<div>Hi,</div><div> </div><div>I tried to solve the problem instances with CPLEX and CPLEX could resolve the issue. So I think that was the problem of CLP as a solver in my code. </div><div> </div><div>Thanks,</div><div>Sepehr Nemati Proon<br>
<br></div><div class="gmail_quote">On Thu, Jun 28, 2012 at 12:17 PM, Francois Margot <span dir="ltr"><<a href="mailto:fmargot@andrew.cmu.edu" target="_blank">fmargot@andrew.cmu.edu</a>></span> wrote:<br><blockquote style="margin:0px 0px 0px 0.8ex;padding-left:1ex;border-left-color:rgb(204,204,204);border-left-width:1px;border-left-style:solid" class="gmail_quote">
Hi Sepher:<br>
<div><div class="h5"><br>
><br>
> During the implementation of my branch-and-price algorithm I have<br>
> encountered a problem when while doing branching, in some nodes, the<br>
> primal feasibility is being lost. I have tried to check the status by<br>
> using<br>
><br>
> getLpProblemPointer()->lp_solver->initialSolve() and it seems that<br>
> initialSolve() is ending with an optimal solution where it is not the case<br>
> when getLpProblemPointer()->lp_solver->resolve() is used. In the latter<br>
> case, the optimal basis is not avaialble and the primal feasibility is<br>
> being lost, for example, I get the following messages<br>
><br>
> LP: **** Processing NODE 7 on LEVEL 4 (dived) ****<br>
> LP: *** Starting iteration 1 ***<br>
> Clp0006I 0 Obj 1789 Primal inf 0.9999998 (2)<br>
> Clp0006I 1 Obj 1801<br>
> Clp0001I Primal infeasible - objective value 1801<br>
> LP: Matrix size: 81 vars x 16 cuts<br>
> LP: Solution value: 1801.0000 / 36 , 1<br>
> optimal basis is available () = 0<br>
> I should note that the during baranchig, I change the upper bounds of some<br>
> of variables, based on my branching decision and also I am not using<br>
> strong<br>
> branching. Also, it is not possible for my relaxed master problems to have<br>
> be primal infeasible because of the artificial variables that I have added<br>
> in the restricted master problem for having a feasibl solution in each<br>
> node<br>
> after branching.<br>
> The LP Solver that I am using is CLP and I am using Bcp-1.3.4 verision.<br>
<br>
</div></div>Can you try to run this with Cplex for example instead of Clp? If the<br>
issue appears only with Clp, it might be related with the Clp tickets<br>
<br>
<a href="https://projects.coin-or.org/Clp/ticket/54" target="_blank">https://projects.coin-or.org/Clp/ticket/54</a><br>
<a href="https://projects.coin-or.org/Clp/ticket/55" target="_blank">https://projects.coin-or.org/Clp/ticket/55</a><br>
<span class="HOEnZb"><font color="#888888"><br>
Francois<br>
<br>
<br>
</font></span></blockquote></div><br><br clear="all"><br>-- <br>Sepehr Nemati<br>PhD Student<br>Department of Industrial Engineering<br>University of Pittsburgh<br>