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d4c79a3078
pytorch/test/test_transformers.py
drisspg d4c79a3078 Add an attention bias subclass for a lower right causal masking (#114823) 
# Summary
This PR introduces a new Tensor subclass that is designed to be used with torch.nn.functional.scaled_dot_product_attention. Currently we have a boolean `is_causal` flag that allows users to do do causal masking without the need to actually create the "realized" attention bias and pass into sdpa. We originally added this flag since there is native support in both fused kernels we support. This provides a big performance gain ( the kernels only need to iterate over ~0.5x the sequence, and for very large sequence lengths this can provide vary large memory improvements.

The flag was introduced when the early on in the kernel development and at the time it was implicitly meant to "upper_left" causal attention. This distinction only matters when the attention_bias is not square. For a more detailed break down see: https://github.com/pytorch/pytorch/issues/108108. The kernels default behavior has since changed, largely due to the rise of autogressive text generation. And unfortunately this would lead to a BC break. In the long term it may actually be beneficial to change the default meaning of `is_causal` to represent lower_right causal masking.

The larger theme though is laid here: https://github.com/pytorch/pytorch/issues/110681. The thesis being that there is alot of innovation in SDPA revolving around the attention_bias being used. This is the first in hopefully a few more attention_biases that we would like to add. The next interesting one would be `sliding_window` which is used by the popular mistral model family.

Results from benchmarking, I improved the meff_attention perf hence the slightly decreased max perf.
```Shell
+---------+--------------------+------------+-----------+-----------+-----------+-----------+----------------+----------+
|  Type   |      Speedup       | batch_size | num_heads | q_seq_len | k_seq_len | embed_dim |     dtype      | head_dim |
+---------+--------------------+------------+-----------+-----------+-----------+-----------+----------------+----------+
| Average | 1.2388050062214226 |            |           |           |           |           |                |          |
|   Max   | 1.831672915579016  |    128     |    32     |   1024    |   2048    |   2048    | torch.bfloat16 |    64    |
|   Min   | 0.9430534166730135 |     1      |    16     |    256    |    416    |   2048    | torch.bfloat16 |   128    |
+---------+--------------------+------------+-----------+-----------+-----------+-----------+----------------+----------+
```

Pull Request resolved: https://github.com/pytorch/pytorch/pull/114823
Approved by: https://github.com/cpuhrsch
2023-12-06 08:29:26 +00:00

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# Owner(s): ["module: nn"]
import contextlib
from functools import partial
from collections import namedtuple
import sys
import torch
import torch.nn as nn
import torch.nn.functional as F
from torch.nn.functional import scaled_dot_product_attention
from torch.nn.attention.bias import CausalVariant, causal_lower_right, causal_upper_left
from torch.nn.parameter import Parameter
import unittest
from unittest import expectedFailure as xfail
from unittest.mock import patch, MagicMock, ANY
import math
from torch.backends.cuda import sdp_kernel, SDPBackend
import torch.optim as optim
from torch.testing._internal.common_device_type import instantiate_device_type_tests, onlyCUDA, onlyCPU
from typing import List, Tuple, Optional
from torch.testing._internal.common_nn import NNTestCase
from torch.testing._internal.common_utils import (
TEST_FAIRSEQ,
run_tests,
parametrize,
freeze_rng_state,
TEST_WITH_CROSSREF,
slowTest,
set_default_dtype,
gradcheck,
make_tensor,
NOTEST_CPU
)
from torch.testing._internal.common_methods_invocations import wrapper_set_seed
from torch.testing._internal.common_cuda import (
SM80OrLater, PLATFORM_SUPPORTS_FLASH_ATTENTION,
PLATFORM_SUPPORTS_MEM_EFF_ATTENTION,
PLATFORM_SUPPORTS_FUSED_ATTENTION
)
if TEST_FAIRSEQ:
import fairseq.models.transformer as fairseq_transformer
SdpaShape = namedtuple('Sdpa_Shape', ['batch', 'num_heads', 'seq_len', 'head_dim'])
Tolerances = namedtuple('Tolerances', ['atol', 'rtol'])
@contextlib.contextmanager
def use_deterministic_algorithims(mode: bool, warn_only: bool):
r"""
This context manager can be used to temporarily enable or disable deterministic algorithms.
Upon exiting the context manager, the previous state of the flag will be restored.
"""
previous_mode: bool = torch.are_deterministic_algorithms_enabled()
previous_warn_only: bool = torch.is_deterministic_algorithms_warn_only_enabled()
try:
torch.use_deterministic_algorithms(mode, warn_only=warn_only)
yield {}
finally:
torch.use_deterministic_algorithms(previous_mode, warn_only=previous_warn_only)
# Found in torch/testing/_comparison.py
default_atol = {torch.float16: 1e-3, torch.bfloat16: 1e-3, torch.float32: 1e-5}
default_rtol = {torch.float16: 1e-3, torch.bfloat16: 1.6e-2, torch.float32: 1.3e-6}
isSM86or89Device = torch.cuda.is_available() and torch.cuda.get_device_capability() in [(8, 6), (8, 9)]
isSM90Device = torch.cuda.is_available() and torch.cuda.get_device_capability() == (9, 0)
isSM5xDevice = torch.cuda.is_available() and torch.cuda.get_device_capability()[0] == 5
def get_rtol(true_value: torch.Tensor, computed_value: torch.Tensor) -> float:
deviation = true_value - computed_value
deviation = torch.abs(deviation / true_value)
# Fill in the nans with the default rtol
torch.nan_to_num_(deviation, nan=default_rtol[computed_value.dtype])
return deviation.max().item()
def get_atol(true_value: torch.Tensor, computed_value: torch.Tensor) -> float:
deviation = true_value - computed_value
atol = torch.abs(deviation).max().item()
return atol
def get_tolerances(
true_value: torch.Tensor,
computed_value: torch.Tensor,
fudge_factor: Optional[float] = None,
) -> Tuple[float, float]:
"""Returns the absolute and relative tolerances for comparing two tensors."""
fudge_factor = fudge_factor if fudge_factor is not None else 1.0
atol = get_atol(true_value, computed_value)
rtol = get_rtol(true_value, computed_value)
atol = fudge_factor * max(atol, default_atol[computed_value.dtype])
rtol = fudge_factor * max(rtol, default_rtol[computed_value.dtype])
# torch.isclose() has weird behavior around see:
# https://github.com/pytorch/pytorch/issues/102400
if rtol > 1e30:
rtol = default_rtol[computed_value.dtype]
return atol, rtol
backend_map = {
SDPBackend.MATH: {"enable_math": True, "enable_flash": False, "enable_mem_efficient": False},
SDPBackend.FLASH_ATTENTION: {"enable_math": False, "enable_flash": True, "enable_mem_efficient": False},
SDPBackend.EFFICIENT_ATTENTION: {
"enable_math": False, "enable_flash": False, "enable_mem_efficient": True}
}
def query_key_value_clones(query: torch.Tensor, key: torch.Tensor, value: torch.Tensor, dtype: torch.dtype = None):
""" Clones the query, key, and value tensors and moves them to the specified dtype. """
if dtype is None:
dtype = query.dtype
query_ref = query.clone().detach().to(dtype).requires_grad_(query.requires_grad)
key_ref = key.clone().detach().to(dtype).requires_grad_(key.requires_grad)
value_ref = value.clone().detach().to(dtype).requires_grad_(value.requires_grad)
return query_ref, key_ref, value_ref
def rand_sdpa_tensor(shape: SdpaShape, device: str, dtype: torch.dtype, type: str,
requires_grad: bool = False, packed: bool = False) -> torch.Tensor:
"""Creates rand dense or nested tensor with given shape and type.
