[
https://issues.apache.org/jira/browse/MATH-650?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13102186#comment-13102186
]
Gilles commented on MATH-650:
-----------------------------
Answering my own question using code committed in revision 1167657.
*Single call*
_--- Previous revision ---_
{noformat}
floor (runs per timed block: 1, timed blocks: 1)
StrictMath: 5.232920e-01 (0.000000e+00) ms
Math: 1.188100e-02 (0.000000e+00) ms
FastMath: 4.942540e+00 (0.000000e+00) ms
{noformat}
_--- Current revision (preset arrays) ---_
{noformat}
floor (runs per timed block: 1, timed blocks: 1)
StrictMath: 5.290030e-01 (0.000000e+00) ms
Math: 1.201200e-02 (0.000000e+00) ms
FastMath: 4.871144e+00 (0.000000e+00) ms
{noformat}
_--- Current revision (computed arrays) ---_
{noformat}
floor (runs per timed block: 1, timed blocks: 1)
StrictMath: 5.150580e-01 (0.000000e+00) ms
Math: 1.236000e-02 (0.000000e+00) ms
FastMath: 4.938346e+00 (0.000000e+00) ms
{noformat}
*100 calls*
_--- Previous revision ---_
{noformat}
floor (runs per timed block: 10, timed blocks: 10)
StrictMath: 6.119510e-03 (1.700389e-02) ms
Math: 8.260500e-04 (3.575574e-04) ms
FastMath: 5.001669e-02 (1.563012e-01) ms
{noformat}
_--- Current revision (preset arrays) ---_
{noformat}
floor (runs per timed block: 10, timed blocks: 10)
StrictMath: 6.157360e-03 (1.718482e-02) ms
Math: 8.144700e-04 (3.643913e-04) ms
FastMath: 4.921887e-02 (1.537010e-01) ms
{noformat}
_--- Current revision (computed arrays) ---_
{noformat}
floor (runs per timed block: 10, timed blocks: 10)
StrictMath: 7.027420e-03 (1.983324e-02) ms
Math: 9.193500e-04 (3.579075e-04) ms
FastMath: 4.789965e-02 (1.498412e-01) ms
{noformat}
So, at startup,
* it takes about the same time to call {{floor}} once and 100 times,
* there is no difference between using preset arrays or computing them
({{floor}} does not need the arrays, so they are not initialized).
> 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
--
This message is automatically generated by JIRA.
For more information on JIRA, see: http://www.atlassian.com/software/jira
