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Date: Thu, 26 Sep 2013 00:14:16 +0200
From: magnum <john.magnum@...hmail.com>
To: "john-dev@...ts.openwall.com" <john-dev@...ts.openwall.com>
Subject: External node distribution (call for help)

Solar, all,

The enclosed patch avoids the modulo operation in External mode when 
distributing work using node/fork/MPI. The speedup depends on several 
parameters but I've seen 10-15% for 8 nodes. This is the same scheme 
that I now use in mask mode.

The downside is that the patch (once you enable it by uncommenting the 
#define) changes the session file format for External mode so it will be 
incompatible with core.

However, there is a way to avoid changing the file format: We could read 
a "seq" number from file and convert it to "my_words" and "their_words". 
And vice versa when saving. That should be fairly easy (although I 
haven't really tried it yet) BUT what if the session was started on core 
John, and "seq" wrapped around it's 32 bits once or several times? And 
only then we resume it using the new code... and let's say our number of 
nodes is a prime... Would this mean our conversion might not be valid? 
Or can I totaly ignore such wrapping? I haven't figured that out yet %-)

magnum

View attachment "0001-Faster-node-fork-MPI-distribution-for-External-mode..patch" of type "text/plain" (3464 bytes)

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