Date: Mon, 4 Jun 2012 21:48:12 +0530 From: SAYANTAN DATTA <std2048@...il.com> To: john-users@...ts.openwall.com, NeonFlash <psykosonik_frequenz@...oo.com> Subject: Re: JtR OMP Questions On Mon, Jun 4, 2012 at 7:32 PM, NeonFlash <psykosonik_frequenz@...oo.com>wrote: > I have a few questions regarding, JtR's OMP Feature: > > Is there a way to control how many logical cores of the multi core CPU are > used by john-omp.exe? By default, it uses all the available logical cores > of the CPU but I would like to control this manually. > > > I did not see any such option listed in the help. > > Does the OMP feature apply only to few hash types? For instance, I can see > the multiple CPU Cores being used for few hash types like DES, Blowfish but > not for others like dynamic_12 and so on. An example from the benchmark: > > C:\JTR\run>john-omp.exe --format=DES --test=3 > Benchmarking: Traditional DES [128/128 BS SSE2]... (8xOMP) DONE > Many salts: 8770K c/s real, 1162K c/s virtual > Only one salt: 7713K c/s real, 1105K c/s virtual > > > C:\JTR\run>john-omp.exe --format=dynamic_12 --test=3 > Benchmarking: dynamic_12: md5(md5($s).md5($p)) (IPB) [SSE2i 10x4x3]... > DONE > Many salts: 2723K c/s real, 2717K c/s virtual > Only one salt: 1966K c/s real, 1969K c/s virtual > > Is there a way to use multiple CPU Cores with a hash type such as > dynamic_12? > > > What is the difference between OMP and MPI? > > On linux platform, I noticed in the Makefile of JtR, that we can enable > the OMPFLAGS to compile the JtR with OpenMP Compatibility and there is also > an option to use MPI with OpenMP. > > However, I would like to understand the difference between the two? > > Thanks. Set OMP_NUM_THREADS=1,2,3,4.... eg. bash$ OMP_NUM_THREAD=3 ./john -te -fo=raw-md5 it will use only 3 threads. While openMP is generally used for fine grain parallelism like within a specific format. On the other hand MPI is generally used for task level parallelism e.g two or more instances of john. Regards, Sayantan
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