Re: [Help-gsl] Timing issues when calling GSL through Java

[Martin Jansche]

What JVM do you use?  IIRC, the math routines improved quite a bit in
speed in 1.5 and 1.6.  You're also right that they may be less precise
(as of JDK 1.3, I believe).  You might want to try to run your
benchmark with StrictMath instead of Math.

-- mj

On 2/21/08, David Lindelöf <address@hidden> wrote:
> Dear all,
>
>  I'm building Java wrapper classes around GSL, the so-called Java GSL
>  project (http://sf.net/projects/jgsl/).
>
>  So far I've been able to implement the special functions, including the
>  proper handling of the result structures, but when timing the GSL
>  against Java's built-in Math library I get results that are consistently
>  slower than Java. Calling GSL's logarithm functions through my wrapper
>  classes, for instance, is typically three times slower than Java's
>  Math.log().
>
>  Of course I expect some overhead from the calls through intermediate JNI
>  wrapper classes, but Math.log() does the same.
>
>  Here is the output from one of my unit tests. Each time I generate a
>  random sample of 2000000 numbers, and let JGSL and Java do the
>  number-crunching.
>
>  Running ch.visnet.jgsl.sf.TestLog
>  JGSL computes 2000000 logarithms in 333 ms.
>  Java computes 2000000 logarithms in 98 ms.
>  JGSL computes 2000000 absolute logarithms in 461 ms.
>  Java computes 2000000 absolute logarithms in 130 ms.
>  JGSL computes 2000000 log(1+x) in 436 ms.
>  Java computes 2000000 log(1+x) in 336 ms.
>
>  Does anyone know why GSL's log functions would be slower than Java's
>  native ones? Are they more precise? If so, how could I test it?
>
>  Kind regards,
>
>  David
>
>
>
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