[Scip] Solving opb instances + initial solutions

[Stefan Heinz]

Hi Luigi,

If you have solution candidate at hand, you can pass it to SCIP. This 
can be done via the interactive shell

SCIP> read <solutionfile>.sol

Therefore the solution has to be in a special form. That is

x_1 value
x_2 value
x_3 value
x_4 value
...
x_n value

If you just want to provide an upper bound you can set an objective limit.

SCIP> set limit objective 100

This can be done after you have load the problem into SCIP.

If you are using SCIP via the callable library. Both versions are also 
possible. For that see:

http://scip.zib.de/doc/html/FAQ.html#Q3.2
http://scip.zib.de/doc/html/scip_8h.html#a4312fff0495bec0484a8fd9cd60cae8b
http://scip.zib.de/doc/html/scip_8h.html#a3fd90b931b38d2d8f344114babc2a67e

I would always prefer the first version (providing the solution) since 
improving heuristics could find a better solution.

Best Stefan



On 01/20/12 16:51, Luigi Malagò wrote:
> hello mailing list,
> right now i'm solving non linear pseudo-boolean functions f, which are 
> parsed from the OPB format, e.g.
>
> * #variable= 5 #constraint= 4
> *
> * this is a dummy instance
> *
> min: 1 x2 -1 x3 ;
> 1 x1 +4 x2 -2 x5 >= 2;
> -1 x1 +4 x2 -2 x5 >= +3;
> 12345678901234567890 x4 +4 x3 >= 10;
> * an equality constraint
> 2 x2 +3 x4 +2 x1 +3 x5 = 5;
>
> (take from the http://www.cril.univ-artois.fr/PB10/format.pdf )
>
> i would like to speed up the solver, since i have (from some 
> heuristic) a candidate optima solution for each instance
>
> i am minimizing f and i would like like to provide an upper bound for 
> it (my candidate solutio from the heuristic).
>
> can i insert it the OPB file?
> if not, in case I re-implement the opb_reader, which method should i 
> call to provide the solver with an initial solution?
> i checked the documentation, but didnt find any usefull method. maybe 
> i'm looking in the wrong place..
>
> thanks alot for your help,
> luigi
>
>
> _______________________________________________
> Scip mailing list
> Scip at zib.de
> http://listserv.zib.de/mailman/listinfo/scip