),Y(13),Y(14),Y(15) * /1.4D-1,1.8D-1,2.2D-1,2.5D-1,2.9D-1,3.2D-1,3.5D-1,3.9D-1, * 3.7D-1,5.8D-1,7.3D-1,9.6D-1,1.34D0,2.1D0,4.39D0/ C Page DO 10 I = 1, 15 TMP1 = I TMP2 = 16 - I TMP3 = TMP1 IF (I .GT. 8) TMP3 = TMP2 FVEC(I) = Y(I) - (X(1) + TMP1/(X(2)*TMP2 + X(3)*TMP3)) 10 CONTINUE RETURN C C LAST CARD OF SUBROUTINE FCN. C END Results obtained with different compilers or machines may be slightly different. FINAL L2 NORM OF THE RESIDUALS 0.9063596D-01 EXIT PARAMETER 1 FINAL APPROXIMATE SOLUTION 0.8241057D-01 0.1133037D+01 0.2343695D+01 Page Documentation for MINPACK subroutine LMDIF Double precision version Argonne National Laboratory Burton S. Garbow, Kenneth E. Hillstrom, Jorge J. More March 1980 1. Purpose. The purpose of LMDIF is to minimize the sum of the squares of M nonlinear functions in N variables by a modification of the Levenberg-Marquardt algorithm. The user must provide a subrou- tine which calculates the functions. The Jacobian is then cal- culated by a forward-difference approximation. 2. Subroutine and type statements. SUBROUTINE LMDIF(FCN,M,N,X,FVEC,FTOL,XTOL,GTOL,MAXFEV,EPSFCN, * DIAG,MODE,FACTOR,NPRINT,INFO,NFEV,FJAC,LDFJAC, * IPVT,QTF,WA1,WA2,WA3,WA4) INTEGER M,N,MAXFEV,MODE,NPRINT,INFO,NFEV,LDFJAC INTEGER IPVT(N) DOUBLE PRECISION FTOL,XTOL,GTOL,EPSFCN,FACTOR DOUBLE PRECISION X(N),FVEC(M),DIAG(N),FJAC(LDFJAC,N),QTF(N), * WA1(N),WA2(N),WA3(N),WA4(M) EXTERNAL FCN 3. Parameters. Parameters designated as input parameters must be specified on entry to LMDIF and are not changed on exit, while parameters designated as output parameters need not be specified on entry and are set to appropriate values on exit from LMDIF. FCN is the name of the user-supplied subroutine which calculate the functions. FCN must be declared in an EXTERNAL statement in the user calling program, and should be written as follows SUBROUTINE FCN(M,N,X,FVEC,IFLAG) INTEGER M,N,IFLAG DOUBLE PRECISION X(N),FVEC(M) ---------- CALCULATE THE FUNCTIONS AT X AND RETURN THIS VECTOR IN FVEC. ---------- RETURN END Page The value of IFLAG should not be changed by FCN unless the user wants to terminate execution of LMDIF. In this case set IFLAG to a negative integer. M is a positive integer input variable set to the number of functions. N is a positive integer input variable set to the number of variables. N must not exceed M. X is an array of length N. On input X must contain an initial estimate of the solution vector. On output X contains the final estimate of the solution vector. FVEC is an output array of length M which contains the function evaluated at the output X. FTOL is a nonnegative input variable. Termination occurs when both the actual and predicted relative reductions in the sum of squares are at most FTOL. Therefore, FTOL measures the relative error desired in the sum of squares. Section 4 con- tains more details about FTOL. XTOL is a nonnegative input variable. Termination occurs when the relative error between two consecutive iterates is at most XTOL. Therefore, XTOL measures the relative error desired in the approximate solution. Section 4 contains more details about XTOL. GTOL is a nonnegative input variable. Termination occurs when the cosine of the angle between FVEC and any column of the Jacobian is at most GTOL in absolute value. Therefore, GTOL measures the orthogonality desired between the function