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Original file line number | Diff line number | Diff line change |
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from typing import List, Optional, Tuple | ||
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import pytest | ||
import torch | ||
from vllm_flash_attn import flash_attn_varlen_func, flash_attn_with_kvcache | ||
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NUM_HEADS = [(16, 16), (32, 8), (64, 8)] | ||
HEAD_SIZES = [128, 256] | ||
BLOCK_SIZES = [16, 32] | ||
DTYPES = [torch.float16, torch.bfloat16] | ||
NUM_BLOCKS = 32768 # Large enough to test overflow in index calculation. | ||
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def ref_paged_attn( | ||
query: torch.Tensor, | ||
key_cache: torch.Tensor, | ||
value_cache: torch.Tensor, | ||
query_lens: List[int], | ||
kv_lens: List[int], | ||
block_tables: torch.Tensor, | ||
scale: float, | ||
sliding_window: Optional[int] = None, | ||
) -> torch.Tensor: | ||
num_seqs = len(query_lens) | ||
block_tables = block_tables.cpu().numpy() | ||
_, block_size, num_kv_heads, head_size = key_cache.shape | ||
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outputs = [] | ||
start_idx = 0 | ||
for i in range(num_seqs): | ||
query_len = query_lens[i] | ||
kv_len = kv_lens[i] | ||
q = query[start_idx:start_idx + query_len] | ||
q *= scale | ||
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num_kv_blocks = (kv_len + block_size - 1) // block_size | ||
block_indices = block_tables[i, :num_kv_blocks] | ||
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k = key_cache[block_indices].view(-1, num_kv_heads, head_size) | ||
k = k[:kv_len] | ||
v = value_cache[block_indices].view(-1, num_kv_heads, head_size) | ||
v = v[:kv_len] | ||
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if q.shape[1] != k.shape[1]: | ||
k = torch.repeat_interleave(k, q.shape[1] // k.shape[1], dim=1) | ||
v = torch.repeat_interleave(v, q.shape[1] // v.shape[1], dim=1) | ||
attn = torch.einsum("qhd,khd->hqk", q, k).float() | ||
empty_mask = torch.ones(query_len, kv_len) | ||
mask = torch.triu(empty_mask, diagonal=kv_len - query_len + 1).bool() | ||
if sliding_window is not None: | ||
sliding_window_mask = torch.triu(empty_mask, | ||
diagonal=kv_len - | ||
(query_len + sliding_window) + | ||
1).bool().logical_not() | ||
mask |= sliding_window_mask | ||
attn.masked_fill_(mask, float("-inf")) | ||
attn = torch.softmax(attn, dim=-1).to(v.dtype) | ||
out = torch.einsum("hqk,khd->qhd", attn, v) | ||
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outputs.append(out) | ||
start_idx += query_len | ||
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return torch.cat(outputs, dim=0) | ||
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@pytest.mark.parametrize("kv_lens", [[1328, 18, 463], [1, 54, 293, 70]]) | ||
@pytest.mark.parametrize("num_heads", NUM_HEADS) | ||
@pytest.mark.parametrize("head_size", HEAD_SIZES) | ||
@pytest.mark.parametrize("block_size", BLOCK_SIZES) | ||
@pytest.mark.parametrize("dtype", DTYPES) | ||
@torch.inference_mode | ||
def test_flash_attn_with_paged_kv( | ||
kv_lens: List[Tuple[int, int]], | ||
num_heads: Tuple[int, int], | ||
head_size: int, | ||
dtype: torch.dtype, | ||
block_size: int, | ||
) -> None: | ||
torch.set_default_device("cuda") | ||
torch.cuda.manual_seed_all(0) | ||
num_seqs = len(kv_lens) | ||
num_query_heads = num_heads[0] | ||
num_kv_heads = num_heads[1] | ||
assert num_query_heads % num_kv_heads == 0 | ||
max_kv_len = max(kv_lens) | ||
scale = head_size**-0.5 | ||
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query = torch.randn(num_seqs, num_query_heads, head_size, dtype=dtype) | ||
key_cache = torch.randn(NUM_BLOCKS, | ||
block_size, | ||
num_kv_heads, | ||
head_size, | ||
dtype=dtype) | ||
value_cache = torch.randn_like(key_cache) | ||
kv_lens_tensor = torch.tensor(kv_lens, dtype=torch.int32) | ||
