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From Michael McCandless <>
Subject Re: [jira] Created: (LUCENE-1172) Small speedups to DocumentsWriter
Date Sun, 10 Feb 2008 19:37:27 GMT

Yonik Seeley wrote:

> I wonder how well a single generic quickSort(Object[] arr, int low,
> int high) would perform vs the type-specific ones?  I guess the main
> overhead would be a cast from Object to the specific class to do the
> compare?  Too bad Java doesn't have true generics/templates.

OK I tested this.

Starting from the patch on LUCENE-1172, which has 3 quickSort methods
(one per type), I created a single quickSort method on Object[] that
takes a Comparator, and made 3 Comparators instead.

Mac OS X 10.4 (JVM 1.5):

     original patch --> 247.1
   simplified patch --> 254.9 (3.2% slower)

Windows Server 2003 R64 (JVM 1.6):

     original patch --> 440.6
   simplified patch --> 452.7 (2.7% slower)

The times are best in 10 runs.  I'm running all tests with these JVM

   -Xms1024M -Xmx1024M -Xbatch -server

I think this is a big enough difference in performance that it's
worth keeping 3 separate quickSorts in DocumentsWriter.


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