[Scip] Problem with Conflict Analysis

[Ambros Gleixner]

Hi Alexander,

is the value of the variable responsible for the lower bound change 
tighter than the value that was stored in inferinfo?

I think this could be correct, if global bound changes have occured in 
the meantime.  Can somebody confirm this?

Ambros




Am 10.10.2013 17:15, schrieb Alexander Schnell:
> Dear Marc,
>
> my problem is not about the variable
> for which the lower bound change is applied (infervar) but about the
> variable responsible for the lower bound change
> (i.e. the lower bound of this variable).
>
> For this variable SCIPvarGetLbAtIndex(...,...,TRUE) and
> SCIPvarGetLbAtIndex(...,...,FALSE) are the same values.
>
> I integrate the lower bound of this variable as an integer inferinfo
> in the function SCIPinferVarLbCons(). Moreover, if I query
> the lower bound of this variable in the CONS_RESPROP function
> by SCIPvarGetLbAtIndex(), this does not correspond to the
> inferinfo value.
>
> Note, that I can be sure that the value returned
> from SCIPvarGetLbAtIndex() is integer (I tested it by
> SCIPisFeasIntegral()).
>
> Best regards,
> Alexander
>
>
>
>
>
>
> On Thu, 2013-10-10 at 16:09 +0200, Marc Pfetsch wrote:
>>
>> Dear Alexander,
>>
>> the function SCIPvarGetLbAtIndex() contains a parameter in which you can
>> specify whether the bound change in questions has already been applied.
>> To which value have you set this value? In principle, you should be able
>> to reconstruct the bound change at that time (using infervar and the
>> above function).
>>
>> Please also check whether the bound change via SCIPinferVarLbCons()
>> actually changed the bound (check return values infeasible and tightened).
>>
>> You can look at other examples of conflict resolution, e.g.,
>> cons_linearordering.c in examples/LOP. Please note that implementing
>> conflict resolution always is a tricky thing.
>>
>> If this does not explain the problem, we would need more details from
>> you in order to be able to reconstruct the problem. Possibly off this
>> list ...
>>
>> Best
>>
>> Marc
>>
>>
>> On 10.10.2013 15:32, Alexander Schnell wrote:
>>> Dear SCIP team,
>>>
>>> I implemented a Constraint Handler for a special
>>> project scheduling problem.
>>>
>>> In the CONS_RESPROP function, I try to explain the bound
>>> changes processed through the propagation algorithm implemented in
>>> the CONS_PROP function.
>>>
>>> In the function for the explanation generation, I observed a problem
>>> with the function SCIPvarGetLbAtIndex(...):
>>>
>>> In the propagation algorithm, the lower bound is propagated with
>>> the function SCIPinferVarLbCons(). I integrate the integer lower bound
>>> of the variable responsible for the processed bound change as an
>>> inferinfo in this function.
>>>
>>> In the CONS_RESPROP function, I compare the latter value with the actual
>>> lower bound of the responsible variable given by
>>> SCIPvarGetLbAtIndex(...) at the given bound change index.
>>>
>>> My problem is that these values are not the same, which should not be
>>> the case in my understanding.
>>>
>>> Thank you in advance for your help.
>>>
>>> Best regards,
>>> Alexander Schnell
>>>
>>>
>>>
>>>
>>>
>>>
>>>
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>
>
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-- 
____________________________________________________________
Ambros M. Gleixner
Zuse Institute Berlin - Matheon - Berlin Mathematical School
http://www.zib.de/gleixner