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RE: [Help-glpk] OPB output file anomaly

From: Joey Rios
Subject: RE: [Help-glpk] OPB output file anomaly
Date: Fri, 29 Feb 2008 11:58:32 -0800

Thanks for the quick response Oscar.

> It is assumed that the coefficients are integers.

All coeff's and b's are integer in my model.

> But, from your explanation it seems like all the coefficients are zero,
> which is strange. Especially since you get an incorrect result when
> removing the empty constraints. (Clearly it would be good to check if
> there are any non-zero coefficients.)

Not too sure by what you mean by "check if there are any non-zero coeff".  If there were non-zero coeffs then we'd be talking about an error in glp_get_mat_row(), right?

> One possible reason is that your model generates some dummy constraints
> that breaks the model and that you also have fractional coefficients that
> are not well handled by the export function leading to an incorrect
> solution.

Everything is integer in the model.  I could see in the export function (lpx_write_pb()) where the coeff values are cast to ints, is this what you mean by 'not well handled'?  I can understand that, but the fact that I never get to that fprintf statement at all because k==0 seems like the issue here.  Any other thoughts about what I should inspect?

Oh, and thanks for writing this module in the first place, it should turn out to be handy for me,


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