[Scip] Problem with Conflict Analysis

[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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