[Numpy-discussion] making numpy.dot faster

[Pauli Virtanen]

Fri, 03 Oct 2008 18:59:02 +0200, Gael Varoquaux wrote:

> I am doing a calculation where one call numpy.dot ends up taking 90% of
> the time (the array is huge: (61373, 500) ).
> 
> Any chance I can make this faster? I would believe BLAS/ATLAS would be
> behind this, but from my quick analysis (ldd on
> numpy/core/multiarray.so) it doesn't seem so. Have I done something
> stupid when building numpy (disclaimer: I am on a system I don't know
> well --Mandriva--, so I could very well have done something stupid).

AFAIK, multiarray.so is never linked against ATLAS. The accelerated dot 
implementation is in _dotblas.so, and can be toggled with alterdot/
restoredot (but the ATLAS one should be active by default).

>>> numpy.dot.__module__
'numpy.core._dotblas'

Are your arrays appropriately contiguous? Numpy needs to copy the data if 
they are not; though I'm not sure if this could account for what you see.

-- 
Pauli Virtanen