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Date: Mon, 30 Mar 2015 12:17:25 +0200
From: magnum <john.magnum@...hmail.com>
To: john-dev@...ts.openwall.com
Subject: Re: [GSoC] John the Ripper support for PHC finalists
On 2015-03-30 12:02, Solar Designer wrote:
> On Mon, Mar 30, 2015 at 10:24:45AM +0300, Solar Designer wrote:
>> So the speed of C code is maybe good - I say maybe because we don't know
>> yet how much better it can be made. One of two OpenCL SDKs running on
>> the CPUs achieves about the same speed, which is a good sanity check.
>> The other fails to vectorize the code, resulting in much lower speed.
>
> Actually, the failure to vectorize is possibly a red herring. POMELO is
> designed to be somewhat SIMD-unfriendly, including in attack
> implementations (with extra parallelism from having multiple candidate
> passwords). So I doubt the other OpenCL SDK vectorized it; perhaps it
> just didn't print the warning. This needs to be looked into for real.
AMD's CPU driver never prints such warnings, and it never reports
succesful auto-vectorization either. Actually I'm not convinced it does
auto-vectorizing at all. I have a few formats that adopt to the device's
reported "best vector width" with pre-vectorized code and the AMD driver
usually respond very well to that iirc.
Anyway the speed difference is almost 15x, that wouldn't be explained
with vectorizing alone.
magnum
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