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Gilles commented on MATH740:

bq. Math.ulp(), Math.IEEEremainder(), Math.getExponent()
Those 3 are implemented in {{FastMath}}.
bq. Math.powerOfTwoD()
What's this?
bq. Also GWT 2.8 supports Math.doubleToLongBits() (probably very slow) but not Math.doubleToRawLongBits()
I'm lost here; there are no such methods in the JDK's {{Math}} class.
Concerning the subject of this issue (i.e. performance), is someone willing to start a discussion
on the "dev" list?
Practically, we should first set up JMH code to provide performance numbers, since discrepancies
among some "homemade" microbenchmarking codes were never explained (nor did they elicit
much interest, as strange as it is, given the heated debate we had about FastMathrelated
code...).
> Some "FastMath" functions are slow
> 
>
> Key: MATH740
> URL: https://issues.apache.org/jira/browse/MATH740
> Project: Commons Math
> Issue Type: Wish
> Reporter: Gilles
> Priority: Minor
> Fix For: 4.0
>
> Attachments: jafamatests.zip
>
>
> 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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