<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<style type="text/css" style="display:none"><!-- p { margin-top: 0px; margin-bottom: 0px; }--></style>
</head>
<body dir="ltr" style="font-size:12pt;color:#000000;background-color:#FFFFFF;font-family:Calibri,Arial,Helvetica,sans-serif;">
<p>Giacomo, Pietro, <br>
</p>
<p><br>
</p>
<p><span style="color: rgb(33, 33, 33); font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 16px; background-color: rgb(255, 255, 255);"><em>"is the solution that you obtain feasible?"</em></span><br>
</p>
<p><span style="color: rgb(33, 33, 33); font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 16px; background-color: rgb(255, 255, 255);"><em><br>
</em></span></p>
<p>Yes, it is. Although I was hoping couenne would give a better solution than the local solver does. <br>
</p>
<p><br>
</p>
<p><span style="color: rgb(33, 33, 33); font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 16px; background-color: rgb(255, 255, 255);"><em>"Can you see any non-Cbc log line that reports the solution with 0.25 objective, or the 0.28 objective?"</em></span><br>
</p>
<p><br>
</p>
<p><span style="color: rgb(33, 33, 33); font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 16px; background-color: rgb(255, 255, 255);">There are no solver log lines, other than cbc and only the 0.25 Objective is reported. </span></p>
<p><span style="color: rgb(33, 33, 33); font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 16px; background-color: rgb(255, 255, 255);"><br>
</span></p>
<p><span style="color: rgb(33, 33, 33); font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 16px; background-color: rgb(255, 255, 255);">I will try to improve my model and hope that couenne would find a better solution more quickly. Thank you very
much for you fast and helpful reply! </span></p>
<p><span style="color: rgb(33, 33, 33); font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 16px; background-color: rgb(255, 255, 255);"><br>
</span></p>
<p><span style="color: rgb(33, 33, 33); font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 16px; background-color: rgb(255, 255, 255);">Best,</span></p>
<p><span style="color: rgb(33, 33, 33); font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 16px; background-color: rgb(255, 255, 255);">Nesrine </span></p>
<div style="color: rgb(33, 33, 33);">
<hr tabindex="-1" style="display:inline-block; width:98%">
<div id="divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" color="#000000" style="font-size:11pt"><b>Von:</b> Pietro Belotti <petr.7b6@gmail.com><br>
<b>Gesendet:</b> Donnerstag, 26. April 2018 19:43<br>
<b>An:</b> Giacomo Nannicini<br>
<b>Cc:</b> Ouanes, Nesrine; couenne@list.coin-or.org<br>
<b>Betreff:</b> Re: [Couenne] Printing best solution found when time limit exceeded</font>
<div> </div>
</div>
<div>
<div dir="ltr">
<div>
<div>Just to add to what Giacomo correctly said: Couenne and Cbc have, for several reason, a different idea of what makes a solution feasible, and sometimes it happens in the opposite sense of what you observed (i.e. Cbc logging a worse solution than what Couenne
holds). Can you see any non-Cbc log line that reports the solution with 0.25 objective, or the 0.28 objective?<br>
<br>
</div>
<div>What would be needed is a single methods for flexibility checking, which Cbc allows for but hasn't been implemented in Couenne yet.<br>
</div>
<div><br>
</div>
Regards,<br>
</div>
Pietro<br>
</div>
<div class="gmail_extra"><br>
