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From "Thomas Neidhart (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (MATH-745) up to 5x Performance Improvement on FasFourierTransformer.java by using a recursive iterative sumation Approach
Date Mon, 13 Feb 2012 13:30:59 GMT

    [ https://issues.apache.org/jira/browse/MATH-745?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13206867#comment-13206867
] 

Thomas Neidhart commented on MATH-745:
--------------------------------------

I was curious to see if a recursion is really faster than a loop. The test results can be
seen here:

fft (calls per timed block: 1000, timed blocks: 100, time unit: ms)
     name      time/call      std error total time      ratio      difference
     Loop 6.97587976e-02 1.15353985e-02 6.9759e+03 1.0000e+00  0.00000000e+00
Recursive 7.11088946e-02 5.04734785e-03 7.1109e+03 1.0194e+00  1.35009693e+02

The function being transformed is sin(x).
                
> up to 5x Performance Improvement on FasFourierTransformer.java by using a recursive iterative
sumation Approach
> ---------------------------------------------------------------------------------------------------------------
>
>                 Key: MATH-745
>                 URL: https://issues.apache.org/jira/browse/MATH-745
>             Project: Commons Math
>          Issue Type: Improvement
>    Affects Versions: 3.0
>            Reporter: Leandro Ariel Pezzente
>              Labels: FFT, Fast, Fourier, Transform
>         Attachments: FastFourierTransformer.patch.txt
>
>
> By swithinch form a loop iterative approach to a recursive iterative approach on fastFourierTransformer.java
a Perfomance Improvement of up to 5x is gained.

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