<br><font size=2 face="sans-serif">Rolf,</font>
<br>
<br><font size=2 face="sans-serif">CbcModel::setCutoffIncrement(0.1);</font>
<br>
<br><font size=2 face="sans-serif">John</font>
<br>
<br>
<br>
<table width=100%>
<tr valign=top>
<td width=40%><font size=1 face="sans-serif"><b>Rolf Steenge <rolf.steenge@planet.nl></b>
</font>
<br><font size=1 face="sans-serif">Sent by: coin-discuss-bounces@list.coin-or.org</font>
<p><font size=1 face="sans-serif">06/06/2006 08:45 AM</font>
<table border>
<tr valign=top>
<td bgcolor=white>
<div align=center><font size=1 face="sans-serif">Please respond to<br>
Discussions about open source software for Operations Research
<coin-discuss@list.coin-or.org></font></div></table>
<br>
<td width=59%>
<table width=100%>
<tr valign=top>
<td>
<div align=right><font size=1 face="sans-serif">To</font></div>
<td><font size=1 face="sans-serif">"'Discussions about open source
software for Operations Research'" <coin-discuss@list.coin-or.org></font>
<tr valign=top>
<td>
<div align=right><font size=1 face="sans-serif">cc</font></div>
<td>
<tr valign=top>
<td>
<div align=right><font size=1 face="sans-serif">Subject</font></div>
<td><font size=1 face="sans-serif">RE: [Coin-discuss] Suggestions on how
to go about tuning?</font></table>
<br>
<table>
<tr valign=top>
<td>
<td></table>
<br></table>
<br>
<br>
<br><font size=3 color=#000080 face="Comic Sans MS">John,</font>
<br><font size=3 color=#000080 face="Comic Sans MS">You wrote :</font>
<br><font size=3> </font>
<br><font size=2 face="Arial"><i>"Again looking at log I saw that
Cbc could work out that valid objective values had to be a multiple of
0.1 so any solution has to be 0.1 better than previous. Going back
to original formulation and setting that value of 0.1 gave 31K nodes
but 305 seconds"</i></font>
<br><font size=3> </font>
<br><font size=3 color=#000080 face="Comic Sans MS">How do you set that
value of 0.1? Or have you added a constraint such as sum of cijxij - 10
xn = 0 with xn a new integer variable.</font>
<br><font size=3> </font>
<br><font size=3 color=#000080 face="Comic Sans MS">Best regards</font>
<br><font size=3 color=#000080 face="Comic Sans MS">Rolf</font>
<br><font size=3> </font>
<br><font size=2 face="Tahoma">-----Original Message-----<b><br>
From:</b> coin-discuss-bounces@list.coin-or.org [mailto:coin-discuss-bounces@list.coin-or.org]
<b>On Behalf Of </b>John J Forrest<b><br>
Sent:</b> Saturday, June 03, 2006 16:02<b><br>
To:</b> Discussions about open source software for Operations Research<b><br>
Subject:</b> Re: [Coin-discuss] Suggestions on how to go about tuning?<br>
</font>
<br><font size=2 face="sans-serif"><br>
Philip,</font><font size=3> <br>
</font><font size=2 face="sans-serif"><br>
I said I would play about with your problem and report on what I did and
how I went about it :</font><font size=3> <br>
</font><font size=2 face="sans-serif"><br>
All these experiments were with stand alone solver - SOS is a bit trickier
and I will get to that later. Also symmetry breaking would help but
I would need help in CglPreProcess and/or pointers to relevant papers.</font><font size=3>
<br>
</font><font size=2 face="sans-serif"><br>
The first thing to do is solve the problem however slowly and look at log
and solution. Using defaults this took 1148 seconds and 150K nodes.
Looking at the log file it looked as if strong branching was not
buying very much. What was more interesting was that all variables
took integer values although only half were declared integer. Assuming
this would always be true I tried setting them all integer. This
time strong branching was kicking in and it took 5K nodes and 413 seconds.
I also saw that cuts and heuristics were not doing much good so switched
them off. </font><font size=3> <br>
</font><font size=2 face="sans-serif"><br>
Again looking at log I saw that Cbc could work out that valid objective
values had to be a multiple of 0.1 so any solution has to be 0.1 better
than previous. Going back to original formulation and setting that
value of 0.1 gave 31K nodes but 305 seconds. Finally in this
phase of tuning I tried switching off strong branching as my hunch was
that it might cost too much for the effect gave an increase in nodes to
38K but the time dropped to 233 seconds.</font><font size=3> <br>
</font><font size=2 face="sans-serif"><br>
Further ideas such as just having some (but not the original set) variables
integer gave various perturbations on time and nodes but no significant
improvement.</font><font size=3> <br>
</font><font size=2 face="sans-serif"><br>
I have started looking at SOS possibilities but am not far along. </font><font size=3>
<br>
</font><font size=2 face="sans-serif"><br>
Basically I use multiple runs and an editor and grep to try and get a feel
for problem.</font><font size=3> <br>
</font><font size=2 face="sans-serif"><br>
John Forrest</font><tt><font size=2>_______________________________________________<br>
Coin-discuss mailing list<br>
Coin-discuss@list.coin-or.org<br>
http://list.coin-or.org/mailman/listinfo/coin-discuss<br>
</font></tt>
<br>