[Scip] Transformed constraints

michael.winkler@zib.de michael.winkler at zib.de
Fri May 14 02:03:41 MEST 2010


Hi Julio,

> [logicor] <both_x1x2_a>: logicor(<t_y12>, <t_x1_neg>, <t_x2_neg>);
> [setppc] <both_x5x6_b_clq_0_0>: +<t_y56> +<t_x6_neg> <= 1;
>
> The second one, I think the presolver took it by decomposing another
> constraint in two. But the first one, I don't have a clue of what it
> means.

Yes, the presolver extracted the second constraint out of another. The
first one is an upgraded special linear constraint.

> Can somebody care to explain what "logicor" and "setppc" mean?

"setppc" and "logicor" constraints are a special type of linear
constraints containing only binary variables and as coefficients and right
hand side and/or left hand side only ones.

"setppc" comprises three subtypes,

set partitioning: sum_i^n x_i = 1

set packing: sum_i^n x_i <= 1

set cover: sum_i^n x_i >= 1

"logicor" constraints looks like set cover constraints, but are handled
differently inside SCIP.

> Is there a way to directly include this kind of constraints using the
> standalone solver?

Do you mean that if the standalone solver is able to read these kind of
constraints in the format above? Then now, SCIP is not able to read this
format (CIP format) directly, but we are working on it and hopefully it
will be possible to read this format after our next release. But you can
easily write these kinds of constraints as (normal) linear constraints
(e.g. in lp format) and SCIP will recognize and upgrade them to their
special linear contraint types.
( If you are programming with SCIP, you can call
SCIPcreateConsLogicor/SCIPcreateConsSetpart/SCIPcreateConsSetpack/SCIPcreateConsSetcover
to directly create these special types of constraints. See more at
http://scip.zib.de/doc/html/index.html )

Hope that helps you a little bit, have fun.

Best regards,

Michael


> Dear all, I'm really new to linear optimization in general and binary
> integer programming in particular. I mostly use very simple models for
> clustering and bundling problems. In one of them I see that there are
> some transformed constraints after the presolver passes by:
>
> [logicor] <both_x1x2_a>: logicor(<t_y12>, <t_x1_neg>, <t_x2_neg>);
> [setppc] <both_x5x6_b_clq_0_0>: +<t_y56> +<t_x6_neg> <= 1;
>
> The second one, I think the presolver took it by decomposing another
> constraint in two. But the first one, I don't have a clue of what it
> means. Can somebody care to explain what "logicor" and "setppc" mean?
> Is there a way to directly include this kind of constraints using the
> standalone solver?
>
> Thanks in advance for your help. Best regards.
> -------------------------------------------------
> Julio Rojas
> jcredberry at gmail.com
> _______________________________________________
> Scip mailing list
> Scip at zib.de
> http://listserv.zib.de/mailman/listinfo/scip
>



More information about the Scip mailing list