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From "Sebb (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (MATH-650) FastMath has static code which slows the first access to FastMath
Date Sat, 11 Feb 2012 17:37:00 GMT

    [ https://issues.apache.org/jira/browse/MATH-650?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13206195#comment-13206195
] 

Sebb commented on MATH-650:
---------------------------

bq. I would lean on the binary side, for "safety" reasons: unwanted modifications are less
likely to occur.

Now that the arrays are cloned, I don't see how modifications can occur at run time.
Source modifications are of course easier. But if that's a concern, let's store all the code
as resources!

bq. reading a presumably longer table, and parsing a presumably larger number of octets for
each double would result in a longer loading time

Why should the literal case need parsing? The compiler already parsed the source when the
class was compiled.
I don't see why the literal case should use more octets either.

I agree it would be nice to know the source of the "conventional wisdom" - maybe the assumptions
it was based on no longer hold.
                
> 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
>             Fix For: 3.0
>
>         Attachments: FastMathLoadCheck.java, LucTestPerformance.java
>
>
> 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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