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## Re: [Help-glpk] Feed GLPK with feasible initial solution?

 From: Andrew Makhorin Subject: Re: [Help-glpk] Feed GLPK with feasible initial solution? Date: Tue, 25 Sep 2007 21:20:39 +0400

```> I have a MIP Problem which I can provide feasible solutions very
> easily. How can I feed the GLPK MIP Solver with a feasible solution,
> to help him.

Unfortunately you cannot do that in MathProg.

>  Running the solver without any help it takes a lot of
> time and can #39;t get even a feasible solution. Do you have a small
> example of this?

> P.S
> . An instance of my model is this one:

I tried you model using glpsol 4.22 (see the log below). The solver
found several integer feasible solutions for 60 secs, however, your
model seems to be hard for glpk.

Generating cost...
Generating R0...
Generating R1...
Generating R2...
Generating R3...
Generating R4...
Generating R5...
Model has been successfully generated
glp_simplex: original LP has 300 rows, 155 columns, 802 non-zeros
glp_simplex: presolved LP has 278 rows, 155 columns, 780 non-zeros
lpx_adv_basis: size of triangular part = 278
0:   objval =   0.000000000e+00   infeas =   1.000000000e+00 (0)
156:   objval =   1.733333333e+01   infeas =   0.000000000e+00 (0)
*   156:   objval =   1.733333333e+01   infeas =   0.000000000e+00 (0)
*   159:   objval =   1.233333333e+01   infeas =   0.000000000e+00 (0)
OPTIMAL SOLUTION FOUND
Integer optimization begins...
+   337: >>>>>   8.416000000e+01 >=   1.233333333e+01  85.3% (104; 0)
+   516: >>>>>   8.188000000e+01 >=   1.233333333e+01  84.9% (179; 7)
+   831: >>>>>   8.185333333e+01 >=   1.233333333e+01  84.9% (319; 9)
+  1006: >>>>>   7.954666667e+01 >=   1.738666667e+01  78.1% (389; 10)
+  1280: >>>>>   7.726666667e+01 >=   1.738666667e+01  77.5% (557; 12)
+  1408: >>>>>   7.493333333e+01 >=   1.738666667e+01  76.8% (634; 13)
+  2330: >>>>>   7.488000000e+01 >=   1.738666667e+01  76.8% (1062; 26)
+  3842: mip =   7.488000000e+01 >=   2.016000000e+01  73.1% (1691; 38)
+  4423: >>>>>   7.270666667e+01 >=   2.238666667e+01  69.2% (1914; 43)
+  5845: mip =   7.270666667e+01 >=   2.241333333e+01  69.2% (2480; 60)
+  6475: >>>>>   7.265333333e+01 >=   2.241333333e+01  69.2% (2741; 64)
+  7022: >>>>>   7.260000000e+01 >=   2.241333333e+01  69.1% (2923; 73)
+  8680: mip =   7.260000000e+01 >=   2.241333333e+01  69.1% (3469; 100)
+ 10446: mip =   7.260000000e+01 >=   2.244000000e+01  69.1% (4117; 114)
+ 12226: mip =   7.260000000e+01 >=   2.244000000e+01  69.1% (4767; 131)
+ 12458: >>>>>   7.037333333e+01 >=   2.244000000e+01  68.1% (4877; 132)
+ 14129: mip =   7.037333333e+01 >=   2.244000000e+01  68.1% (5365; 178)
+ 15993: mip =   7.037333333e+01 >=   2.244000000e+01  68.1% (5990; 194)
+ 17871: mip =   7.037333333e+01 >=   2.469333333e+01  64.9% (6670; 209)
+ 19853: mip =   7.037333333e+01 >=   2.469333333e+01  64.9% (7384; 226)
+ 21032: mip =   7.037333333e+01 >=   2.469333333e+01  64.9% (7801; 237)
TIME LIMIT EXCEEDED; SEARCH TERMINATED
Time used:   60.0 secs
Memory used: 5.8 Mb (6112853 bytes)

```