On Mon, Jan 23, 2012 at 5:34 AM, Andreas <[email protected]> wrote:
> Hi everybody.
> While reviewing the label propagation PR, I thought about the pairwise
> rbf functions.
> Would it be possible to compute an sparse, approximate RBF kernel matrix
> using ball trees?
> The idea would be that if the distance between two points is some
> "large" multiple of gamma, the kernel can be assumed
> to be zero.
> Do you think this is feasible to implement and helpful for real data?

Locality Sensitive Hashing could be use for fast approximate radius
search. The radius should be easy to determine: choose it such that
the exponential approximately rounds to 0.

Mathieu

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