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Date: Sat, 13 Mar 2010 15:10:51 +0100
From: "Magnum, P.I." <>
Subject: Re: Is JTR MPIrun can be optimized for more cores ?

> Anyway, the tests show that MPI-john has no overhead in itself, just as 
> I expected. Running on one core, it performs just as vanilla john. It's 
> *only* a matter of how we split the jobs. So I did another test, using 
> ...

I just found something odd though. Can anyone explain this?

[I snipped the ETA from output to avoid linewraps]

$ ./john -stdout -w=sd.lst -ru=s >file1
words: 62570773  time: 0:00:00:12 100.00%  w/s: 5171K  current: snip

$ ./john -stdout -w=sd.lst -ru=s >/dev/null
words: 62570773  time: 0:00:00:10 100.00%  w/s: 5804K  current: snip

$ ./john -stdout -w=sd.lst -ru=s >file2
words: 62570773  time: 0:00:03:45 100.00%  w/s: 277021  current: snip
                              ^^^^               ^^^^^^
$ ./john -stdout -w=sd.lst -ru=s >/dev/null
words: 62570773  time: 0:00:00:29 100.00%  w/s: 2124K  current: snip

$ diff -s file1 file2
Files file1 and file2 are identical

The speed to /dev/null is bad, the one to file is awful. It looks like 
we're flushing too often but I can't find where, and there must also be 
some other problem. And this does not seem to happen when cracking, only 
when using --stdout

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