<font face="arial,helvetica,sans-serif">Dear Forrest/Ted,<br><br>I have this surprisingly small </font><font face="arial,helvetica,sans-serif">MIP</font><font face="arial,helvetica,sans-serif"> (few hundred of variables and constraints) where CBC misses the optimal solution if I deactivate cuts.<br>
<br><a href="http://www.decom.ufop.br/haroldo/files/C_I_6_4_S_1-124_1.lp">http://www.decom.ufop.br/haroldo/files/C_I_6_4_S_1-124_1.lp</a><br><br>CPLEX and GLPK instantly</font><font face="arial,helvetica,sans-serif"> </font><font face="arial,helvetica,sans-serif">found the optimal solution (77) no matter if cuts/heuristics are activated or not.<br>
<br>Cbc, however, found a sub-optimal solution (136 or 124, depending on the machine) when I deactivate cuts and declares is as optimal. </font><font face="arial,helvetica,sans-serif">There are no very large/small coefficients so this is not due to numerical instability.</font><br>
<font face="arial,helvetica,sans-serif"><br>cbc C_I_6_4_S_1-124_1.lp cuts off solve (wrong result)<br><br>If I call cbc with cuts<br><br></font><font face="arial,helvetica,sans-serif">cbc C_I_6_4_S_1-124_1.lp cuts on solve (correct result)</font><br>
<br>Cheers,<br><br>Haroldo<br clear="all"><br>-- <br>=============================================================De<br>Haroldo Gambini Santos<br>Computing Department - Universidade Federal de Ouro Preto - UFOP<br>email: haroldo [at ] <a href="http://iceb.ufop.br" target="_blank">iceb.ufop.br</a><br>
home/research page: <a href="http://www.decom.ufop.br/haroldo/" target="_blank">www.decom.ufop.br/haroldo/</a><br> <br>"Computer science is no more about computers than astronomy <br>is about telescopes." Edsger Dijkstra<br>
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