<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=us-ascii">
<style type="text/css" style="display:none;"> P {margin-top:0;margin-bottom:0;} </style>
</head>
<body dir="ltr">
<div style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);" class="elementToProof">
Hi Ambros,</div>
<div style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);" class="elementToProof">
<br>
</div>
<div style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);" class="elementToProof">
I installed PAPILO (it was not previously being used) and switched the relevant constraints from logicor to setcover, but I am still not getting the expected presolving. Find attached a test instance and a script file showing the missing presolve (I was expecting
variable v#1 to be removed.)</div>
<div style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);" class="elementToProof">
<br>
</div>
<div style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);" class="elementToProof">
My current working hypothesis is that I'm being stupid and missing some reason why this presolve step should not go ahead, but I just can't see why it should not.</div>
<div style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);" class="elementToProof">
<br>
</div>
<div style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);" class="elementToProof">
Thanks for your help,</div>
<div style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);" class="elementToProof">
<br>
</div>
<div style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);" class="elementToProof">
James<br>
</div>
<div class="elementToProof">
<div style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">
<br>
</div>
<div id="Signature">
<div>
<div style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">
</div>
<div style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">
James Cussens</div>
<div style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">
Room MVB 3.26<br>
</div>
<div style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">
Dept of Computer Science, University of Bristol</div>
<div style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">
Phone: +44 (0)117 455 8723<br>
</div>
<div style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">
<a href="https://jcussens.github.io/">https://jcussens.github.io/</a></div>
<div style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">
<span style="font-size:11.5pt">Funded PhDs available in Bristol in the following areas: <a href="http://www.bristol.ac.uk/cdt/compass/" target="_blank" rel="noopener noreferrer"><span>Data Science</span></a>, <a href="http://www.bristol.ac.uk/cdt/interactive-ai/" target="_blank" rel="noopener noreferrer"><span>Interactive
AI</span></a>, <a href="http://www.bristol.ac.uk/cdt/cyber-security/" target="_blank" rel="noopener noreferrer"><span>Cyber Security</span></a> or <a href="http://www.bristol.ac.uk/cdt/digital-health/" target="_blank" rel="noopener noreferrer"><span>Digital
Health</span></a>. </span><br>
</div>
</div>
</div>
</div>
<div id="appendonsend"></div>
<hr style="display:inline-block;width:98%" tabindex="-1">
<div id="divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" style="font-size:11pt" color="#000000"><b>From:</b> Scip <scip-bounces@zib.de> on behalf of Ambros Gleixner <gleixner@zib.de><br>
<b>Sent:</b> 14 June 2023 11:26<br>
<b>To:</b> scip@zib.de <scip@zib.de><br>
<b>Subject:</b> Re: [SCIP] presolving query</font>
<div> </div>
</div>
<div class="BodyFragment"><font size="2"><span style="font-size:11pt;">
<div class="PlainText">Hi James,<br>
<br>
the presolving step you mention is very basic und so you are right to <br>
expect it from SCIP. The linear and the setppc constraint handlers <br>
implement it, however, it seems to be missing in the logicor constraint <br>
handler.<br>
<br>
Also the PaPILO library behind presol_milp.cpp should detect it. Can it <br>
be that you are running without PaPILO?<br>
<br>
You could use setppc (or general linear) constraints instead, but I <br>
assume this has other negative implications? If you are stuck with <br>
logicor constraints, then I don't see a simple parameter switch to <br>
enable this presolving step. (Except possibly activating PaPILO.)<br>
<br>
Best,<br>
Ambros<br>
<br>
<br>
<br>
<br>
Am 14.06.2023 um 09:17 schrieb James Cussens:<br>
> Hi all,<br>
> <br>
> I have a problem which after presolving contains the following vars and <br>
> conss (among a bunch of other stuff):<br>
> <br>
> OBJECTIVE<br>
> Sense : minimize<br>
> Offset : -62.7528704623564<br>
> VARIABLES<br>
> ...<br>
> [binary] <t_pa#1>: obj=8.51719319141624, global bounds=[-0,1], local <br>
> bounds=[-0,1]<br>
> ....<br>
> [binary] <t_v#0>: obj=33.6097102878493, global bounds=[-0,1], local <br>
> bounds=[-0,1]<br>
> ...<br>
> CONSTRAINTS<br>
> ...<br>
> [logicor] <cluster_or>: logicor(<t_v#0>[B],<~t_pa#1>[B]);<br>
> ...<br>
> <br>
> The variable t_v#0 appears only in the above logicor constraint. So <br>
> clearly in any optimal solution t_pa#1 = t_v#0. So I was expecting t_v#0 <br>
> and its constraint to be<br>
> removed and the objective coefficient of t_pa#1 to be increased by <br>
> 33.609. But this isn't happening. Is there perhaps some presolving <br>
> parameter I could set to make this happen?<br>
> <br>
> It's not a big deal for me to do this presolving "manually" as I <br>
> construct the problem instance but it would be nicer if it "just happened".<br>
> <br>
> James<br>
> <br>
> James Cussens<br>
> Room MVB 3.26<br>
> Dept of Computer Science, University of Bristol<br>
> Phone: +44 (0)117 455 8723<br>
> <a href="https://jcussens.github.io/">https://jcussens.github.io/</a> <<a href="https://jcussens.github.io/">https://jcussens.github.io/</a>><br>
> Funded PhDs available in Bristol in the following areas: Data Science <br>
> <<a href="http://www.bristol.ac.uk/cdt/compass/">http://www.bristol.ac.uk/cdt/compass/</a>>, Interactive AI
<br>
> <<a href="http://www.bristol.ac.uk/cdt/interactive-ai/">http://www.bristol.ac.uk/cdt/interactive-ai/</a>>, Cyber Security
<br>
> <<a href="http://www.bristol.ac.uk/cdt/cyber-security/">http://www.bristol.ac.uk/cdt/cyber-security/</a>> or Digital Health
<br>
> <<a href="http://www.bristol.ac.uk/cdt/digital-health/">http://www.bristol.ac.uk/cdt/digital-health/</a>>.<br>
> <br>
> _______________________________________________<br>
> Scip mailing list<br>
> Scip@zib.de<br>
> <a href="https://listserv.zib.de/mailman/listinfo/scip">https://listserv.zib.de/mailman/listinfo/scip</a><br>
_______________________________________________<br>
Scip mailing list<br>
Scip@zib.de<br>
<a href="https://listserv.zib.de/mailman/listinfo/scip">https://listserv.zib.de/mailman/listinfo/scip</a><br>
</div>
</span></font></div>
</body>
</html>