[Scip] Why is SCIP not applying my cuts?

Daniel Karch karch at math.tu-berlin.de
Wed Feb 6 13:25:17 MET 2013


Hi Stefan,

that was indeed the problem. I had used SCIPcreateEmptyRowCons, but my
conshdlr pointer was not
set correctly.

Thanks for your help.

  Daniel

2013/2/3 Stefan Heinz <heinz at zib.de>

> Hi Daniel,
>
> it is most like that there is a "technical" issue. Meaning that your cuts
> are applied but not counted. Therefore, we first need to check this.
>
> Which method are you using to create a row. You should use one of the
> following:
>
> SCIPcreateRowCons()
> http://scip.zib.de/doc/html/**scip_8h.shtml#**
> a8f71263b6e58cb5182ff009720342**651<http://scip.zib.de/doc/html/scip_8h.shtml#a8f71263b6e58cb5182ff009720342651>
>
> SCIPcreateEmptyRowCons()
> http://scip.zib.de/doc/html/**scip_8h.shtml#**
> a41ae66e0ec0e8b636a3185825092f**39f<http://scip.zib.de/doc/html/scip_8h.shtml#a41ae66e0ec0e8b636a3185825092f39f>
>
> Note that SCIPcreateEmptyRow() and SCIPcreateRow() are deprecated since
> the 3.0.0 release.
> See documentation:
> http://scip.zib.de/doc/html/**scip_8h.shtml#**
> a0f3f5d2982142da67c59fb8de0ccb**d9c<http://scip.zib.de/doc/html/scip_8h.shtml#a0f3f5d2982142da67c59fb8de0ccbd9c>
> http://scip.zib.de/doc/html/**scip_8h.shtml#**
> ad250ffa5f36870fc0eb2c10e1e2ea**a67<http://scip.zib.de/doc/html/scip_8h.shtml#ad250ffa5f36870fc0eb2c10e1e2eaa67>
>
> Using one of the "new" methods and passing your constraint handler as
> third argument allows for counting the applied cuts. This actually is the
> reason why we changed the interface for the row creation. With the new
> methods we are now able to print the statistics which type of cuts are
> applied in the end (at least once). Therefore, we (the SCIP core) needs to
> know to which separator or constraint handler a cut belongs.
>
> Are you using the "new" methods?
>
> Best Stefan
>
>
>
>
> On 02/01/2013 04:54 PM, Daniel Karch wrote:
>
>> Hi,
>>
>> I have written a constraint handler for precedence constrained knapsack
>> constraints.
>> When a fractional solution is available, the constraint handler looks for
>> violated induced cover
>> inequalities, and separates them as cuts.
>> However, the cuts are not applied. When the problem is solved, the output
>> shows that
>> e.g. 60 cuts have been found, but 0 applied.
>> Why is that? I am making sure that the inequalities are in fact violated
>> by
>> the LP solution,
>> but the cuts are not applied ...
>>
>> Best regards,
>>
>>    Daniel
>>
>>
>>
>> ______________________________**_________________
>> Scip mailing list
>> Scip at zib.de
>> http://listserv.zib.de/**mailman/listinfo/scip<http://listserv.zib.de/mailman/listinfo/scip>
>>
>
>
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