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Math Forum » Discussions » Software » comp.soft-sys.matlab

Topic: Efficiently computing large numbers of vector norms
Replies: 16   Last Post: Nov 15, 2012 8:32 AM

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Harry Commin

Posts: 11
Registered: 10/8/10
Re: Efficiently computing large numbers of vector norms
Posted: Nov 13, 2012 1:22 PM
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> It would be interesting to know the data dimensions you're working with.

For my tests, I had:

N1 = 3;
N2 = 4;
Q1 = 180;
Q2 = 63;

If I increase N1 and/or N2, the improvement (due to KronProd) decreases.

For more complicated cases, I can't see how to use KronProd at all. In particular, when there is element-by-element multiplication, e.g.:

kron(kron(A1(:,i),A2(:,i).*A3(:,j)),A4(:,j))'*X3

That is, A1 and A2 'belong' to the same loop and, similarly, A3 and A4 belong together to a different loop. However, A2(:,i).*A3(:,j) mixes the two and I can't see how to deal with it!

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