[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [Help-glpk] [Fwd: Difference between glpsol and C-API]
From: |
Andrew Makhorin |
Subject: |
Re: [Help-glpk] [Fwd: Difference between glpsol and C-API] |
Date: |
Sun, 02 Mar 2014 18:32:27 +0400 |
> I have a question concerning the difference between glpsol and the C-API
> of glpk.
>
> The attached C source code file test.c contains a very tiny linear
> optimization problem, the problem gets solved by glp_simplex and the
> value of the objective function and of the primary variables after
> optimization are printed out. Before the optimization, the problem will
> be written to an lp file test.lp.
>
> Using this file with glpsol, gives another result than the C-API
> (objective value stays the same, but the values of the variables differ
> in some cases).
>
> glpsol --lp test.lp -o test.sol
>
> I am using glpk version 4.45 on debian wheezy (stable).
Please note that the most recent version is 4.53.
>
> Is there any explanation for this behavior?
>
This usually happens when the lp is dual degenerate, in which case it
has multiple optima. (Imagine that the objective function is zero; then
every feasible solution would be optimal.) If, for example, you don't
use the lp presolver and/or scaling while glpsol does (by default), you
may obtain different optimal solutions.
[Prev in Thread] |
Current Thread |
[Next in Thread] |
- Re: [Help-glpk] [Fwd: Difference between glpsol and C-API],
Andrew Makhorin <=