vector and the columns of the Jacobian. Section 4 contains more details about GTOL. MAXFEV is a positive integer input variable. Termination occur when the number of calls to FCN is at least MAXFEV by the end of an iteration. EPSFCN is an input variable used in determining a suitable step for the forward-difference approximation. This approximation assumes that the relative errors in the functions are of the order of EPSFCN. If EPSFCN is less than the machine preci- sion, it is assumed that the relative errors in the functions are of the order of the machine precision. DIAG is an array of length N. If MODE = 1 (see below), DIAG is internally set. If MODE = 2, DIAG must contain positive entries that serve as multiplicative scale factors for the variables. MODE is an integer input variable. If MODE = 1, the variables will be scaled internally. If MODE = 2, the scaling is Page specified by the input DIAG. Other values of MODE are equiva- lent to MODE = 1. FACTOR is a positive input variable used in determining the ini- tial step bound. This bound is set to the product of FACTOR and the Euclidean norm of DIAG*X if nonzero, or else to FACTO itself. In most cases FACTOR should lie in the interval (.1,100.). 100. is a generally recommended value. NPRINT is an integer input variable that enables controlled printing of iterates if it is positive. In this case, FCN is called with IFLAG = 0 at the beginning of the first iteration and every NPRINT iterations thereafter and immediately prior to return, with X and FVEC available for printing. If NPRINT is not positive, no special calls of FCN with IFLAG = 0 are made. INFO is an integer output variable. If the user has terminated execution, INFO is set to the (negative) value of IFLAG. See description of FCN. Otherwise, INFO is set as follows. INFO = 0 Improper input parameters. INFO = 1 Both actual and predicted relative reductions in th sum of squares are at most FTOL. INFO = 2 Relative error between two consecutive iterates is at most XTOL. INFO = 3 Conditions for INFO = 1 and INFO = 2 both hold. INFO = 4 The cosine of the angle between FVEC and any column of the Jacobian is at most GTOL in absolute value. INFO = 5 Number of calls to FCN has reached or exceeded MAXFEV. INFO = 6 FTOL is too small. No further reduction in the sum of squares is possible. INFO = 7 XTOL is too small. No further improvement in the approximate solution X is possible. INFO = 8 GTOL is too small. FVEC is orthogonal to the columns of the Jacobian to machine precision. Sections 4 and 5 contain more details about INFO. NFEV is an integer output variable set to the number of calls t FCN. FJAC is an output M by N array. The upper N by N submatrix of FJAC contains an upper triangular matrix R with diagonal ele- ments of nonincreasing magnitude such that Page T T T P *(JAC *JAC)*P = R *R, where P is a permutation matrix and JAC is the final calcu- lated Jacobian. Column j of P is column IPVT(j) (see below) of the identity matrix. The lower trapezoidal part of FJAC contains information generated during the computation of R. LDFJAC is a positive integer input variable not less than M which specifies the leading dimension of the array FJAC. IPVT is an integer output array of length N. IPVT defines a permutation matrix P such that JAC*P = Q*R, where JAC is the final calculated Jacobian, Q is orthogonal (not stored), and is upper triangular with diagonal elements of nonincreasing magnitude. Column j of P is column IPVT(j) of the identity matrix. QTF is an output array of length N which contains the first N elements of the vector (Q transpose)*FVEC. WA1, WA2, and WA3 are work arrays of length N. WA4 is a work array of length M. 4. Successful completion. The accuracy of LMDIF is controlled by the convergence parame- ters FTOL, XTOL, and GTOL. These parameters are used in tests which make three types of comparisons between the approximation X and a solution XSOL. LMDIF terminates when any of the tests is satisfied. If any of the convergence parameters is less than the machine precision (as defined by the MINPACK function DPMPAR(1)), then LMDIF only attempts to satisfy the test define by the machine precision. Further progress is not usually pos- sible. The tests assume that the functions are reasonably well behaved If this condition is not satisfied, then LMDIF may incorrectly indicate convergence. The validity of the answer can be checked, for example, by rerunning LMDIF with tighter toler- ances. First convergence test. If ENORM(Z) denotes the Euclidean norm of a vector Z, then this test attempts to guarantee that ENORM(FVEC) .LE. (1+FTOL)*ENORM(FVECS), where FVECS denotes the functions evaluated at XSOL. If this condition is satisfied with FTOL = 10**(-K), then the final residual norm ENORM(FVEC) has K significant decimal digits an INFO is set to 1 (or to 3 if the second test is also satis- fied). Unless high precision solutions are required, the Page recommended value for FTOL is the square root of the machine precision. Second convergence test. If D is the diagonal matrix whose entries are defined by the array DIAG, then this test attempt to guarantee that ENORM(D*(X-XSOL)) .LE. XTOL*ENORM(D*XSOL). If this condition is satisfied with XTOL = 10**(-K), then the larger components of D*X have K significant decimal digits an INFO is set to 2 (or to 3 if the first test is also satis- fied). There is a danger that the smaller components of D*X may have large relative errors, but if MODE = 1, then the accuracy of the components of X is usually related to their sensitivity. Unless high precision solutions are required, the recommended value for XTOL is the square root of the machine precision. Third convergence test. This test is satisfied when the cosine of the angle between FVEC and any column of the Jacobian at X is at most GTOL in absolute value. There is no clear rela- tionship between this test and the accuracy of LMDIF, and furthermore, the test is equally well satisfied at other crit- ical points, namely maximizers and saddle points. Therefore, termination caused by this test (INFO = 4) should be examined carefully. The recommended value for GTOL is zero. 5. Unsuccessful completion. Unsuccessful termination of LMDIF can be due to improper input parameters, arithmetic interrupts, or an excessive number of function evaluations. Improper input parameters. INFO is set to 0 if N .LE. 0, or M .LT. N, or LDFJAC .LT. M, or FTOL .LT. 0.D0, or XTOL .LT. 0.D0, or GTOL .LT. 0.D0, or MAXFEV .LE. 0, or FACTOR .LE. 0.D0. Arithmetic interrupts. If these interrupts occur in the FCN subroutine during an early stage of the computation, they may be caused by an unacceptable choice of X