Re: [Help-glpk] un reduced filed

[Kevin Hunter]

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
> > superfluous.
>
> 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.

http://cygnus.ce.ncsu.edu/~kevin/tmp/leaves_zero_coeffs.lp.xz [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
 [...]

Cheers,

Kevin

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