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From Ted Dunning <>
Subject Re: Taste-GenericItemBasedRecommender
Date Sun, 13 Dec 2009 19:02:18 GMT
The issue is when adding a sparse vector to a dense vector (with the dense
vector being mutated) that the dense vector doesn't know how to use the
sparse iterator.

Following up on Jake's comment, could we have a marker interface that
indicates a function maps 0 to 0?  The abstract vector and matrix
implementations could use instanceOf to decide what to do.

On Sun, Dec 13, 2009 at 5:12 AM, Sean Owen <> wrote:

> In my particular case, I just need "Scale" instead of "PlusWithScale",
> and that can take advantage of sparseness.
> My (er, Ted's) current approach is to sum SparseVectors. This takes
> advantage of sparseness already.
> Am I missing why a Scale/PlusWithScale implementation, when using
> sparseness, would be notably faster?

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