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Re: [Help-glpk] post-processing without defined variables?


From: glpk xypron
Subject: Re: [Help-glpk] post-processing without defined variables?
Date: Mon, 02 Jul 2012 07:45:34 +0200

Hello Kevin,

either you can use the GLPK library from another programming language (C, Java, 
...) or you can use scripting around glpsol, cf.
http://en.wikibooks.org/wiki/GLPK/Scripting_plus_MathProg

Best regards

Xypron

-------- Original-Nachricht --------
> Datum: Sat, 30 Jun 2012 19:52:41 -0400
> Betreff: [Help-glpk] post-processing without defined variables?

> Hello GLPK List,
> 
> I see from the GLPK Wikibook that there's no ability to create reporting 
> variables (err, just learned that others call them "defined variables").
> 
> https://en.wikibooks.org/wiki/GLPK/GMPL_Workarounds#Mimicking_an_AMPL_defined_variable
> 
> I want to explore the last sentence in that section ("But you can use a 
> structural variable and a constraint instead to achieve the same effect 
> — the downside being that this formulation may render your problem 
> harder to solve").  The models that I'm working with are necessarily 
> large (roughly 1e5 [C] x 1e5 [R], give or take an order of magnitude 
> depending on the input), and I'd like to avoid adding any more variables 
> to the solver's matrix.
> 
> Given that I can't create constraints /after/ a solve statement (i.e. to 
> re-solve starting from the previous solution), does that mean that my 
> only option is a post-GMPL step with another tool (e.g. C, Perl, Python)?
> 
> Thanks,
> 
> Kevin
> 
> 
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