[Scip] SCIP v3.2.0 Hanging on Problem
Benjamin Müller
benjamin.mueller at zib.de
Thu Jul 2 11:02:18 CEST 2015
Dear Jonathan,
sorry, I now realized that SCIP does not only run into the time limit
but also gets stuck at node 415. I will have a deeper look at the
problem and write a mail if I figured out the problem.
Best,
Benny
On 07/02/2015 09:08 AM, Benjamin Müller wrote:
> Dear Jonathan,
>
> the problem is that the LP relaxation of this problem is unbounded and
> SCIP has some troubles to find a bounded (linear) one. It would
> definitely help if you give your variables some artificial bounds. I
> tried to replace infinity by M (=1000) and solved the problem in 2s
> and got as solution
>
>
> objective value: -0.250000756970904
> t_xvar0 0.793669420214128 (obj:0)
> t_xvar1 0.707148562806428 (obj:0)
> t_xvar2 0.529706057231088 (obj:0)
> t_xvar3 0.840921294489214 (obj:0)
> t_nlobj -0.250000756970904 (obj:1)
> nlreform0 0.62991145338235 (obj:0)
> nlreform1sp 0.499941002617224 (obj:0)
> nlreform2 0.66741358081024 (obj:0)
> nlreform3 0.374581225460006 (obj:0)
>
> which is far away from M for each variable. Maybe you find some
> artificial bounds which are fine for your purposes.
>
>
> Best regards,
>
> Benny
>
>
> On 07/02/2015 02:31 AM, Jonathan Currie wrote:
>> Hi All,
>>
>> The attached problem hangs (well, fails to make any reasonable progress) in my latest build of SCIP v3.2 with default settings. Original problem:
>>
>> Min -x(1)*x(2)*x(3)*x(4)
>> s.t. x(1)^3 + x(2)^2 - 1 == 0
>> x(1)^2*x(4) - x(3) == 0
>> x(4)^2 - x(2) == 0
>>
>> Any ideas?
>>
>> Thanks,
>> Jonathan
>>
>> SCIP: Solving Constraint Integer Programs [v3.2.0, Built Jul 2 2015, VS2013]
>> - SoPlex [v220] (ZIB Academic License)
>> - Ipopt [v3.12.3] (Eclipse Public License)
>> - CppAD [v20140000.3] (Eclipse Public License)
>>
>> presolving:
>> (round 1, fast) 0 del vars, 0 del conss, 0 add conss, 1 chg bounds, 0 chg sides, 0 chg coeffs, 1 upgd conss, 0 impls, 0 clqs
>> (round 2, fast) 0 del vars, 0 del conss, 0 add conss, 2 chg bounds, 0 chg sides, 0 chg coeffs, 1 upgd conss, 0 impls, 0 clqs
>> (round 3, fast) 0 del vars, 0 del conss, 4 add conss, 2 chg bounds, 0 chg sides, 0 chg coeffs, 1 upgd conss, 0 impls, 0 clqs
>> (round 4, fast) 0 del vars, 0 del conss, 4 add conss, 3 chg bounds, 0 chg sides, 0 chg coeffs, 7 upgd conss, 0 impls, 0 clqs
>> (round 5, fast) 0 del vars, 0 del conss, 4 add conss, 4 chg bounds, 0 chg sides, 0 chg coeffs, 8 upgd conss, 0 impls, 0 clqs
>> presolving (6 rounds: 6 fast, 1 medium, 1 exhaustive):
>> 0 deleted vars, 0 deleted constraints, 4 added constraints, 4 tightened bounds, 0 added holes, 0 changed sides, 0 changed coefficients
>> 0 implications, 0 cliques
>> presolved problem has 9 variables (0 bin, 0 int, 0 impl, 9 cont) and 8 constraints
>> 2 constraints of type <abspower>
>> 6 constraints of type <quadratic>
>> Presolving Time: 0.00
>>
>> time | node | left |LP iter|LP it/n| mem |mdpt |frac |vars |cons |cols |rows |cuts |confs|strbr| dualbound | primalbound | gap
>> 0.0s| 1 | 0 | 0 | - | 219k| 0 | - | 9 | 8 | 9 | 10 | 0 | 0 | 0 | -- | -- | Inf
>>
>> ******************************************************************************
>> This program contains Ipopt, a library for large-scale nonlinear optimization.
>> Ipopt is released as open source code under the Eclipse Public License (EPL).
>> For more information visithttp://projects.coin-or.org/Ipopt
>> ******************************************************************************
>>
>> 0.1s| 1 | 0 | 2 | - | 223k| 0 | - | 9 | 8 | 9 | 11 | 1 | 0 | 0 | -- | -- | Inf
>> (node 1) LP relaxation is unbounded (LP 1)
>> q 0.1s| 1 | 0 | 15 | - | 225k| 0 | - | 9 | 8 | 9 | 11 | 1 | 0 | 0 | -- |0.000000e+000 | Inf
>> 0.1s| 1 | 0 | 15 | - | 225k| 0 | - | 9 | 8 | 9 | 11 | 1 | 0 | 0 | -- |0.000000e+000 | Inf
>> (node 1) LP relaxation is unbounded (LP 4)
>> 0.1s| 1 | 2 | 15 | - | 224k| 0 | - | 9 | 8 | 9 | 11 | 1 | 0 | 0 | -- |0.000000e+000 | Inf
>> y 0.1s| 2 | 1 | 15 | 13.0 | 224k| 1 | - | 9 | 8 | 0 | 0 | 1 | 0 | 0 | -- |-2.500000e-001 | Inf
>> 0.2s| 100 | 77 | 40 | 0.4 | 254k| 77 | - | 9 | 8 | 9 | 0 | 26 | 0 | 0 | -- |-2.500000e-001 | Inf
>> 0.2s| 200 | 45 | 40 | 0.2 | 259k| 112 | - | 9 | 8 | 0 | 0 | 26 | 0 | 0 | -- |-2.500000e-001 | Inf
>> 0.3s| 300 | 65 | 40 | 0.1 | 273k| 171 | - | 9 | 8 | 9 | 0 | 26 | 0 | 0 | -- |-2.500000e-001 | Inf
>> 0.3s| 400 | 153 | 555 | 1.4 | 372k| 255 | 0 | 9 | 8 | 9 | 79 | 574 | 0 | 0 | -- |-2.500000e-001 | Inf
>>
>> SCIP Status : solving was interrupted [time limit reached]
>> Solving Time (sec) : 1000.00
>> Solving Nodes : 415
>> Primal Bound : -2.50000000000035e-001 (2 solutions)
>> Dual Bound : -1.00000000000000e+020
>> Gap : infinite
>>
>>
>> _______________________________________________
>> Scip mailing list
>> Scip at zib.de
>> http://listserv.zib.de/mailman/listinfo/scip
>
> --
> ______________________________
> Benjamin Müller
> Zuse Institute Berlin
> Takustr. 7, 14195 Berlin
> benjamin.mueller at zib.de
> +49 30 841 85-195
>
>
> _______________________________________________
> Scip mailing list
> Scip at zib.de
> http://listserv.zib.de/mailman/listinfo/scip
--
______________________________
Benjamin Müller
Zuse Institute Berlin
Takustr. 7, 14195 Berlin
benjamin.mueller at zib.de
+49 30 841 85-195
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