[SCIP] question on a warning
Kamp, Dominik
Dominik.Kamp at uni-bayreuth.de
Tue Aug 1 18:26:04 CEST 2023
Hello James,
you are right. Since the objective value from the warning does not correspond to the main objective value, the warning must be thrown by a subscip. These warnings can be triggered due to numerics but there is also the chance that you have found a bug. Therefore, we would be very glad if you could share the corresponding instance with us (or file a bug report), so that we can get to the bottom of this potential issue.
Best regards,
Dominik
> Am 01.08.2023 um 18:03 schrieb James Cussens <james.cussens at bristol.ac.uk>:
>
> Hi all,
>
> I am getting the following warning:
>
> time | node | left |LP iter|LP it/n|mem/heur|mdpt |vars |cons |rows |cuts |sepa|confs|strbr| dualbound | primalbound | gap | compl.
> 0.0s| 1 | 0 | 39 | - | 1118k | 0 | 20 | 36 | 63 | 30 | 31 | 1 | 0 |-1.804449e+02 | 0.000000e+00*| Inf | unknown
> 0.0s| 1 | 0 | 40 | - | 1118k | 0 | 20 | 36 | 64 | 31 | 32 | 1 | 0 |-1.802198e+02 | 0.000000e+00*| Inf | unknown
> 0.0s| 1 | 0 | 41 | - | 1124k | 0 | 20 | 36 | 65 | 32 | 33 | 1 | 0 |-1.801160e+02 | 0.000000e+00*| Inf | unknown
> 0.1s| 1 | 2 | 41 | - | 1128k | 0 | 20 | 36 | 65 | 32 | 34 | 1 | 15 |-1.800907e+02 | 0.000000e+00*| Inf | unknown
> r 0.1s| 15 | 14 | 57 | 1.1 |rounding| 14 | 20 | 36 | 65 | 33 | 0 | 1 | 42 |-1.758398e+02 |-1.151438e+01 |1427.13%| unknown
> r 0.1s| 16 | 15 | 65 | 1.6 |rounding| 15 | 20 | 36 | 65 | 33 | 0 | 1 | 45 |-1.758398e+02 |-1.604484e+01 | 995.93%| unknown
> * 0.1s| 17 | 14 | 66 | 1.6 | LP | 16 | 20 | 36 | 65 | 33 | 1 | 1 | 45 |-1.758398e+02 |-2.039660e+01 | 762.10%| unknown
> r 0.1s| 24 | 17 | 78 | 1.6 |rounding| 16 | 20 | 36 | 66 | 35 | 0 | 1 | 50 |-1.758398e+02 |-2.640592e+01 | 565.91%| unknown
> * 0.1s| 34 | 21 | 95 | 1.6 | LP | 17 | 20 | 36 | 69 | 39 | 1 | 1 | 54 |-1.758398e+02 |-2.719577e+01 | 546.57%| unknown
> * 0.1s| 37 | 22 | 99 | 1.6 | LP | 18 | 20 | 36 | 70 | 40 | 1 | 1 | 54 |-1.758398e+02 |-6.270300e+01 | 180.43%| unknown
> r 0.2s| 57 | 30 | 144 | 1.8 |rounding| 18 | 20 | 36 | 72 | 54 | 1 | 1 | 61 |-1.758398e+02 |-6.485425e+01 | 171.13%| unknown
> 0.2s| 100 | 63 | 235 | 2.0 | 1345k | 18 | 20 | 36 | 69 | 73 | 2 | 1 | 69 |-1.758398e+02 |-6.485425e+01 | 171.13%| unknown
> 0.3s| 200 | 159 | 480 | 2.2 | 1845k | 18 | 20 | 36 | 71 | 149 | 2 | 1 | 71 |-1.758398e+02 |-6.485425e+01 | 171.13%| unknown
> WARNING: Dual bound 69.0721 is larger than the objective of the primal solution 68.1511. The solution might not be optimal.
> 0.5s| 300 | 253 | 758 | 2.4 | 2248k | 18 | 20 | 36 | 76 | 226 | 1 | 1 | 71 |-1.758398e+02 |-6.485425e+01 | 171.13%| unknown
> 0.6s| 400 | 351 | 1029 | 2.5 | 2670k | 18 | 20 | 36 | 73 | 312 | 1 | 1 | 71 |-1.758398e+02 |-6.485425e+01 | 171.13%| unknown
> time | node | left |LP iter|LP it/n|mem/heur|mdpt |vars |cons |rows |cuts |sepa|confs|strbr| dualbound | primalbound | gap | compl.
> 0.7s| 500 | 443 | 1254 | 2.4 | 2799k | 18 | 20 | 36 | 70 | 367 | 1 | 1 | 71 |-1.758398e+02 |-6.485425e+01 | 171.13%| unknown
> 0.8s| 600 | 537 | 1467 | 2.4 | 3062k | 18 | 20 | 36 | 70 | 411 | 1 | 3 | 71 |-1.758398e+02 |-6.485425e+01 | 171.13%| unknown
> 1.0s| 700 | 633 | 1696 | 2.4 | 3247k | 18 | 20 | 36 | 70 | 470 | 1 | 3 | 71 |-1.758398e+02 |-6.485425e+01 | 171.13%| unknown
>
> SCIP Status : solving was interrupted [time limit reached]
>
> The solutions I am getting are fine and I have no obvious errors, but I am curious as to what might have generated the warning. Perhaps it comes from some subscip run by a heuristic since the dual bound the warning mentions (69.0721) is some distance from that of the main problem ( -1.758398e+02). Can anyone explain what might be happening here; perhaps this indicates some problem I have not yet noticed.
>
> James
>
> James Cussens
> Room MVB 3.26
> Dept of Computer Science, University of Bristol
> Phone: +44 (0)117 455 8723
> https://jcussens.github.io/
> Funded PhDs available in Bristol in the following areas: Data Science, Interactive AI, Cyber Security or Digital Health.
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