[Scip] Heuristics - Shift and Propagate

[Jacob Spönemann]

  Hi Stefan,

thanks for the fast reply!

I am using 2.0.1 and, if possible, want stay with it, since I already 
did lots of evaluations with that version.

The only plugin I found which uses a second SCIP instance seems to be 
the heuristic "Crossover", which is called right before the execution of 
"Shift and Propagate" (-> stack trace). So adding 
SCIPcopyParamSettings() in heur_crossover.c right after 
SCIP_CALL(SCIPcreate(&subscip)); could fix my problem?

Unfortunately, the error occurs after more than 3 hours of solving (the 
error does not occur in smaller instances of the underlying problem), so 
testing bugfixes takes some time...

Best regards,

Jacob

Am 02.11.2011 12:51, schrieb Stefan Heinz:
> Hi Jacob,
>
> which SCIP version are you using (I hope 2.1.0 ;-)). Can you send us 
> additionally a back trace.
>
> We are assuming that this problem occurs in subscip where the settings 
> of the master SCIP are not copied. Are you using within one of your 
> plugins a second SCIP instance? If so you should copy the settings by 
> using:
>
> SCIPcopyParamSettings()
> http://scip.zib.de/doc/html/scip_8h.html#ade1245b4b0ecd94c85251d9330ed85ef 
>
>
> Best Stefan
>
> On 11/02/11 09:52, Jacob Spönemann wrote:
>> Hi all,
>>
>> I implemented a column generation algorithm using SCIP and Gurobi.
>>
>> I am running into problems when the heuristic "Shift and Propagate" 
>> is executed (in the end convertSides in lpi_grb.c causes the error 
>> because the Gurobi interface cannot handle ranged rows). I tried to 
>> disable the heuristic by setting the frequency parameter to -1, but 
>> nevertheless the heuristic is executed.
>>
>> I observed that the value of the frequency parameter is set to 0 
>> during solution process. Is there any chance to prevent that?
>>
>> Best regards,
>>
>> Jacob
>>
>> Am 31.01.2011 04:29, schrieb Stephen J Maher:
>>> Hi Gregor,
>>>
>>> I have been using the updated file that you sent to me. It worked well.
>>>
>>> Unfortunately I am having another problem with the shift and 
>>> propagate heuristic. I have disabled it by setting the frequency 
>>> parameter to -1, however I am getting the error
>>>
>>> src/scip/heur_shiftandpropagate.c:1464: heurExecShiftandpropagate: 
>>> Assertion `SCIPisFeasEQ(scip, lb, ub)' failed
>>>
>>> Is there a way for me to avoid this error?
>>>
>>> Thanks for your help,
>>>
>>> Steve
>>>
>>>
>>>
>>> Gregor Hendel wrote:
>>>> Hi Steve,
>>>>
>>>> I have changed the file heur_shiftandpropagate.c, s.t. it should 
>>>> work now. In the attachment, you'll find the file. Just replace
>>>> the old version in <scip-base-dir>/src/scip by the new one. I'm not 
>>>> able to test it on column generation codes, so
>>>> please inform me if this bugfix has fixed your problem sufficiently.
>>>>
>>>>> HI Gregor,
>>>>>
>>>>> I have run my code using the debugger gdb and it seems that the 
>>>>> problem with this heuristic occurs when the rens heuristic is 
>>>>> called. The problem still exists when I disable both, the rens and 
>>>>> shift-and-propagate, heuristics. If I disable all of the 
>>>>> heuristics the problem doesn't occur.
>>>>>
>>>>> I am adding variables dynamically. I have a variable pricer that 
>>>>> adds variables representing network flows. I am also adding 
>>>>> constraints of the problem through a version of benders 
>>>>> decomposition. At each iteration I am removing all variables from 
>>>>> the master problem and reinitialising using the optimal variables 
>>>>> from the previous iteration.
>>>>>
>>>>> The problem is written as a MIP with the network flow variables 
>>>>> being binary and there is a set of continuous variables as well.
>>>>>
>>>>> Thanks a lot for your help.
>>>> Thank you for helping us developing a more stable SCIP version.
>>>>
>>>> Best, gregor
>>>
>>>
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>>
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