by LMDIF. In this case, it may be possible to remedy the situation by rerunning LMDIF with a smaller value of FACTOR. Excessive number of function evaluations. A reasonable value for MAXFEV is 200*(N+1). If the number of calls to FCN reaches MAXFEV, then this indicates that the routine is con- verging very slowly as measured by the progress of FVEC, and INFO is set to 5. In this case, it may be helpful to restart LMDIF with MODE set to 1. Page 6. Characteristics of the algorithm. LMDIF is a modification of the Levenberg-Marquardt algorithm. Two of its main characteristics involve the proper use of implicitly scaled variables (if MODE = 1) and an optimal choice for the correction. The use of implicitly scaled variables achieves scale invariance of LMDIF and limits the size of the correction in any direction where the functions are changing rapidly. The optimal choice of the correction guarantees (under reasonable conditions) global convergence from starting points far from the solution and a fast rate of convergence for prob- lems with small residuals. Timing. The time required by LMDIF to solve a given problem depends on M and N, the behavior of the functions, the accu- racy requested, and the starting point. The number of arith- metic operations needed by LMDIF is about N**3 to process each evaluation of the functions (one call to FCN) and M*(N**2) to process each approximation to the Jacobian (N calls to FCN). Unless FCN can be evaluated quickly, the timing of LMDIF will be strongly influenced by the time spent in FCN. Storage. LMDIF requires M*N + 2*M + 6*N double precision sto- rage locations and N integer storage locations, in addition t the storage required by the program. There are no internally declared storage arrays. 7. Subprograms required. USER-supplied ...... FCN MINPACK-supplied ... DPMPAR,ENORM,FDJAC2,LMPAR,QRFAC,QRSOLV FORTRAN-supplied ... DABS,DMAX1,DMIN1,DSQRT,MOD 8. References. Jorge J. More, The Levenberg-Marquardt Algorithm, Implementation and Theory. Numerical Analysis, G. A. Watson, editor. Lecture Notes in Mathematics 630, Springer-Verlag, 1977. 9. Example. The problem is to determine the values of x(1), x(2), and x(3) which provide the best fit (in the least squares sense) of x(1) + u(i)/(v(i)*x(2) + w(i)*x(3)), i = 1, 15 to the data Page y = (0.14,0.18,0.22,0.25,0.29,0.32,0.35,0.39, 0.37,0.58,0.73,0.96,1.34,2.10,4.39), where u(i) = i, v(i) = 16 - i, and w(i) = min(u(i),v(i)). The i-th component of FVEC is thus defined by y(i) - (x(1) + u(i)/(v(i)*x(2) + w(i)*x(3))). C ********** C C DRIVER FOR LMDIF EXAMPLE. C DOUBLE PRECISION VERSION C C ********** INTEGER J,M,N,MAXFEV,MODE,NPRINT,INFO,NFEV,LDFJAC,NWRITE INTEGER IPVT(3) DOUBLE PRECISION FTOL,XTOL,GTOL,EPSFCN,FACTOR,FNORM DOUBLE PRECISION X(3),FVEC(15),DIAG(3),FJAC(15,3),QTF(3), * WA1(3),WA2(3),WA3(3),WA4(15) DOUBLE PRECISION ENORM,DPMPAR EXTERNAL FCN C C LOGICAL OUTPUT UNIT IS ASSUMED TO BE NUMBER 6. C DATA NWRITE /6/ C M = 15 N = 3 C C THE FOLLOWING STARTING VALUES PROVIDE A ROUGH FIT. C X(1) = 1.D0 X(2) = 1.D0 X(3) = 1.D0 C LDFJAC = 15 C C SET FTOL AND XTOL TO THE SQUARE ROOT OF THE MACHINE PRECISION C AND GTOL TO ZERO. UNLESS HIGH PRECISION SOLUTIONS ARE C REQUIRED, THESE ARE THE RECOMMENDED SETTINGS. C FTOL = DSQRT(DPMPAR(1)) XTOL = DSQRT(DPMPAR(1)) GTOL = 0.D0 C MAXFEV = 800 EPSFCN = 0.D0 MODE = 1 FACTOR = 