Args:
shape (Tuple[int]): Shape of Tensor to construct
device (str): which device to create tensor on
dtype (torch.dtype): Tensors' dtype
type (str): Nested or Dense
requires_grad (bool, optional): Tensors grad status. Defaults to False.
packed (bool, optional): Whether to create a single QKV packed or not. Defaults to False.
Returns:
torch.Tensor: A new tensor
"""
batch, num_heads, seq_len, head_dim = shape.batch, shape.num_heads, shape.seq_len, shape.head_dim
if type == "nested":
if isinstance(seq_len, list):
def _size(i):
return (seq_len[i], num_heads, head_dim) if not packed else (seq_len[i], 3 * num_heads * head_dim)
return torch.nested.nested_tensor([
torch.randn(_size(i), device=device, dtype=dtype, requires_grad=requires_grad)
for i in range(batch)])
else:
size = (seq_len, num_heads, head_dim) if not packed else (seq_len, 3 * num_heads * head_dim)
return torch.nested.nested_tensor([
torch.randn(size, device=device, dtype=dtype, requires_grad=requires_grad)
for _ in range(batch)])
else:
assert (isinstance(seq_len, int))
size = (batch, seq_len, num_heads, head_dim) if not packed else (batch, seq_len, 3 * num_heads * head_dim)
return torch.randn(size, device=device, dtype=dtype, requires_grad=requires_grad)
def calculate_nt_tolerances(nt_ref_hp, nt_ref_lp, default_dtype, fudge_factor=1):
# TODO use NT ops when we have implemented Max for NestedTensor instead of unrolling
ref_atol = default_atol[default_dtype]
ref_rtol = default_rtol[default_dtype]
for tensor_component_ref, tensor_component_ref_lp in zip(nt_ref_hp.unbind(), nt_ref_lp.unbind()):
ref_atol = max((fudge_factor * torch.abs(tensor_component_ref - tensor_component_ref_lp)).max().item(), ref_atol)
ref_rtol = max(get_rtol(tensor_component_ref, tensor_component_ref_lp), ref_rtol)
return ref_atol, ref_rtol
class TestTransformers(NNTestCase):
_do_cuda_memory_leak_check = True
_do_cuda_non_default_stream = True
@onlyCUDA
@unittest.skip("4D mask not supported yet - activate when 4D mask supported")
def test_self_attn_TxT_attn_mask(self, device):
embed_dim = 16
num_heads = 4
batch_size = 10
tgt_len = 16
query = torch.rand(batch_size, tgt_len, embed_dim, device=device) # [N, T, D]
attn_mask = torch.randint(0, 2, (tgt_len, tgt_len)).cuda().float() # [T, T]
attn_mask = attn_mask.masked_fill(attn_mask == 0, float('-inf')).masked_fill(attn_mask == 1, 0.0)
attn_mask_4d = attn_mask.expand(batch_size, num_heads, tgt_len, tgt_len)
mta_model = torch.nn.MultiheadAttention(embed_dim, num_heads, batch_first=True).cuda()
mta_model.eval()
# Generate 3D results
with torch.inference_mode():
output_mask_4d = mta_model(query, query, query, attn_mask=attn_mask_4d)[0]
output_mask_4d = output_mask_4d.transpose(0, 1) # [N, T, D]
output_mask_TxT = mta_model(query, query, query, attn_mask=attn_mask)[0]
output_mask_TxT = output_mask_TxT.transpose(0, 1) # [N, T, D]
self.assertEqual(output_mask_4d, output_mask_TxT)
@slowTest
def test_train_with_pad_and_catch_error(self, device):
iters = 100
pad_mask = torch.tensor([[1, 1, 0, 0]], dtype=torch.bool).to(device)
layer = nn.TransformerEncoderLayer(
d_model=2,
dim_feedforward=4,
nhead=2,
batch_first=True,
activation="gelu",
dropout=0,
)
criterion = nn.MSELoss()
encoder = nn.TransformerEncoder(layer, 2).to(device)
optimizer = optim.SGD(encoder.parameters(), lr=0.1, momentum=0.9)
encoder.train()
for i in range(iters):
encoder.train()
optimizer.zero_grad()
inputs = torch.cat([torch.randn(1, 2, 2), torch.zeros(1, 2, 2)], dim=1).to(device)
outputs = encoder(inputs, src_key_padding_mask=pad_mask)
loss = criterion(outputs[:, 0:2, :], inputs[:, 0:2, :])
loss.backward()
optimizer.step()
with torch.no_grad():
test = torch.cat([torch.randn(1, 2, 2), torch.zeros(1, 2, 2)], dim=1).to(device)
# Expect uint8 type not supported
ex = None
try:
test_train_uint8 = encoder(test, src_key_padding_mask=pad_mask.to(torch.uint8))
except AssertionError as e:
continue
self.assertFalse(e, "Failed to catch unsupported uint8 type exception")
test_train_bool = encoder(test, src_key_padding_mask=pad_mask)
encoder.eval()
# Expect long type not supported
ex = None
try:
test_eval_uint8 = encoder(test, src_key_padding_mask=pad_mask.to(torch.int64))
except AssertionError as e:
continue
self.assertFalse(e, "Failed to catch unsupported Long type exception")
test_eval_bool = encoder(test, src_key_padding_mask=pad_mask)
l1_bool = nn.L1Loss()(test_train_bool[:, 0:2, :], test_eval_bool[:, 0:2, :]).item()
self.assertTrue(l1_bool < 1e-4, "Eval/Train difference in pad_mask BOOL")
@parametrize("attn_mask_dim", [2, 3, None])
@parametrize("key_padding_mask_dim", [2, None])
@parametrize("mask_dtype", [torch.bool, torch.float32])
def test_multiheadattention_fastpath_attn_mask(self, device, attn_mask_dim, key_padding_mask_dim, mask_dtype):
with torch.no_grad():
B = 2
L = 4
D = 8
H = 4
if attn_mask_dim == 2:
attn_mask = make_tensor((L, L), dtype=mask_dtype, device=device)
elif attn_mask_dim == 3:
attn_mask = make_tensor((B * H, L, L), dtype=mask_dtype, device=device)
elif attn_mask_dim is None:
attn_mask = None
if key_padding_mask_dim == 2:
key_padding_mask = make_tensor((B, L), dtype=mask_dtype, device=device)
elif key_padding_mask_dim is None:
key_padding_mask = None
mha = nn.MultiheadAttention(D, H, batch_first=True, device=device)
X = torch.randn(B, L, D, device=device)
mha.train() # disable fast path
out, _ = mha(X, X, X, attn_mask=attn_mask, key_padding_mask=key_padding_mask, need_weights=False)
mha.eval() # enable fast path
out_fp, _ = mha(X, X, X, attn_mask=attn_mask, key_padding_mask=key_padding_mask, need_weights=False)
self.assertEqual(out, out_fp)
@parametrize("nhead", [1, 4, 8])
def test_transformerencoderlayer_src_mask(self, device, nhead):
batch_size = 2
seqlen = 4
d_model = 8
dim_feedforward = 32
model = torch.nn.TransformerEncoderLayer(
d_model=d_model,
nhead=nhead,
dim_feedforward=dim_feedforward,
batch_first=True).to(device)
src = torch.rand(batch_size, seqlen, d_model).to(device) # bs, seqlen, d_model
src_mask = torch.zeros(seqlen, seqlen).to(torch.bool).to(device)
model(src, src_mask=src_mask)
model.eval()
with torch.no_grad():
model(src, src_mask=src_mask)
@parametrize("use_torchscript", [False])
@parametrize("enable_nested_tensor", [True, False])
@parametrize("use_autocast", [True, False])
@parametrize("d_model", [12, 256])
def test_transformerencoder_fastpath(self, device, use_torchscript, enable_nested_tensor, use_autocast, d_model):
"""
Test TransformerEncoder fastpath output matches slowpath output
"""
torch.manual_seed(1234)
nhead = 4
dim_feedforward = d_model
batch_first = True
model = torch.nn.TransformerEncoder(
torch.nn.TransformerEncoderLayer(
d_model=d_model,
nhead=nhead,
dim_feedforward=dim_feedforward,
batch_first=batch_first),
num_layers=2,
enable_nested_tensor=enable_nested_tensor
).to(device).eval()
if use_torchscript:
model = torch.jit.script(model)
# each input is (input, mask)
input_mask_pairs = [
(
torch.rand(3, 2, d_model),
[
[0, 1],
[0, 1],
[1, 1]
]
),
(
torch.rand(2, 100, d_model),
[
[0] * 98 + [1] * 2,
[0] * 90 + [1] * 10
]
