[GitHub] [spark] HyukjinKwon edited a comment on issue #25545: [SPARK-28843][PYTHON] Set OMP_NUM_THREADS to executor cores for python

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HyukjinKwon edited a comment on issue #25545: [SPARK-28843][PYTHON] Set OMP_NUM_THREADS to executor cores for python
URL: https://github.com/apache/spark/pull/25545#issuecomment-524595422
 
 
   I doubt if it is always better. What if, for instance, `spark.executor.cores` is set to 16 because logical cores are 16 by hyper-threading. Physical cores is, let's say 8. I don't know which one `OMP_NUM_THREADS` respects by default but from my rough research it depends on case-by-case.
   
   Are we sure if `OMP_NUM_THREADS` = 16 is better or `OMP_NUM_THREADS` = 8 is better, or are we sure which number `OMP_NUM_THREADS` will pick?
   
   It is already configurable by users and pretty clear about how to use it. I think we should better investigate to confirm this case is always better with describing the investigation made in PR description, rather than targeting one specific case. Otherwise I wouldn't fix it.

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