1.D2 NPRINT = 0 C CALL LMDIF(FCN,M,N,X,FVEC,FTOL,XTOL,GTOL,MAXFEV,EPSFCN, * DIAG,MODE,FACTOR,NPRINT,INFO,NFEV,FJAC,LDFJAC, * IPVT,QTF,WA1,WA2,WA3,WA4) Page FNORM = ENORM(M,FVEC) WRITE (NWRITE,1000) FNORM,NFEV,INFO,(X(J),J=1,N) STOP 1000 FORMAT (5X,31H FINAL L2 NORM OF THE RESIDUALS,D15.7 // * 5X,31H NUMBER OF FUNCTION EVALUATIONS,I10 // * 5X,15H EXIT PARAMETER,16X,I10 // * 5X,27H FINAL APPROXIMATE SOLUTION // 5X,3D15.7) C C LAST CARD OF DRIVER FOR LMDIF EXAMPLE. C END SUBROUTINE FCN(M,N,X,FVEC,IFLAG) INTEGER M,N,IFLAG DOUBLE PRECISION X(N),FVEC(M) C C SUBROUTINE FCN FOR LMDIF EXAMPLE. C INTEGER I DOUBLE PRECISION TMP1,TMP2,TMP3 DOUBLE PRECISION Y(15) DATA Y(1),Y(2),Y(3),Y(4),Y(5),Y(6),Y(7),Y(8), * Y(9),Y(10),Y(11),Y(12),Y(13),Y(14),Y(15) * /1.4D-1,1.8D-1,2.2D-1,2.5D-1,2.9D-1,3.2D-1,3.5D-1,3.9D-1, * 3.7D-1,5.8D-1,7.3D-1,9.6D-1,1.34D0,2.1D0,4.39D0/ C IF (IFLAG .NE. 0) GO TO 5 C C INSERT PRINT STATEMENTS HERE WHEN NPRINT IS POSITIVE. C RETURN 5 CONTINUE DO 10 I = 1, 15 TMP1 = I TMP2 = 16 - I TMP3 = TMP1 IF (I .GT. 8) TMP3 = TMP2 FVEC(I) = Y(I) - (X(1) + TMP1/(X(2)*TMP2 + X(3)*TMP3)) 10 CONTINUE RETURN C C LAST CARD OF SUBROUTINE FCN. C END Results obtained with different compilers or machines may be slightly different. FINAL L2 NORM OF THE RESIDUALS 0.9063596D-01 NUMBER OF FUNCTION EVALUATIONS 21 EXIT PARAMETER 1 FINAL APPROXIMATE SOLUTION Page 0.8241057D-01 0.1133037D+01 0.2343695D+01 Page Documentation for MINPACK subroutine CHKDER Double precision version Argonne National Laboratory Burton S. Garbow, Kenneth E. Hillstrom, Jorge J. More March 1980 1. Purpose. The purpose of CHKDER is to check the gradients of M nonlinear functions in N variables, evaluated at a point X, for consis- tency with the functions themselves. The user must call CHKDER twice, first with MODE = 1 and then with MODE = 2. 2. Subroutine and type statements. SUBROUTINE CHKDER(M,N,X,FVEC,FJAC,LDFJAC,XP,FVECP,MODE,ERR) INTEGER M,N,LDFJAC,MODE DOUBLE PRECISION X(N),FVEC(M),FJAC(LDFJAC,N),XP(N),FVECP(M), * ERR(M) 3. Parameters. Parameters designated as input parameters must be specified on entry to CHKDER and are not changed on exit, while parameters designated as output parameters need not be specified on entry and are set to appropriate values on exit from CHKDER. M is a positive integer input variable set to the number of functions. N is a positive integer input variable set to the number of variables. X is an input array of length N. FVEC is an array of length M. On input when MODE = 2, FVEC must contain the functions evaluated at X. FJAC is an M by N array. On input when MODE = 2, the rows of FJAC must contain the gradients of the respective functions evaluated at X. LDFJAC is a positive integer input variable not less than M which specifies the leading dimension of the array FJAC. XP is an array of length N. On output when MODE = 1, XP is set to a neighboring point of X. Page FVECP is an array of length M. On input when MODE = 2, FVECP must contain the functions evaluated at XP. MODE is an integer input variable set to 1 on the first call an 2 on the second. Other values of MODE are equivalent to MODE = 1. ERR is an array of length M. On output when MODE = 2, ERR con- tains measures of correctness of the respective gradients. I there is no severe loss of significance, then if ERR(I) is 1. the I-th gradient is correct, while if ERR(I) is 0.0 the I-th gradient is incorrect. For values of ERR between 0.0 and 1.0 the categorization is less certain. In general, a value of ERR(I) greater than 0.5 indicates that the I-th gradient is probably correct, while a value of ERR(I) less than 0.5 indi- cates that the I-th gradient is probably incorrect. 