Balancing Speed and Stability: The Trade-offs of FP8 vs. BF16 Training in LLMs

TL;DR

This paper investigates the trade-offs between FP8 and BF16 numerical formats in training large language models, focusing on speed, stability, and performance implications for efficient large-scale NLP model training.

Contribution

It provides a comprehensive analysis of FP8 versus BF16 in LLM training, highlighting the practical benefits and challenges of adopting FP8 in real-world scenarios.

Findings

FP8 can reduce training time compared to BF16.

FP8 may impact training stability and downstream performance.

Adoption of FP8 involves balancing speed gains with potential stability issues.

Abstract

Large Language Models (LLMs) have attracted significant attention due to their human-like language understanding and generation capabilities, as well as their applicability across various domains. These models, characterized by their massive scale and extensive training data, continue to push the boundaries of what is possible in natural language processing. The Llama 3 series, for instance, exemplifies this trend with its flagship model boasting 405 billion parameters trained on 15.6 trillion tokens. The immense computational demands associated with training such models have spurred ongoing research into optimizing the efficiency of the training process, particularly through the use of lower-precision formats. NVIDIA's H100 GPU, which introduces support for FP8 in addition to the more conventional FP16 and BF16 formats, has emerged as a focal point in this optimization effort. Preliminary studies suggest that FP8 could offer substantial reductions in training time without sacrificing model performance when compared to BF16, making it a promising candidate for large-scale model training. However, the broader implications of adopting FP8, particularly in terms of training stability and downstream task performance, have yet to be fully understood. In this study, we delve into the practical trade-offs involved in adopting FP8 over BF16 for training LLMs.