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## Re: [Help-glpk] Undefined or infeasible solution?

**From**: |
Andrew Makhorin |

**Subject**: |
Re: [Help-glpk] Undefined or infeasible solution? |

**Date**: |
Wed, 11 Sep 2013 21:45:46 +0400 |

>* I've been trying different solvers for my mixed integer programming*
>* problems. For a specific problem (LP file:*
>* http://pastebin.com/3tih0fqg), I get a INTEGER UNDEFINED status with*
>* GLPK. However, I believe the correct status should be no integer*
>* feasible solution which is what I get when I use CBC from COIN-OR.*
>* *
>* The solution output file for this problem is:*
>* *
>* Problem: *
>* Rows: 47*
>* Columns: 1345 (1344 integer, 1344 binary)*
>* Non-zeros: 1633*
>* Status: INTEGER UNDEFINED*
>* Objective: OBJ = 0 (MINimum)*
>* *
>* Any clue as to why GLPK is returning an undefined status instead of an*
>* infeasible one for this problem?*
This may happen when infeasibility is detected by the mip preprocessor
(not by the mip solver), which _erroneously_ does not change the mip
solution status, so it remains undefined. In any case, if you see on the
terminal something like follows:
Preprocessing...
PROBLEM HAS NO PRIMAL FEASIBLE SOLUTION
it means that no integer feasible solution exists.
>* *
>* I'm using GLPK version 4.52.1 . I've also got the output from it*
>* (http://pastebin.com/ysQiktir).*
>* *