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Re: [Help-glpk] un reduced filed

From: Kevin Hunter
Subject: Re: [Help-glpk] un reduced filed
Date: Sun, 07 Nov 2010 01:50:03 -0400
User-agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv: Gecko/20101027 Thunderbird/3.1.6

At 7:29pm -0400 Sat, 06 Nov 2010, Andrew Makhorin wrote:
Right.  I'm aware that I don't need to specify them, but they're in the
LP output of another like program, with which I've recently become
acquainted.  I'm asking why does GLPK leaves them in?  Aren't they

Do you mean that the lp file produced by glpsol contains zero
coefficients (except cases I mentioned in my previous mail)? If so, it
is a bug, not a feature. Please post me an example. Thanks.

Heh, since GLPK is not the only solver that does this, I had assumed it was something I didn't understand. (Gurobi also leaves the zero-coefficient terms in.) I'm somewhat relieved to know that perhaps I /did/ understand it. I'm a relative weakling/noob to the OR world.

Here's an LP file that recreates the 0-coefficient terms that I'm seeing. (Note that I'm aware that the LP file is horribly put together.) With this example file, GLPK appears to leave 0-coefficient terms not only in the objective function, but also in later constraints. [27KiB]

The version of GLPK, and what I'm doing:

$ glpsol --version | head -1 ;
GLPSOL: GLPK LP/MIP Solver, v4.43

$ glpsol --lp tmp.lp --wlp tmp.glpk.lp --check



P.S. Where is the repository? All I see on the page is the release tarballs. I would like to check out the HEAD from time to time.

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