[New Feature] fa3 支持flash mask #3184
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gzy19990617
reviewed
Aug 5, 2025
| naive_attn_out = naive_attn(q_input, k_input, v_input, mask) | ||
| paddle_attn_out = paddle_flash_attn_mask(q_input, k_input, v_input, mask) | ||
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| print((paddle_attn_out.reshape([-1]) - paddle.to_tensor(naive_attn_out).reshape([-1])).max()) |
yuanlehome
approved these changes
Aug 5, 2025
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在flash attention 3的基础上支持了mask形式，其中mask是一个shape为[q_seq_len]的int 数组，对于第i个token，那么qkgemm矩阵的第i行，第mask[i]列之后的数字都会被mask 掉，即qkgemm[i,mask[i]:] 会被mask掉，例如要使用casual mask的话，mask的数组就为[1,2,3,4,5,.......]
若mask传入None，默认采用casual mask