DataDecide: How to Predict Best Pretraining Data with Small Experiments
Authors: name: Ian Magnusson; name: Nguyen Tai; name: Ben Bogin; name: David Heineman; name: Jena D. Hwang; name: Luca Soldaini; name: Akshita Bhagia; name: Jiacheng Liu; name: Dirk Groeneveld; name: Oyvind Tafjord; name: Noah A. Smith; name: Pang Wei Koh; name: Jesse Dodge
Published: 2025-04-15 17:02:15

Abstract: Because large language models are expensive to pretrain on different
datasets, using smaller-scale experiments to decide on data is crucial for
reducing costs. Which benchmarks and methods of making decisions from observed
performance at small scale most accurately predict the datasets that yield the
best large models? To empower open exploration of this question, we release
models, data, and evaluations in DataDecide -- the most extensive open suite of
models over differences in data and scale. We conduct controlled pretraining
experiments across 25 corpora with differing sources, deduplication, and
filtering up to 100B tokens, model sizes up to 1B parameters, and 3 random
seeds. We find that the ranking of models at a single, small size (e.g., 150M
parameters) is a strong baseline for predicting best models at our larger
target scale (1B) (~80% of com parisons correct). No scaling law methods among
8 baselines exceed the compute-decision frontier of single-scale predictions,
but DataDecide can measure improvement in future scaling laws. We also identify
that using continuous likelihood metrics as proxies in small experiments makes
benchmarks including MMLU, ARC, HellaSwag, MBPP, and HumanEval >80% predictable
at the target 1B scale with just 0.01% of the compute.