[SCIP] Dealing with a problem that contains a specific structure with a standard MILP solver

[Abbas Omidi]

Dear Alexander,

Thank you so much for your quick response.
Please, let me explain more about what I meant.

I am currently working on a scheduling problem and its structures, indeed
from the modeling point of view, to investigate how a standard MIP solver
like SCIP or Gurobi can solve this problem efficiently.
For that, I am using GCG, actually PyGCGopt, to analyze these problems. In
my previous email, I asked about some parameters at GCG that seed up the
solving process, and the comment by Prof. Lübbecke was really helpful.

Now, at the moment I do not need to use/implement this method manually and
I think everything can be done automatically. Also, on the other hand, I am
not aware of that the SCIP has a tool that applies cons_components
<https://www.scipopt.org/doc-8.0.2/html/cons__components_8c.php> as a
successful presolving technique. By that, my questions are:

1) Is it possible to employ the mentioned decomposition by using the
command line? (e.g. read problem -> set this method -> optimize)
2) Is there any Python implementation, PySCIPopt, that shows how we can use
this method? (unfortunately, I do not have more experience with C/C++)
3) Based on the mentioned "successful presolving technique", can we infer
that commercial solvers like Gurobi and CPLEX have gained from such
techniques under a hood?

Best regards
Abbas


On Mon, Feb 5, 2024 at 2:09 PM Hoen, Alexander <hoen at zib.de> wrote:

> Hi Abbas,
>
>
> SCIP allows the user to provide a problem decomposition. Section 4.2 in
> the SCIP 7 Release report describes how SCIP uses the decomposition.
>
> On https://www.scipopt.org/doc-8.0.2/html/DECOMP.php there is an
> explanation of how to provide such a decomposition.
>
> Best,
>
> Alex
> ------------------------------
> *From:* Scip <scip-bounces at zib.de> on behalf of Abbas Omidi <
> abb.omidi at gmail.com>
> *Sent:* Monday, February 5, 2024 10:49:50 AM
> *To:* scip at zib.de
> *Subject:* [SCIP] Dealing with a problem that contains a specific
> structure with a standard MILP solver
>
> Dear support team,
>
> Suppose we have a specific formulation which contains a particular
> structure. For example, the formulation contains a block diagonal format
> with some linking constraints or variables.
>
> As far as I know, this format would be suitable for the decomposition
> scheme. Now, I am interested to know if is there any benefit to using this
> special structure with a standard MILP solver line SCIP or Gurobi.
>
> All the best
> Abbas
>
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