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CBC team:<br>
Attached is the MPS file and below is a description of the issue.<br>
CoinMP and CPLEX give very different results.<br>
I know you are all probably heading to the INFORMS conference --
have a good conference!<br>
Regards,<br>
Sean<br>
<br>
<br>
-------- Original Message --------<br>
Subject: CoinMP / CBC error<br>
Date: Fri, 12 Oct 2012 10:45:25 -0500<br>
From: Sean<br>
To: ted@<br>
<br>
<div class="moz-forward-container"> I apologize for contacting you
this way, but I tried to go on the CBC project page to log a
ticket but upon trying to register I got the error at the bottom
of this email from the TRAC system. I did try.<br>
Anyway, I use CoinMP, and I sent a problem to Bjarni Kristjansson
and he suggested I send it to the CBC team as Maximal is convinced
the problem lies in CBC.<br>
<br>
Would you like me to send you the MPS file or to someone else?<br>
<br>
Regards,<br>
Sean<br>
<br>
<br>
<br>
here is the email exchange on the problem:<br>
<font color="#006600"><br>
Hi Sean,<br>
<br>
Thanks for sending the model. We ran it with CPLEX and few other
solvers and we come to the conclusion CoinMP is not returning
the correct solution. The problem is most likely caused in CBC
which is a mixed solver used by CoinMP. We will suggest that you
report this to the project manager of CBC along with the MPS
file.<br>
<br>
Regards,<br>
<br>
Farida Abou Draa<br>
<br>
<br>
On Thu, Oct 11, 2012 at 10:50 AM, Sean MacDermant <span
dir="ltr"><<a moz-do-not-send="true" href="seanmac"
target="_blank">seanmac</a>></span> wrote:<br>
Bjarni,<br>
You must be finalizing plans for the INFORMS conference, but I <br>
wanted to share this problem with you.<br>
<br>
It is a problem where, when Using the 64-bit version of MPL, <br>
you get different results for CPLEX from what you get with
CoinMP.<br>
This is a MIP with 968 BV variables.<br>
<br>
All the default solver parameters were set for both. <br>
<br>
I did notice a 'NONLINEAR' LINE that MPL put in the MPS file,
right<br>
before the BOUNDS section, but this is a linear MIP.<br>
<br>
Can you tell what is going on?<br>
Have a great time at INFORMS.<br>
<br>
<br>
Regards,<br>
Sean<br>
<br>
<br>
<br>
CPLEX 12.3:<br>
<img src="cid:part2.03000705.01010309@gmail.com" alt=""><br>
<br>
<br>
<br>
COIN MP 1.6:<br>
<img src="cid:part3.05020904.09060202@gmail.com" alt=""><br>
<br>
<br>
</font><br>
<div id="content" class="error">
<h1><br>
</h1>
<h1>TRAC ERROR</h1>
<p>==================================================<br>
</p>
<h1>Oops…</h1>
<div class="message"> <strong>Trac detected an internal error:</strong>
<pre>IOError: [Errno 2] No such file or directory: ''</pre>
</div>
<p>There was an internal error in Trac. It is recommended that
you notify your local Trac administrator with the information
needed to reproduce the issue.</p>
<form class="newticket" method="get" action="/Cbc/newticket#">
<p>To that end, you could <span class="inlinebuttons"> </span>
a ticket.</p>
</form>
<p>The action that triggered the error was:</p>
<pre>POST: /register</pre>
<p> <a moz-do-not-send="true"
href="https://projects.coin-or.org/Cbc/wiki/TracGuide">TracGuide</a>
— The Trac User and Administration Guide </p>
</div>
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