),
# softmax.cu switches from fast->slowpath at masked seqlen 1024. test 1024.
(
torch.rand(2, 1024, d_model),
[
[0] * 1020 + [1] * 4,
[0] * 1024,
]
),
(
torch.rand(1, 1026, d_model),
[[0] * 1024 + [1] * 2]
),
# softmax.cu switches from fast->slowpath at masked seqlen 1024. test range of masks above 1024.
(
torch.rand(4, 1040, d_model),
[
[0] * 1024 + [1] * 16,
[0] * 1025 + [1] * 15,
[0] * 1031 + [1] * 9,
[0] * 1040,
]
)
]
input_mask_pairs = [
(
torch.tensor(pair[0], device=device, dtype=torch.get_default_dtype()), # float input
torch.tensor(pair[1], device=device, dtype=torch.bool) # bool mask
) for pair in input_mask_pairs
]
maybe_autocast = torch.autocast("cuda", dtype=torch.float16) if use_autocast else contextlib.nullcontext()
with maybe_autocast:
for input, src_key_padding_mask in input_mask_pairs:
with torch.no_grad():
fastpath_output = model(input, src_key_padding_mask=src_key_padding_mask)
slowpath_output = model(input, src_key_padding_mask=src_key_padding_mask) # reference
# Make sure fastpath_output is same shape as slowpath_output and mask.
# When enable_nested_tensor=true, fastpath_output may be smaller than input tensor.
# Eg if input bs=1, seqlen=6, and we mask out 2 tokens, fastpath_output will have bs=1, seqlen=4.
# Expand back to old size to match.
bs, true_seqlen, embed_dim = fastpath_output.shape
expanded_seqlen = src_key_padding_mask.shape[1]
fastpath_output_expanded = torch.zeros(bs, expanded_seqlen, embed_dim, device=device)
fastpath_output_expanded[:, :true_seqlen, :] = fastpath_output
# no garauntees on output corresponding to masked tokens, so they may vary between slow/fast path. set all to 0.
fastpath_output_expanded = fastpath_output_expanded.masked_fill(src_key_padding_mask.unsqueeze(-1), 0)
slowpath_output = slowpath_output.masked_fill(src_key_padding_mask.unsqueeze(-1), 0)
torch.testing.assert_close(fastpath_output_expanded, slowpath_output, rtol=1e-7, atol=1e-5)
@parametrize("with_no_grad", [True, False])
@parametrize("training", [True, False])
@parametrize("enable_nested_tensor", [False])
def test_transformerencoder_square_input(self, with_no_grad, training, enable_nested_tensor, device):
"""
Test for edge cases when input of shape (batch size, sequence length, embedding dimension) has
batch size == sequence length
"""
model = torch.nn.TransformerEncoder(
torch.nn.TransformerEncoderLayer(d_model=4, nhead=2, dim_feedforward=16, dropout=0.0, batch_first=True),
num_layers=2,
enable_nested_tensor=enable_nested_tensor
).to(device)
with torch.no_grad():
# set constant weights of the model
for idx, p in enumerate(model.parameters()):
x = p.data
sz = x.view(-1).size(0)
shape = x.shape
x = torch.cos(torch.arange(0, sz).float().view(shape))
p.data.copy_(x)
if training:
model = model.train()
else:
model = model.eval()
x = torch.arange(0, 16).reshape(2, 2, 4).to(torch.get_default_dtype()).to(device)
src_mask = torch.Tensor([[0, 1], [0, 0]]).to(torch.bool).to(device)
if with_no_grad:
cm = torch.no_grad()
else:
cm = contextlib.nullcontext()
with cm:
result = model(x, mask=src_mask)
ref_output = torch.Tensor([[[2.420306205749512, 0.017629241570830, -0.607857942581177, -0.085519507527351],
[2.420306205749512, 0.017629241570830, -0.607857942581177, -0.085519507527351]],
[[2.419836044311523, 0.017548924311996, -0.608187675476074, -0.085347734391689],
[2.419836044311523, 0.017548924311996, -0.608187675476074, -0.085347734391689]]]
).to(device)
self.assertEqual(tuple(result.shape), tuple(ref_output.shape))
torch.testing.assert_close(result, ref_output, rtol=1e-7, atol=1e-5)
@parametrize("batch_first", [True, False])
@parametrize("training", [True, False])
@parametrize("enable_nested_tensor", [True, False])
def test_transformerencoder(self, batch_first, training, enable_nested_tensor, device):
def get_a_test_layer(activation, batch_first=False):
d_model = 4
nhead = 2
dim_feedforward = 16
dropout = 0.0
layer = nn.TransformerEncoderLayer(
d_model,
nhead,
dim_feedforward=dim_feedforward,
dropout=dropout,
activation=activation,
batch_first=batch_first,
).to(device)
with torch.no_grad():
# set constant weights of the model
for idx, p in enumerate(layer.parameters()):
x = p.data
sz = x.view(-1).size(0)
shape = x.shape
x = torch.cos(torch.arange(0, sz).float().view(shape))
p.data.copy_(x)
return layer
# this is a deterministic test for TransformerEncoder
activation = F.relu
def _test(batch_first, training, enable_nested_tensor):
def perm_fn(x):
return x.transpose(1, 0) if batch_first else x
encoder_layer = get_a_test_layer(activation=activation,
batch_first=batch_first)
model = nn.TransformerEncoder(
encoder_layer, 1, enable_nested_tensor=enable_nested_tensor
).to(device)
if not training:
model = model.eval()
# deterministic input
encoder_input = perm_fn(torch.tensor([[[0.7462, 0.6653, 0.5679, 0.4891],
[0.5387, 0.1655, 0.3565, 0.0471]],
[[0.8335, 0.2799, 0.5031, 0.2947],
[0.1402, 0.0318, 0.7636, 0.1346]],
[[0.6333, 0.9344, 0.1376, 0.9938],
[0.8924, 0.2872, 0.6692, 0.2944]],
[[0.9897, 0.6915, 0.3154, 0.1733],
[0.8645, 0.3513, 0.3064, 0.0767]],
[[0.8117, 0.2366, 0.4838, 0.7881],
[0.3718, 0.4945, 0.9511, 0.0864]]]
)).to(device)
result = model(encoder_input)
ref_output = perm_fn(torch.tensor([[[2.428589, 0.020835, -0.602055, -0.085249],
