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From "William Rossi (JIRA)" <j...@apache.org>
Subject [jira] Created: (MATH-375) Elementary functions in JDK are slower than necessary and not as accurate as they could be.
Date Tue, 08 Jun 2010 23:28:15 GMT
Elementary functions in JDK are slower than necessary and not as accurate as they could be.
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                 Key: MATH-375
                 URL: https://issues.apache.org/jira/browse/MATH-375
             Project: Commons Math
          Issue Type: New Feature
         Environment: JDK 1.4 - 1.6
            Reporter: William Rossi


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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