<div dir="ltr">Hi Felipe,<div><br></div><div>Thanks a lot! That is also the only explanation that I could imagine. Just wonder if SCIP does something unexpected. </div><div><br></div><div>Best,</div></div><div class="gmail_extra"><br><div class="gmail_quote">On Fri, Aug 7, 2015 at 10:51 AM, Felipe Serrano <span dir="ltr"><<a href="mailto:fserranom5@gmail.com" target="_blank">fserranom5@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr">Hi Yongjia<div><br></div><div>I can imagine that SCIP doesn't deal with the extra complications automatically.</div><div>Actually, in the binpacking example explicit logicor constraints are added to the pricing problem in order to avoid generating the same packing.</div><div>So I am guessing that you would need to add some constraint that avoids the generation of a fixed route to your pricing problem.</div><div><br></div><div>I do not have any explanation for the behavior you describe apart from: SCIP might be generating the same variable on the branch where it is supposed to be fix to 0.</div><div><br></div><div>Best,</div><div>Felipe</div></div><div class="HOEnZb"><div class="h5"><div class="gmail_extra"><br><div class="gmail_quote">On Fri, Aug 7, 2015 at 4:02 PM, Yongjia Song <span dir="ltr"><<a href="mailto:ysong3@vcu.edu" target="_blank">ysong3@vcu.edu</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div text="#000000" bgcolor="#ffffff"><div><div style="font-family:Calibri,sans-serif;font-size:11pt">Hi Benny,<br><br>Thanks a lot! I actually tried a set partitioning formulation with only master variables, and claim them to be integer so branching has to be done for these variables. I only specify a pricer as the one in the VRP example. Will Scip automatically take care of the extra complication in pricing because of branching? I actually tried this, and sometimes it gave the correct solution(maybe out of luck) but it also happened that no progress is made at all after the root. Any explanation on this? Thanks a lot!<br><br>Best,</div></div><div dir="ltr"><hr><span style="font-family:Calibri,sans-serif;font-size:11pt;font-weight:bold">From: </span><span style="font-family:Calibri,sans-serif;font-size:11pt"><a href="mailto:benjamin.mueller@zib.de" target="_blank">Benjamin Müller</a></span><br><span style="font-family:Calibri,sans-serif;font-size:11pt;font-weight:bold">Sent: </span><span style="font-family:Calibri,sans-serif;font-size:11pt">8/7/2015 3:50 AM</span><br><span style="font-family:Calibri,sans-serif;font-size:11pt;font-weight:bold">To: </span><span style="font-family:Calibri,sans-serif;font-size:11pt"><a href="mailto:ysong3@vcu.edu" target="_blank">Yongjia Song</a>; <a href="mailto:scip@zib.de" target="_blank">SCIP mailing list</a></span><br><span style="font-family:Calibri,sans-serif;font-size:11pt;font-weight:bold">Subject: </span><span style="font-family:Calibri,sans-serif;font-size:11pt">Re: [Scip] Question about branching on master variables in SCIP</span><br><br></div><div><div>
Hi Yongjia,<br>
<br>
you are completely right, branching on the reformulated variables
does change the nature of your pricing problem. If your model does
only contain the routing variables and you declare them as integral
then SCIP will branch on those as SCIP would usually do. The user
has to respect the branching decisions made by SCIP in his pricer.
You could add your own branching rule in order to branch on the
original variables even though they are not in the model (see
Ryan/Foster branching in the Binpacking example). <br>
<br>
Note that, in the VRP example the routine variables are continuous
and thus branching will only be applied on edge variables. Those
branching decisions does not influence the pricing problem too much
(excluding edges from the graph).<br>
<br>
<br>
Best,<br>
<br>
Benny<br>
<br>
<br>
<div>On 08/06/2015 08:01 PM, Yongjia Song
wrote:<br>
</div>
<blockquote type="cite">
<div dir="ltr">Hi all,
<div><br>
</div>
<div>I have a question about how SCIP handles branching when
only the master variables present in the model. Taking VRP as
an example, suppose we only have the route variables (without
the original edge variables or the linking constraints between
edge variables and route variables), and we impose the
integrality constraints on these variables, it is not clear
how branching on these variables are implemented in SCIP.
Indeed, when a branching decision is made on some route
variable, it complicates the pricing by forcing the pricing
algorithm to avoid generating that route. Without specific
problem structure, it is not clear to me how SCIP handles this
case. Thanks a lot for your help!</div>
<div><br>
</div>
<div>Best,<br clear="all">
<div><br>
</div>
-- <br>
<div>
<div dir="ltr">
<div>SONG, Yongjia</div>
<div>Assistant Professor</div>
<div>Department of Statistical Sciences and Operations
Research</div>
<div>Virginia Commonwealth University </div>
<div>PO Box 843083 </div>
<div>Richmond, VA 23284-3083 </div>
<div><a href="tel:804-828-1149" value="+18048281149" target="_blank">804-828-1149</a><br>
</div>
<div><a href="mailto:Ysong3@vcu.edu" target="_blank">Ysong3@vcu.edu</a></div>
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Zuse Institute Berlin
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</div></div></blockquote></div><br><br clear="all"><div><br></div>-- <br><div class="gmail_signature"><div dir="ltr"><div>SONG, Yongjia</div><div>Assistant Professor</div><div>Department of Statistical Sciences and Operations Research</div><div>Virginia Commonwealth University </div><div>PO Box 843083 </div><div>Richmond, VA 23284-3083 </div><div>804-828-1149<br></div><div><a href="mailto:Ysong3@vcu.edu" target="_blank">Ysong3@vcu.edu</a></div></div></div>
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