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Date: Mon, 27 Aug 2018 19:36:25 +0200
From: magnum <>
Subject: Re: Beignet: unable to find good values for

On 2018-08-27 11:54, Matus UHLAR - fantomas wrote:
> for a few weeks, the beignet OpenCL driver reports this message:
> Loaded 1 password hash (mysql-sha1-opencl, MySQL 4.1+ [SHA1 OpenCL])
> Beignet: "unable to find good values for local_work_size[i], please
> provide\n" " local_work_size[] explicitly, you can find good values with\n"
> " trial-and-error method."
> I understand it as the driver does not provide any useful value and the 
> john
> is just guesssing.
> How can I test for the proper value? can I do it at runtime?

That message comes from Beignet, not john. What is triggering it is 
likely that we deliberately use a local work size of NULL for incomplete 
batches (eg. the very last batch in a session). There's not really any 
way you can provide it... short of reverting to some commit before where we had 
another scheme (which had other problems).

I would report it to them as a bug, because according to the OpenCL 
spec. it should handle it. I believe what most drivers/runtimes do is 
find greatest divisor of GWS that is less than or equal to highest 
possible LWS, and use that.

Does it crash/abort or is this just a warning message? It could be that 
it simply warns and then use an LWS of 1 which is suboptimal but works 
fine in this case.


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