[Bug-glpk] Crash in glp_interior

[Jiri Spitz]

Hi,

I modified the introductory example from the manual to use the 
interior-point method:

#include <stdio.h>
#include <stdlib.h>
#include <glpk.h>
int main(void)
{
   glp_prob *lp;
   int ia[1+1000], ja[1+1000];
   double ar[1+1000], z, x1, x2, x3;
   lp = glp_create_prob();
   glp_set_prob_name(lp, "sample");
   glp_set_obj_dir(lp, GLP_MAX);
   glp_add_rows(lp, 3);
   glp_set_row_name(lp, 1, "p");
   glp_set_row_bnds(lp, 1, GLP_UP, 0.0, 100.0);
   glp_set_row_name(lp, 2, "q");
   glp_set_row_bnds(lp, 2, GLP_UP, 0.0, 600.0);
   glp_set_row_name(lp, 3, "r");
   glp_set_row_bnds(lp, 3, GLP_UP, 0.0, 300.0);
   glp_add_cols(lp, 3);
   glp_set_col_name(lp, 1, "x1");
   glp_set_col_bnds(lp, 1, GLP_LO, 0.0, 0.0);
   glp_set_obj_coef(lp, 1, 10.0);
   glp_set_col_name(lp, 2, "x2");
   glp_set_col_bnds(lp, 2, GLP_LO, 0.0, 0.0);
   glp_set_obj_coef(lp, 2, 6.0);
   glp_set_col_name(lp, 3, "x3");
   glp_set_col_bnds(lp, 3, GLP_LO, 0.0, 0.0);
   glp_set_obj_coef(lp, 3, 4.0);
   ia[1] = 1, ja[1] = 1, ar[1] = 1.0;
   ia[2] = 1, ja[2] = 2, ar[2] = 1.0;
   ia[3] = 1, ja[3] = 3, ar[3] = 1.0;
   ia[4] = 2, ja[4] = 1, ar[4] = 10.0;
   ia[5] = 3, ja[5] = 1, ar[5] = 2.0;
   ia[6] = 2, ja[6] = 2, ar[6] = 4.0;
   ia[7] = 3, ja[7] = 2, ar[7] = 2.0;
   ia[8] = 2, ja[8] = 3, ar[8] = 5.0;
   ia[9] = 3, ja[9] = 3, ar[9] = 6.0;
   glp_load_matrix(lp, 9, ia, ja, ar);
   glp_interior(lp, NULL);
   z = glp_ipt_obj_val(lp);
   x1 = glp_ipt_col_prim(lp, 1);
   x2 = glp_ipt_col_prim(lp, 2);
   x3 = glp_ipt_col_prim(lp, 3);
   printf("\nz = %g; x1 = %g; x2 = %g; x3 = %g\n", z, x1, x2, x3);
   glp_delete_prob(lp);
   return 0;
}


It compiles and runs but finishes with a null pointer:

address@hidden:~/pure/glpk/pure-glpk$ ./ipt_test
Original LP has 3 row(s), 3 column(s), and 9 non-zero(s)
Working LP has 3 row(s), 6 column(s), and 12 non-zero(s)
Matrix A has 12 non-zeros
Matrix S = A*A' has 6 non-zeros (upper triangle)
Approximate minimum degree ordering (AMD)...
xfree: ptr = (nil); null pointer
Error detected in file glplib07.c at line 175
Aborted
address@hidden:~/pure/glpk/pure-glpk$


There seems to be something wrong with the parameter block in the 
glp_interior call. When I define the parameter block, try to change the 
ordering method and pass the block to glp_interior I always receive 
precisely the same output including AMD ordering method.

Other problems loaded from MPS files are solved. However, any attempt to 
change the ordering method is ignored.

I am using glpk version 4.38 under Kubuntu 9.04 with gcc 4.3.3. The same 
example worked well with glpk 4.37.


BTW, there is a typo in the paragraph 2.8.2 of the manual:

there should be the synopsis

   void glp_ipt_status(glp_prob *lp);

instead of

   int glp_ipt_status(glp_prob *lp);


Regards,

Jiri Spitz