Re: [Help-glpk] not retrieving integer solutions

[Robbie Morrison]

Hello Marc

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To:          "address@hidden" <address@hidden>
Subject:      [Help-glpk] not retrieving integer solutions
Message-ID:  <address@hidden>
From:        "Meketon, Marc" <address@hidden>
Date:         Thu, 12 Jul 2012 17:14:39 -0500
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> I am solving a small integer program (37 rows and 29
> columns) using the C# interface from
> http://yoyovicks.blog.free.fr/
>
> I've tested the code on quite a few datasets and it
> worked fine.  But today I changed some objective
> function coefficients (just changed the sign of them),
> and for one particular problem I'm retrieving
> non-integer results despite the fact that an integer
> optimal was found.
>
> [snip: code and results]
>
> Would anyone have a guess why the output is non-integer
> despite solving to integer optimality and
> double-checking that these variables are integer?
>
> BTW, when I write the problem out to GLPK format, and
> solve it using glpsol, the output is fully integer.

Please see:

  
http://en.wikibooks.org/wiki/GLPK/Troubleshooting#Continuous_solution_to_mixed-integer_problem

Could a be a bug in the C# wrapper or your
use of the wrong calls?

(Given C# supports polymorphism, could this
wrapper not be written to proved the correct
recovery using a generic interface?)

Robbie
---
Robbie Morrison
PhD student -- policy-oriented energy system simulation
Institute for Energy Engineering (IET)
Technical University of Berlin (TU-Berlin), Germany
University email (redirected) : address@hidden
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