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The Fast Johnson–Lindenstrauss Transform and Approximate Nearest Neighbors

2009/01/01 by Nir Ailon, Bernard Chazelle · 498 citations
Computer Science · Engineering · Mathematics · #Advanced Image and Video Retrieval Techniques #Algorithm #Artificial intelligence #Combinatorics #Computational Geometry and Mesh Generation #Computer science #Discrete mathematics #Distortion (music) #Embedding #Fourier transform #Hypercube #Mathematical analysis #Mathematics #Random projection #Sparse and Compressive Sensing Techniques

paper · doi:10.1137/060673096

published in SIAM Journal on Computing 39(1), 302-322 (Society for Industrial and Applied Mathematics)

openalex publication_date 2009/01/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/06/20

Abstract

We introduce a new low-distortion embedding of ℓ2d into ℓpO(log n) (p=1,2) called the fast Johnson–Lindenstrauss transform (FJLT). The FJLT is faster than standard random projections and just as easy to implement. It is based upon the preconditioning of a sparse projection matrix with a randomized Fourier transform. Sparse random projections are unsuitable for low-distortion embeddings. We overcome this handicap by exploiting the “Heisenberg principle” of the Fourier transform, i.e., its local-global duality. The FJLT can be used to speed up search algorithms based on low-distortion embeddings in ℓ1 and ℓ2. We consider the case of approximate nearest neighbors in ℓ2d. We provide a faster algorithm using classical projections, which we then speed up further by plugging in the FJLT. We also give a faster algorithm for searching over the hypercube.

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