Re: [Numpy-discussion] matrix multiplication A x, x has some zeros

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idx=N.ravel(x)!=0 A[:,idx]*x[idx]

On Fri, 14 Dec 2007, dmitrey apparently wrote:

I expect <A,x> being vector of length n A and x change every iter. A is not sparse.

Still, whenever x has a lot of zeros, this should have a substantial payoff. That seems the only exploitable information you have offered in the problem. Cheers, Alan