[2.427987, 0.021213, -0.602496, -0.084103]],
[[2.424689, 0.019155, -0.604793, -0.085672],
[2.413863, 0.022211, -0.612486, -0.072490]],
[[2.433774, 0.021598, -0.598343, -0.087548],
[2.425104, 0.019748, -0.604515, -0.084839]],
[[2.436185, 0.022682, -0.596625, -0.087261],
[2.433556, 0.021891, -0.598509, -0.086832]],
[[2.416246, 0.017512, -0.610712, -0.082961],
[2.422901, 0.024187, -0.606178, -0.074929]]]
)).to(device)
self.assertEqual(tuple(result.shape), tuple(ref_output.shape))
torch.testing.assert_close(result, ref_output, rtol=1e-7, atol=1e-5)
# all 0 src_mask
src_mask = torch.zeros([5, 5]).to(device) == 1
result = model(encoder_input, mask=src_mask)
self.assertEqual(tuple(result.shape), tuple(ref_output.shape))
torch.testing.assert_close(result, ref_output, rtol=1e-7, atol=1e-5)
# all 0
mask = torch.zeros([2, 5]).to(device) == 1
result = model(encoder_input, src_key_padding_mask=mask)
self.assertEqual(tuple(result.shape), tuple(ref_output.shape))
torch.testing.assert_close(result, ref_output, rtol=1e-7, atol=1e-5)
mask[0, 1] = 1
mask[1, 3] = 1
mask[1, 4] = 1
result = model(encoder_input, src_key_padding_mask=mask)
ref_output = perm_fn(torch.tensor([[[2.429026, 0.020793, -0.601741, -0.085642],
[2.428811, 0.021445, -0.601912, -0.084252]],
[[2.425009, 0.019155, -0.604566, -0.085899],
[2.415408, 0.02249, -0.611415, -0.073]],
[[2.434199, 0.021682, -0.598039, -0.087699],
[2.42598, 0.019941, -0.603896, -0.085091]],
[[2.436457, 0.022736, -0.59643, -0.08736],
[2.434021, 0.022093, -0.598179, -0.08679]],
[[2.416531, 0.017498, -0.610513, -0.083181],
[2.4242, 0.024653, -0.605266, -0.074959]]]
)).to(device)
self.assertEqual(tuple(result.shape), tuple(ref_output.shape))
torch.testing.assert_close(result, ref_output, rtol=1e-7, atol=1e-5)
# test case 2, multiple layers no norm
model = nn.TransformerEncoder(encoder_layer, 2, enable_nested_tensor=enable_nested_tensor).to(device)
if not training:
model = model.eval()
result = model(encoder_input, src_key_padding_mask=mask)
ref_output = perm_fn(torch.tensor([[[2.419051, 0.017446, -0.608738, -0.085003],
[2.419102, 0.017452, -0.608703, -0.085026]],
[[2.419043, 0.017445, -0.608744, -0.084999],
[2.419052, 0.017446, -0.608738, -0.085004]],
[[2.419067, 0.017448, -0.608727, -0.085010],
[2.419098, 0.017452, -0.608706, -0.085024]],
[[2.419072, 0.017449, -0.608724, -0.085012],
[2.419119, 0.017455, -0.608691, -0.085034]],
[[2.419019, 0.017442, -0.608761, -0.084989],
[2.419075, 0.017449, -0.608722, -0.085014]]]
)).to(device)
self.assertEqual(tuple(result.shape), tuple(ref_output.shape))
torch.testing.assert_close(result, ref_output, rtol=1e-7, atol=1e-5)
model = nn.TransformerEncoder(encoder_layer, 6, enable_nested_tensor=enable_nested_tensor).to(device)
if not training:
model = model.eval()
result = model(encoder_input, src_key_padding_mask=mask)
ref_output = perm_fn(torch.tensor([[[2.419101, 0.017453, -0.608703, -0.085025],
[2.419101, 0.017453, -0.608704, -0.085025]],
[[2.419101, 0.017453, -0.608703, -0.085025],
[2.419101, 0.017453, -0.608704, -0.085025]],
[[2.419101, 0.017453, -0.608703, -0.085025],
[2.419101, 0.017453, -0.608704, -0.085025]],
[[2.419101, 0.017453, -0.608703, -0.085025],
[2.419101, 0.017453, -0.608704, -0.085025]],
[[2.419101, 0.017453, -0.608703, -0.085025],
[2.419101, 0.017453, -0.608704, -0.085025]]]
)).to(device)
self.assertEqual(tuple(result.shape), tuple(ref_output.shape))
torch.testing.assert_close(result, ref_output, rtol=1e-7, atol=1e-5)
# test case 3, multiple layers with norm
# d_model = 4
norm = nn.LayerNorm(4)
model = nn.TransformerEncoder(encoder_layer, 2, norm=norm,
enable_nested_tensor=enable_nested_tensor).to(device)
if not training:
model = model.eval()
result = model(encoder_input, src_key_padding_mask=mask)
ref_output = perm_fn(torch.tensor([[[1.695949, -0.357635, -0.893077, -0.445238],
[1.695955, -0.357639, -0.893050, -0.445266]],
[[1.695948, -0.357634, -0.893082, -0.445233],
[1.695950, -0.357635, -0.893077, -0.445238]],
[[1.695951, -0.357636, -0.893069, -0.445246],
[1.695955, -0.357639, -0.893052, -0.445264]],
[[1.695952, -0.357636, -0.893066, -0.445249],
[1.695957, -0.357641, -0.893041, -0.445276]],
[[1.695946, -0.357632, -0.893095, -0.445220],
[1.695952, -0.357637, -0.893065, -0.445251]]]
)).to(device)
self.assertEqual(tuple(result.shape), tuple(ref_output.shape))
torch.testing.assert_close(result, ref_output, rtol=1e-7, atol=1e-5)
model = nn.TransformerEncoder(encoder_layer, 6, norm=norm,
enable_nested_tensor=enable_nested_tensor).to(device)
if not training:
model = model.eval()
result = model(encoder_input, src_key_padding_mask=mask)
ref_output = perm_fn(torch.tensor([[[1.695955, -0.357639, -0.893051, -0.445265],
[1.695955, -0.357639, -0.893051, -0.445265]],
[[1.695955, -0.357639, -0.893051, -0.445265],
[1.695955, -0.357639, -0.893051, -0.445265]],
[[1.695955, -0.357639, -0.893051, -0.445265],
[1.695955, -0.357639, -0.893051, -0.445265]],
[[1.695955, -0.357639, -0.893051, -0.445265],
[1.695955, -0.357639, -0.893051, -0.445265]],
[[1.695955, -0.357639, -0.893051, -0.445265],
[1.695955, -0.357639, -0.893051, -0.445265]]]
)).to(device)
self.assertEqual(tuple(result.shape), tuple(ref_output.shape))
torch.testing.assert_close(result, ref_output, rtol=1e-7, atol=1e-5)
