Hi,
I am trying to access constraint coefficient matrix. When I use function glp_get_num_rows, I am getting unexpected number of rows.
In model assign.mod (from standard glpk examples), there are 8 elements in each of set I and set J. So total number of constraints should be 16. But function glp_get_num_rows returns 17. Number of columns are as expected (64).
It seems that, glpk is counting obj. function as a constraint. Is this intentional behaviour? But there is separate function glp_get_obj_func for accessing obj. fun. coefficients.
Am I missing something obvious? I am using glpk 4.29, which I compiled myself. For some reason, instead of installing glpk, I copied libglpk.a and statically linked with my application (code below).
Whenever I get chance, I will try using some other version of the glpk and test against it.
------------------------------------
#include <stdio.h>
#include <stdlib.h>
#include <assert.h>
#include "glpk.h"
int main()
{
glp_prob * lp = NULL;
int row_cnt = 0, col_cnt = 0, row_nz_cnt;
int ri, ci;
lp = lpx_read_model("assign.mod", NULL, NULL);
assert(lp != NULL);
row_cnt = glp_get_num_rows(lp);
col_cnt = glp_get_num_cols(lp);
printf("row_cnt = %d, col_cnt = %d\n", row_cnt, col_cnt);
/* Access all matrix coefficients and print. */
/* Iterate over all rows. ri = 1 to row_cnt. */
for(ri = 1; ri <= row_cnt; ri++) {
int * ind = NULL;
double * val = NULL;
/* Non-zero coefficient count in the row. */
row_nz_cnt = glp_get_mat_row(lp, ri, NULL, NULL);
assert(row_nz_cnt != 0);
ind = (int*) calloc(row_nz_cnt + 1, sizeof(int));
val = (double*) calloc(row_nz_cnt + 1, sizeof(double));
glp_get_mat_row(lp, ri, ind, val);
/* Print coefficient/value. */
for(ci = 1; ci <= row_nz_cnt; ci++)
printf("%5.1lf ", val[ci]);
printf("\n");
free(ind); ind = NULL;
free(val); val = NULL;
}
glp_delete_prob(lp);
return 0;
}
-----------
address@hidden:~/projects/matrix$ ./test
Reading model section from assign.mod...
Reading data section from assign.mod...
77 lines were read
Generating phi...
Generating psi...
Generating obj...
Model has been successfully generated
row_cnt = 17, col_cnt = 64
1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0
1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0
1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0
1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0
1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0
1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0
1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0
1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0
1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0
1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0
1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0
1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0
1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0
1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0
1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0
1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0
43.0 37.0 31.0 45.0 17.0 5.0 20.0 26.0 24.0 22.0 40.0 34.0 3.0 38.0 34.0 16.0 46.0 28.0 16.0 14.0 15.0 39.0 19.0 42.0 48.0 12.0 34.0 24.0 18.0 45.0 6.0 21.0 40.0 11.0 22.0 12.0 8.0 7.0 54.0 34.0 37.0 13.0 21.0 26.0 36.0 13.0 32.0 35.0 8.0 4.0 11.0 40.0 41.0 25.0 36.0 12.0 11.0 22.0 26.0 8.0 12.0 20.0 21.0 13.0
--
Vijay Patil