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From: ludo@gnu.org (Ludovic =?utf-8?Q?Court=C3=A8s?=)
Subject: Re: OpenBLAS and performance
Date: Thu, 21 Dec 2017 15:43:16 +0100
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In-Reply-To: <20171220192802.GA8426@thebird.nl> (Pjotr Prins's message of
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To: Pjotr Prins <pjotr.public12@thebird.nl>
Cc: guix-devel@gnu.org, Dave Love <fx@gnu.org>

Pjotr Prins <pjotr.public12@thebird.nl> skribis:

> On Wed, Dec 20, 2017 at 07:15:16PM +0100, Ricardo Wurmus wrote:

[...]

>> The FAQ document[1] says this:
>>=20
>>   The environment variable which control the kernel selection is
>>   OPENBLAS_CORETYPE (see driver/others/dynamic.c) e.g. export
>>   OPENBLAS_CORETYPE=3DHaswell. And the function char*
>>   openblas_get_corename() returns the used target.
>>=20
>> [1]: https://github.com/xianyi/OpenBLAS/wiki/Faq
>>=20
>> Have you tried this and compared the performance?
>
> About 10x difference on 24+ cores for matrix multiplication (my
> version vs what comes with Guix).

Even when you use OPENBLAS_CORETYPE=3Dhaswell (lower-case?)?

That would be surprising: it=E2=80=99s the same code after all.  The only
difference should be what happens at load time.

Ludo=E2=80=99.