Jan Blechta <[email protected]> writes:

> It is OpenBLAS.
>
> Citing from https://github.com/xianyi/OpenBLAS/wiki/faq#multi-threaded
>
>   If your application is already multi-threaded, it will conflict with
>   OpenBLAS multi-threading.
>
> We must be cautious of this. (Are PETSc devs? CCing Jed Brown.) 

I consider threaded BLAS to always be a mistake for Level 1 BLAS (the
part that is used for sparse linear algebra).  In general, I think it's
better to deal with threads at a higher level.  But PETSc can't fail
when a user configures with threaded BLAS (and we can't even portably
determine that it's threaded).

BLAS with threads is a disaster and vendors still pretend like it's
acceptable to make threading decisions at link time.  The right fix is
at the interface level, but nobody will do that.  I suggest turning off
threads always (threads are often a performance mess even when not
over-subscribed).

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