[Bug-gsl] bug in SVD

[Darren Wilkinson]

There is a bug in the SVD routine in the linalg section of the library which 
causes the SVD routine to hang when given certain matrices as input. The 
attached short program illustrates the problem.

I'm not certain which version of the library I'm using (sorry), but it is the 
binary version in the current stable release of Debian, so it's certainly not 
ancient - I think it is 1.1.1.

Cheers,
--
Darren Wilkinson   Email:  address@hidden
                     WWW:  www.darrenjwilkinson.btinternet.co.uk

/*
svd-test.c

test out GSL SVD code

gcc -lgsl -lgslcblas svd-test.c -o svd-test

*/

#include <gsl/gsl_matrix.h>
#include <gsl/gsl_linalg.h>

int main(void)
{
  gsl_matrix *A,*V;
  gsl_vector *S,*work;

  A=gsl_matrix_calloc(3,3);
  V=gsl_matrix_calloc(3,3);
  S=gsl_vector_calloc(3);
  work=gsl_vector_calloc(3);

  gsl_matrix_set(A,0,0,0);
  gsl_matrix_set(A,0,1,1);
  gsl_matrix_set(A,0,2,0);

  gsl_matrix_set(A,1,0,0);
  gsl_matrix_set(A,1,1,0);
  gsl_matrix_set(A,1,2,1);

  gsl_matrix_set(A,2,0,0);
  gsl_matrix_set(A,2,1,-1);
  gsl_matrix_set(A,2,2,-1);

  printf("gets to here\n");
  gsl_linalg_SV_decomp(A,V,S,work);
  printf("doesn't get to here\n");

  return(0);
}

/* eof */