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From "xiaoming gu" <xiaoming...@gmail.com>
Subject patch for HARMONY-5901 is ready
Date Tue, 05 Aug 2008 04:03:56 GMT
Hi, guys. The patch for harmony-5901 is ready.

I compared the performance for all the 5 benchmarks in "Java vs. C
benchmark" by Stefan Krause on my desktop
workstation (Intel Core 2 Quad Q9550@2.83GHz, 3.23G RAM, Windows XP SP2).
With MUL/DIV replaced by shift,
spectralnorm is improved more than 29% (from 450258 msec to 319578 msec) and
no noticeable change in other
4 benchmarks.

In the webpage http://www.stefankrause.net/wp/?p=9#more-9 you may see
spectralnorm is the one which drags
the total score of Harmony most. Attachments are the detailed experiment
inputs and results.

With further thoughts, I found we'd better do more for this "numerical
strength reduction" optimization. In
Integer.parseInt() method, there is a hot *10 operation if the code is
inlined. Actually gcc does this optimization for
multiplications if one of multipliers is constant and not too large. I'm
going to take care of the generalized work these
days.

Thanks.

Xiaoming

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