Efficient Minimum Bayes Risk Decoding using Low-Rank Matrix Completion Algorithms

Firas Trabelsi; David Vilar; Mara Finkelstein; Markus Freitag

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arXiv · 2406.02832

Efficient Minimum Bayes Risk Decoding using Low-Rank Matrix Completion Algorithms

Firas Trabelsi·David Vilar·Mara Finkelstein·Markus Freitag

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Abstract

Minimum Bayes Risk (MBR) decoding is a powerful decoding strategy widely used for text generation tasks, but its quadratic computational complexity limits its practical application. This paper presents a novel approach for approximating MBR decoding using matrix completion techniques, focusing on the task of machine translation. We formulate MBR decoding as a matrix completion problem, where the utility metric scores between candidate hypotheses and pseudo-reference translations form a low-rank matrix. First, we empirically show that the scores matrices indeed have a low-rank structure. Then, we exploit this by only computing a random subset of the scores and efficiently recover the missing entries in the matrix by applying the Alternating Least Squares (ALS) algorithm, thereby enabling a fast approximation of the MBR decoding process. Our experimental results on machine translation tasks demonstrate that the proposed method requires 1/16 utility metric computations compared to vanilla MBR decoding while achieving equal translation quality measured by COMET22 on the WMT22 dataset (en<>de and en<>ru). We also benchmark our method against other approximation methods and we show gains in quality when comparing to them.

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Firas Trabelsi, David Vilar, Mara Finkelstein, Markus Freitag. 2024-06-05. Efficient Minimum Bayes Risk Decoding using Low-Rank Matrix Completion Algorithms. https://arxiv.org/abs/2406.02832

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