[Scip] Heuristics - Shift and Propagate

[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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