4. Successful completion. CHKDER usually guarantees that if ERR(I) is 1.0, then the I-th gradient at X is consistent with the I-th function. This sug- gests that the input X be such that consistency of the gradient at X implies consistency of the gradient at all points of inter est. If all the components of X are distinct and the fractional part of each one has two nonzero digits, then X is likely to be a satisfactory choice. If ERR(I) is not 1.0 but is greater than 0.5, then the I-th gra- dient is probably consistent with the I-th function (the more s the larger ERR(I) is), but the conditions for ERR(I) to be 1.0 have not been completely satisfied. In this case, it is recom- mended that CHKDER be rerun with other input values of X. If ERR(I) is always greater than 0.5, then the I-th gradient is consistent with the I-th function. 5. Unsuccessful completion. CHKDER does not perform reliably if cancellation or rounding errors cause a severe loss of significance in the evaluation of a function. Therefore, none of the components of X should be unusually small (in particular, zero) or any other value which may cause loss of significance. The relative differences between corresponding elements of FVECP and FVEC should be at least two orders of magnitude greater than the machine precision (as defined by the MINPACK function DPMPAR(1)). If there is a severe loss of significance in the evaluation of the I-th func- tion, then ERR(I) may be 0.0 and yet the I-th gradient could be correct. If ERR(I) is not 0.0 but is less than 0.5, then the I-th gra- dient is probably not consistent with the I-th function (the more so the smaller ERR(I) is), but the conditions for ERR(I) t Page be 0.0 have not been completely satisfied. In this case, it is recommended that CHKDER be rerun with other input values of X. If ERR(I) is always less than 0.5 and if there is no severe loss of significance, then the I-th gradient is not consistent with the I-th function. 6. Characteristics of the algorithm. CHKDER checks the I-th gradient for consistency with the I-th function by computing a forward-difference approximation along suitably chosen direction and comparing this approximation with the user-supplied gradient along the same direction. The prin- cipal characteristic of CHKDER is its invariance to changes in scale of the variables or functions. Timing. The time required by CHKDER depends only on M and N. The number of arithmetic operations needed by CHKDER is about N when MODE = 1 and M*N when MODE = 2. Storage. CHKDER requires M*N + 3*M + 2*N double precision stor- age locations, in addition to the storage required by the pro gram. There are no internally declared storage arrays. 