[Symphony] Incorrect solution for a simple linear programming model

[Ted Ralphs]

Sorry for the delay. Since this problem is an LP and does get pre-processed
by SYMPHONY, it is simply passed through to the LP solver, which is Clp by
default. This must be a bug in Clp. It seems to be related to some bugs
reported on other mailing lists. I will check into it. I suppose it should
be a simple fix.

Cheers,

Ted

On Thu, Jul 19, 2012 at 4:46 PM, Federico Larumbe <
federico.larumbe at polymtl.ca> wrote:

> Hi,
>
> I am testing Symphony with a simple example in AMPL format:
>
> symphony -F file.mod -D file.dat
>
> -- file.mod ------------------
> var y >= 0;
>
> minimize ObjectiveFunction: y;
>
> subject to C1:   y >= 1.0;
> subject to C2:   y <= 2.0;
> subject to C3:   y  = 1.1;
>
> end;
> ------------------------------
>
> -- file.dat ------------------
> data;
> end;
> ------------------------------
>
>
> The solution given by the program is 2.0 instead of 1.1 (see attached
> file). If I choose maximize, the solution is 1.0. If I remove C3, the
> problem is unbounded. Is there any option that I missing?
>
> I compiled Sympthony in SUSE Linux with gcc 4.5.1 with the following
> commands:
>
> ./configure --with-gmpl --enable-openm
> make
>
>
> Thanks a lot,
> Federico.
>
> --
> Federico Larumbe
> École Polytechnique de Montréal
> Montréal H3C 3A9
>
> Group for Research in Decision Analysis (GERAD)
> tel   +1 514 3406053 xt 6931
> fax   +1 514 3405665
> http://www.gerad.ca/en/directory/details.php?id=1214
>
> _______________________________________________
> Symphony mailing list
> Symphony at list.coin-or.org
> http://list.coin-or.org/mailman/listinfo/symphony
>
>


-- 
Dr. Ted Ralphs
Associate Professor, Lehigh University
(610) 628-1280
ted 'at' lehigh 'dot' edu
coral.ie.lehigh.edu/~ted <http://coral.ie.lehigh.edu/%7Eted>
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