partition heuristic and threads

Dear Gurobi-Team,

I set parameter Threads to value 64 so I got:

CPU model: AMD EPYC 7502 32-Core Processor, instruction set [SSE2|AVX|AVX2]
Thread count: 64 physical cores, 64 logical processors, using up to 64 threads

I try to solve a problem with 48 partitions (points in time) defined. In the solver log I see:

Starting partition heuristic: 48 partitions, 62 threads

First of all, I ask myself why 62 threads and not 64? If I had to guess, I would say one thread is reserved for a primal optimization and another one for a dual optimization in the background for the main problem?
But above all I ask myself, how 62 threads are used for 48 partitions? Wouldn't it be better to only use 48 threads for the partition heuristic and take the remaining processor capacity for the "normal optimization"?

Can I optimize some parameters?

Thanks

Thomas

David Torres Sanchez

Gurobi Staff

September 05, 2023 08:08

Hi Thomas,

That is an interesting question.
We don't find many cases where this heuristic is useful so right now there's no way to control the number of threads used for it. I can imagine that using more threads than the number of partitions may be useful in cases for example with less and larger partitions e.g. the whole set of variables into 2 partitions.

Have you found this heuristic to be useful for your problem? If so, we can look into whether this would help.

Cheers,
David

Thomas Leveringhaus

September 07, 2023 09:37

Hi David,

I redeveloped/improved my optimization modell. In the past I saw improvements with the heuristic, but actually gurobi does not even start the heuristic although I set PartitionPlace to 31.

Actually there are other problems in my model - I will come back to your offer of help later.

Best regards

partition heuristic and threads

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