Date: Mon, 30 Jan 2012 13:44:35 +0000 From: Alex Sicamiotis <alekshs@...mail.com> To: <john-users@...ts.openwall.com> Subject: RE: DES with OpenMP > > > > On Fri, Jan 20, 2012 at 09:35:26PM +0000, Alex Sicamiotis wrote: > > > ...the OMP version is scoring +200k in many salts over the noOMP despite threads=1, > > > > Yes. > > > > > when it should be equal. > > > > No, it should not. It should be close, but not equal. Normally, OpenMP > > build running with 1 thread is slightly slower than non-OpenMP build, > > but it can also be the other way around. The code is different in many > > ways. Even the chunk size (number of passwords being hashed per > > crypt_all() call) differs by a factor of 32 between these builds. > > Normally, this hurts performance when you don't actually run multiple > > threads, but in certain builds and on certain machines it can be the > > other way around as you have seen. > > I was looking now at the john.log, and for openMP 2 threads it was 0:00:00:00 - Candidate passwords will be buffered and tried in chunks of 8192 for openMP 1 thread it was 0:00:11:32 - Candidate passwords will be buffered and tried in chunks of 4096 and for non-openMP it was 0:00:11:38 - Candidate passwords will be buffered and tried in chunks of 128 ...and I remembered what you said about this code difference. So.. supposing this can give, say +200k c/s which I'm seeing between the openmp and non-openmp, where do I tweak the code to test various values?
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