[SCIP] Multiple threads with SCIP and Google OR Tools

[Ines Spenke]

Hi SCIP Team,

I try to solve a MIP with SCIP within Google OR-Tools. It is set up with 8 threads and a time limit of 90min. I do not know if the following problem is due to Google OR or SCIP.

In the console output, I see a progress table with dualbounds and primalbounds as below.

The final primal bound reported at termination (4.03e+04) is much worse than the last values shown in the table (e.g. 2.50e+04). The same for dual.

This looks like SCIP found better solutions during the run, but they are not kept until the end.

Could you please help me to understand what exactly is shown in the progress table and if there is a good reason to see better values there than in the final solution?

Thank you very much!
Best regards,
Ines

time | mem | dualbound | primalbound | gap
$ 506s|1407M| 6.131990e+03 | 3.899735e+09 | Large
...
$3186s|2181M| 6.582145e+03 | 4.037315e+04 | 513.37%
...
$5165s|3298M| 6.956456e+03 | 2.509565e+04 | 260.75%
concurrent solver 'scip-2' stopped with status time limit reached
concurrent solver 'scip-5' stopped with status time limit reached
concurrent solver 'scip-3' stopped with status time limit reached
concurrent solver 'scip-8' stopped with status time limit reached
concurrent solver 'scip-6' stopped with status time limit reached
concurrent solver 'scip-7' stopped with status time limit reached
5402s|3106M| 6.967374e+03 | 2.509565e+04 | 260.19%
concurrent solver 'scip-1' stopped with status time limit reached
concurrent solver 'scip-4' stopped with status time limit reached
5402s|3106M| 6.967374e+03 | 2.509565e+04 | 260.19%

SCIP Status : solving was interrupted [time limit reached]
Solving Time (sec) : 5402.00
Solving Nodes : 3941
Primal Bound : +4.03731513404846e+04 (44 solutions)
Dual Bound : +6.24112774276733e+03
Gap : 546.89 %


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