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https://issues.apache.org/jira/browse/MATH-650?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13099185#comment-13099185
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Sebb commented on MATH-650:
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It appears that the new code is almost twice as fast as the old.
However, it can still take 20-30ms to initialise the class.
This seems to be because of the large array initialisations.
I hacked the code to comment out most of the array entries, leaving just one or
two in each of the large arrays, and that improved the startup time to about 6
times as fast - about 6-7ms. [Of course that code won't work properly]
So it might be worth attempting initialisation on demand, using a static holder
class that contains the pre-calculated data.
There was also a slight speed up from removing all the unused initialisation
code and its data items.
> FastMath has static code which slows the first access to FastMath
> -----------------------------------------------------------------
>
> Key: MATH-650
> URL: https://issues.apache.org/jira/browse/MATH-650
> Project: Commons Math
> Issue Type: Improvement
> Affects Versions: Nightly Builds
> Environment: Android 2.3 (Dalvik VM with JIT)
> Reporter: Alexis Robert
> Priority: Minor
>
> Working on an Android application using Orekit, I've discovered that a simple
> FastMath.floor() takes about 4 to 5 secs on a 1GHz Nexus One phone (only the
> first time it's called). I've launched the Android profiling tool (traceview)
> and the problem seems to be linked with the static portion of FastMath code
> named "// Initialize tables"
> The timing resulted in :
> - FastMath.slowexp (40.8%)
> - FastMath.expint (39.2%)
> \- FastMath.quadmult() (95.6% of expint)
> - FastMath.slowlog (18.2%)
> Hoping that would help
> Thanks!
> Alexis Robert
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