[Scip] Segmentation Fault

[Julio Rojas]

Thanks for the patch, but how can I apply it?
-------------------------------------------------
Julio Rojas
jcredberry at gmail.com


On Thu, Nov 19, 2009 at 11:16 AM, Stefan Vigerske
<stefan at math.hu-berlin.de>wrote:

> Hi,
>
> there is a bug in the SCIP/CLP interface.
> The patch is attached.
>
> Stefan
>
> Am 19.11.2009 10:04, schrieb Julio Rojas:
> > Dear all, I have been using SCIP-CLP to solve some BIP problems of my PhD
> > work. One of the problems has the generic form:
> >
> > Min Sum(Xi)
> > s.t.
> > Xi+Xk <= 1, if Aik=1 and i<k, for i,k in {1,...,n}
> > Xi-Xk = 0, if {Xi,Xk} in Pj for all j in {1,...,g}, g<n
> > Sum(Xi)>=floor(n/2)+1
> > Xi in {0,1}
> >
> > I know that for some setups this problem is unfeasible, but sometimes I
> get
> > segmentation fault errors like in the attached example.
> >
> > I use the standalone solver. After loading it the message presented is
> the
> > following:
> >
> > original problem has 75 variables (0 bin, 75 int, 0 impl, 0 cont) and 846
> > constraints
> >
> > After presolve, the message is:
> >
> > presolving:
> > (round 1) 69 del vars, 690 del conss, 0 chg bounds, 0 chg sides, 0 chg
> > coeffs, 0 upgd conss, 1046 impls, 0 clqs
> > (round 2) 69 del vars, 842 del conss, 0 chg bounds, 0 chg sides, 0 chg
> > coeffs, 0 upgd conss, 1046 impls, 0 clqs
> > (round 3) 69 del vars, 842 del conss, 0 chg bounds, 0 chg sides, 0 chg
> > coeffs, 3 upgd conss, 1046 impls, 0 clqs
> > (round 4) 69 del vars, 842 del conss, 0 chg bounds, 0 chg sides, 0 chg
> > coeffs, 4 upgd conss, 1046 impls, 0 clqs
> > (round 5) 70 del vars, 842 del conss, 0 chg bounds, 2 chg sides, 4 chg
> > coeffs, 4 upgd conss, 1056 impls, 0 clqs
> > (round 6) 71 del vars, 843 del conss, 0 chg bounds, 3 chg sides, 6 chg
> > coeffs, 4 upgd conss, 1060 impls, 0 clqs
> > (round 7) 71 del vars, 846 del conss, 1 chg bounds, 5 chg sides, 8 chg
> > coeffs, 4 upgd conss, 1062 impls, 0 clqs
> > (round 8) 72 del vars, 846 del conss, 1 chg bounds, 5 chg sides, 8 chg
> > coeffs, 4 upgd conss, 1062 impls, 0 clqs
> > presolving (9 rounds):
> >  72 deleted vars, 846 deleted constraints, 1 tightened bounds, 0 added
> > holes, 5 changed sides, 8 changed coefficients
> >  1062 implications, 0 cliques
> > presolved problem has 3 variables (3 bin, 0 int, 0 impl, 0 cont) and 3
> > constraints
> >       1 constraints of type <knapsack>
> >       2 constraints of type <logicor>
> > Presolving Time: 0.01
> >
> > So, as you can see, the problem should be unfeasible, but when I run the
> > solving routine I get the following message:
> >
> >  time | node  | left  |LP iter| mem |mdpt |frac |vars |cons |ccons|cols
> > |rows |cuts |confs|strbr|  dualbound   | primalbound  |  gap
> > t 0.0s|     1 |     0 |     0 | 449k|   0 |   - |   3 |   3 |   3 |   0 |
> > 0 |   0 |   0 |   0 |      --      | 1.192662e+03 |    Inf
> > t 0.0s|     1 |     0 |     0 | 449k|   0 |   - |   3 |   3 |   3 |   0 |
> > 0 |   0 |   0 |   0 |      --      | 1.170286e+03 |    Inf
> > Segmentation fault
> >
> > Any idea on what's happening? Is there a way to avoid this problem? I'm
> > running the standalone solver from an R script, so I don't know if by
> using
> > C I can catch this problem. I don't program in C. Can I trust that when
> this
> > happens the solution is unfeasible? I can cope with this problem if it is
> > presented when the solution is unfeasible and some set of features exist
> in
> > the model.
> >
> > Thank you very much for your help.
> > -------------------------------------------------
> > Julio Rojas
> > jcredberry at gmail.com
> >
> >
> >
> >
> > _______________________________________________
> > Scip mailing list
> > Scip at zib.de
> > http://listserv.zib.de/mailman/listinfo/scip
>
>
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