[SCIP] How to add priced variable to a row?

[Matheus Ota]

Hi Gerald,

Nevermind, I made it work now. I disabled the primal heuristics using:

SCIPsetHeuristics(scip, SCIP_PARAMSETTING_OFF, TRUE)



2018-06-05 16:48 GMT-03:00 Matheus Ota <matheusota at gmail.com>:

> Dear Gerald,
>
> Thanks to your answer I was able to solve the problem. What I did is that
> I removed the SCIPreleaseRow when creating the cut and check with
> SCIProwIsInLP before trying to add the variable to the row. I also remove
> from the data structure and release the row if it is not in the LP.
>
> Now I'm getting another error, after calling the CONSEPALP method from the
> constraint handler, the code goes into infinite loop and just stops after
> pressing CTRL+C 2 times.
>
> Debugging the CONSEPALP I discovered that the current solution is feasible
> but not integer. Therefore, no cuts are added. So the code exit with result
> = SCIP_DIDNOTFIND.
> After the CONSEPALP I would expect SCIP to call the my Branching Rule, but
> this only happens after pressing CTRL+C 2 times (and the solution that I
> get is not optimal).
>
> Here is a part of my output:
>
>> ...
>> [cvrpcutscallbackscip.cpp:85] debug: consepalp
>> ^Cpressed CTRL-C 1 times (5 times for forcing termination) -> INFINITE
>> LOOP HERE
>> ^Cpressed CTRL-C 1 times (5 times for forcing termination)
>> [cvrpcutscallbackscip.cpp:106] debug: consenfolp
>> [cvrpbranchingrule.cpp:294] debug: branching execlp
>> ...
>>
>
> Do you have any tips here?
>
> Thanks,
> Matheus
>
> 2018-06-05 13:29 GMT-03:00 Gerald Gamrath <gamrath at zib.de>:
>
>> Dear Matheus,
>>
>> probably, you are not capturing the rows using SCIPcaptureRow(). In that
>> case, the row structure may have been freed in the meantime, resulting in
>> the segmentation fault.
>> Note that the cuts that you add to the LP are in fact added to the
>> sepastore, which filters the cuts and finally adds some of them to the LP
>> and discards the others. Also, rows may be removed later from the LP due to
>> aging. Those rows are freed if they were not captured or added to the cut
>> pool as well, which however, is not possible for modifiable cuts.
>> If you capture the rows when creating them (and release them at some time
>> after solving), you avoid the segmentation fault. Additionally, you might
>> want to check if the row is still in the LP via SCIProwIsInLP() and update
>> it only if this returns TRUE (you might even release it then and remove it
>> from your data structures).
>>
>> There is no such thing as a transformed row since rows can only be
>> created after the problem is transformed, so there cannot be rows in the
>> original space. concerning your code snipped for the constraints: I would
>> recommend to get the transformed counterparts of the original constraints
>> once and use those directly later. This should typically be done in the
>> INIT callback of a plugin.
>>
>> Best,
>> Gerald
>>
>>
>> On 05.06.2018 02:05, Matheus Ota wrote:
>>
>> Hi All,
>>
>> I'm sorry for asking again, but I'm not able to find the answer on the
>> internet. I'm implementing a Branch-Cut-and-Price algorithm. The Constraint
>> Handler creates rows and adds them using SCIPaddCut. Then, when a new
>> variable is generated during column generation, it should be inserted in
>> the rows created by the Constraint Handler. The problem is that I'm getting
>> a segmentation fault when doing this.
>>
>> What I'm doing is calling a "pricing" routine on the PRICERFARKAS and
>> PRICERREDCOST methods. This pricing routing tries to adds to the row using
>> the following piece of code:
>>
>> SCIP_CALL(SCIPaddVarToRow(scip, row, var, coef));
>>
>> I also already made sure that when creating the rows they are set to
>> modifiable = true
>>
>> Should I use some kind of "getTransformedRow" before calling the addVar?
>>
>> The following is my code for SCIP_CONS, instead of SCIP_ROWS, and it
>> works fine:
>>
>> SCIP_CONS *transfCons;
>> SCIPgetTransformedCons(scip, cons, &transfCons);
>> SCIP_CALL(SCIPaddCoefLinear(scip, transfCons, var, coef));
>>
>> Do anyone have some tips here?
>>
>> Thanks,
>> Matheus
>>
>>
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>>
>>
>>
>
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