[Scip] cutting plane questions

Tobias Achterberg achterberg at zib.de
Mon Jul 29 21:08:28 MEST 2013


Hi Felix,

FYI: also for your parity_6.lp model, 0 is the optimal objective value.
I solved this with CPLEX 12.5.1, letting it run for some time in default 
settings and then switching to polishing. Polishing itself only took 550 
seconds to improve the incumbent of objective value 7 to one with value 0.

If you are interested in the x vector of the solution, just contact me 
privately.


Regards,

Tobias


On 07/28/13 20:42, Felix Breuer wrote:
> Hello everyone!
>
> I am trying to solve a hard mixed-integer program to optimality.
> However, branch and bound seems to be largely ineffective at finding an
> optimal solution, simply because the search space is way too large.
> (There are 512 binary variables in my program, and I know for
> theoretical reasons that all 2^512 ways of fixing these variables lead
> to a feasible solution.) I'd like to experiment with using cutting
> planes more aggressively to solve the problem, and I have a couple of
> questions:
>
> 0) The "cuts" given by SCIP on the command line when solving the problem
> - do these number give the number of cuts currently in the system, or do
> they give the total number of cuts that have been added in the entire run?
>
> 1) I tried adjusting the many parameters the SCIP offers for controlling
> separators. However, I have been unable to make SCIP use more than about
> 150 cuts. How can make SCIP use even more cutting planes?
>
> 2) In particular, is there a way to configure SCIP not to use
> branch-and-bound at all but only cutting planes to solve the problem? I
> know that conventional wisdom says this is hopelessly inefficient. But
> I'd like to investigate how this approach fares on my problems.
>
> Thank you!
>
> Felix
>
>
>
> --
> http://www.felixbreuer.net
>
>
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