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[FIX] Fix Alibi implementation in PagedAttention kernel (#945)

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* [FIX] Fix Alibi implementation in PagedAttention kernel

* Fix test_attention

* Fix

---------

Co-authored-by: Woosuk Kwon <woosuk.kwon@berkeley.edu>
Co-authored-by: Oliver-ss <yuansongwx@outlook.com>
This commit is contained in:
Zhuohan Li 2023-09-07 15:53:14 -07:00 committed by GitHub
parent c957c741d9
commit db09d4ad83
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2 changed files with 4 additions and 3 deletions
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2
csrc/attention/attention_kernels.cu
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@ -178,7 +178,7 @@ __global__ void single_query_cached_kv_attention_kernel(
// This includes a reduction across the threads in the same thread group.
float qk = scale * Qk_dot<scalar_t, THREAD_GROUP_SIZE>::dot(q_vecs[thread_group_offset], k_vecs);
// Add the ALiBi bias if slopes are given.
qk += (alibi_slope != 0) ? alibi_slope * (token_idx - context_len) : 0;
qk += (alibi_slope != 0) ? alibi_slope * (token_idx - context_len + 1) : 0;
if (thread_group_offset == 0) {
// Store the partial reductions to shared memory.

5
tests/kernels/test_attention.py
View File

@ -17,7 +17,7 @@ NUM_PREFILL_SEQS = [1, 3, 7] # Arbitrary values for testing
NUM_HEADS = [(40, 40), (64, 8)] # Arbitrary values for testing
HEAD_SIZES = [64, 80, 96, 112, 128, 256]
BLOCK_SIZES = [8, 16, 32]
USE_ALIBI = [False] # TODO(woosuk): Add USE_ALIBI=True
USE_ALIBI = [False, True]
SEEDS = [0]
@ -83,7 +83,7 @@ def ref_single_query_cached_kv_attention(
if alibi_slopes is not None:
# Create the ALiBi bias used in the paged attention kernel.
position_ids = torch.arange(context_len, device="cuda").int()
alibi_bias = (context_len - position_ids).float()
alibi_bias = (position_ids - context_len + 1).float()
alibi_bias = alibi_slopes.view(-1, 1, 1) * alibi_bias.view(
1, 1, -1)
@ -224,6 +224,7 @@ def ref_multi_query_kv_attention(
return ref_output
# TODO(woosuk): Add tests for USE_ALIBI=True.
@pytest.mark.parametrize("num_seqs", NUM_PREFILL_SEQS)
@pytest.mark.parametrize("num_heads", NUM_HEADS)
@pytest.mark.parametrize("head_size", HEAD_SIZES)