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William Rossi commented on MATH375:

The parameter "extra" to exp() is extra input percision such that x+extra
is the input parameter.
The hiPrec[] inputs to exp and log are to return a higher precision output
such that hiPrec[0] + hiPrec[1] is the desired result.
I'm currently working on implementations of asin and acos.
> Elementary functions in JDK are slower than necessary and not as accurate as they could
be.
> 
>
> Key: MATH375
> URL: https://issues.apache.org/jira/browse/MATH375
> Project: Commons Math
> Issue Type: New Feature
> Environment: JDK 1.4  1.6
> Reporter: William Rossi
> Fix For: 2.2
>
> Attachments: atanpatch.txt.gz, FastMath.tar.gz
>
>
> I would like to contribute improved versions on exp(), log(), pow(), etc. to the project.
Please refer to this discussion thread http://markmail.org/message/zyeoguw6gwtofm62.
> I have developed over the past year a set of elementary functions similar to those in
java.lang.Math, but with the following characteristics:
> * Higher performance.
> * Better accuracy. Results are accurate to slightly more that +/ 0.5 ULP.
> * Pure Java. The standard Math class is impleneted via JNI, and thus takes a performance
hit.
> Note that some functions such as exp are nearly twice as fast in my implementation.
I've seen it 3 times faster on different processors. The preformance varies by the relative
speed of calculation vs memory lookups.
> The functions are implemented as tables of values in extra precision (approx 70 bits),
and then interpolated with a minimax polynomial.

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