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From "Luc Maisonobe (JIRA)" <j...@apache.org>
Subject [jira] [Issue Comment Edited] (MATH-650) FastMath has static code which slows the first access to FastMath
Date Sun, 11 Sep 2011 11:15:09 GMT

    [ https://issues.apache.org/jira/browse/MATH-650?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13102262#comment-13102262
] 

Luc Maisonobe edited comment on MATH-650 at 9/11/11 11:14 AM:
--------------------------------------------------------------

{quote}
We are not dealing with a "few seconds" of absolute running time: For each of the 3 runs (single
call, one hundred and one million calls), we gain no more than about 45 milliseconds!
{quote}

On which type of computer do you get these figures ? The initial problem was raised for low
end devices. In fact, in the application we are speaking of, I get a loading time that is
very very long (tens of seconds, almost one minute, not milliseconds). However, it is impossible
for me to separate the time which is due to FastMath from the time which is due to other initialization
parts. The initial benchmarks showed that FastMath was the major bottleneck.

      was (Author: luc):
    {quote}
We are not dealing with a "few seconds" of absolute running time: For each of the 3 runs (single
call, one hundred and one million calls), we gain no more than about 45 milliseconds!
{quote}

On which type of computer do you get these figures ? The initial problem was raised for low
end devices. In fact, in the application we are speaking of, I get a loading time that is
very very long (tens of seconds, almost one minute, not milliseconds). However, it is impossible
for me to separate the time that is due to FastMath from the time taht is due to other initialization
parts. The initial benchmarks showed that FastMath was the major bottleneck.
  
> 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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