<div dir="ltr"><div>User cuts are controlled more precisely in SCIP than in some other systems. When calling `SCIPcreateConsLinear` to add an LP constraint, there are a number of flags that can be set, that regulate the behavior of SCIP, and make it act like a necessary constraint, a user cut, a lazy constraint, or a so-called "optimality constraint". You can glance at the extended list of arguments here: <a href="https://scipopt.org/doc/html/cons__linear_8c_source.php#l17832">https://scipopt.org/doc/html/cons__linear_8c_source.php#l17832</a> The flags range from "initial" to "stickingatnode".</div><div><br></div><div>The simpler function, `SCIPcreateConsBasicLinear`, you can see at <a href="https://scipopt.org/doc/html/cons__linear_8c_source.php#l18021">https://scipopt.org/doc/html/cons__linear_8c_source.php#l18021</a> -- and it provides default values for all those flags, as {TRUE, TRUE, TRUE, TRUE, TRUE, FALSE, FALSE, FALSE, FALSE, FALSE}.</div><div><br></div><div>For adding user cuts, the recommended approach is to change `initial` to false, `enforce` and `check` to false, and `removable' to true, so that it looks like {FALSE, TRUE, FALSE, FALSE, TRUE, FALSE, FALSE, FALSE, TRUE, FALSE}. These are how the flags are set in reader_lp.c, at least: <a href="https://scipopt.org/doc/html/reader__lp_8c_source.php#l01773">https://scipopt.org/doc/html/reader__lp_8c_source.php#l01773</a></div><div><br></div><div>The documentation can explain exactly what flipping those four flags does, better than I can. :) You should definitely set the `check` to false and `removable` to true, but I think `initial` and `enforce` could each go either way -- you might want to try it both ways and see which gives you better performance.<br></div><div><br></div><div>Best,</div><div>Alex</div><div>_______________________________<br></div><div><div><div dir="ltr" class="gmail_signature" data-smartmail="gmail_signature"><div dir="ltr">Alexander Meiburg, PhD</div><div>University of California, Santa Barbara<br></div></div></div><br></div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Thu, Jul 20, 2023 at 5:23 AM Lastra Diaz Jose <<a href="mailto:j.lastra@lectra.com">j.lastra@lectra.com</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div class="msg-7641710115109958428">
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<p class="MsoNormal"><span style="font-size:10pt;font-family:"Arial",sans-serif" lang="ES">Dear all,<u></u><u></u></span></p>
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<p class="MsoNormal"><span style="font-size:10pt;font-family:"Arial",sans-serif">I wonder if SCIP implements valid user cuts. They are valid inequalities which the user inserts into the model before solving it, and the solver decides when and how use them
to cut off LP solutions.<u></u><u></u></span></p>
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<p class="MsoNormal"><span style="font-size:10pt;font-family:"Arial",sans-serif">Regards,<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:10pt;font-family:"Arial",sans-serif">Juan<u></u><u></u></span></p>
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<p class="MsoNormal"><b><span style="font-size:10pt;font-family:"Arial",sans-serif;color:black" lang="FR">Juan J. Lastra Díaz, PhD</span></b><span style="font-size:10pt;font-family:"Arial",sans-serif;color:black" lang="FR"><u></u><u></u></span></p>
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