# TODO: remove set default dtype to double by making ref_output more precise.
# Added because this test was copied from test_nn.py, which has default
# dtype double. If default dtype is float, tests will say tensors not close because
# ref output precision too low
with set_default_dtype(torch.double):
if training:
cm = contextlib.nullcontext()
else:
cm = torch.no_grad() # transformer fast path requires no grad
with cm:
_test(batch_first, training, enable_nested_tensor)
@unittest.skipIf(sys.version_info < (3, 11), "not supported on pre-3.11 Python")
def test_encoder_padding_and_src_mask_bool(self):
encoder_layer = nn.TransformerEncoderLayer(
d_model=16,
nhead=2,
dim_feedforward=32,
dropout=0.1,
activation='relu',
batch_first=True,
)
encoder_norm = nn.LayerNorm(16)
encoder = nn.TransformerEncoder(
encoder_layer, 2, encoder_norm
)
inputs = torch.randn(2, 3, 16)
src_mask = torch.ones(3, 3, dtype=torch.bool).triu_(diagonal=1)
input_seq_len = torch.tensor([3, 2])
padding_mask = (
torch.arange(3)[None, :].cpu() >= input_seq_len[:, None]
)
with self.assertNoLogs(None):
encoder(
inputs,
mask=src_mask,
src_key_padding_mask=padding_mask,
)
@unittest.skipIf(sys.version_info < (3, 11), "not supported on pre-3.11 Python")
def test_decoder_padding_and_src_mask_bool(self):
def transformer_decoder(inputs, input_seq_len, memory):
decoder_layer = nn.TransformerDecoderLayer(
d_model=16,
nhead=2,
dim_feedforward=32,
dropout=0.1,
activation='relu',
batch_first=True,
)
decoder_norm = nn.LayerNorm(16)
decoder = nn.TransformerDecoder(
decoder_layer, 2, decoder_norm
)
src_mask = torch.ones(
inputs.shape[1], inputs.shape[1], dtype=torch.bool
).triu_(diagonal=1)
padding_mask = (
torch.arange(inputs.shape[1])[None, :].cpu()
>= input_seq_len[:, None]
)
return decoder(
inputs,
memory,
tgt_mask=src_mask,
tgt_key_padding_mask=padding_mask,
memory_key_padding_mask=padding_mask,
)
inputs = torch.randn(2, 3, 16)
memory = torch.randn(2, 3, 16)
input_seq_len = torch.tensor([3, 2])
with self.assertNoLogs(None):
transformer_decoder(inputs, input_seq_len, memory)
def test_encoder_is_causal(self):
d_model = 3
layer = torch.nn.TransformerEncoderLayer(d_model, 1, 6, batch_first=True)
layer.eval()
x = torch.randn(1, 5, d_model)
unmasked_output = layer(x)
mask = torch.nn.Transformer.generate_square_subsequent_mask(x.size(1))
is_causal_output = layer(x, src_mask=mask, is_causal=True)
masked_output = layer(x, src_mask=mask)
self.assertEqual(masked_output, is_causal_output)
@onlyCUDA
@parametrize("nb_heads", [1, 8])
@parametrize("bias", [True, False])
def test_mha_native_args(self, nb_heads, bias):
B, L, F = 8, 100, 128
batch_first = True
fast_path = True
use_pad_mask = (bias % 2) == 1
mha = nn.MultiheadAttention(
embed_dim=F,
num_heads=nb_heads,
batch_first=batch_first,
bias=bias
).cuda()
mha.eval()
ctx = torch.no_grad if fast_path else contextlib.nullcontext
with ctx():
x = torch.randn(B, L, F).cuda()
if not batch_first:
x = x.transpose(0, 1)
pad_mask = None
if use_pad_mask:
pad_mask = torch.zeros((B, L), dtype=torch.bool).cuda()
mha(query=x, key=x, value=x, key_padding_mask=pad_mask)
def test_kpm_mask_trailing_column_with_nested_tensor(self, device):
encoder_layer = nn.TransformerEncoderLayer(
d_model=256,
nhead=4,
dim_feedforward=512,
activation='gelu',
norm_first=False,
batch_first=False,
)
transformer_encoder = nn.TransformerEncoder(encoder_layer, num_layers=3, enable_nested_tensor=True).to(device)
x = torch.randn(10, 6, 256).to(device)
mask = torch.ones(6, 10)
mask[0, :] = 0 # here I masked 5 columns instead of just one
mask = mask.bool().to(device)
out = transformer_encoder(src=x, src_key_padding_mask=mask)
self.assertEqual(out.shape[1], 6)
# CPU unit test has_torch_functions in test environment,
# preventing successful completion
@onlyCUDA
def test_with_nested_tensor_input(self, device):
encoder_layer = nn.TransformerEncoderLayer(
d_model=256,
nhead=4,
dim_feedforward=512,
activation='gelu',
norm_first=False,
batch_first=True,
)
transformer_encoder = nn.TransformerEncoder(encoder_layer, num_layers=3, enable_nested_tensor=True).to(device)
transformer_encoder.eval()
with torch.no_grad():
x = torch.randn(6, 10, 256).to(device)
mask = torch.ones(6, 10)
mask[0, 0:] = 0 # here I masked 5 columns instead of just one
mask[2, 2:] = 0 # here I masked 5 columns instead of just one
mask[4, 4:] = 0 # here I masked 5 columns instead of just one
mask[5, 8:] = 0 # here I masked 5 columns instead of just one
mask = mask.bool().to(device)
x = torch._nested_tensor_from_mask(x, mask.logical_not(), mask_check=False)
out = transformer_encoder(src=x, src_key_padding_mask=None)
self.assertEqual(out.is_nested, True)
def test_script_encoder_subclass(self, device):
class MyCustomLayer(nn.TransformerEncoderLayer):
pass
encoder = nn.TransformerEncoder(
MyCustomLayer(d_model=256, nhead=8), num_layers=6
).to(device=device)
torch.jit.script(encoder)
# brazenly adapted from test_transformerencoderlayer_src_mask to test execution of
# torchscripted transformerencoderlayer subclass
def test_transformerencoderlayer_subclass(self, device):
class MyCustomLayer(nn.TransformerEncoderLayer):
pass
nhead = 4
batch_size = 2
seqlen = 4
d_model = 8
dim_feedforward = 32
model = MyCustomLayer(
d_model=d_model,
nhead=nhead,
dim_feedforward=dim_feedforward,
batch_first=True).to(device)
script_model = torch.jit.script(model)
src = torch.rand(batch_size, seqlen, d_model).to(device) # bs, seqlen, d_model
src_mask = torch.zeros(seqlen, seqlen).to(torch.bool).to(device)
torch.manual_seed(42)
result = model(src, src_mask=src_mask)
torch.manual_seed(42)
scripted_result = script_model(src, src_mask=src_mask)
self.assertEqual(result, scripted_result)
model.eval()
script_model = torch.jit.script(model)
with torch.no_grad():
result = model(src, src_mask=src_mask)
scripted_result = script_model(src, src_mask=src_mask)
self.assertEqual(result, scripted_result)
def test_transformerencoderlayer_subclass_model(self, device):
class MyCustomLayer(nn.TransformerEncoderLayer):
pass
nhead = 4
batch_size = 2
seqlen = 4
d_model = 8
dim_feedforward = 32
layer = MyCustomLayer(
d_model=d_model,
nhead=nhead,
dim_feedforward=dim_feedforward,
batch_first=True)
model = nn.TransformerEncoder(
layer, num_layers=6
).to(device=device)
script_model = torch.jit.script(model)
src = torch.rand(batch_size, seqlen, d_model).to(device) # bs, seqlen, d_model
