A comprehensive walkthrough of implementing Flash Attention for NVIDIA RTX 5090 in CUDA C++, progressing through five optimization versions. Starting with a basic implementation achieving 68% of theoretical peak performance, the author systematically applies optimizations including shared memory swizzling to eliminate bank
Table of contents
Table of ContentsFlash Attention algorithmVersion 1 - Basic implementationVersion 2 - Shared memory swizzlingVersion 3 - 2-stage pipeliningVersion 4 - ldmatrix.x4 for K and VVersion 5 - better pipeliningWhat’s next?Sort: