Diverse Beam Search: Decoding Diverse Solutions from Neural Sequence Models

TL;DR

Diverse Beam Search (DBS) enhances neural sequence decoding by generating more varied outputs, improving solution quality across tasks like image captioning and translation with minimal additional computational cost.

Contribution

This paper introduces Diverse Beam Search, a novel decoding algorithm that produces diverse output sequences from neural models, outperforming standard beam search and previous methods.

Findings

DBS finds better top-1 solutions than beam search.

DBS maintains computational efficiency comparable to beam search.

DBS improves diversity and quality across multiple tasks.

Abstract

Neural sequence models are widely used to model time-series data. Equally ubiquitous is the usage of beam search (BS) as an approximate inference algorithm to decode output sequences from these models. BS explores the search space in a greedy left-right fashion retaining only the top-B candidates - resulting in sequences that differ only slightly from each other. Producing lists of nearly identical sequences is not only computationally wasteful but also typically fails to capture the inherent ambiguity of complex AI tasks. To overcome this problem, we propose Diverse Beam Search (DBS), an alternative to BS that decodes a list of diverse outputs by optimizing for a diversity-augmented objective. We observe that our method finds better top-1 solutions by controlling for the exploration and exploitation of the search space - implying that DBS is a better search algorithm. Moreover, these gains are achieved with minimal computational or memory over- head as compared to beam search. To demonstrate the broad applicability of our method, we present results on image captioning, machine translation and visual question generation using both standard quantitative metrics and qualitative human studies. Further, we study the role of diversity for image-grounded language generation tasks as the complexity of the image changes. We observe that our method consistently outperforms BS and previously proposed techniques for diverse decoding from neural sequence models.