[SCIP] Disable knapsack cardinality cuts

[Marc Pfetsch]

Dear Tobias,

from what I see in the code, there is no parameter that allows to turn 
off knapsack separation. We will probably add this some time in the future.

For you, the best would probably to add the parameter yourself and then 
change it for the instances in which separation hurts you.

Best

Marc


On 29/10/2021 12.30, Stengel, Tobias wrote:
> Hello,
> 
> I'm using SCIP 7.0.3 for branch&cut with problem specific cut generation 
> (constraint handler adding rows). All separators are turned off by not 
> including the plugins.
> 
> I noticed that SCIP is spending a significant amount of time separating 
> knapsack cardinality cuts at the root node within the linear constraint 
> handler. Those cuts do not improve the dual bound for my problem.
> 
> As far as I can see this is caused by cons_linear.c line 15872ff because 
> in the root node the local bound equals the global bound and therefore
> 
> /SCIPisLE(scip, loclowerbound, maxbound);/
> 
> return TRUE (with equality) no matter what value I set to 
> "/constraints/linear/maxcardbounddist/".
> 
> There are a few other parameter controlling the separation of linear 
> constraints, but I'm not sure what side effects it can have to disable 
> separation of linear constraints e.g. by setting
> 
> constraints/linear/maxrounds = 0
> 
>   All my linear constraints are initial=TRUE and removable=FALSE.
> 
> As a workaround I can modify  cons_linear.c but it will probably hurt 
> for general MIP I'd like to solve with the same build...
> 
> Is there a clean way to disable knapsack cardinality cuts by setting 
> parameters?
> 
> With best regards,
> Tobias Stengel
> 
> Siemens Digital Logistics GmbH
> SL SDL TEC R&D SCS
> Stumpfstr. 1
> 76131 Karlsruhe, Germany
> mailto:tobias.stengel at siemens-logistics.com 
> <mailto:tobias.stengel at siemens-logistics.com>
> www.siemens-digital-logistics.com <http://www.siemens-digital-logistics.com>
> 
> Management: Christopher Christian, Christian Schmidt
> Registered office: Nachtweideweg 1-7, 67227 Frankenthal, Germany
> Register Court: Ludwigshafen am Rhein, HRB 64386
> 
> 
> _______________________________________________
> Scip mailing list
> Scip at zib.de
> https://listserv.zib.de/mailman/listinfo/scip
>