<html><head><meta http-equiv="Content-Type" content="text/html charset=windows-1252"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class="">Hi, Gregor,<div class=""><br class=""></div><div class=""><br class=""></div><div class="">Thanks for your information. I have search the user parameters but cannot find the right parameter. </div><div class=""><br class=""></div><div class="">I am solving a number of (e.g. 1000) NLPs with different parameters in the model. Many cases are unbounded. The following is the output of SCIP for the smallest case:</div><div class=""><br class=""></div><div style="margin: 0px; line-height: normal; font-family: 'Andale Mono'; color: rgb(41, 249, 20); background-color: rgb(0, 0, 0);" class=""><span style="font-variant-ligatures: no-common-ligatures" class=""> node | left |LP iter|LP it/n| mem | dualbound | primalbound | gap </span></div><div style="margin: 0px; line-height: normal; font-family: 'Andale Mono'; color: rgb(41, 249, 20); background-color: rgb(0, 0, 0);" class=""><span style="font-variant-ligatures: no-common-ligatures" class=""> 1 | 0 | 1 | - | 209k| -- |-1.000000e+05 | Inf </span></div><div style="margin: 0px; line-height: normal; font-family: 'Andale Mono'; color: rgb(41, 249, 20); background-color: rgb(0, 0, 0);" class=""><span style="font-variant-ligatures: no-common-ligatures" class="">(node 1) LP relaxation is unbounded (LP 1)</span></div><div style="margin: 0px; line-height: normal; font-family: 'Andale Mono'; color: rgb(41, 249, 20); background-color: rgb(0, 0, 0);" class=""><span style="font-variant-ligatures: no-common-ligatures" class=""> 1 | 2 | 4 | - | 210k| -- |-1.000000e+05 | Inf </span></div><div style="margin: 0px; line-height: normal; font-family: 'Andale Mono'; color: rgb(41, 249, 20); background-color: rgb(0, 0, 0);" class=""><span style="font-variant-ligatures: no-common-ligatures" class="">* 2 | 1 | 6 | 5.0 | 211k| -- |-6.800000e+17 | Inf </span></div><div class=""><span style="color: rgb(41, 249, 20); font-family: 'Andale Mono'; background-color: rgb(0, 0, 0);" class=""> </span><span style="color: rgb(41, 249, 20); font-family: 'Andale Mono'; background-color: rgb(0, 0, 0);" class="">100 |</span><span style="color: rgb(41, 249, 20); font-family: 'Andale Mono'; background-color: rgb(0, 0, 0);" class=""> </span><span style="color: rgb(41, 249, 20); font-family: 'Andale Mono'; background-color: rgb(0, 0, 0);" class="">99 | </span><span style="color: rgb(41, 249, 20); font-family: 'Andale Mono'; background-color: rgb(0, 0, 0);" class=""> </span><span style="color: rgb(41, 249, 20); font-family: 'Andale Mono'; background-color: rgb(0, 0, 0);" class="">6 | </span><span style="color: rgb(41, 249, 20); font-family: 'Andale Mono'; background-color: rgb(0, 0, 0);" class=""> </span><span style="color: rgb(41, 249, 20); font-family: 'Andale Mono'; background-color: rgb(0, 0, 0);" class="">0.1 | 241k|</span><span style="color: rgb(41, 249, 20); font-family: 'Andale Mono'; background-color: rgb(0, 0, 0);" class=""> </span><span style="color: rgb(41, 249, 20); font-family: 'Andale Mono'; background-color: rgb(0, 0, 0);" class="">--</span><span style="color: rgb(41, 249, 20); font-family: 'Andale Mono'; background-color: rgb(0, 0, 0);" class=""> </span><span style="color: rgb(41, 249, 20); font-family: 'Andale Mono'; background-color: rgb(0, 0, 0);" class="">|-6.800000e+17 |</span><span style="color: rgb(41, 249, 20); font-family: 'Andale Mono'; background-color: rgb(0, 0, 0);" class=""> </span><span style="color: rgb(41, 249, 20); font-family: 'Andale Mono'; background-color: rgb(0, 0, 0);" class="">Inf</span><span style="color: rgb(41, 249, 20); font-family: 'Andale Mono'; background-color: rgb(0, 0, 0);" class=""> </span> </div><div class=""><br class=""></div><div class="">…</div><div class=""><div style="margin: 0px; line-height: normal; font-family: 'Andale Mono'; color: rgb(41, 249, 20); background-color: rgb(0, 0, 0);" class=""><div style="margin: 0px; line-height: normal;" class=""><div style="margin: 0px; line-height: normal;" class=""><span style="font-variant-ligatures: no-common-ligatures" class=""> node | left |LP iter|LP it/n| mem | dualbound | primalbound | gap </span></div><div style="margin: 0px; line-height: normal;" class=""><span style="font-variant-ligatures: no-common-ligatures" class=""> 10575k| 9648k| 6 | 0.0 |2501M| -- |-1.000000e+18 | Inf </span></div><div style="margin: 0px; line-height: normal;" class=""><span style="font-variant-ligatures: no-common-ligatures" class=""> 10575k| 9648k| 6 | 0.0 |2501M| -- |-1.000000e+18 | Inf </span></div></div></div></div><div