src_mask = torch.zeros(seqlen, seqlen).to(torch.bool).to(device)
torch.manual_seed(42)
result = model(src, mask=src_mask)
torch.manual_seed(42)
scripted_result = script_model(src, mask=src_mask)
self.assertEqual(result, scripted_result)
model.eval()
script_model = torch.jit.script(model)
with torch.no_grad():
result = model(src, mask=src_mask)
scripted_result = script_model(src, mask=src_mask)
self.assertEqual(result, scripted_result)
@onlyCUDA
@unittest.skipIf(not TEST_FAIRSEQ, "Fairseq not found")
def test_decoder_only_layer(self):
DEFAULT_PADDING_IDX = 0
class FairseqDecoder(torch.nn.Module):
def __init__(
self,
embed_dim,
attention_heads,
ffn_embed_dim,
num_layers,
embedding_layer, # torch.nn.Embedding. Must have a padding_idx field
dropout=0,
normalize_before=False,
torch_encoder=None, # torch encoder that you can map weights from
activation="relu",
):
super().__init__()
cfg = fairseq_transformer.TransformerConfig()
cfg.decoder.embed_dim = embed_dim
cfg.decoder.output_dim = embed_dim
cfg.decoder.attention_heads = attention_heads
cfg.decoder.ffn_embed_dim = ffn_embed_dim
cfg.dropout = dropout
cfg.decoder.normalize_before = normalize_before
cfg.decoder.layers = num_layers
# make embedding behavior same as other encoders
cfg.no_token_positional_embeddings = True
cfg.no_scale_embedding = True
cfg.activation_fn = activation
dictionary = {} # TODO: verify what this is
self.decoder = fairseq_transformer.TransformerDecoder(
cfg,
dictionary,
embedding_layer,
no_encoder_attn=True,
output_projection=None,
)
if torch_encoder is not None:
self.decoder = torch_to_fairseq(torch_encoder, self.decoder)
self.decoder = self.decoder.eval().cuda().half()
def forward(
self,
tokens,
src_lengths=None,
with_triangle_mask=False,
incremental_state=None,
):
return self.decoder(
prev_output_tokens=tokens,
encoder_out=None,
incremental_state=incremental_state,
features_only=True,
full_context_alignment=not with_triangle_mask,
alignment_layer=None,
alignment_heads=None,
src_lengths=src_lengths,
return_all_hiddens=False,
)[0]
@parametrize("input_dim,attn_mask_dim,is_causal",
[(3, None, False), (3, 2, False), (3, 2, True), (3, 3, False), (3, 3, True),
(4, None, False), (4, 2, False), (4, 2, True), (4, 4, False), (4, 4, True)],
name_fn=lambda input_dim, attn_dim, is_causal: (
f"{input_dim}D_input_dim_" + (
f"{attn_dim}D_{'causal_' if is_causal else ''}attn_mask"
if attn_dim is not None else "no_attn_mask")))
@parametrize("dropout_p", [0.0, 0.2, 0.5])
@sdp_kernel(enable_flash=False, enable_mem_efficient=False)
def test_scaled_dot_product_attention(self, device, input_dim, attn_mask_dim, is_causal, dropout_p):
def sdp_ref(
q,
k,
v,
attn_mask=None,
dropout_p=0.0):
E = q.size(-1)
q = q / math.sqrt(E)
# (B, Nt, E) x (B, E, Ns) -> (B, Nt, Ns)
if attn_mask is not None:
attn = torch.baddbmm(attn_mask, q, k.transpose(-2, -1))
else:
attn = torch.bmm(q, k.transpose(-2, -1))
attn = torch.nn.functional.softmax(attn, dim=-1)
if dropout_p > 0.0:
attn = torch.nn.functional.dropout(attn, p=dropout_p)
# (B, Nt, Ns) x (B, Ns, E) -> (B, Nt, E)
output = torch.bmm(attn, v)
return output
# TODO: Support cross-device / dtype testing properly when instantiate_device_type_tests() is used.
dtypes = [torch.double, torch.float]
for dtype in dtypes:
def rand_tensor(*shape):
return torch.randn(shape, device=device, dtype=dtype)
# This test compares python and C++ implementations of SDP.
N, N_prime, L, S, E = 5, 2, 4, 3, 6
if input_dim == 3:
query = rand_tensor(N, L, E)
key = rand_tensor(N, S, E)
value = rand_tensor(N, S, E)
elif input_dim == 4:
query = rand_tensor(N, N_prime, L, E)
key = rand_tensor(N, N_prime, S, E)
value = rand_tensor(N, N_prime, S, E)
else:
self.fail(f'Invalid input_dim {input_dim} encountered in SDP test')
attn_mask = None
if attn_mask_dim is not None:
assert attn_mask_dim in [2, input_dim]
mask_size = (L, S) if attn_mask_dim == 2 else ((N, L, S) if input_dim == 3 else (N, N_prime, L, S))
attn_mask = (torch.ones(mask_size, device=device, dtype=torch.bool).tril() if is_causal
else torch.randint(0, 2, size=mask_size, device=device, dtype=torch.bool))
with freeze_rng_state():
# Python impl only supports float mask and 3D inputs.
attn_mask_float = attn_mask
if attn_mask_float is not None:
attn_mask_float = torch.zeros_like(attn_mask, dtype=query.dtype)
attn_mask_float.masked_fill_(attn_mask.logical_not(), float("-inf"))
q, k, v = query.view(-1, L, E), key.view(-1, S, E), value.view(-1, S, E)
a = attn_mask_float
if a is not None and attn_mask_dim > 3:
a = a.view(-1, L, S)
expected = sdp_ref(q, k, v, attn_mask=a, dropout_p=dropout_p)
if input_dim > 3:
expected = expected.view(-1, N_prime, L, E)
with freeze_rng_state():
if is_causal:
# NB: Don't pass attn_mask here
actual = torch.nn.functional.scaled_dot_product_attention(
query, key, value, None, dropout_p, is_causal)
# Error case: both explicit attn_mask and is_causal are set
with self.assertRaisesRegex(RuntimeError,
"Explicit attn_mask should not be set when is_causal=True"):
torch.nn.functional.scaled_dot_product_attention(
query, key, value, attn_mask, dropout_p, is_causal)
else:
actual = torch.nn.functional.scaled_dot_product_attention(
query, key, value, attn_mask, dropout_p, is_causal)
self.assertEqual(actual, expected)
if attn_mask_dim is None:
q = q.double().clone()
k = k.double().clone()
v = v.double().clone()
q.requires_grad_()
k.requires_grad_()
v.requires_grad_()
assert gradcheck(lambda *args, **kwargs: wrapper_set_seed(sdp_ref, *args, **kwargs),
(q, k, v, attn_mask, dropout_p))
assert gradcheck(lambda *args, **kwargs:
wrapper_set_seed(torch.nn.functional.scaled_dot_product_attention, *args, **kwargs),
(q, k, v, attn_mask, dropout_p))
def test_incompatible_mask(self, device):
def ones_tensor(*shape):
return torch.ones(shape, dtype=torch.float32)
S, L, E, H = 1, 2, 4, 1
qkv = ones_tensor(S, L, E)
mha = nn.MultiheadAttention(E, H)
mha.in_proj_weight = Parameter(torch.ones((E * 3, E)))
mha.out_proj.weight = Parameter(torch.ones((E, E)))
qkv = qkv.to(float)
kpm = ones_tensor(S, L) * float("-inf")
am = ones_tensor(L, L).to(bool)
def func():
return mha(qkv, qkv, qkv, need_weights=False, key_padding_mask=kpm, attn_mask=am)
self.assertRaises(RuntimeError, func)
@unittest.skipIf(TEST_WITH_CROSSREF, 'Fastpath not available with crossref')
@torch.no_grad()
def test_mask_check_fastpath(self):
"""
Test that fastpath is executed independently of the masks that are passed.
