GitHub user Krimit opened a pull request:

    https://github.com/apache/spark/pull/17263

    [SPARK-19922][ML] small speedups to findSynonyms

    Currently generating synonyms using a large model (I've tested with 3m 
words) is very slow. These efficiencies have sped things up for us by ~17%
    
    I wasn't sure if such small changes were worthy of a jira, but the 
guidelines seemed to suggest that that is the preferred approach
    
    ## What changes were proposed in this pull request?
    
    Address a few small issues in the findSynonyms logic:
    1) remove usage of ``Array.fill`` to zero out the ``cosineVec`` array. The 
default float value in Scala and Java is 0.0f, so explicitly setting the values 
to zero is not needed
    2) use Floats throughout. The conversion to Doubles before doing the 
``priorityQueue`` is totally superfluous, since all the similarity computations 
are done using Floats anyway. Creating a second large array just serves to put 
extra strain on the GC
    3) convert the slow ``for(i <- cosVec.indices)`` to an ugly, but faster, 
``while`` loop
    
    These efficiencies are really only apparent when working with a large model
    ## How was this patch tested?
    
    Existing unit tests + some in-house tests to time the difference
    
    cc @jkbradley @MLNick @srowen 

You can merge this pull request into a Git repository by running:

    $ git pull https://github.com/Krimit/spark fasterFindSynonyms

Alternatively you can review and apply these changes as the patch at:

    https://github.com/apache/spark/pull/17263.patch

To close this pull request, make a commit to your master/trunk branch
with (at least) the following in the commit message:

    This closes #17263
    
----
commit f22f47f5b341f930b42ccea507a3697c0953abc1
Author: Asher Krim <krim.asher@gmail>
Date:   2017-03-12T01:19:24Z

    small speedups to findSynonyms
    
    Currently generating synonyms using a model with 3m words is painfully 
slow. These efficiencies have sped things up by more than 17%.
    
    Address a few issues in the findSynonyms logic:
    1) no need to zero out the cosineVec array each time, since default value 
for float arrays is 0.0f. This should offer some nice speedups
    2) use floats throughout. The conversion to Doubles before doing the 
priorityQueue is totally superflous, since all the computations are done using 
floats anyway
    3) convert the slow for(i <- cosVec.indices), which combines a scala 
closure with a Range, to an ugly but faster while loop

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