class=""><br class=""></div><div class="">As you can see, at node 2, SCIP have already find a prime bound of -6.8e17, which is so small that I can view it as unbounded for my model. I want SCIP at node 2 to stop and return me this prime bound. However, SCIP is still running after exploring more than 10 million nodes. Setting a solution limit of 1 is not appropriate for my problem, because the primal bound in the node 1 is not large enough for me to declare that the problem is unbounded. </div><div class=""><br class=""></div><div class=""><br class=""></div><div class="">Regard,</div><div class="">Yankai</div><div class=""><br class=""></div><div class=""><br class=""></div><div class=""><br class=""></div><div class=""><br class=""></div><div class=""><br class=""></div><div class=""><br class=""></div><div class=""><br class=""><div><blockquote type="cite" class=""><div class="">On Feb 17, 2017, at 10:23 AM, Gregor Hendel <<a href="mailto:hendel@zib.de" class="">hendel@zib.de</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><div class="">Hi Yankai,<br class=""><br class="">please read the documentation of SCIP, especially search the limits in the user parameters<br class=""><br class=""><a href="http://scip.zib.de/doc/html/PARAMETERS.php" class="">http://scip.zib.de/doc/html/PARAMETERS.php</a><br class=""><br class="">to find something that matches your purpose. IMHO, there is nothing to speed up the detection of unboundedness. What you should rather do, is set up a proper lower bound for your model, and set a solution limit of 1 to stop if feasibility of this modified model was proven.<br class=""><br class="">Happy scipping,<br class="">Gregor<br class=""><br class=""><br class=""><br class="">Am 17.02.2017 um 17:02 schrieb Yankai Cao:<br class=""><blockquote type="cite" class="">Dear Benjamin,<br class=""><br class=""><br class="">Thanks so much for your reply. Is there any parameter I can set to help SCIP detect if the problem is unbound. For example, for my model, if SCIP find an upper bound <= ub (e.g. -1e10), I want SCIP to stop and declare the problem is unbound. Otherwise, it will takes SCIP much much more time to continue. Thanks.<br class=""><br class=""><br class="">Regards,<br class="">Yankai<br class=""><br class=""><br class=""><blockquote type="cite" class="">On Feb 17, 2017, at 7:19 AM, Benjamin Müller <benjamin.mueller@zib.de> wrote:<br class=""><br class="">Dear Yankai,<br class=""><br class="">you can use<br class=""><br class=""><span class="Apple-tab-span" style="white-space:pre"> </span>set/limits/objective<br class=""><br class="">in order to set an objective limit. SCIP will then only look for solutions that have a better value than the given objective limit. You can think of it as an artificial upper bound for your (minimization) problem.<br class=""><br class="">As far as I can see it, there is no parameter to set an initial dual bound in SCIP. There is SCIPupdateLocalDualbound in the API that could be called during the SCIP_STAGE_PROBLEM stage.<br class=""><br class="">Regards,<br class="">Benjamin<br class=""><br class=""><br class="">On 02/17/2017 07:24 AM, Yankai Cao wrote:<br class=""><blockquote type="cite" class="">Hi, All,<br class=""><br class="">I am new to SCIP. I want to know how to set a parameter ub (e.g. -1e10) so that if SCIP find the upper bound is smaller than ub SCIP can stop and declare that the problem is unbounded?<br class=""><br class="">Also, how to provide known upper/lower bounds before b&b, which might help speed the solution time of SCIP?<br class=""><br class="">Thanks very much!<br class=""><br class=""><br class="">Regards,<br class="">Yankai<br class=""><br class=""><br class="">_______________________________________________<br class="">Scip mailing list<br class="">Scip@zib.de<br class="">http://listserv.zib.de/mailman/listinfo/scip<br class=""><br class=""></blockquote>-- <br class="">______________________________<br class="">Benjamin Müller<br class="">Zuse Institute Berlin<br class="">Takustr. 7, 14195 Berlin<br class="">benjamin.mueller@zib.de<br class="">+49 30 841 85-195<br class=""></blockquote><br class="">_______________________________________________<br class="">Scip mailing list<br class="">Scip@zib.de<br class="">http://listserv.zib.de/mailman/listinfo/scip<br class=""></blockquote><br class=""><br class="">_______________________________________________<br class="">Scip mailing list<br class="">Scip@zib.de<br class="">http://listserv.zib.de/mailman/listinfo/scip<br class=""></div></div></blockquote></div><br class=""></div></body></html>