<br><font size=2 face="sans-serif">This advice looks very promising. So
far, however, the results are a bit confusing.</font>
<br>
<br><font size=2 face="sans-serif">Using "Version A" as described
earlier, the branch-and-bound algorithm processed 24 nodes to find and
prove an optimal solution to our test problem.</font>
<br>
<br><font size=2 face="sans-serif">When I redesigned our application to
follow the calling sequence in driver4.cpp, the sequence of messages changed
quite drastically. There is now a series of messages of type Cbc0038I
describing the operation of the "feasibility pump". Then
a Cbc0012I message reports that an integer solution was found by the feasibility
pump.</font>
<br>
<br><font size=2 face="sans-serif">Immediately thereafter, a Cbc0027I message
announces "Exiting on user event"; this is followed by a Cbc0005I
message which says, "Partial search - ... took 0 iterations and 0
nodes", and then we launch into a post-mortem, mostly without message
codes, that adds "Result - user ctrl-c Objective ..." This
suggests that the application thinks I have interrupted the run. Could
the pseudo-command-line "-quit" command be being processed prematurely?
Or is all the work that used to be done by branch-and-bound now somehow
being done by the feasibility pump instead?</font>
<br>
<br><font size=2 face="sans-serif">It certainly looks as if something is
interrupting the search. Maybe I should remove the -quit command?</font>
<br>
<br><font size=2 face="sans-serif">Thank you for your assistance.</font>
<br>
<br>
<br>
<table width=100%>
<tr valign=top>
<td><font size=1 color=#5f5f5f face="sans-serif">From:</font>
<td><font size=1 face="sans-serif">John J Forrest <jjforre@us.ibm.com></font>
<tr valign=top>
<td><font size=1 color=#5f5f5f face="sans-serif">To:</font>
<td>
<tr>
<td valign=top><font size=1 color=#5f5f5f face="sans-serif">Cc:</font>
<td><font size=1 face="sans-serif">cbc@list.coin-or.org</font>
<tr valign=top>
<td><font size=1 color=#5f5f5f face="sans-serif">Date:</font>
<td><font size=1 face="sans-serif">12/17/2008 04:30 AM</font>
<tr valign=top>
<td><font size=1 color=#5f5f5f face="sans-serif">Subject:</font>
<td><font size=1 face="sans-serif">Re: [Cbc] Clues sought on how to diagnose
Cbc performance changes</font></table>
<br>
<hr noshade>
<br>
<br>
<br><font size=3>Allan,<br>
<br>
I would suggest looking at the example driver4.cpp. With that you should
get all the performance advantages of the stand-alone solver.<br>
<br>
John Forrest<br>
<br>
</font><img src=cid:_1_078F5494078F510C0077EF4485257524 alt="Inactive hide details for acw---12/16/2008 07:15:55 PM---A little while ago I sent the following message to Coin-discuss. The l"><font size=3 color=#424282>acw---12/16/2008
07:15:55 PM---A little while ago I sent the following message to Coin-discuss.
The last time I paid serious attention, there was no mailing</font><font size=3><br>
</font>
<table width=100%>
<tr valign=top>
<td width=21%><img src=cid:_1_078F63E8078F5FE80077EF4485257524><font size=2 color=#5f5f5f><br>
From:</font>
<td width=78%><img src=cid:_1_07A45E64078F68F80077EF4485257524><font size=2><br>
acw@ascent.com</font>
<tr valign=top>
<td><img src=cid:_1_07A4656007A461600077EF4485257524><font size=2 color=#5f5f5f><br>
To:</font>
<td><img src=cid:_1_07A46B3807A467640077EF4485257524><font size=2><br>
cbc@list.coin-or.org</font>
<tr valign=top>
<td><img src=cid:_1_07A4711007A46D3C0077EF4485257524><font size=2 color=#5f5f5f><br>
Date:</font>
<td><img src=cid:_1_07A476E807A473140077EF4485257524><font size=2><br>
12/16/2008 07:15 PM</font>
<tr valign=top>
<td><img src=cid:_1_078EA04407A478EC0077EF4485257524><font size=2 color=#5f5f5f><br>
Subject:</font>
<td><img src=cid:_1_078EA4CC07A47A3C0077EF4485257524><font size=2><br>
[Cbc] Clues sought on how to diagnose Cbc performance changes</font></table>
<br>
<hr noshade><font size=3><br>
<br>
<br>
<br>
A little while ago I sent the following message to Coin-discuss. The last
time I paid serious attention, there was no mailing list devoted to Cbc,
but now I discover that there is, and this was probably a better place
to ask my question. I apologize to those who are seeing my query twice.</font><font size=4>
</font><font size=2 color=#800080><br>
