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From "Ted Dunning (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (MAHOUT-653) Approximations to standard functions
Date Thu, 07 Apr 2011 19:54:05 GMT

    [ https://issues.apache.org/jira/browse/MAHOUT-653?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13017104#comment-13017104
] 

Ted Dunning commented on MAHOUT-653:
------------------------------------

Small values of x give egregious errors in the log approximation here.  At 0.001, the absolute
error is 1.5

> Approximations to standard functions
> ------------------------------------
>
>                 Key: MAHOUT-653
>                 URL: https://issues.apache.org/jira/browse/MAHOUT-653
>             Project: Mahout
>          Issue Type: New Feature
>            Reporter: Lance Norskog
>         Attachments: MAHOUT-653.patch, MAHOUT-653.patch
>
>
> These give approximate versions of pow(value, exponent), exp(value), and natural log(value).
> log() and exp() stolen from:
> [http://martin.ankerl.com/2007/02/11/optimized-exponential-functions-for-java/]
> pow() stolen from:
> [http://martin.ankerl.com/2007/10/04/optimized-pow-approximation-for-java-and-c-c/]

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