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[Triton] Fix benchmark_causal, mention Triton version

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This commit is contained in:
Tri Dao 2023-03-22 00:51:16 -07:00
parent dc08ea1c33
commit 5d079fdd7a
2 changed files with 9 additions and 3 deletions
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4
benchmarks/benchmark_causal.py
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@ -93,8 +93,8 @@ benchmark_all(flash_attn_unpadded_qkvpacked_func, rearrange(qkv, 'b s ... -> (b
benchmark_all(attention_pytorch, qkv, dropout_p, causal=causal,
repeats=repeats, desc='PyTorch Attention')
benchmark_all(flash_attn_qkvpacked_func, qkv, causal, repeats=repeats, desc='FlashAttention Triton')
pytorch_profiler(flash_attn_qkvpacked_func, qkv, causal, backward=True)
benchmark_all(flash_attn_qkvpacked_func, qkv, causal=causal, repeats=repeats, desc='FlashAttention Triton')
pytorch_profiler(flash_attn_qkvpacked_func, qkv, causal=causal, backward=True)
q, k, v = [torch.randn(batch_size, nheads, seqlen, headdim, device=device, dtype=dtype,
requires_grad=True) for _ in range(3)]

8
flash_attn/flash_attn_triton.py
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@ -1,5 +1,10 @@
"""
*Experimental* implementation of FlashAttention in Triton.
Tested with triton==2.0.0.dev20221202.
Triton 2.0 has a new backend (MLIR) but seems like it doesn't yet work for head dimensions
other than 64:
https://github.com/openai/triton/blob/d376020f90002757eea3ea9475d4f7cfc2ec5ead/python/triton/ops/flash_attention.py#L207
We'll update this implementation with the new Triton backend once this is fixed.
We use the FlashAttention implementation from Phil Tillet a starting point.
https://github.com/openai/triton/blob/master/python/tutorials/06-fused-attention.py
@ -773,7 +778,8 @@ class FlashAttnKVPackedFunc(torch.autograd.Function):
@staticmethod
def backward(ctx, do):
q, kv, o, lse, bias = ctx.saved_tensors
assert not ctx.needs_input_grad[2], 'FlashAttention does not support bias gradient yet'
if len(ctx.needs_input_grad) >= 3:
assert not ctx.needs_input_grad[2], 'FlashAttention does not support bias gradient yet'
# Triton's autotune causes the Tensor._version to change, and so Pytorch autograd
# does a memcpy. To avoid this we run in inference_mode, which doesn't track the version.
with torch.inference_mode():