[Numpy-discussion] numpy ufuncs and COREPY - any info?

Francesc Alted faltet@pytables....
Fri May 22 07:17:50 CDT 2009

A Friday 22 May 2009 13:59:17 Andrew Friedley escrigué:
> Using multiple cores is pretty easy for element-wise ufuncs; no
> communication needs to occur and the work partitioning is trivial.  And
> actually I've found with some initial testing that multiple cores does
> still help when you are memory bound.  I don't fully understand why yet,
> though I have some ideas.  One reason is multiple memory controllers due
> to multiple sockets (ie opteron).

Yeah.  I think this must likely be the reason.  If, as in your case, you have 
several independent paths from different processors to your data, then you can 
achieve speed-ups even if you are having a memory bound in a one-processor 

> Another is that each thread is
> pulling memory from a different bank, utilizing more bandwidth than a
> single sequential thread could.  However if that's the case, we could
> possibly come up with code for a single thread that achieves (nearly)
> the same additional throughput..

Well, I don't think you can achieve important speed-ups in this case, but 
experimenting never hurts :)

Good luck!

Francesc Alted

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