If the passed key padding mask is left aligned or mask_check=False, test that nested tensors are used
(sparsity fastpath), otherwise use fastpath with traditional tensors.
Also test that fast path is executed with both key padding mask and attention mask passed at the same time.
"""
x = torch.Tensor([[[1, 2], [3, 4], [5, 6]]]).to(torch.float)
def _test_fastpath(model, key_padding_mask, mock_return_value, attn_mask=None, nested_tensors=True):
with patch('torch._transformer_encoder_layer_fwd') as fastpath_mock:
fastpath_mock.return_value = mock_return_value
model(x, src_key_padding_mask=key_padding_mask, mask=attn_mask)
# If mock was called, fastpath was taken
self.assertTrue(fastpath_mock.called)
# If mock was called with nested tensors, sparsity fastpath was taken
for call_args, _ in fastpath_mock.call_args_list:
self.assertEqual(call_args[0].is_nested, nested_tensors)
encoder_layer = torch.nn.TransformerEncoderLayer(d_model=2, nhead=2, dim_feedforward=8, batch_first=True)
model = torch.nn.TransformerEncoder(encoder_layer, num_layers=2, enable_nested_tensor=True, mask_check=True)
model.eval()
aligned_key_padding_mask = torch.Tensor([[0, 0, 1]]).to(torch.bool)
not_aligned_key_padding_mask = torch.Tensor([[1, 0, 1]]).to(torch.bool)
attn_mask = torch.Tensor([[1, 0, 1], [0, 1, 0], [1, 0, 1]]).to(torch.bool)
nested_tensor_return_value = torch.nested.nested_tensor([torch.ones((2, 2), dtype=torch.float)])
tensor_return_value = torch.ones((1, 3, 2), dtype=torch.float)
# Left aligned mask results in sparsity fastpath
_test_fastpath(model, aligned_key_padding_mask, nested_tensor_return_value, nested_tensors=True)
# Not aligned mask results in fastpath
_test_fastpath(model, not_aligned_key_padding_mask, tensor_return_value, nested_tensors=False)
model = torch.nn.TransformerEncoder(encoder_layer, num_layers=2, enable_nested_tensor=False, mask_check=True)
model.eval()
# If nested tensor disabled, fastpath is always taken
_test_fastpath(model, aligned_key_padding_mask, tensor_return_value, nested_tensors=False)
_test_fastpath(model, not_aligned_key_padding_mask, tensor_return_value, nested_tensors=False)
# Fast path is taken if both attention mask and key padding mask are present
_test_fastpath(model, aligned_key_padding_mask, tensor_return_value, attn_mask=attn_mask, nested_tensors=False)
model = torch.nn.TransformerEncoder(encoder_layer, num_layers=2, enable_nested_tensor=True, mask_check=False)
model.eval()
# Mask check disabled results in sparisty fastpath, independently of the mask
_test_fastpath(model, aligned_key_padding_mask, nested_tensor_return_value, nested_tensors=True)
_test_fastpath(model, not_aligned_key_padding_mask, nested_tensor_return_value, nested_tensors=True)
# Test failing MHA when bias was NoneType
def test_bias_is_none(self):
x = torch.rand((1, 5, 10))
model = torch.nn.modules.activation.MultiheadAttention(10, 1, bias=False, batch_first=True)
model.eval()
model(x, x, x)
# completes without error
def test_train_with_is_causal(self, device):
# training with is_causal
S, L, E, H = 1, 2, 2, 1
layer = nn.TransformerEncoderLayer(
d_model=2,
dim_feedforward=4,
nhead=H,
batch_first=True,
activation="gelu",
dropout=0,
)
criterion = nn.MSELoss()
encoder = nn.TransformerEncoder(layer, 2).to(device)
optimizer = optim.SGD(encoder.parameters(), lr=0.1, momentum=0.9)
encoder.train()
encoder.train()
optimizer.zero_grad()
inputs = torch.randn(S, L, E).to(device)
mask = torch.nn.Transformer.generate_square_subsequent_mask(
inputs.size(1), device=device
)
outputs = encoder(inputs, mask=mask, is_causal=True)
loss = criterion(outputs[:, 0:2, :], inputs[:, 0:2, :])
loss.backward()
optimizer.step()
# inference with is_causal
t_qvk = torch.randn((S, L, E), device=device, dtype=torch.float32)
mha = nn.MultiheadAttention(E, H).to(device)
mask = torch.nn.Transformer.generate_square_subsequent_mask(
S, device=device
)
attn_out, _ = mha(t_qvk, t_qvk, t_qvk, attn_mask=mask, is_causal=True)
# Can't give only is_causal
attn_mask = torch.randint(0, 2, size=(L, L), device=device, dtype=torch.bool)
with self.assertRaises(RuntimeError):
_ = mha(t_qvk, t_qvk, t_qvk, is_causal=True)
# # Passing a causal mask sets is_causal to 1
causal_mask = torch.triu(
torch.ones(L, L, device=inputs.device) * float('-inf'), diagonal=1
).to(torch.bool)
mock_layer = MagicMock(torch.nn.MultiheadAttention(E, H), return_value=inputs)
encoder.layers[1] = mock_layer
outputs = encoder(inputs, mask=causal_mask)
mock_layer.assert_called_with(ANY, src_mask=ANY, is_causal=True, src_key_padding_mask=ANY)
# check expected numerical values with all kernels
self.is_causal_kernels(["math"], device)
def is_causal_kernels(self, kernels, device):
def ones_tensor(*shape):
return torch.ones(shape, device=device, dtype=torch.float32).to(device)
S, L, E, H = 1, 2, 4, 1
qkv = ones_tensor(S, L, E)
mha = nn.MultiheadAttention(E, H).to(device)
mha.in_proj_weight = Parameter(torch.ones((E * 3, E), device=device))
mha.out_proj.weight = Parameter(torch.ones((E, E), device=device))
expected = torch.ones(size=(S, L, E)).to(device) * 16
mask = torch.nn.Transformer.generate_square_subsequent_mask(
qkv.size(1), device=device
)
for kernel in kernels:
with torch.backends.cuda.sdp_kernel(
enable_math=(kernel == 'math'),
enable_flash=(kernel == 'flash'),
enable_mem_efficient=(kernel == 'meff')
):
actual, _ = mha(qkv, qkv, qkv, attn_mask=mask, need_weights=False, is_causal=True)
self.assertTrue(torch.equal(actual, expected))
if kernel != 'math':
# fails with embedding size not multiple of 4
with self.assertRaisesRegex(RuntimeError, "No available kernel"):
qkv_f, mha_f = ones_tensor(S, L, 2), nn.MultiheadAttention(2, H).to(device)
mask = torch.nn.Transformer.generate_square_subsequent_mask(
qkv_f.size(1), device=device
)
_ = mha_f(qkv_f, qkv_f, qkv_f, attn_mask=mask, need_weights=False, is_causal=True)
torch.cuda.synchronize()
@unittest.skipIf(
not PLATFORM_SUPPORTS_FLASH_ATTENTION, "Platform does not supposrt fused SDPA or pre-SM80 hardware"
)
def test_is_causal_gpu(self):
device = 'cuda'
self.is_causal_kernels(["math", "meff"], device)
def test_script_mha_in_proj_weight_none(self):
mha = torch.nn.MultiheadAttention(
