[SCIP] reoptimization

[Jakob Witzig]

Hi James,

what do you mean exactly with you suspect you doing it wrong? Do you got 
wrong results?

Yes, the parameter mentioned below should exactly do the same as you are 
doing by hand. Do you observe any differences between using the 
parameter and separating OPTSOL by hand?

Cheers,
Jakob


Am 15.09.2016 um 14:03 schrieb James Cussens:
> Dear SCIPers,
>
> I am using reoptimization to solve a series of binary IPs, and I suspect
> I am doing it wrong.
>
> My problem is analogous, I think, to the k-Constrained Shortest Path
> Problem mentioned in Section 4.2 of Jakob Witzig's master thesis. For my
> original IP I want to get the optimal solution, then the 2nd best, then
> 3rd best and so on. The objective function never changes.
>
> I have set reoptimization/enable to TRUE and then do the following:
>
> Do k times:
> ---Solve problem    SCIP_CALL( SCIPsolve(scip) );
> ---store information sufficient to identify optimal solution OPTSOL
> ---SCIP_CALL( SCIPfreeTransform(scip) );
> ---add in constraint ruling out just OPTSOL
>
> I notice that there is a parameter
> # separate the optimal solution, i.e., for constrained shortest path
> # [type: bool, range: {TRUE,FALSE}, default: FALSE]
> reoptimization/sepabestsol = FALSE
>
> which, I suspect, can be used to do what I am doing 'by hand'. Is this
> the case?
>
> More generally, I would appreciate knowing the correct recipe for doing
> this sort of thing (when using the SCIP callable library).
>
> James
>
> --
> James Cussens
> Dept of Computer Science &
> York Centre for Complex Systems Analysis
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>
>
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-- 
Jakob Witzig

Zuse Institute Berlin (ZIB)

Division Mathematical Optimization and Scientific Information
Research Group Mathematical Optimization Methods

Takustrasse 7
14195 Berlin

Tel. : +49 (0)30 84185-416
Fax  : +49 (0)30 84185-269
email: witzig at zib.de