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<body class='hmmessage'><div dir='ltr'><font face="Courier New" color="#000000">Dear Ambros,</font><div><font face="Courier New"><br></font><div><div><font face="Courier New">Thank's for replying,</font></div><div><font face="Courier New"><br></font></div><div><font face="Courier New">Yes, I don't have a choice, I tried with the indicator constraint, but I don't get it right.</font></div><div><font face="Courier New">Now, I'm trying to use big-M notation or other MIP reformulation </font></div><div><font face="Courier New">Kind regards</font></div></div><div><br><div><font face="Courier New">--</font></div><font face="Courier New">A. Ouali</font><br><br><div>> Date: Fri, 18 Jul 2014 09:16:04 +0200<br>> From: gleixner@zib.de<br>> To: scip@zib.de<br>> Subject: Re: [Scip] help : for expressing constraint<br>> <br>> Dear Abdelkader Ouali,<br>> <br>> SCIP does not provide a constraint handler for this type of equivalence. <br>> If you do not want to model it via simple linear big-M constraints, <br>> then you could use two indicator constraints, see<br>> <br>> http://scip.zib.de/doc/html/cons__indicator_8h.php<br>> <br>> For the implication Y == 0 -> Ct Xt != 0 you can use SCIPgetNegatedVar() <br>> on Y, see<br>> <br>> <br>> http://scip.zib.de/doc/html/scip_8h.php#a94ec8a6bca8e6e621751b4257bf0d4c1<br>> <br>> I assume that because Xt are binary, you can express Ct Xt != 0 as a <br>> linear equality or inequality constraint.<br>> <br>> (Because the indicator constraint handler only enforces inequalities, <br>> maybe you need to indicator constraints to model Y==1 -> Ct Xt == 0 as <br>> Ct Xt <= 0 and Ct Xt >= 0, if one of them is not globally valid. In <br>> this case it may be more efficient to write an your own big-M formulation.)<br>> <br>> Best regards,<br>> ambros<br>> <br>> <br>> <br>> Am 16.07.2014 16:52, schrieb Abdelkader Ouali:<br>> > Dear SCIP users,<br>> ><br>> > I have a constraint as follow :<br>> ><br>> > Y=1 <-> Ct Xt = 0<br>> > where :<br>> > Y : is binary variable<br>> > Xt : is binary set of binary variables<br>> > Ct : is constant (coefficient) associated to each Xt<br>> > I had some problems to formulate it in SCIP, since there is equivalence<br>> > between to linear constraints<br>> ><br>> > Can you give some help to implement it ?<br>> ><br>> > ---<br>> > A. Ouali<br>> ><br>> ><br>> > _______________________________________________<br>> > Scip mailing list<br>> > Scip@zib.de<br>> > http://listserv.zib.de/mailman/listinfo/scip<br>> ><br>> <br>> -- <br>> ____________________________________________________________<br>> Ambros M. Gleixner<br>> Zuse Institute Berlin - Matheon - Berlin Mathematical School<br>> http://www.zib.de/gleixner<br>> _______________________________________________<br>> Scip mailing list<br>> Scip@zib.de<br>> http://listserv.zib.de/mailman/listinfo/scip<br></div></div></div> </div></body>
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