mlsanityData to 14 Oct 2026

OPORP: One Permutation + One Random Projection

arXiv 2302.03505 ↗First posted 7 Feb 2023stat.ML cs.LGcited by 12

Not on the map. Why?

Abstract (arXiv)

Consider two D-dimensional data vectors (e.g., embeddings): u, v. In many embedding-based retrieval (EBR) applications where the vectors are generated from trained models, D=256~ 1024 are common. In this paper, OPORP (one permutation + one random projection) uses a variant of the ``count-sketch'' type of data structures for achieving data reduction/compression. With OPORP, we first apply a permutation on the data vectors. A random vector r is generated i.i.d. with moments: E(ri) = 0, E(ri2)=1, E(ri3) =0, E(ri4)=s. We multiply (as dot product) r with all permuted data vectors. Then we break the D columns into k equal-length bins and aggregate (i.e., sum) the values in each bin to obtain k samples from each data vector. One crucial step is to normalize the k samples to the unit l2 norm. We show that the estimation variance is essentially: (s-1)A + fracD-kD-1frac1kleft[ (1-ρ2)2 -2Aright], where A≥ 0 is a function of the data (u,v). This formula reveals several key properties: (1) We need s=1. (2) The factor fracD-kD-1 can be highly beneficial in reducing variances. (3) The term frac1k(1-ρ2)2 is a substantial improvement compared with frac1k(1+ρ2), which corresponds to the un-normalized estimator. We illustrate that by letting the k in OPORP to be k=1 and repeat the procedure m times, we exactly recover the work of ``very spars random projections'' (VSRP). This immediately leads to a normalized estimator for VSRP which substantially improves the original estimator of VSRP. In summary, with OPORP, the two key steps: (i) the normalization and (ii) the fixed-length binning scheme, have considerably improved the accuracy in estimating the cosine similarity, which is a routine (and crucial) task in modern embedding-based retrieval (EBR) applications.

Key facts. Cited by 12 papers in the map (data through 14 Oct 2026). Builds on 29 of its 87 references that are in the map. First posted on arXiv 7 Feb 2023.

Builds on

29 of 87 references.

References · 29

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17 more
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Cited by year (2026 to 14 Oct)

Citing papers per year: 2023: 2; 2024: 4; 2025: 2; 2026: 4.

12 papers.