[Cbc] Performance

[John J Forrest]

Anthony,

Unlike for LP's,  tiny changes to the code can make a large difference in
the running time for MIP's.  I have had cases where what seemed to be a
trivial change has increased the runtime for one problem by a factor of a
100 - without any logical reason that I could see.

However that is not very helpful to you.  Compiling without threads should
make no difference.  Without more information it is difficult to help.  I
would try allowing strong branching and maybe playing with
"trustPseudoCost"

John Forrest


                                                                                                                                             
  From:       Anthony Presley <anthony at resolution.com>                                                                                       
                                                                                                                                             
  To:         cbc at list.coin-or.org                                                                                                           
                                                                                                                                             
  Date:       12/07/2007 01:15 PM                                                                                                            
                                                                                                                                             
  Subject:    [Cbc] Performance                                                                                                              
                                                                                                                                             





All:

I just thought I'd post some performance data we saw with a data set.
It's an integer minimization problem.  I downloaded and tried out cbc 2
(in comparison to cbc 1.2), and ran the model with these parameters (in
both versions):

             import file
             sec 82
             allow 82
             strong 0
             threads 3
             solve

I also tried with threads -1, 1, 2, 3, and 0.

Overall, the end result is that cbc 1.2 takes 30 - 32 seconds, and cbc
2.0 takes about 78 - 80 seconds.

The only difference that I know of (besides the version and features in
the software) is that cbc 2.0 was compiled with
--enable-cbc-parallel  .... ie, I so no speed improvement with parallel
enabled.

I haven't tried cbc 2 without the "--enable-cbc-parallel".

We will continue using CBC 1.2, but just wanted to see if there was
anything we might want to look at that may be slowing down the solution.
Did some of the defaults change?


--
Anthony

_______________________________________________
Cbc mailing list
Cbc at list.coin-or.org
http://list.coin-or.org/mailman/listinfo/cbc