Re: OpenBLAS and performance

[Ludovic Courtès]

Pjotr Prins <address@hidden> skribis:

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

[...]

>> The FAQ document[1] says this:
>> 
>>   The environment variable which control the kernel selection is
>>   OPENBLAS_CORETYPE (see driver/others/dynamic.c) e.g. export
>>   OPENBLAS_CORETYPE=Haswell. And the function char*
>>   openblas_get_corename() returns the used target.
>> 
>> [1]: https://github.com/xianyi/OpenBLAS/wiki/Faq
>> 
>> 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=haswell (lower-case?)?

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

Ludo’.