Flashattention

By Tri Daoy et al
Published on June 24, 2022
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Table of Contents

1 Introduction
2 Background
3 FlashAttention : Algorithm, Analysis, and Extensions

Summary

FlashAttention is a fast and memory-efficient exact attention algorithm that addresses the issues faced by Transformers on long sequences. By introducing IO-awareness and using tiling techniques, FlashAttention reduces the number of memory reads/writes between different levels of GPU memory, leading to significant speedups in model training. The algorithm computes exact attention with fewer memory accesses, making it both memory-efficient and faster in wall-clock time. The analysis of its IO complexity shows a substantial reduction in HBM accesses compared to standard attention methods. Additionally, the extension of FlashAttention to block-sparse attention further improves efficiency and scalability. The empirical results demonstrate faster model training and higher quality models, with significant speedups over existing attention methods.
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