Scaling Laws for Optimal Data Mixtures
Authors: name: Mustafa Shukor; name: Louis Bethune; name: Dan Busbridge; name: David Grangier; name: Enrico Fini; name: Alaaeldin El-Nouby; name: Pierre Ablin
Published: 2025-07-12 21:16:08

Abstract: Large foundation models are typically trained on data from multiple domains,
with the data mixture--the proportion of each domain used--playing a critical
role in model performance. The standard approach to selecting this mixture
relies on trial and error, which becomes impractical for large-scale
pretraining. We propose a systematic method to determine the optimal data
mixture for any target domain using scaling laws. Our approach accurately
predicts the loss of a model of size N trained with D tokens and a specific
domain weight vector h. We validate the universality of these scaling laws by
demonstrating their predictive power in three distinct and large-scale
settings: large language model (LLM), native multimodal model (NMM), and large
vision models (LVM) pretraining. We further show that these scaling laws can
extrapolate to new data mixtures and across scales: their parameters can be
accurately estimated using a few small-scale training runs, and used to
estimate the performance at larger scales and unseen domain weights. The
scaling laws allow to derive the optimal domain weights for any target domain
under a given training budget (N,D), providing a principled alternative to
costly trial-and-error methods.