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[SPARK-21305][ML][MLLIB]Add options to disable multi-threading of native BLAS #18551

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[SPARK-21305][ML][MLLIB]Add options to disable multi-threading of native BLAS #18551

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d0d94e1
disable multi-threading in spark-env.sh
Jul 6, 2017
adfa6f1
revise the doc
Jul 6, 2017
08e900b
revise the doc
Jul 6, 2017
7ef8b80
add link
Jul 6, 2017
a4d4f50
add OpenBlas multi-threading introduction
Jul 6, 2017
141d92d
add recommended setting for native blas link
Jul 11, 2017
e01a613
fix ml-guide.md
Jul 11, 2017
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4 changes: 4 additions & 0 deletions conf/spark-env.sh.template
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Expand Up @@ -61,3 +61,7 @@
# - SPARK_IDENT_STRING A string representing this instance of spark. (Default: $USER)
# - SPARK_NICENESS The scheduling priority for daemons. (Default: 0)
# - SPARK_NO_DAEMONIZE Run the proposed command in the foreground. It will not output a PID file.
# Options for native BLAS, like Intel MKL, OpenBLAS, and so on.
# You shoud enable these options if using native BLAS (see SPARK-21305).
# - MKL_NUM_THREADS=1 Disable multi-threading of Intel MKL
# - OPENBLAS_NUM_THREADS=1 Disable multi-threading of OpenBLAS
5 changes: 5 additions & 0 deletions docs/ml-guide.md
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Expand Up @@ -61,6 +61,11 @@ To configure `netlib-java` / Breeze to use system optimised binaries, include
project and read the [netlib-java](https://github.com/fommil/netlib-java) documentation for your
platform's additional installation instructions.

The most popular native BLAS such as [Intel MKL](https://software.intel.com/en-us/mkl), [OpenBLAS](http://www.openblas.net), are based on multi-threading.
For example, when OpenBLAS is loaded, it will create a thread pool with `MAX_CPU_NUMBER` threads, and the threads are using spinlock by default, which will conflict with Spark.
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@srowen srowen Jul 7, 2017

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Is it always worse? for example can it multi-thread a single computation? it's possible that's advantageous if the other tasks on the machine aren't CPU-intensive. But probably counterproductive if all the tasks are CPU intensive.

Maybe we can soften the language slightly, to say you might get better performance by setting these to 1.

Also I don't think users will know what spinlock or MAX_CPU_NUMBER is (not a Spark value?)

Also, I don't think we ever explain here what MKL or OpenBLAS is, in any docs. You might briefly mention that this is explained in the netlib docs.

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@mpjlu mpjlu Jul 10, 2017

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Hi @srowen , it is not always worse, here is one test result: https://issues.apache.org/jira/browse/SPARK-21305?focusedCommentId=16076152&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-16076152
I will soften the language slightly. And give two links about recommended settings for calling native blas. How do you think about it?
https://github.com/xianyi/OpenBLAS/wiki/faq#multi-threaded
https://software.intel.com/en-us/articles/recommended-settings-for-calling-intel-mkl-routines-from-multi-threaded-applications


If using a native BLAS based on multi-threading, for the best performance you must set it to use single thread first ([SPARK-21305](https://issues.apache.org/jira/browse/SPARK-21305)).

To use MLlib in Python, you will need [NumPy](http://www.numpy.org) version 1.4 or newer.

[^1]: To learn more about the benefits and background of system optimised natives, you may wish to
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