Perplexed by Perplexity: Perplexity-Based Data Pruning With Small
  Reference Models
Authors: name: Zachary Ankner; name: Cody Blakeney; name: Kartik Sreenivasan; name: Max Marion; name: Matthew L. Leavitt; name: Mansheej Paul
Published: 2024-05-30 23:50:20

Abstract: In this work, we investigate whether small language models can determine
high-quality subsets of large-scale text datasets that improve the performance
of larger language models. While existing work has shown that pruning based on
the perplexity of a larger model can yield high-quality data, we investigate
whether smaller models can be used for perplexity-based pruning and how pruning
is affected by the domain composition of the data being pruned. We demonstrate
that for multiple dataset compositions, perplexity-based pruning of pretraining
data can significantly improve downstream task performance: pruning
based on perplexities computed with a 125 million parameter model improves the
average performance on downstream tasks of a 3 billion parameter model by up to
2.04 and achieves up to a 1.45times reduction in pretraining steps to reach
commensurate baseline performance. Furthermore, we demonstrate that such
perplexity-based data pruning also yields downstream performance gains in the
over-trained and data-constrained regimes.