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Great work. Can you elaborate on how the radix selection works and how to get that working with float's and inner product distance? I just quickly checked the code, I'm not familiar with radix selection, but really interested in making extremely fast GPU indices.

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The radix selection algorithm is a modified radix sort that, since we don't care to sort the whole list but rather just the top K results, manages to cut some of the time out of the algorihm. It was an awesome way to get experience in CUDA programming.

Radix sort works with any ordered sets--it just lends itself well for GPUs since it is designed to be run in parallel. I used the modified version to get the best hamming distance results quickly, and implemented a few other distance measures as well (e.g., cosine distance)

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