GSL: Bugs

[flexoron]

This bundle is mathematically error free:

matrix_calloc
permutation_alloc
LU_decomp
LU_det

Exercisers:

$ cat x.c
#include <stdio.h>
#include <gsl/gsl_version.h>
#include <gsl/gsl_linalg.h>

int main (int argc, char *argv[]) {
  int sig, stat;
  double det;
  int rows = atoi(argv[1]);
  int cols = atoi(argv[2]);
  printf("v%s %dx%d\n",GSL_VERSION,rows,cols);
  gsl_matrix *mat = gsl_matrix_calloc(rows, cols);
  gsl_permutation *perm = gsl_permutation_alloc(rows);
  stat = gsl_linalg_LU_decomp(mat, perm, &sig);
   det = gsl_linalg_LU_det(mat, sig);
  printf("%lf\n",det);
  gsl_permutation_free(perm);
  gsl_matrix_free(mat);
  return 0;
}

$ cat x.pl
:- use_module(library(gsl)).
tst(Rows,Cols)  :-
              gsl_matrix_calloc(Rows, Cols, M),
              gsl_permutation_alloc(Rows, P),
              gsl_linalg_LU_decomp(M, P, Sig, Stat),
              gsl_linalg_LU_det(M, Sig, Det),
              write(Det),nl,
              gsl_permutation_free(P),
              gsl_matrix_free(M).

RESULTS:

GSL 2.7.1
$ ./a.out 127 127
v2.7.1 127x127
-nan  #  Libgsl: known bug in v2.7
$ 
$ tpl x.pl
?- tst(127,127).
-.0nan   % Trealla morphs -nan into -.0nan
   true.
?- halt.
$

GSL 2.8
$ ./a.out 127 127
v2.8 127x127
: 
# printf in function gsl_linalg_LU_decomp() of gsl-git/linalg/lu.c
# convert ipiv array to permutation
# unsigned int pivi = gsl_vector_uint_get(ipiv, i);
:  
FF pivi 13 i 13  
FF pivi 14 i 14
FF pivi 15 i 15
FF pivi 0 i 16  #  Trealla Crash here
FF pivi 0 i 17
FF pivi 0 i 18
: 
FF pivi 0 i 124
FF pivi 0 i 125
FF pivi 0 i 126
-0.000000   # expected, v2.7 bug '-nan' has been fixed
$

$ tpl x.pl
?- tst(127,127).  % First Call
: 
FF pivi 13 i 13
FF pivi 14 i 14
FF pivi 15 i 15
FF pivi 210299952 i 16  % looks like Trealla puts an address somewhere in an array
Segmentation fault (core dumped)
$