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Date: Fri, 05 Jul 2013 12:22:21 +0530
From: Sayantan Datta <std2048@...il.com>
To: john-dev@...ts.openwall.com
Subject: Re: bug: GPU use in CPU-only formats

On Friday 05 July 2013 05:23 AM, magnum wrote:
> On 5 Jul, 2013, at 1:24 , magnum <john.magnum@...hmail.com> wrote:
>> I'm looking into some weirdness with mscash2-opencl when using multiple devices, I may have to tweak something.
> That problem was not introduced now so I'll leave it to Sayantan. It only happens with --test=0:
>
> $ ../run/john -t=0 -form:mscash2-opencl -dev=gpu
> Warning: doing quick benchmarking - the performance numbers will be inaccurate
> Device 0: GeForce GTX 570
> Device 1: Tahiti (AMD Radeon HD 7900 Series)
> Optimal Work Group Size:256
> Kernel Execution Speed (Higher is better):1.565550
> Optimal Global Work Size:253952
> WARNING: Device 0 is too slow and might cause degradation in performance.
> WARNING: Devices are NOT arranged in DECREASING order of performance and might cause degradation in performance.
> Benchmarking: mscash2-opencl, M$ Cache Hash 2 (DCC2) [PBKDF2-SHA1 OpenCL]... OpenCL error (CL_INVALID_WORK_GROUP_SIZE) in file (common_opencl_pbkdf2.c) at line (353) - (Enque Kernel Failed)

What does the -t=0 option does ? It seems like 570 isn't being tested at 
all.

> $ ../run/john -t -form:mscash2-opencl -dev=gpu
> Device 0: GeForce GTX 570
> Optimal Work Group Size:128
> Kernel Execution Speed (Higher is better):0.470798
> Optimal Global Work Size:81920
> Device 1: Tahiti (AMD Radeon HD 7900 Series)
> Optimal Work Group Size:256
> Kernel Execution Speed (Higher is better):1.565677
> Optimal Global Work Size:253952
> WARNING: Devices are NOT arranged in DECREASING order of performance and might cause degradation in performance.
> Benchmarking: mscash2-opencl, M$ Cache Hash 2 (DCC2) [PBKDF2-SHA1 OpenCL]... DONE
> Raw:    64291 c/s real, 64129 c/s virtual
>
> I think that "decreasing order" requirement should be taken care of by the format, not the user. When using --device=gpu you select all GPU devices available but on Bull they happen to come in increasing order of performance.
>
> magnum

Oh, yes I intend to fix this soon.  Maybe this week if I have time.

Regards,
Sayantan

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