<html dir="ltr">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
</head>
<body bgcolor="#FFFFFF" fpstyle="1" ocsi="0">
<div style="direction: ltr;font-family: Tahoma;color: #000000;font-size: 10pt;"><br>
<div style="font-family: Times New Roman; color: #000000; font-size: 16px">
<hr tabindex="-1">
<div id="divRpF788489" style="direction: ltr;"><font face="Tahoma" size="2" color="#000000"><b>From:</b> Ahmed Ibrahim<br>
<b>Sent:</b> Sunday, March 06, 2016 11:03 AM<br>
<b>To:</b> Gerald Gamrath<br>
<b>Subject:</b> RE: [SCIP] Constraint cutting planes in constraint handlers<br>
</font><br>
</div>
<div></div>
<div>
<div style="direction:ltr; font-family:Tahoma; color:#000000; font-size:10pt">Hi Gerald,
<div><br>
</div>
<div>Thanks for this response. Actually it fixed a misunderstanding I had. May I also ask, whether the same applies for quadratic constraint separators?</div>
<div><br>
</div>
<div>Regards,</div>
<div>Ahmed<br>
<div style="font-family:Times New Roman; color:#000000; font-size:16px">
<hr tabindex="-1">
<div id="divRpF713384" style="direction:ltr"><font face="Tahoma" size="2" color="#000000"><b>From:</b> Gerald Gamrath [gamrath@zib.de]<br>
<b>Sent:</b> Tuesday, March 01, 2016 9:36 AM<br>
<b>To:</b> Ahmed Ibrahim; scip@zib.de<br>
<b>Subject:</b> Re: [SCIP] Constraint cutting planes in constraint handlers<br>
</font><br>
</div>
<div></div>
<div>
<div class="moz-cite-prefix">Dear Ahmed,<br>
<br>
the logic or, setppc, and varbound constraint handlers have separation routines, but these only generates the linear rows representing the specific constraints. They do not create 'real' cutting planes.<br>
<br>
Remember that a constraint is not directly present in the LP, but it will normally create one or more rows to add the constraint (or a relaxation of it) to the LP. For linear constraints or their specializations (e.g., logic or, setppc, and varbound), the constraint
can be represented by one linear row.<br>
If constraints have their 'initial' flag set to TRUE when created (which is the default), the initial relaxation will be added to the LP when building the LP data structure at the root node. Linear constraints and specializations are then fully represented
in the LP and no separation is needed later, anymore.<br>
<br>
On the other hand, if 'initial' is set to FALSE or 'removable' to TRUE, the row corresponding to a constraint may not be in the LP. The separation procedure then checks whether the row would by violated by the current LP solution and adds it, if needed. This
is similar to the concept of lazy constraints used in, e.g., CPLEX.<br>
<br>
Best,<br>
Gerald<br>
<br>
On 29.02.2016 20:51, Ahmed Ibrahim wrote:<br>
</div>
<blockquote type="cite"><style type="text/css" id="owaParaStyle">
<!--
-->
</style>
<div style="direction:ltr; font-family:Tahoma; color:#000000; font-size:10pt">Hi all,
<div>I was wondering if any one knows where can I find an explanation of how cutting planes for logic or setppc and varbound constraint handlers are obtained? </div>
<div><br>
</div>
<div>Regards,</div>
<div>Ahmed</div>
</div>
<br>
<fieldset class="mimeAttachmentHeader" target="_blank"></fieldset> <br>
<pre>_______________________________________________
Scip mailing list
<a class="moz-txt-link-abbreviated" href="mailto:Scip@zib.de" target="_blank">Scip@zib.de</a>
<a class="moz-txt-link-freetext" href="http://listserv.zib.de/mailman/listinfo/scip" target="_blank">http://listserv.zib.de/mailman/listinfo/scip</a>
</pre>
</blockquote>
<br>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</body>
</html>