[Scip] Segmentation Fault

[Stefan Vigerske]

Hi,

did you compile SCIP with CLP from source or you downloaded a binary?

If you got it from source, go into the scip-1.2.0 directory and do
  patch -p1 < scip.patch
Then recompile.
Or you can look at scip.patch and change things in the souce by hand.
Important are those in lpi_clp.cpp and heur_trivial.c.

If you downloaded a binary, then for which platform?

Stefan


Am 19.11.2009 11:21, schrieb 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
>>
>>
>