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<div dir="ltr" align="left"><span class="304255102-02112009"><font face="Arial" color="#0000ff" size="2">Hi again John,</font></span></div>
<div dir="ltr" align="left"><span class="304255102-02112009"><font face="Arial" color="#0000ff" size="2"></font></span> </div>
<div dir="ltr" align="left"><span class="304255102-02112009"><font face="Arial" color="#0000ff" size="2">As I mentioned before this solution works well, thanks again. Total runtime is around 300 seconds.</font></span></div>
<div dir="ltr" align="left"><span class="304255102-02112009"><font face="Arial" color="#0000ff" size="2">However, when I went to implement this solution in my TP application I found that the runtime drastically increased to over 2 hours.</font></span></div>
<div dir="ltr" align="left"><span class="304255102-02112009"><font face="Arial" color="#0000ff" size="2"></font></span> </div>
<div dir="ltr" align="left"><span class="304255102-02112009"><font face="Arial" color="#0000ff" size="2">After some investigation I found that the solution found by RENS in the TP application was not within the 0.01% gap, but it is when I use driver4 with the
settings below.</font></span></div>
<div dir="ltr" align="left"><span class="304255102-02112009"><font face="Arial" color="#0000ff" size="2">The only difference I could find was that in my TP application the problem is modelled as a maximization but because the driver1 program reads an mps file
containing the problem, this is already a minimization.</font></span></div>
<div dir="ltr" align="left"><span class="304255102-02112009"></span><span class="304255102-02112009"><font face="Arial" color="#0000ff" size="2">When I negated the all the objective function coefficients and made the original problem a minimization in the TP
application itself, the runtime was back down to about 300 seconds.</font></span></div>
<div dir="ltr" align="left"><span class="304255102-02112009"><font face="Arial" color="#0000ff" size="2"></font></span> </div>
<div dir="ltr" align="left"><span class="304255102-02112009"><font face="Arial" color="#0000ff" size="2">Regards,</font></span></div>
<div dir="ltr" align="left"><span class="304255102-02112009"><font face="Arial" color="#0000ff" size="2">Michael De Feyter</font></span></div>
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<font face="Tahoma" size="2"><b>From:</b> John J Forrest [mailto:jjforre@us.ibm.com]
<br>
<b>Sent:</b> Thursday, 29 October 2009 11:04 PM<br>
<b>To:</b> Defeyter, Michael<br>
<b>Subject:</b> Re: [Cbc] Cbc hanging<br>
</font><br>
</div>
<div></div>
<p>Michael,<br>
<br>
I don't think it is hanging - just wasting time doing cuts and strong branching.<br>
<br>
One problem is that the heuristics don't seem to work well. There are two which have a chance - rounding and one called RENS. Neither worked with tp.mps. However I noticed that you have pairs of identical rows which are >=0 and <=0. There is code in Cbc to
find identical rows, but I see that it only looks for identical rhs or where one is inside the other. If I manually make all such rows ==0, then rounding and RENS both work well. Cplex has a default to stop if the gap is less than 0.01%. If I do the same in
Cbc it solves in two minutes.<br>
<br>
I have fixed trunk to do something for intersecting identical rows. Very oddly, rounding still does not find anything - but RENS did.<br>
<br>
If you look at driver4.cpp - you can see how to use command line version. With trunk I used<br>
<br>
cbc tp.mps -divingc off -rens on -cuts off -ratio 0.0001 -trust 1 -strong 1 -hot 10 -solve<br>
<br>
The -trust... stuff is just to stop it spending much time in strong branching.<br>
<br>
John Forrest<br>
<br>
<img height="16" alt="Inactive hide details for "Defeyter, Michael" ---10/28/2009 12:27:10 AM---Hi John, I've been testing Cbc with Clp to solve tran" src="cid:304255102@02112009-0BDC" width="16" border="0"><font color="#424282">"Defeyter, Michael" ---10/28/2009
12:27:10 AM---Hi John, I've been testing Cbc with Clp to solve transport assignment problem, normally I use Cplex.</font><br>
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<font color="#5f5f5f" size="2">From:</font></td>
<td width="100%"><img height="1" alt="" src="cid:304255102@02112009-0BE3" width="1" border="0"><br>
<font size="2">"Defeyter, Michael" <Michael.Defeyter@bluescopesteel.com></font></td>
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<font color="#5f5f5f" size="2">To:</font></td>
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<font size="2">"cbc@list.coin-or.org" <cbc@list.coin-or.org></font></td>
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<font color="#5f5f5f" size="2">Date:</font></td>
<td width="100%"><img height="1" alt="" src="cid:304255102@02112009-0BE3" width="1" border="0"><br>
<font size="2">10/28/2009 12:27 AM</font></td>
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<font color="#5f5f5f" size="2">Subject:</font></td>
<td width="100%"><img height="1" alt="" src="cid:304255102@02112009-0BE3" width="1" border="0"><br>
<font size="2">[Cbc] Cbc hanging</font></td>
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<font color="#5f5f5f" size="2">Sent by:</font></td>
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<font size="2">cbc-bounces@list.coin-or.org</font></td>
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<br>
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<font face="Arial">Hi John,</font><br>
<font size="4"></font><br>
<font face="Arial">I've been testing Cbc with Clp to solve transport assignment problem, normally I use Cplex.</font><br>
<font face="Arial">Cbc works fine on smaller versions of the problem but when I use it on the full size problem, it seems to hang after a while.</font><br>
<font face="Arial">The same problem solves fine using Cplex.</font><br>
<font face="Arial">You can download the mps file from this location (it's a 2.6Mb zip file, I was not sure how to upload it to the mailing list so I've put it on my website):</font><br>
<a href="http://www.flightdeckce.com/Download/tp.zip"><u><font face="Arial" color="#0000ff">http://www.flightdeckce.com/Download/tp.zip</font></u></a><br>
<font size="4"></font><br>
<font face="Arial">I solve this using the sample2 code with the preprocess option turned on, when I don't use the preprocess option it solves for a bit longer but eventually hangs as well.</font><br>
<font face="Arial">Thanks in advance,</font><br>
<font size="4"></font><br>
<font face="Arial">Regards,</font><br>
<font face="Arial">Michael De Feyter</font><br>
<font size="4"><br>
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