<html><head><meta http-equiv="Content-Type" content="text/html charset=us-ascii"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class=""><div><div class=""><meta http-equiv="Content-Type" content="text/html charset=us-ascii" class=""><div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class=""><div class=""></div><div class=""><br class=""></div><div class="">The cause of the huge effort to solve your problem are the products of the variables in your objective function:</div><div class=""><br class=""></div><div class=""><span class="Apple-tab-span" style="white-space:pre"> </span><i class="">revenue: sum{i in depts, j in locs, m in depts, o in depts, n in loc1, p in loc2, u in level: <br class=""><span class="Apple-tab-span" style="white-space:pre"> </span>c[i,j] * x[i,j] + <br class=""><span class="Apple-tab-span" style="white-space:pre"> </span><b class="">x[m, n] * x[o, p]</b> * adj[u, n, p] * rev[u, m, o]<br class=""><span class="Apple-tab-span" style="white-space:pre"> </span>} -> max;</i></div><div class=""><br class=""></div><div class="">This is a non-linear term. Cmpl reformulates such products of binary variables equivalently by a set of in-equations. Please take a look at the pages 46ff in the manual. The size of the model after the reformulations isn't very huge but the structure is quite complicated for the solver.</div><div class=""><br class=""></div><div class="">Isn't there a different way to formulate your model and to avoid products of variables. It seems that it is a multistage transportation model, for that it could be possible to find alternative formulations. </div><div class=""><br class=""></div><div class="">If you can't reformulate it then I would like to propose to use Cplex or Gurobi. You can obtain a free version via the IBM academic initiative or via the Gurobi web page. </div><div class=""><a href="https://www.ibm.com/developerworks/community/blogs/jfp/entry/cplex_studio_in_ibm_academic_initiative?lang=en" class="">https://www.ibm.com/developerworks/community/blogs/jfp/entry/cplex_studio_in_ibm_academic_initiative?lang=en</a></div><div class=""><a href="http://www.gurobi.com/products/licensing-and-pricing/academic-licensing" class="">http://www.gurobi.com/products/licensing-and-pricing/academic-licensing</a></div><div class=""><br class=""></div><div class="">For both solvers Cmpl's solutionPool feature can be used that can be combined with a mip gap to decrease the computation times. </div><div class="">You can use the following Cmpl header entries for Cplex:</div><div class=""><div class=""><i class="">%arg -solver cplex</i></div><div class=""><i class="">%opt cplex mip/tolerances/mipgap 0.10</i></div><div class=""><i class="">%display solutionPool</i></div></div><div class=""><br class=""></div><div class=""><br class=""></div><div class="">Cheers,</div><div class=""><br class=""></div><div class="">Mike</div><div class=""><br class=""></div><div class=""> </div><div class=""><br class=""></div><div class=""><br class=""></div><div class=""><br class=""></div><div class=""><br class=""><div class=""><blockquote type="cite" class=""><div class="">Am 03.12.2014 um 03:00 schrieb Indrajit Sen Gupta <<a href="mailto:indrajitsg@gmail.com" class="">indrajitsg@gmail.com</a>>:</div><br class="Apple-interchange-newline"><div class=""><div dir="ltr" class=""><div class="">The optimizer finally completed after about 5.3 hours. Attached are the files. It is a store space optimization problem which I am trying to solve. As a proof of concept, this data has been reduced to 1/5 th of the actual problem.</div><div class=""> </div><div class="">Is there way to reduce the time it takes or generate intermediate outputs so that we don't have to wait till it completes?</div><div class=""> </div><div class="">Regards,</div><div class="">Indrajit</div><div class=""> </div></div><div class="gmail_extra"><br class=""><div class="gmail_quote">On Wed, Dec 3, 2014 at 2:34 AM, Mike Steglich <span dir="ltr" class=""><<a href="mailto:mike.steglich@th-wildau.de" target="_blank" class="">mike.steglich@th-wildau.de</a>></span> wrote:<br class=""><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="auto" class=""><div class="">Hi Indrajit,</div><div class=""><br class=""></div><div class="">Can you send the model for a better understanding?</div><div class=""><br class=""></div><div class="">Thanks,</div><div class=""><br class=""></div><div class="">Mike<br class=""><br class=""><br class=""></div><div class=""><br class="">Am 02.12.2014 um 17:38 schrieb Indrajit Sen Gupta <<a href="mailto:indrajitsg@gmail.com" target="_blank" class="">indrajitsg@gmail.com</a>>:<br class=""><br class=""></div><div class=""><div class="h5"><blockquote type="cite" class=""><div class=""><div dir="ltr" class=""><div class="">Hi Mike,</div><div class=""> </div><div class="">I am running CMPL on a small version of very big problem I need to solve. The current problem has 100 binary variables and about 20 constraints. The objective function is a bit non linear as it has a term x[i,j] * x[k, m]. The program has been running for about 3 hours now and the output is showing:</div><div class=""> </div><div class=""><font face="monospace" class="">After 20300 nodes, 5239 on tree, -51762900 best solution, best possible -62975151 (10407.49 seconds)</font></div><div class=""><font face="Courier New" class=""></font> </div><div class=""><font face="arial,helvetica,sans-serif" class="">Any idea how much time it will take to complete? I understand, with binary variables it is difficult to predict, but supposing I were to stop in mid way, is there any way to get the current best solution?</font></div><div class=""> </div><div class="">Regrads,</div><div class="">Indrajit</div></div>
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