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Date: Thu, 27 Aug 2015 01:01:27 +0200
From: magnum <john.magnum@...hmail.com>
To: john-dev@...ts.openwall.com
Subject: Re: LWS and GWS auto-tuning
On 2015-08-27 00:41, Solar Designer wrote:
> On Wed, Aug 26, 2015 at 10:21:31PM +0200, magnum wrote:
>> On 2015-08-26 21:37, Solar Designer wrote:
>>> Unfortunately, LWS auto-tuning tries unreasonably high values (like
>>> 8192) and sometimes fails totally (results in an error from OpenCL and
>>> program abort) for some formats when tested with one or the other OpenCL
>>> SDK on "well". Can you look into this, and perhaps commit a fix?
>>
>> That's odd, can you name a format?
>
> For example:
>
> $ ./john -test -form=phpass-opencl -dev=0 -v=4
> Device 0: Intel(R) Core(TM) i7-4770K CPU @ 3.50GHz
> Benchmarking: phpass-opencl ($P$9 lengths 0 to 15) [MD5 OpenCL]... Options used: -I ./kernels -cl-mad-enable -D__CPU__ -DDEVICE_INFO=33 -DDEV_VER_MAJOR=1 -DDEV_VER_MINOR=2 -D_OPENCL_COMPILER
> Build log: Compilation started
> Compilation done
> Linking started
> Linking done
> Device build started
> Device build done
> Kernel <phpass> was not vectorized
> Done.
> Calculating best global worksize (GWS); max. 100ms single kernel invocation.
> gws: 256 24569 c/s 24569 rounds/s 10.419ms per crypt_all()!
> gws: 512 24150 c/s 24150 rounds/s 21.200ms per crypt_all()
> gws: 1024 26315 c/s 26315 rounds/s 38.912ms per crypt_all()+
> gws: 2048 26323 c/s 26323 rounds/s 77.800ms per crypt_all()
> Calculating best local worksize (LWS)
> Testing LWS=128 GWS=1024 ... 151.439ms+
> Testing LWS=256 GWS=1024 ... 302.382ms
> Testing LWS=512 GWS=1024 ... 604.730ms
> Testing LWS=1024 GWS=1024 ... 1.209s
> Testing LWS=2048 GWS=2048 ...Segmentation fault
The device actually supports 8192 per the queries, and that's why it is
tried. This is also seen in our list output:
Platform version: OpenCL 1.2
Device #0 (0) name: Intel(R) Core(TM) i7-4770K CPU @ 3.50GHz
Device vendor: Intel(R) Corporation
Device type: CPU (LE)
Device version: OpenCL 1.2 (Build 9756)
Driver version: 1.2.0.9756
Native vector widths: char 32, short 16, int 8, long 4
Preferred vector width: char 1, short 1, int 1, long 1
Global Memory: 31.0 GB
Global Memory Cache: 256.2 KB
Local Memory: 32.0 KB (Global)
Max memory alloc. size: 7.0 GB
Max clock (MHz): 3500
Profiling timer res.: 1 ns
Max Work Group Size: 8192 <---- here!
Parallel compute cores: 8
I'm do not think the de-facto limit of 1024 we've been used to is an
actual maximum per any specifications. Also, when I tried this it ran
just fine through the tests up to 8192 but picked a lower number as
best. If it wasn't actually supported, we should get an
CL_INVALID_WORK_GROUP_SIZE error and it would have been caught and
handled properly.
I presume your segfault was unrelated to the work size.
magnum
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