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Message-ID: <20130528020601.GA598@openwall.com>
Date: Tue, 28 May 2013 06:06:01 +0400
From: Solar Designer <solar@...nwall.com>
To: john-dev@...ts.openwall.com
Subject: Re: OMP for raw formats
On Mon, May 27, 2013 at 05:08:54PM -0400, jfoug@....net wrote:
> So if we 8 threads, and 1024 items, it will start 8 threads, and give each thread 129 items to work on (last thread will only get 121 items). Thus, there is no thread switching. That should help.
No, it should not. A sane OpenMP implementation already does it (and
each thread gets exactly 128 items). This corresponds to
schedule(static) or maybe schedule(static, 128). Other alternatives,
which may be better for things such as SunMD5, are schedule(dynamic) and
schedule(guided). You may experiment with these. The default may vary
between OpenMP implementations, and it may be overridden via the
OMP_SCHEDULE environment variable.
https://computing.llnl.gov/tutorials/openMP/#DO
https://computing.llnl.gov/tutorials/openMP/#EnvironmentVariables
Alexander
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