[Scip] SCIP_DIDNOTRUN in SCIP_DECL_PRICERREDCOST ?

[Gerald Gamrath]

Dear Sandra,

it looks like you are still using SCIP 3.1. The issue should have been 
fixed with the latest bugfix release 3.1.1, please check if this is the 
case.

A general remark: When doing branch-and-price, you should also implement 
your own branching rule, since the default rules branching on variables 
aren't well suited for a branch-and-price algorithm. Just have a look at 
Coloring or Binpacking example and some discussions on the mailing list 
in the last months.

Best,
Gerald

> Hello,
>
> I am doing a Branch-and-Price with SCIP, where the subproblem (pricer) 
> consists in solving a MIP with IloConcert (Cplex), with a predefined 
> time limit DeltaT. DeltaT = "total time allowed for the entire 
> branch-and-price" minus "time elapsed since the beginning of the 
> branch-and-price".
>
> If cplex finds the optimal solution, we set *result=SCIP_SUCCESS, then 
> add the columns found, if there are any. Otherwise (if cplex stops 
> because of the time limit DeltaT), we set *result=SCIP_DIDNOTRUN.
>
> For some instances, the following assertion fails: 
> rc/scip/branch_relpscost.c:928: execRelpscost: Assertion 
> `SCIPisLT(scip, provedbound, SCIPgetCutoffbound(scip))' failed.
>
> It seems to happen only when DeltaT was unsufficient to solve a 
> subproblem, therefore when *result was set to SCIP_DIDNOTRUN.
>
> In the LOP example, the lower bound pointer is set just after setting 
> *result=SCIP_DIDNOTRUN (line 503 of pricer_coloring.c). Is it 
> mandatory for the code to be correct ? Is the absence of this 
> instruction the raison of the failed assertion ? Is it possible to set 
> *lowerbound = -SCIP(infinity) or *lowerbound=0 ?
>
> Thank you for your help,
>
> Best regards,
>
> Sandra
>
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