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Date: Thu, 08 Aug 2013 10:06:20 -0300
From: Claudio André <>
Subject: Re: --fork using different OpenCL devices

> I think slow formats would benefit as well. [...]
> Regards,
> Milen
Well, when I (somehow) tested it, I was using [1].

The main idea is that each node will run in one OpenCL device.
Node 1 run using OpenCL device[0].
Node 2 run using OpenCL device[1].
And so on.

$ ../run/john -form:sha512crypt-opencl -dev=1,2 ~/testhashes #It 
translates to --fork=2; node=1->dev=1, node=2->dev=2
Local worksize (LWS) 64, global worksize (GWS) 32768
Loaded 30 password hashes with no different salts (sha512crypt-opencl, 
crypt(3) $6$ [SHA512 OpenCL])
Node numbers 1-2 of 2 (fork)
Local worksize (LWS) 1, global worksize (GWS) 1024 ...
1 15g 0:00:02:48 3/3 0.08897g/s 1433p/s 1433c/s 31337C/s abdesy..sevoty
2 15g 0:00:03:44 3/3 0.06668g/s 1808p/s 1808c/s 32620C/s ciaga1..223qra ----

Magnum already pointed out some important details:
- Faster GPU(s) finish their work first.
- How should JtR handle it?
- Faster devices run faster, slower run slower. They do not impact each 
other (different processes). Note: faster devices will have to wait 
slower units finish their work.
- For fast hashes, maybe is better to focus on one device? All nodes 
should send data to the same device?


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