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Date: Mon, 4 Jun 2012 07:02:42 -0700 (PDT)
From: NeonFlash <>
To: "" <>
Subject: JtR OMP Questions

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?


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