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Work in progress for eventual contribution to scikit-learn

branch: master
README.rst

Note: this module should be considered unsupported. It probably won't compile, and if it does, it may contain errors in some cases. See a more developed version of this functionality in scikit-learn: https://github.com/scikit-learn/scikit-learn/pull/1732/

pyDistances

Fast cython distance computations in a variety of metrics which expose pointers to C functions.

This is a framework that will allow general distance metrics to be incorporated into tree-based neighbors searches. The idea is that we need a fast way to compute the distance between two points under a given metric. In the basic framework here, this involves creating an object which exposes C-pointers to a function and a parameter structure so that the distance function can be called from python as normal, or alternatively can be called directly from cython without python overhead.

pdist/cdist

The code has functions which duplicate the behavior of scipy.spatial.distances.pdist and scipy.spatial.distances.cdist.

BallTree

The code features a BallTree object which can quickly return nearest neighbors under any of the available metrics.

Benchmarks

run bench.py for a comparison of runtimes between pyDistance and scipy.spatial for the available metrics. Times are comparable in most cases, much faster in a few cases, and slightly slower in a few cases.

TODO

Search TODO within distmetrics.pyx to see a list. One big one (which should be straightforward) is to make the distance metrics work with CSR matrices. This will involve writing an alternate version of each core distance function.

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