[Numpy-discussion] Matrix dot product over an axis(for a 3d array/list of matrices)

Charles R Harris charlesr.harris@gmail....
Thu Jul 15 13:09:57 CDT 2010


On Thu, Jul 15, 2010 at 12:00 PM, Emmanuel Bengio <bengioe@gmail.com> wrote:

> Ok I get it. Thanks!
>
> Numpy syntax that works for me:
> numpy.sum(a[:,:,:,numpy.newaxis]*b[:,numpy.newaxis,:,:],axis=-2)
>
>
The leading "..." gives the same thing, but iterates over all the leading
indicies in case you want multidimensional arrays of matrices ;) You can
also use the sum method which might be a bit more economical:

(a[:,:,:,numpy.newaxis]*b[:,numpy.newaxis,:,:]).sum(axis=-2)

How do the execution times compare?

<snip>

Chuck
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