[Coin-discuss] Feasibility of linear relaxation

[mathieu lacroix]

Hi,
I use BCP and CLP as an branch and cut solver for a mixed integer linear 
problem. I have tested my problem for many data. Allmost work well. But 
there is an error for one data file. I have an error : "LP : no var/cut 
in pool but couldn't select branching object.". The problem seems to 
come from the lp solver. Indeed, test_feasibility method is called after 
the LP is solved. Bcp has found that lp program has been solved to 
optimality (getLpProblemPointer()->lp_solver->isProvenOptimal () is 
equal to one) and an lp solution is send to method test_feasibility. But 
the given solution is not feasible (and the lp optimal value is negative 
although variables and cost are positive). In order to understand, I 
have change in the file BCP_lp_main_loop.cpp the command  
"p.lp_solver->resolve();" (used to solve the linear relaxation) by the 
command "p.lp_solver->initialSolve();". And now, it works fine (I obtain 
optimal solution). Is it normal that the two methods don't give the same 
thing? Does anybody have the same problem as me? if yes, how to correct 
it? I can give more informations if necessary.
Thank you

Best regards,

Mathieu LACROIX

-- 
Mathieu LACROIX
mathieu.lacroix at isima.fr
Université Blaise Pascal - Clermont Fd II
Laboratoire LIMOS
Bâtiment ISIMA - Bureau D112
Complexe scientifique des Cézeaux
63 177 Aubière, Cedex - France
Tel : 04.73.40.79.48
Fax : 04.73.40.76.39