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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).
>