----- Forwarded by Allan C Wechsler/Cambridge/Ascent on 12/16/2008 07:11
PM -----</font><font size=4> </font>
<table width=100%>
<tr valign=top>
<td width=10%><font size=2 color=#5f5f5f>From:</font><font size=4> </font>
<td width=89%><font size=2>acw@ascent.com</font><font size=4> </font>
<tr valign=top>
<td><font size=2 color=#5f5f5f>To:</font><font size=4> </font>
<td><font size=2>coin-discuss@list.coin-or.org</font><font size=4> </font>
<tr valign=top>
<td><font size=2 color=#5f5f5f>Date:</font><font size=4> </font>
<td><font size=2>12/16/2008 06:14 PM</font><font size=4> </font>
<tr valign=top>
<td><font size=2 color=#5f5f5f>Subject:</font><font size=4> </font>
<td><font size=2>[Coin-discuss] Clues sought on how to diagnose Cbc performance
changes</font></table>
<br><font size=3><br>
</font>
<hr noshade><font size=4><br>
</font><font size=3><br>
<br>
<br>
About two years ago, we built an application around the then-current release
of Cbc. For the sake of discussion, call this "Version A."</font><font size=4>
</font><font size=3><br>
<br>
Very recently, we downloaded a much more recent release, and re-architected
the application. This "Version B" has exactly the same API as
Version A, but the details of the systems integration are different in
a variety of ways. <br>
<br>
Version A was essentially a hack-job on CbcMain's command-line interface:
for example, it launched the Cbc solver by faking a "branch"
command. Version B, in contrast, was written along the lines of some of
the simpler examples in Cbc/examples, and since it leaves out most of the
machinery of the command-line interface, it's about a factor of ten shorter.</font><font size=4>
</font><font size=3><br>
<br>
To my (perhaps naive) surprise, Version B is far less efficient than Version
A. On one small example problem, Version A processed 24 nodes to solve
the problem, while Version B processed 52 nodes, more than twice as many.</font><font size=4>
</font><font size=3><br>
<br>
It is obvious that we have made at least one ill-advised change in cut,
node, or branch selection, or in presolve/postsolve processing. We have
avoided customizations we did not understand, and in most cases used the
default choices that were implicit in the two versions of Cbc.</font><font size=4>
</font><font size=3><br>
<br>
We have tried more-or-less blind flailing in our attempts to regain the
lost performance efficiency, exploring Version A and experimenting with
transplanting various customizations from there to Version B, but nothing
has had an effect of more than about 10%, compared to the more than 2-to-1
discrepancy between the two versions.</font><font size=4> </font><font size=3><br>
<br>
Obviously Cbc has not regressed; it is our own ignorance of how to configure
it that is at fault. But we don't even know how to begin the analysis that
would reveal fruitful avenues to take. We would appreciate any advice.
I haven't provided much detail about our configuration, because I don't
know what aspects of it are important, but I'd be pleased to answer any
questions that would help someone give us some guidance.</font><font size=4>
</font><font size=3><br>
<br>
Thank you for your consideration, and for the enormous amount of work that
has clearly been put into making Cbc a useful tool.</font><tt><font size=3>_______________________________________________<br>
Coin-discuss mailing list<br>
Coin-discuss@list.coin-or.org</font></tt><font size=3 color=blue><u><br>
</u></font><a href="http://list.coin-or.org/mailman/listinfo/coin-discuss"><tt><font size=3 color=blue><u>http://list.coin-or.org/mailman/listinfo/coin-discuss</u></font></tt></a><tt><font size=3>_______________________________________________<br>
Cbc mailing list<br>
Cbc@list.coin-or.org</font></tt><tt><font size=3 color=blue><u><br>
</u></font></tt><a href="http://list.coin-or.org/mailman/listinfo/cbc"><tt><font size=3 color=blue><u>http://list.coin-or.org/mailman/listinfo/cbc</u></font></tt></a><font size=3><br>
<br>
</font><tt><font size=2>_______________________________________________<br>
Cbc mailing list<br>
Cbc@list.coin-or.org<br>
</font></tt><a href="http://list.coin-or.org/mailman/listinfo/cbc"><tt><font size=2>http://list.coin-or.org/mailman/listinfo/cbc</font></tt></a><tt><font size=2><br>
</font></tt>
<br>