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From: "jimmaureenrogers@worldnet.att.net" <jimmaureenrogers@worldnet.att.net>
Newsgroups: comp.lang.ada
Subject: Re: Request for comments on simple Ada program
Date: 16 Nov 2005 06:46:03 -0800
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Date: 2005-11-16T06:46:03-08:00
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tmoran@acm.org wrote:
> >using a packed array of boolean. The space savings from packing
> >the array will frequently result in an array that will be kept in the
> >CPU cache.
> >
> >Even though it is less efficient to access individual bits, the program
> >execution speed, by my measurements, will increase by a factor of
> >approximately 3. The execution advantage is explained by the lack
> >of I/O overhead to off-cpu memory.
>   I'm surprised.  What size cache do you have and what value of Upper
> did you use for timing?

My timings were done on a similar program which can be found at
http://shootout.alioth.debian.org/benchmark.php?test=nsieve&lang=gnat&id=0

My home system has an AMD 64 3400+ processor with 512 Mb L2 cache.
I ran my tests using Win XP Service Pack 1.

The program takes input from the command line and calculates 3
different values of Upper. It simply reports the number of primes
calculated during the run. The output for a command line value
of '9' is:

PROGRAM OUTPUT
==============
Primes up to  5120000   356244
Primes up to  2560000   187134
Primes up to  1280000    98610

Jim Rogers