<html><head><meta http-equiv="Content-Type" content="text/html charset=us-ascii"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class="">Hi Ted,<div class=""><br class=""></div><div class="">Thanks for offering your help!</div><div class=""><br class=""></div><div class="">DIP seems promising indeed.</div><div class=""><br class=""></div><div class="">I have a cutting-stock problem where the demands that must be satisfied have a predefined width and a _total_ length. In other words, you may/must cut several elements to satisfy a demand but you can freely choose the length of each element (within some reasonable range).</div><div class=""><br class=""></div><div class="">The cutting patterns are 2D guillotine cuts whose order is fixed: first cut to fix the elements' length, then cut to determine the elements' width. </div><div class="">You can cut in 2 stages: the elements just obtained can be cut into elements of smaller width but equal length.</div><div class=""><br class=""></div><div class="">I decided to tackle the problem as follows:</div>- a pattern is a tree of widths (a tree to represent 2 stage cutting).<div class="">- the master problem decides over which length to apply each pattern. These decision variables are semi-continuous.</div><div class="">- the subproblem finds the best pattern (or several good ones)</div><div class=""><br class=""></div><div class="">I wonder whether DIP would be a better option for my problem.</div><div class=""><br class=""></div><div class="">Thanks,</div><div class="">david.</div><div class=""><br class=""></div><div class="">PS: It seems that the documents that <a href="http://projects.coin-or.org/Dip" class="">projects.coin-or.org/Dip</a> refers to are currently not accessible. I'll have a closer look at DIP as soon as possible.</div><div class="">
<br class=""><div><blockquote type="cite" class=""><div class="">On 19 Mar 2016, at 16:24, Ted Ralphs <<a href="mailto:tkralphs@lehigh.edu" class="">tkralphs@lehigh.edu</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><div dir="ltr" class="">Hi David,<div class=""><br class=""></div><div class="">I can probably help you a bit with BCP, but it would be useful if you could describe a little more about what you're trying to do exactly, since there may be better options, such as DIP (<a href="http://projects.coin-or.org/Dip" class="">projects.coin-or.org/Dip</a>), which is actively developed. It's been a long time since I really delved into BCP, so it might take some time to answer your questions if you want to continue with BCP. </div><div class=""><br class=""></div><div class="">Cheers,</div><div class=""><br class=""></div><div class="">Ted</div></div><div class="gmail_extra"><br class=""><div class="gmail_quote">On Sun, Mar 13, 2016 at 4:46 AM, David Catteeuw <span dir="ltr" class=""><<a href="mailto:david.catteeuw@yazzoom.com" target="_blank" class="">david.catteeuw@yazzoom.com</a>></span> wrote:<br class=""><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Hi all,<br class="">
<br class="">
Do I understand correctly that semi-continuous, SOS variables, etc. must be dealt with manually?<br class="">
<br class="">
In other words, in BCP you cannot do something like:<br class="">
BCP_var_algo(BCP_SemiContinuousVar, cost_coefficient, lower_bound, upper_bound);<br class="">
to create a variable whose value is either between lower_bound and upper_bound, or 0.<br class="">
<br class="">
Thanks,<br class="">
david.<br class="">
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</blockquote></div><br class=""><br clear="all" class=""><div class=""><br class=""></div>-- <br class=""><div class="gmail_signature"><div dir="ltr" class=""><div class=""><span style="font-size:12.8000001907349px" class="">Dr. Ted Ralphs</span><br style="font-size:12.8000001907349px" class=""><span style="font-size:12.8000001907349px" class="">Professor, Lehigh University</span><br style="font-size:12.8000001907349px" class=""><span style="font-size:12.8000001907349px" class="">(610) 628-1280</span><br style="font-size:12.8000001907349px" class=""><span style="font-size:12.8000001907349px" class="">ted 'at' lehigh 'dot' edu</span><br style="font-size:12.8000001907349px" class=""><a href="http://coral.ie.lehigh.edu/~ted" style="font-size:12.8000001907349px" target="_blank" class="">coral.ie.lehigh.edu/~ted</a><br class=""></div></div></div>
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