FlashAttention and IO-Aware Attention
WHAT IT TESTS: hardware-aware optimization of attention. OUTLINE: FlashAttention is IO-aware, tiling and fusing attention in fast SRAM to avoid materializing the n-by-n matrix in slow HBM. RED FLAG: claiming it changes the math or lowers asymptotic compute.
WHAT IT TESTS: deep understanding that attention is memory-bandwidth bound, not compute bound. ANSWER OUTLINE: FlashAttention keeps the exact softmax attention but reorders computation to be IO-aware. It tiles queries, keys, and values into blocks that fit in fast on-chip SRAM, fuses the score, softmax, and value steps in one kernel, and uses online softmax with running statistics so it never writes the full n-by-n matrix to slow HBM. This cuts memory from quadratic to linear and boosts throughput.
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- #flashattention
- #attention
- #gpu
- #optimization
- #long-context
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