Faiss: How to use OPQ to reduce the dimensions

Created on 13 Nov 2017  ·  1Comment  ·  Source: facebookresearch/faiss

I have read the paper:Polysemous Codes in ECCV2016

I have an question:In the paper, you say “Alexandre Sablayrolles had the idea of extending the OPQ method to reduce the number of dimensions”. The original OPQ can not reduce the dimensions.

I want to know how to use OPQ to reduce the dimensions?

Thank you!

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Most helpful comment

If you look at the formulation in the original paper "Optimized Product Quantization for Approximate Nearest Neighbor Search" (CVPR'13), it turns out you can use Algorithm 1 with a non-square R matrix (say d*p). You just need to initialize it so that R^T R = I and you follow the steps described, as all the subsequent matrices will have the right number of dimensions.

>All comments

If you look at the formulation in the original paper "Optimized Product Quantization for Approximate Nearest Neighbor Search" (CVPR'13), it turns out you can use Algorithm 1 with a non-square R matrix (say d*p). You just need to initialize it so that R^T R = I and you follow the steps described, as all the subsequent matrices will have the right number of dimensions.

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