Workers should adjust BLAS/LAPACK/Numpy threads

[ravwojdyla]

Should workers by default adjust BLAS/LAPACK/Numpy threads as per dask-best-practices? Since we have access to the number of threads/workers and cores, it should be possible adjust those accordingly. wdyt?

[jacobtomlinson]

Absolutely. There is work happening already in dask/distributed#4377 to address this.

[ravwojdyla]

@jacobtomlinson please correct me if I'm wrong, does dask/distributed#4377 really address this issue? Looking briefly into that, it seems like it's more about the number of Dask processes and thread but not the BLAS/LAPACK/Numpy threads?

[jacobtomlinson]

Ah right I see, I misunderstood the request.

Most cluster managers support an env_vars configuration option, so folks can set things however they want.

[ravwojdyla]

@jacobtomlinson thanks for prompt response. I understand, but do you think dask-cloudprovider could set sensible defaults given that it has information about number of Dask workers/threads and VM types (#CPUs)? wdyt?

[jacobtomlinson]

That's is definitely a possibility. I'm not sure whether we do this in any other cluster managers. Perhaps someone else from @dask/maintenance might know?

[martindurant]

Sounds like another point where spec-cluster might be able to give a consolidated view over different deployment types - like how many CPU cores are available to each worker, possibly different than the number of threads requested. I suspect, though, that in most cases setting all the threading options to 1 is the right thing to do.