Re: It Complies, links, & runs...

[Brian Gough <bjg at network-theory dot co dot uk>]

An example,

gcc -g -Wall tmp.c -lgsl -llapack -lblas -lf2c -lm

==> tmp.c <==

/* With gcc: add an underscore to the end of the function name and
   convert all arguments into pointers.  The Fortran routines use the
   transpose of matrices as they are stored in C, so you can either
   transpose the matrix before input or remember that the output is
   transposed.  I use the liblapack.a library from the Debian lapack-dev
   package, so I did not have to compile lapack myself, although I could
   have done that with g77.  */

#include <gsl/gsl_math.h>
#include <gsl/gsl_complex.h>
#include <gsl/gsl_complex_math.h>
#include <gsl/gsl_matrix.h>

int
main ()
{
  size_t M = 5, N = 5;
  size_t L = GSL_MIN (M, N);

  gsl_matrix_complex *m = gsl_matrix_complex_alloc (M, N);
  gsl_vector *s = gsl_vector_alloc (L);
  gsl_matrix_complex *u = gsl_matrix_complex_alloc (M, N);
  gsl_matrix_complex *v = gsl_matrix_complex_alloc (M, N);

  int lwork = 2 * L + GSL_MAX (M, N);
  gsl_vector_complex *work = gsl_vector_complex_alloc (lwork);
  gsl_vector_complex *rwork = gsl_vector_complex_alloc (5 * L);

  int status;
  size_t i, j;

  for (i = 0; i < M; i++)
    for (j = 0; j < N; j++)
      {
	gsl_complex z = gsl_complex_xy (1.0 / (i + j + 1.0), 0.0);
	gsl_matrix_complex_set (m, i, j, z);
      }

  zgesvd_ ("A", "A",		/*  these are char * pointer arguments */
	   (int *) &(m->size1), (int *) &(m->size2),
	   m->data, (int *) &(m->tda),
	   s->data,
	   u->data, (int *) &(u->tda),
	   v->data, (int *) &(v->tda),
	   work->data, &lwork, rwork->data, &status);

  gsl_matrix_complex_fprintf (stdout, m, "%g");
  printf ("\n");
  gsl_matrix_complex_fprintf (stdout, u, "%g");
  printf ("\n");
  gsl_matrix_complex_fprintf (stdout, v, "%g");
  printf ("\n");

  gsl_vector_fprintf (stdout, s, "%g");
  printf ("\n");
}