[Cbc] CBC misses optimal solution depending on activation of cuts
john.forrest at fastercoin.com
Thu Oct 20 06:23:12 EDT 2011
Thanks for finding this. Because only one variable had a cost, Cbc
decides in its wisdom that it is worth trying strong branching on that
variable even if it is satisfied. This got into a part of the code
where it expects ceil(value)-value to be nonzero and bad things happened.
Should be fixed in trunk and 2.7
On 19/10/11 21:31, Haroldo Santos wrote:
> Dear Forrest/Ted,
> I have this surprisingly small MIP(few hundred of variables and
> constraints) where CBC misses the optimal solution if I deactivate cuts.
> CPLEX and GLPK instantlyfound the optimal solution (77) no matter if
> cuts/heuristics are activated or not.
> Cbc, however, found a sub-optimal solution (136 or 124, depending on
> the machine) when I deactivate cuts and declares is as optimal. There
> are no very large/small coefficients so this is not due to numerical
> cbc C_I_6_4_S_1-124_1.lp cuts off solve (wrong result)
> If I call cbc with cuts
> cbc C_I_6_4_S_1-124_1.lp cuts on solve (correct result)
> 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/
> "Computer science is no more about computers than astronomy
> is about telescopes." Edsger Dijkstra
> Cbc mailing list
> Cbc at list.coin-or.org
-------------- next part --------------
An HTML attachment was scrubbed...
More information about the Cbc