[Numpy-discussion] Simplified question on tensordot

[josef.pktd at gmail.com]

On Fri, Sep 3, 2010 at 7:48 AM, Rick Muller <rpmuller at gmail.com> wrote:
> Sorry for the rapid repost, but I thought of a much easier way to ask the
> question I asked a few minutes ago.
>
> I have two matrices, A and B, both of which are n x m. n is big (~10,000),
> and m is small (~10).
>
> I want to take the product AB such that I get a length-n vector, as in:
>
>>>> AB = zeros(n,'d')
>>>> for i in xrange(n):
>>>>    AB[i] = dot(A[i,:],B[i,:])

Isn't this just (A*B).sum(1)  ?

Josef

>
> only I don't want the for-loop. The various things I've tried with dot and
> tensordot inevitably give me a n x n matrix, which isn't what I want. Can
> anyone help me find an easier way to do this?
>
> --
> Rick Muller
> rpmuller at gmail.com
>
>
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