<br><font size=2 face="sans-serif">We are in the process of migrating from
OSL to COIN/Bcp. Mostly the process has gone quite well, but recently
I received quite a shock concerning performance.</font>
<br>
<br><font size=2 face="sans-serif">I have a MIP problem which OSL completes
in about 25 seconds; the same problem takes COIN/Bcp about 290 seconds.
This is more than an order of magnitude discrepancy, which would
be unacceptable on some of our larger problems.</font>
<br>
<br><font size=2 face="sans-serif">I can think of several possible explanations.</font>
<br>
<br><font size=2 face="sans-serif">We are using the BranchAndCut example
almost unchanged; the only modifications we have made were to interface
the code to our LP server. Perhaps BranchAndCut uses cut generation
and variable selection that is only appropriate to small problems, and
we have to do more research to figure out how to guide the branching process.
Maybe it's as simple as selecting the right values for the branching
control parameters.</font>
<br>
<br><font size=2 face="sans-serif">Perhaps the main time-sink is communication
between the TM and LP modules. BranchAndCut uses the "BCP_message_single"
communications protocol, which has to pack and unpack every LP problem
and solution. Doubtless this could be streamlined, but we don't want
to open that can of worms unless the potential gain is great (like a factor
of 3 or more).</font>
<br>
<br><font size=2 face="sans-serif">And of course there is the possibility
that we are doing something else completely stupid that we're not even
aware of.</font>
<br>
<br><font size=2 face="sans-serif">So I'm appealing to the community. What
experiences have you had regarding performance? What approaches have
worked? What stupid mistakes should we be careful to avoid?</font>
<br>
<br><font size=2 face="sans-serif">If there is interest, I can post an
MPS file containing the test problem in question.</font>
<br>
<br><font size=2 face="sans-serif">Thanks in advance.</font>