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Re: [Help-glpk] glp_find_col
From: |
Andrew Makhorin |
Subject: |
Re: [Help-glpk] glp_find_col |
Date: |
Fri, 04 Sep 2015 12:44:26 +0300 |
On Fri, 2015-09-04 at 11:06 +0200, Yaser Tohidi wrote:
> No, I have assigned a name to jth column. When I print "name" the name
> of jth column is shown.
> The problem is that I want to use glp_find _col. I use the same "name"
> coming from glp_get_col_name but glp_find_col returns zero.
> I hope it's clear now.
>
> On Thu, Sep 3, 2015 at 8:53 PM, Andrew Makhorin <address@hidden> wrote:
> On Thu, 2015-09-03 at 16:36 +0200, Yaser Tohidi wrote:
> > I cannot use "glp_find_col". It retrieves zero always even I
> use the
> > following code. I also create index at the beginning by
> > glp_create-index.
> >
> >
> > const char *name;
> > name= glp_get_col_name(lp1,j);
> > i=glp_find_col(lp1,name);
> >
> >
> >
> > Please let me know what I'm missing.
> >
>
>
> Looks like you didn't assign a name to j-th column, so
> glp_get_col_name
> returns NULL.
>
>
>
>
>
Please check you code. The following example works fine for me:
/* sample.c */
#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;
s1: lp = glp_create_prob();
s2: glp_set_prob_name(lp, "sample");
s3: glp_set_obj_dir(lp, GLP_MAX);
s4: glp_add_rows(lp, 3);
s5: glp_set_row_name(lp, 1, "p");
s6: glp_set_row_bnds(lp, 1, GLP_UP, 0.0, 100.0);
s7: glp_set_row_name(lp, 2, "q");
s8: glp_set_row_bnds(lp, 2, GLP_UP, 0.0, 600.0);
s9: glp_set_row_name(lp, 3, "r");
s10: glp_set_row_bnds(lp, 3, GLP_UP, 0.0, 300.0);
s11: glp_add_cols(lp, 3);
s12: glp_set_col_name(lp, 1, "x1");
s13: glp_set_col_bnds(lp, 1, GLP_LO, 0.0, 0.0);
s14: glp_set_obj_coef(lp, 1, 10.0);
s15: glp_set_col_name(lp, 2, "x2");
s16: glp_set_col_bnds(lp, 2, GLP_LO, 0.0, 0.0);
s17: glp_set_obj_coef(lp, 2, 6.0);
s18: glp_set_col_name(lp, 3, "x3");
s19: glp_set_col_bnds(lp, 3, GLP_LO, 0.0, 0.0);
s20: glp_set_obj_coef(lp, 3, 4.0);
s21: ia[1] = 1, ja[1] = 1, ar[1] = 1.0; /* a[1,1] = 1 */
s22: ia[2] = 1, ja[2] = 2, ar[2] = 1.0; /* a[1,2] = 1 */
s23: ia[3] = 1, ja[3] = 3, ar[3] = 1.0; /* a[1,3] = 1 */
s24: ia[4] = 2, ja[4] = 1, ar[4] = 10.0; /* a[2,1] = 10 */
s25: ia[5] = 3, ja[5] = 1, ar[5] = 2.0; /* a[3,1] = 2 */
s26: ia[6] = 2, ja[6] = 2, ar[6] = 4.0; /* a[2,2] = 4 */
s27: ia[7] = 3, ja[7] = 2, ar[7] = 2.0; /* a[3,2] = 2 */
s28: ia[8] = 2, ja[8] = 3, ar[8] = 5.0; /* a[2,3] = 5 */
s29: ia[9] = 3, ja[9] = 3, ar[9] = 6.0; /* a[3,3] = 6 */
s30: glp_load_matrix(lp, 9, ia, ja, ar);
s31: glp_simplex(lp, NULL);
s32: z = glp_get_obj_val(lp);
s33: x1 = glp_get_col_prim(lp, 1);
s34: x2 = glp_get_col_prim(lp, 2);
s35: x3 = glp_get_col_prim(lp, 3);
s36: printf("\nz = %g; x1 = %g; x2 = %g; x3 = %g\n",
z, x1, x2, x3);
#if 1
{ int j;
const char *name;
glp_create_index(lp);
for (j = 1; j <= 3; j++)
{ name = glp_get_col_name(lp, j);
printf("name = |%s| find_col = %d\n",
name, glp_find_col(lp, name));
}
}
#endif
s37: glp_delete_prob(lp);
return 0;
}
/* eof */
address@hidden:~/Desktop$ gcc sample.c -lglpk
address@hidden:~/Desktop$ ./a.out
GLPK Simplex Optimizer, v4.45
3 rows, 3 columns, 9 non-zeros
* 0: obj = 0.000000000e+00 infeas = 0.000e+00 (0)
* 2: obj = 7.333333333e+02 infeas = 0.000e+00 (0)
OPTIMAL SOLUTION FOUND
z = 733.333; x1 = 33.3333; x2 = 66.6667; x3 = 0
name = |x1| find_col = 1
name = |x2| find_col = 2
name = |x3| find_col = 3
address@hidden:~/Desktop$