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Date: Wed, 1 Sep 2010 16:47:54 -0400 (EDT)
From: "Jeff Hain (JIRA)" <jira@apache.org>
To: issues@commons.apache.org
Subject: [jira] Issue Comment Edited: (MATH-375) Elementary functions in JDK
 are slower than necessary and not as accurate as they could be.
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    [ https://issues.apache.org/jira/browse/MATH-375?page=3Dcom.atlassian.j=
ira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=3D129052=
10#action_12905210 ]=20

Jeff Hain edited comment on MATH-375 at 9/1/10 4:46 PM:
--------------------------------------------------------

Hello.

William, I've also contracted the fast-math disease some time ago, which en=
ded up into some FastMath class as well (http://sourceforge.net/projects/ja=
fama).
Though, your form seems more severe, since you felt the need to stay within=
 about +-0.5 ULP :)

Anyway, I did run my "FastMath" tests on your class (with the patch), and f=
ound some troubles with special cases, especially +-Infinity, NaN, or huge =
values:
see "test_fastmath_wr.zip" attachment, which contains test code, and a log =
of their run.

Also, running your tests, I had this exception:
-19.731458173549257=092.696103718050787E-9=092.6961037180507868E-9=091.5340=
29657343928E-16=090.5025524399680612
Exception in thread "main" java.lang.RuntimeException: exp() had errors in =
excess of 0.502 ULP
=09at FastMathWRTest.testExpAccuracy(FastMathWRTest.java:458)
=09at FastMathWRTest.main(FastMathWRTest.java:18)

May it help you improve your treatments!

Regards,

Jeff


      was (Author: jeff):
    Hello.

William, I've also contracted the fast-math disease some time ago, which en=
ded up into some FastMath class as well (http://sourceforge.net/projects/ja=
fama).
Though, your form seems more severe, since you felt the need to stay within=
 about +-0.5 ULP :)

Anyway, I did run my "FastMath" tests on your class, and found some trouble=
s with special cases, especially +-Infinity, NaN, or huge values:
see "test_fastmath_wr.zip" attachment, which contains test code, and a log =
of their run.

Also, running your tests, I had this exception:
-19.731458173549257=092.696103718050787E-9=092.6961037180507868E-9=091.5340=
29657343928E-16=090.5025524399680612
Exception in thread "main" java.lang.RuntimeException: exp() had errors in =
excess of 0.502 ULP
=09at FastMathWRTest.testExpAccuracy(FastMathWRTest.java:458)
=09at FastMathWRTest.main(FastMathWRTest.java:18)

May it help you improve your treatments!

Regards,

Jeff

 =20
> Elementary functions in JDK are slower than necessary and not as accurate=
 as they could be.
> -------------------------------------------------------------------------=
------------------
>
>                 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
>             Fix For: 2.2
>
>         Attachments: atanpatch.txt.gz, FastMath.tar.gz, test_fastmath_wr.=
zip
>
>
> I would like to contribute improved versions on exp(), log(), pow(), etc.=
  to the project.  Please refer to this discussion thread http://markmail.o=
rg/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 UL=
P.
> * Pure Java.  The standard Math class is impleneted via JNI, and thus tak=
es a performance hit.
> Note that some functions such as exp are nearly twice as fast in my imple=
mentation. =C2=A0 I've seen it 3 times faster on different processors. =C2=
=A0 The preformance varies by the relative speed of calculation vs memory l=
ookups.
> The functions are implemented as tables of values in extra precision (app=
rox 70 bits), and then interpolated with a minimax polynomial.

--=20
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