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max_num_blocks_per_seq = (max_kv_len + block_size - 1) // block_size | ||
block_tables = torch.randint(0, | ||
NUM_BLOCKS, | ||
(num_seqs, max_num_blocks_per_seq), | ||
dtype=torch.int32) | ||
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output = flash_attn_with_kvcache( | ||
q=query.unsqueeze(1), | ||
k_cache=key_cache, | ||
v_cache=value_cache, | ||
softmax_scale=scale, | ||
causal=True, | ||
block_table=block_tables, | ||
cache_seqlens=kv_lens_tensor, | ||
).squeeze(1) | ||
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ref_output = ref_paged_attn( | ||
query=query, | ||
key_cache=key_cache, | ||
value_cache=value_cache, | ||
query_lens=[1] * num_seqs, | ||
kv_lens=kv_lens, | ||
block_tables=block_tables, | ||
scale=scale, | ||
) | ||
assert torch.allclose(output, ref_output, atol=1e-2, rtol=1e-2), \ | ||
f"{torch.max(torch.abs(output - ref_output))}" | ||
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@pytest.mark.parametrize("seq_lens", [[(1, 1328), (5, 18), (129, 463)]]) | ||
@pytest.mark.parametrize("num_heads", NUM_HEADS) | ||
@pytest.mark.parametrize("head_size", HEAD_SIZES) | ||
@pytest.mark.parametrize("block_size", BLOCK_SIZES) | ||
@pytest.mark.parametrize("sliding_window", [None]) | ||
@pytest.mark.parametrize("dtype", DTYPES) | ||
@torch.inference_mode | ||
def test_varlen_with_paged_kv( | ||
seq_lens: List[Tuple[int, int]], | ||
num_heads: Tuple[int, int], | ||
head_size: int, | ||
sliding_window: Optional[int], | ||
dtype: torch.dtype, | ||
block_size: int, | ||
) -> None: | ||
torch.set_default_device("cuda") | ||
torch.cuda.manual_seed_all(0) | ||
num_seqs = len(seq_lens) | ||
query_lens = [x[0] for x in seq_lens] | ||
kv_lens = [x[1] for x in seq_lens] | ||
num_query_heads = num_heads[0] | ||
num_kv_heads = num_heads[1] | ||
assert num_query_heads % num_kv_heads == 0 | ||
max_query_len = max(query_lens) | ||
max_kv_len = max(kv_lens) | ||
window_size = ((sliding_window, | ||
sliding_window) if sliding_window is not None else | ||
(-1, -1)) | ||
scale = head_size**-0.5 | ||
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query = torch.randn(sum(query_lens), | ||
num_query_heads, | ||
head_size, | ||
dtype=dtype) | ||
key_cache = torch.randn(NUM_BLOCKS, | ||
block_size, | ||
num_kv_heads, | ||
head_size, | ||
dtype=dtype) | ||
value_cache = torch.randn_like(key_cache) | ||
# Normalize the scale of the key and value caches to mitigate | ||
# numerical instability. | ||
key_cache /= head_size**0.5 | ||
value_cache /= head_size**0.5 | ||
cu_query_lens = torch.tensor([0] + query_lens, | ||
dtype=torch.int32).cumsum(dim=0, | ||
dtype=torch.int32) | ||
cu_kv_lens = torch.tensor([0] + kv_lens, | ||
dtype=torch.int32).cumsum(dim=0, | ||
dtype=torch.int32) | ||
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max_num_blocks_per_seq = (max_kv_len + block_size - 1) // block_size | ||
block_tables = torch.randint(0, | ||
NUM_BLOCKS, | ||
(num_seqs, max_num_blocks_per_seq), | ||
dtype=torch.int32) | ||
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output = flash_attn_varlen_func( | ||
q=query, | ||
k=key_cache, | ||
v=value_cache, | ||
cu_seqlens_q=cu_query_lens, | ||
cu_seqlens_k=cu_kv_lens, | ||
max_seqlen_q=max_query_len, | ||
max_seqlen_k=max_kv_len, | ||
softmax_scale=scale, | ||
causal=True, | ||
window_size=window_size, | ||
block_table=block_tables, | ||
) | ||
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ref_output = ref_paged_attn( | ||
query=query, | ||
key_cache=key_cache, | ||
value_cache=value_cache, | ||
query_lens=query_lens, | ||
kv_lens=kv_lens, | ||
block_tables=block_tables, | ||
scale=scale, | ||
sliding_window=sliding_window, | ||
) | ||
assert torch.allclose(output, ref_output, atol=1e-2, rtol=1e-2), \ | ||
f"{torch.max(torch.abs(output - ref_output))}" |
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