[Cbc] Pre-Processing Bug
john.forrest at fastercoin.com
Sat Jan 21 09:38:40 EST 2012
Is this in trunk or stable?
I just tried it in trunk and it stopped at line 154 of main.cpp saying
INFEASIBLE. However this is because the code says
printf("Optimal solution found.\n");
which looks the wrong way round. So it seems OK in trunk.
On 20/01/12 18:35, Haroldo Santos wrote:
> I think I've found a bug in pre-processing phase of CBC.
> What I was doing (and worked flawlessly for all MIPs except this one)
> was to inform to CBC a feasible solution found using a greedy
> heuristic. This solution was informed considering variables of the
> pre-processed model (checking for the original variables in
> originalColumns() ).
> What happened is that the pre-processed model for this case included a
> new set of constraints (expected) which make this valid solution to be
> considered infeasible (unexpected). When I fix the same set of
> variables in the original LP there is no problem.
> To make it easy to check for this problem I've wrote a small code
> which fixes the same variables in the original and in the
> pre-processed problem and made it available here:
> In infRows.txt I listed tree constraints that when removed allows
> feasibility to be obtained again.
> Thanks in advance,
> Haroldo Gambini Santos
> Computing Department - Universidade Federal de Ouro Preto - UFOP
> email: haroldo [at ] iceb.ufop.br <http://iceb.ufop.br>
> home/research page: www.decom.ufop.br/haroldo/
> Cbc mailing list
> Cbc at list.coin-or.org
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