[Numpy-discussion] Simplified question on tensordot

Pauli Virtanen pav@iki...
Fri Sep 3 06:57:22 CDT 2010


Fri, 03 Sep 2010 05:48:31 -0600, Rick Muller wrote:
[clip]
> 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,:])

>>> AB = np.sum(A*B, axis=1)

It does create an intermediate (n, d) matrix, however. If this is a 
problem because of memory issues, you can try numexpr [1],

>>> numexpr.evaluate("sum(A*B, axis=1)")

.. [1] http://code.google.com/p/numexpr/

-- 
Pauli Virtanen



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