<div dir="ltr"><div dir="ltr"><font face="arial, sans-serif" style="background-color:rgb(255,255,255)" color="#000000">Dear Alexander,</font><div><font face="arial, sans-serif" style="background-color:rgb(255,255,255)" color="#000000"><br></font></div><div><font face="arial, sans-serif" style="background-color:rgb(255,255,255)" color="#000000">Thank you so much for your quick response. </font></div><div><font face="arial, sans-serif" style="background-color:rgb(255,255,255)" color="#000000">Please, let me explain more about what I meant.</font></div><div><font face="arial, sans-serif" style="background-color:rgb(255,255,255)" color="#000000"><br></font></div><div><font face="arial, sans-serif" style="background-color:rgb(255,255,255)" color="#000000">I am currently working on a scheduling problem and its structures, indeed from the modeling point of view, to investigate how a standard MIP solver like SCIP or Gurobi can solve this problem efficiently.</font></div><div><font face="arial, sans-serif" style="background-color:rgb(255,255,255)" color="#000000">For that, I am using GCG, actually PyGCGopt, to analyze these problems. In my previous email, I asked about some parameters at GCG that seed up the solving process, and the comment by Prof. Lübbecke was really helpful. </font></div><div><font face="arial, sans-serif" style="background-color:rgb(255,255,255)" color="#000000"><br></font></div><div><font face="arial, sans-serif" style="background-color:rgb(255,255,255)" color="#000000">Now, at the moment I do not need to use/implement this method manually and I think everything can be done automatically. Also, on the other hand, I am not aware of that the SCIP has a tool that applies <a class="el" href="https://www.scipopt.org/doc-8.0.2/html/cons__components_8c.php" style="box-sizing:border-box;background-image:initial;background-position:0px 0px;background-size:initial;background-repeat:initial;background-origin:initial;background-clip:initial;text-decoration-line:underline;outline:0px">cons_components</a> as a successful presolving technique. By that, my questions are:</font></div><div><font face="arial, sans-serif" style="background-color:rgb(255,255,255)" color="#000000"><br></font></div><div><font face="arial, sans-serif" style="background-color:rgb(255,255,255)" color="#000000">1) Is it possible to employ the mentioned decomposition by using the command line? (e.g. read problem -> set this method -> optimize)</font></div><div><font face="arial, sans-serif" style="background-color:rgb(255,255,255)" color="#000000">2) Is there any Python implementation, PySCIPopt, that shows how we can use this method? (unfortunately, I do not have more experience with C/C++)</font></div><div><font face="arial, sans-serif" style="background-color:rgb(255,255,255)" color="#000000">3) Based on the mentioned "successful presolving technique", can we infer that commercial solvers like Gurobi and CPLEX have gained from such techniques under a hood?</font></div><div><font face="arial, sans-serif" style="background-color:rgb(255,255,255)" color="#000000"><br></font></div><div><font face="arial, sans-serif" style="background-color:rgb(255,255,255)" color="#000000">Best regards</font></div><div><font face="arial, sans-serif" style="background-color:rgb(255,255,255)" color="#000000">Abbas</font></div><div><br></div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Mon, Feb 5, 2024 at 2:09 PM Hoen, Alexander <<a href="mailto:hoen@zib.de" target="_blank">hoen@zib.de</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
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<div id="m_-89375102679366714m_2434439602759906148divtagdefaultwrapper" style="font-size:12pt;color:rgb(0,0,0);font-family:Calibri,Helvetica,sans-serif" dir="ltr">
<p>Hi Abbas,<br>
</p>
<p><br>
</p>
<p>SCIP allows the user to provide a problem decomposition. Section 4.2 in the SCIP 7 Release report describes how SCIP uses the decomposition.<br>
<br>
On <a href="https://www.scipopt.org/doc-8.0.2/html/DECOMP.php" id="m_-89375102679366714m_2434439602759906148LPlnk74537" target="_blank">https://www.scipopt.org/doc-8.0.2/html/DECOMP.php</a> there is an explanation of how to provide such a decomposition.<br>
<br>
Best,</p>
<p>Alex</p>
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<div id="m_-89375102679366714m_2434439602759906148divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" style="font-size:11pt" color="#000000"><b>From:</b> Scip <<a href="mailto:scip-bounces@zib.de" target="_blank">scip-bounces@zib.de</a>> on behalf of Abbas Omidi <<a href="mailto:abb.omidi@gmail.com" target="_blank">abb.omidi@gmail.com</a>><br>
<b>Sent:</b> Monday, February 5, 2024 10:49:50 AM<br>
<b>To:</b> <a href="mailto:scip@zib.de" target="_blank">scip@zib.de</a><br>
<b>Subject:</b> [SCIP] Dealing with a problem that contains a specific structure with a standard MILP solver</font>
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<div dir="ltr"><font face="arial, sans-serif" style="background-color:rgb(255,255,255)" color="#000000">Dear support team,<br>
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<div><font face="arial, sans-serif" style="background-color:rgb(255,255,255)" color="#000000">Suppose we have a specific formulation which contains a particular structure. For example, the formulation contains a block diagonal format with some linking constraints
or variables. </font></div>
<div><font face="arial, sans-serif" style="background-color:rgb(255,255,255)" color="#000000"><br>
</font></div>
<div><font face="arial, sans-serif" style="background-color:rgb(255,255,255)" color="#000000">As far as I know, this format would be suitable for the decomposition scheme. Now, I am interested to know if is there any benefit to using this special structure
with a standard MILP solver line SCIP or Gurobi.<br>
</font></div>
<div><span style="background-color:rgb(255,255,255)"><font face="arial, sans-serif" color="#000000"><br>
</font></span></div>
<div><span style="background-color:rgb(255,255,255)"><font face="arial, sans-serif" color="#000000">All the best</font></span></div>
<div><span style="background-color:rgb(255,255,255)"><font face="arial, sans-serif" color="#000000">Abbas</font></span></div>
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