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[Help-glpk] Re: Simplex method infeasible, IP method feasible
From: |
Andrew Makhorin |
Subject: |
[Help-glpk] Re: Simplex method infeasible, IP method feasible |
Date: |
Thu, 11 Sep 2003 23:46:21 +0400 |
>>
>> Why infeasible? I tried your example with both simplex and interior.
>> Here are the results below.
>
> Ok, but If you check the constraints, A*xmin -b <= 0, you'll find that
> some constraints are violated:
Please pull the model from my previous message, name it infeas.mod,
and run the following program:
------------------------------------------------------------------------
#include <stdlib.h>
#include "glpk.h"
int main(void)
{ LPX *lp; int j; double x[1+3];
lp = lpx_read_model("infeas.mod", NULL, NULL);
insist(lp != NULL);
insist(lpx_get_num_cols(lp) == 3);
lpx_simplex(lp);
for (j = 1; j <= 3; j++)
{ lpx_get_col_info(lp, j, NULL, &x[j], NULL);
print("x[%d] = %22.15e", j, x[j]);
}
print("a[1] * x - b[1] = %22.15e",
-1*x[1] + 1*x[2] + 1*x[3] - 0);
print("a[2] * x - b[2] = %22.15e",
1*x[1] + 0*x[2] + 0*x[3] - 68.855);
print("a[3] * x - b[3] = %22.15e",
0*x[1] -0.22252*x[2] + 0.97493*x[3] - 39.483);
print("a[4] * x - b[4] = %22.15e",
0*x[1] -0.90097*x[2] + 0.43388*x[3] - 5.2338);
print("a[5] * x - b[5] = %22.15e",
0*x[1] -0.90097*x[2] -0.43388*x[3] - (-73.042));
print("a[6] * x - b[6] = %22.15e",
0*x[1] + 0.62349*x[2] -0.78183*x[3] - 76.044);
lpx_delete_prob(lp);
return 0;
}
------------------------------------------------------------------------
You will see the following:
Reading model section from infeas.mod...
Reading data section from infeas.mod...
31 lines were read
Generating Z...
Generating row...
Model has been successfully generated
0: objval = -1.000000000e+06 infeas = 1.000000000e+00 (0)
4: objval = 6.885450326e+01 infeas = 0.000000000e+00 (0)
OPTIMAL SOLUTION FOUND
x[1] = 6.885450325591295e+01
x[2] = 9.241775273999546e+01
x[3] = -2.356324948408252e+01
a[1] * x - b[1] = 0.000000000000000e+00
a[2] * x - b[2] = -4.967440870586870e-04
a[3] * x - b[3] = -8.302031715922035e+01
a[4] * x - b[4] = -9.872304537230744e+01
a[5] * x - b[5] = 6.765421556309548e-15
a[6] * x - b[6] = 1.025568518997488e-14
Best regards,
Andrew Makhorin
- [Help-glpk] Simplex method infeasible, IP method feasible, Nicolo' Giorgetti, 2003/09/09
- [Help-glpk] Re: Simplex method infeasible, IP method feasible, Andrew Makhorin, 2003/09/10
- Re: [Help-glpk] Re: Simplex method infeasible, IP method feasible, Nicolo' Giorgetti, 2003/09/11
- [Help-glpk] Re: Simplex method infeasible, IP method feasible,
Andrew Makhorin <=
- Re: [Help-glpk] Re: Simplex method infeasible, IP method feasible, Nicolo' Giorgetti, 2003/09/12
- [Help-glpk] Re: Simplex method infeasible, IP method feasible, Andrew Makhorin, 2003/09/12
- [Help-glpk] Re: Simplex method infeasible, IP method feasible, Nicolo' Giorgetti, 2003/09/12
- [Help-glpk] Re: Simplex method infeasible, IP method feasible, Andrew Makhorin, 2003/09/12
- Re: [Help-glpk] Re: Simplex method infeasible, IP method feasible, Nicolo' Giorgetti, 2003/09/13
- [Help-glpk] Re: Simplex method infeasible, IP method feasible, Andrew Makhorin, 2003/09/11