7. Subprograms required. MINPACK-supplied ... DPMPAR FORTRAN-supplied ... DABS,DLOG10,DSQRT 8. References. None. 9. Example. This example checks the Jacobian matrix for the problem that determines the values of x(1), x(2), and x(3) which provide the best fit (in the least squares sense) of x(1) + u(i)/(v(i)*x(2) + w(i)*x(3)), i = 1, 15 to the data y = (0.14,0.18,0.22,0.25,0.29,0.32,0.35,0.39, 0.37,0.58,0.73,0.96,1.34,2.10,4.39), where u(i) = i, v(i) = 16 - i, and w(i) = min(u(i),v(i)). The i-th component of FVEC is thus defined by y(i) - (x(1) + u(i)/(v(i)*x(2) + w(i)*x(3))). Page C ********** C C DRIVER FOR CHKDER EXAMPLE. C DOUBLE PRECISION VERSION C C ********** INTEGER I,M,N,LDFJAC,MODE,NWRITE DOUBLE PRECISION X(3),FVEC(15),FJAC(15,3),XP(3),FVECP(15), * ERR(15) C C LOGICAL OUTPUT UNIT IS ASSUMED TO BE NUMBER 6. C DATA NWRITE /6/ C M = 15 N = 3 C C THE FOLLOWING VALUES SHOULD BE SUITABLE FOR C CHECKING THE JACOBIAN MATRIX. C X(1) = 9.2D-1 X(2) = 1.3D-1 X(3) = 5.4D-1 C LDFJAC = 15 C MODE = 1 CALL CHKDER(M,N,X,FVEC,FJAC,LDFJAC,XP,FVECP,MODE,ERR) MODE = 2 CALL FCN(M,N,X,FVEC,FJAC,LDFJAC,1) CALL FCN(M,N,X,FVEC,FJAC,LDFJAC,2) CALL FCN(M,N,XP,FVECP,FJAC,LDFJAC,1) CALL CHKDER(M,N,X,FVEC,FJAC,LDFJAC,XP,FVECP,MODE,ERR) C DO 10 I = 1, M FVECP(I) = FVECP(I) - FVEC(I) 10 CONTINUE WRITE (NWRITE,1000) (FVEC(I),I=1,M) WRITE (NWRITE,2000) (FVECP(I),I=1,M) WRITE (NWRITE,3000) (ERR(I),I=1,M) STOP 1000 FORMAT (/5X,5H FVEC // (5X,3D15.7)) 2000 FORMAT (/5X,13H FVECP - FVEC // (5X,3D15.7)) 3000 FORMAT (/5X,4H ERR // (5X,3D15.7)) C C LAST CARD OF DRIVER FOR CHKDER EXAMPLE. C END SUBROUTINE FCN(M,N,X,FVEC,FJAC,LDFJAC,IFLAG) INTEGER M,N,LDFJAC,IFLAG DOUBLE PRECISION X(N),FVEC(M),FJAC(LDFJAC,N) C C SUBROUTINE FCN FOR CHKDER EXAMPLE. C Page INTEGER I DOUBLE PRECISION TMP1,TMP2,TMP3,TMP4 DOUBLE PRECISION Y(15) DATA Y(1),Y(2),Y(3),Y(4),Y(5),Y(6),Y(7),Y(8), * Y(9),Y(10),Y(11),Y(12),Y(13),Y(14),Y(15) * /1.4D-1,1.8D-1,2.2D-1,2.5D-1,2.9D-1,3.2D-1,3.5D-1,3.9D-1, * 3.7D-1,5.8D-1,7.3D-1,9.6D-1,1.34D0,2.1D0,4.39D0/ C IF (IFLAG .EQ. 2) GO TO 20 DO 10 I = 1, 15 TMP1 = I TMP2 = 16 - I TMP3 = TMP1 IF (I .GT. 8) TMP3 = TMP2 FVEC(I) = Y(I) - (X(1) + TMP1/(X(2)*TMP2 + X(3)*TMP3)) 10 CONTINUE GO TO 40 20 CONTINUE DO 30 I = 1, 15 TMP1 = I TMP2 = 16 - I C C ERROR INTRODUCED INTO NEXT STATEMENT FOR ILLUSTRATION. C CORRECTED STATEMENT SHOULD READ TMP3 = TMP1 . C TMP3 = TMP2 IF (I .GT. 8) TMP3 = TMP2 TMP4 = (X(2)*TMP2 + X(3)*TMP3)**2 FJAC(I,1) = -1.D0 FJAC(I,2) = TMP1*TMP2/TMP4 FJAC(I,3) = TMP1*TMP3/TMP4 30 CONTINUE 40 CONTINUE RETURN C C LAST CARD OF SUBROUTINE FCN. C END Results obtained with different compilers or machines may be different. In particular, the differences FVECP - FVEC are machine dependent. FVEC -0.1181606D+01 -0.1429655D+01 -0.1606344D+01 -0.1745269D+01 -0.1840654D+01 -0.1921586D+01 -0.1984141D+01 -0.2022537D+01 -0.2468977D+01 -0.2827562D+01 -0.3473582D+01 -0.4437612D+01 -0.6047662D+01 -0.9267761D+01 -0.1891806D+02 FVECP - FVEC -0.7724666D-08 -0.3432405D-08 -0.2034843D-09 Page 0.2313685D-08 0.4331078D-08 0.5984096D-08 0.7363281D-08 0.8531470D-08 0.1488591D-07 0.2335850D-07 0.3522012D-07 0.5301255D-07 0.8266660D-07 0.1419747D-06 0.3198990D-06 ERR 0.1141397D+00 0.9943516D-01 0.9674474D-01 0.9980447D-01 0.1073116D+00 0.1220445D+00 0.1526814D+00 0.1000000D+01 0.1000000D+01 0.1000000D+01 0.1000000D+01 0.1000000D+01 0.1000000D+01 0.1000000D+01 0.1000000D+01 cminpack-1.3.6/dogleg.c 0000664 0000000 0000000 00000014144 13054046253 0014721 0 ustar 00root root 0000000 0000000 /* dogleg.f -- translated by f2c (version 20020621). You must link the resulting object file with the libraries: -lf2c -lm (in that order) */ #include "cminpack.h" #include