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From "Gilles (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (MATH-740) Some "FastMath" functions are slow
Date Sun, 05 Aug 2012 00:44:02 GMT

    [ https://issues.apache.org/jira/browse/MATH-740?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13428709#comment-13428709
] 

Gilles commented on MATH-740:
-----------------------------

{noformat}
log and log10 (calls per timed block: 1000000, timed blocks: 100, time unit: ms)
               name      time/call      std error total time      ratio      difference
        Math log(x) 3.61083035e-05 2.28393527e-06 3.6108e+03 1.0000e+00  0.00000000e+00
      Math log10(x) 3.66085799e-05 3.22000007e-06 3.6609e+03 1.0139e+00  5.00276380e+01
  StrictMath log(x) 9.51341413e-05 2.66850659e-06 9.5134e+03 2.6347e+00  5.90258378e+03
StrictMath log10(x) 1.23497329e-04 3.77763096e-06 1.2350e+04 3.4202e+00  8.73890257e+03
    FastMath log(x) 6.35533555e-05 5.03781330e-06 6.3553e+03 1.7601e+00  2.74450520e+03
  FastMath log10(x) 1.66252138e-04 6.30307785e-06 1.6625e+04 4.6043e+00  1.30143835e+04
FastMath log(10, x) 1.17000075e-04 3.14090930e-06 1.1700e+04 3.2403e+00  8.08917711e+03
{noformat}

This table shows that
# FastMath's log is about 1.7 times slower than Math's log
# FastMath's log10 is about 4.5 times slower than Math's log10
# FastMath's log(10, x), which calls log twice, is about 3.2 times slower than Math's log10

Small note: the performance difference between Math's log and log10 is not significant (in
some runs, log is faster, in others log10 is faster).

                
> Some "FastMath" functions are slow
> ----------------------------------
>
>                 Key: MATH-740
>                 URL: https://issues.apache.org/jira/browse/MATH-740
>             Project: Commons Math
>          Issue Type: Wish
>            Reporter: Gilles
>            Priority: Minor
>             Fix For: 3.1
>
>
> From the two benchmarks we currently have in "FastMathTestPerfomance", we have that the
following functions are much slower in "FastMath" than in either "Math" or "StrictMath" (the
performance *loss*, for each of the benchmarks, is given in parentheses):
> * log10 (46%, 36%)
> * log1p (68%, 112%)
> * tan (11%, 61%)
> * atan (26%, 125%)
> * atan2 (44%, 40%)

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