<div class="gmail_quote">On Thu, Apr 26, 2018 at 12:24 PM, Giacomo Nannicini <span dir="ltr">
<<a href="mailto:giacomo.n@gmail.com" target="_blank">giacomo.n@gmail.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex; border-left:1px #ccc solid; padding-left:1ex">
Nesrine,<br>
is the solution that you obtain feasible?<br>
In my experience, the log is wrong: Cbc (the branch-and-bound part of<br>
Couenne) thinks that it found a feasible solution of value 0.25, but<br>
Couenne internally rejects it according to its own tolerances.<br>
At the end of the search, Couenne prints the best solution it found -<br>
which is worse than the "fictitious" 0.25 solution.<br>
<br>
Giacomo<br>
<div>
<div class="h5"><br>
On Wed, Apr 25, 2018 at 2:26 PM, Ouanes, Nesrine<br>
<<a href="mailto:nesrine.ouanes@campus.tu-berlin.de">nesrine.ouanes@campus.tu-<wbr>berlin.de</a>> wrote:<br>
> Hello,<br>
><br>
><br>
> I'm solving a NLP Problem with couenne. My model is written in Python and<br>
> Pyomo.<br>
><br>
><br>
> In my case, Couenne takes very long without exiting with an optimal<br>
> solution. The best solution is given after a few iterations and doesn't<br>
> change after hours of execution:<br>
><br>
><br>
> Cbc0010I After 7100 nodes, 3364 on tree, 0.25239475 best solution, best<br>
> possible 0.15 (14.72 seconds)<br>
><br>
><br>
> Therefore, I've set the option time_limit to a smaller value (100 seconds),<br>
> to be able to retrieve the best solution found so far and print it to a<br>
> file. However couenne prints another solution than the one stated in the<br>
> solver log:<br>
><br>
><br>
> instead of 0.25239475, I get 0.281323177 as a value for the objective<br>
> function.<br>
><br>
><br>
> The value printed by Couenne is the same one I get if I solve my model using<br>
> Ipopt.<br>
><br>
><br>
> 1) Do you have any idea, why this occurs? Is it possible that Couenne is<br>
> printing the best solution found by ipopt, since it's used in Couenne?<br>
><br>
><br>
> 2) Is there a way to obtain the better solution given in the solver log?<br>
><br>
><br>
> I look forward to your reply.<br>
><br>
><br>
> Best,<br>
><br>
> Nesrine<br>
><br>
><br>
><br>
><br>
><br>
><br>
><br>
><br>
><br>
><br>
><br>
><br>
</div>
</div>
> ______________________________<wbr>_________________<br>
> Couenne mailing list<br>
> <a href="mailto:Couenne@list.coin-or.org">Couenne@list.coin-or.org</a><br>
> <a href="https://urldefense.proofpoint.com/v2/url?u=https-3A__list.coin-2Dor.org_mailman_listinfo_couenne&d=DwICAg&c=Ngd-ta5yRYsqeUsEDgxhcqsYYY1Xs5ogLxWPA_2Wlc4&r=8FaVxIx99H879Ebkij38NpcRZoYLK-7QMl1LqyvBccA&m=TKDQWNLB4YWq5VR5iJ4Bpb5iCCr7hDVDR-UF_vMD9ao&s=s7IjlPTu9bAJDemY_xIfISefaKeijm2HjN-3_ozHi1c&e=" rel="noreferrer" target="_blank">
https://urldefense.proofpoint.<wbr>com/v2/url?u=https-3A__list.<wbr>coin-2Dor.org_mailman_<wbr>listinfo_couenne&d=DwICAg&c=<wbr>Ngd-<wbr>ta5yRYsqeUsEDgxhcqsYYY1Xs5ogLx<wbr>WPA_2Wlc4&r=<wbr>8FaVxIx99H879Ebkij38NpcRZoYLK-<wbr>7QMl1LqyvBccA&m=<wbr>TKDQWNLB4YWq5VR5iJ4Bpb5iCCr7hD<wbr>VDR-UF_vMD9ao&s=<wbr>s7IjlPTu9bAJDemY_<wbr>xIfISefaKeijm2HjN-3_ozHi1c&e=</a><br>
<br>
______________________________<wbr>_________________<br>
Couenne mailing list<br>
<a href="mailto:Couenne@list.coin-or.org">Couenne@list.coin-or.org</a><br>
<a href="https://list.coin-or.org/mailman/listinfo/couenne" rel="noreferrer" target="_blank">https://list.coin-or.org/<wbr>mailman/listinfo/couenne</a><br>
</blockquote>
</div>
<br>
</div>
</div>
</div>
</body>
</html>