embed_dim=128, num_heads=8, kdim=256, vdim=256
).eval()
torch.jit.script(mha)
class TestSDPAFailureModes(NNTestCase):
""" Used to test the failure modes of scaled_dot_product_attention
"""
_do_cuda_memory_leak_check = True
_do_cuda_non_default_stream = True
@onlyCUDA
@unittest.skipIf(not PLATFORM_SUPPORTS_FLASH_ATTENTION or not isSM86or89Device,
"Does not support fused SDPA or not SM86+ hardware")
@parametrize("head_dim", [193, 204, 256])
def test_flash_backward_failure_sm86plus(self, device, head_dim: int):
dtype = torch.float16
make_tensor = partial(torch.rand, device=device, dtype=dtype)
# See check_requires_grad_and_head_dim_gt64_and_sm_ge86 in pytorch/aten/src/ATen/native/transformers/cuda/sdp_utils.h
size = (2, 2, 4, head_dim)
q, k, v = make_tensor(size), make_tensor(size), make_tensor(size)
with sdp_kernel(enable_mem_efficient=False, enable_flash=False, enable_math=True):
math_ref = torch.nn.functional.scaled_dot_product_attention(q, k, v, None, 0.0, False)
with sdp_kernel(enable_mem_efficient=False, enable_flash=True, enable_math=False):
# Should not fail because inputs don't require grad
flash_ref = torch.nn.functional.scaled_dot_product_attention(q, k, v, None, 0.0, False)
self.assertEqual(math_ref, flash_ref, atol=1e-3, rtol=1e-3)
# Should fail because inputs require grad
q = make_tensor(size, requires_grad=True)
k = make_tensor(size, requires_grad=True)
v = make_tensor(size, requires_grad=True)
self.assertRaises(RuntimeError, lambda: torch.nn.functional.scaled_dot_product_attention(
q, k, v, None, 0.0, False))
@onlyCUDA
def test_dispatch_fails_no_backend(self, device):
dtype = torch.float16
with sdp_kernel(enable_flash=False, enable_math=False, enable_mem_efficient=False):
size = (2, 3, 4)
q = torch.randn(size, device=device, dtype=dtype)
k = torch.randn(size, device=device, dtype=dtype)
v = torch.randn(size, device=device, dtype=dtype)
self.assertRaisesRegex(RuntimeError, "No viable backend for scaled_dot_product_attention was found.",
lambda: torch._fused_sdp_choice(q, k, v))
self.assertRaisesRegex(RuntimeError, "No viable backend for scaled_dot_product_attention was found.",
lambda: torch.nn.functional.scaled_dot_product_attention(q, k, v))
@onlyCUDA
@unittest.skipIf(not PLATFORM_SUPPORTS_FUSED_ATTENTION, "Does not support fused scaled dot product attention")
@parametrize(
"kernel",
[SDPBackend.FLASH_ATTENTION, SDPBackend.EFFICIENT_ATTENTION]
if PLATFORM_SUPPORTS_FLASH_ATTENTION
else [SDPBackend.EFFICIENT_ATTENTION],
)
def test_invalid_fused_inputs_dim_3(self, device, kernel: SDPBackend):
with sdp_kernel(**backend_map[kernel]):
# Dim is not 4
size = (2, 3, 8)
dtype = torch.float16
q = torch.randn(size, device=device, dtype=dtype)
k = torch.randn(size, device=device, dtype=dtype)
v = torch.randn(size, device=device, dtype=dtype)
with self.assertWarnsRegex(UserWarning, "Both fused kernels requires query, key and value to be 4 dimensional"):
self.assertRaises(RuntimeError, lambda: torch.nn.functional.scaled_dot_product_attention(
q, k, v, None, 0.0, False))
@onlyCUDA
@unittest.skipIf(not PLATFORM_SUPPORTS_FUSED_ATTENTION, "Does not support fused scaled dot product attention")
@parametrize(
"kernel",
[SDPBackend.FLASH_ATTENTION, SDPBackend.EFFICIENT_ATTENTION]
if PLATFORM_SUPPORTS_FLASH_ATTENTION
else [SDPBackend.EFFICIENT_ATTENTION],
)
def test_invalid_fused_inputs_broadcast(self, device, kernel: SDPBackend):
with sdp_kernel(**backend_map[kernel]):
# Fused Kernels don't support broadcasting for dense inputs
dtype = torch.float16
size = (2, 4, 3, 8)
size_broadcast = (1, 4, 3, 8)
q = torch.randn(size_broadcast, device=device, dtype=dtype)
k = torch.randn(size, device=device, dtype=dtype)
v = torch.randn(size, device=device, dtype=dtype)
self.assertRaises(RuntimeError, lambda: torch.nn.functional.scaled_dot_product_attention(
q, k, v, None, 0.0, False))
@onlyCUDA
@unittest.skipIf(not PLATFORM_SUPPORTS_FUSED_ATTENTION, "Does not support fused scaled dot product attention")
@parametrize("kernel", [SDPBackend.FLASH_ATTENTION, SDPBackend.EFFICIENT_ATTENTION] if
PLATFORM_SUPPORTS_FLASH_ATTENTION else [SDPBackend.EFFICIENT_ATTENTION])
def test_invalid_sequence_lengths(self, device, kernel: SDPBackend):
with sdp_kernel(**backend_map[kernel]):
# Passing in a q,k,v with 0 length sequences will error
dtype = torch.float16
make_tensor = partial(torch.rand, device=device, dtype=dtype)
size = SdpaShape(2, 2, 0, 8)
q, k, v = make_tensor(size), make_tensor(size), make_tensor(size)
with self.assertWarnsRegex(UserWarning, "Both fused kernels do not support zero seq_len_q or seq_len_kv."):
self.assertRaises(RuntimeError, lambda: torch.nn.functional.scaled_dot_product_attention(
q, k, v, None, 0.0, False))
@onlyCUDA
@unittest.skipIf(not PLATFORM_SUPPORTS_FUSED_ATTENTION, "Does not support fused scaled dot product attention")
@parametrize("kernel", [SDPBackend.FLASH_ATTENTION, SDPBackend.EFFICIENT_ATTENTION] if
PLATFORM_SUPPORTS_FLASH_ATTENTION else [SDPBackend.EFFICIENT_ATTENTION])
def test_invalid_last_dim_stride(self, device, kernel: SDPBackend):
with sdp_kernel(**backend_map[kernel]):
# Passing in a q,k,v with 0 length sequences will error
dtype = torch.float16
make_tensor = partial(torch.rand, device=device, dtype=dtype)
size = SdpaShape(2, 2, 8, 8)
q, k, v = make_tensor(size), make_tensor(size), make_tensor(size)
q.as_strided_(size, [2, 2, 2, 2])
with self.assertWarnsRegex(UserWarning, "Both fused kernels require the last dimension of the input to have stride 1."):
self.assertRaises(RuntimeError, lambda: torch.nn.functional.scaled_dot_product_attention(
q, k, v, None, 0.0, False))
@onlyCUDA
@unittest.skipIf(not PLATFORM_SUPPORTS_FLASH_ATTENTION, "Does not flash_attention fused scaled dot product attention")
@parametrize("kernel", [SDPBackend.FLASH_ATTENTION, SDPBackend.EFFICIENT_ATTENTION])
def test_invalid_fused_inputs_head_dim(self, device, kernel: SDPBackend):
with sdp_kernel(**backend_map[kernel]):
# The embed dim per head is not divisible by 8 for flash attention
dtype = torch.float16
make_tensor = partial(torch.rand, device=device, dtype=dtype)
size = SdpaShape(2, 2, 3, 9) if kernel == SDPBackend.EFFICIENT_ATTENTION else SdpaShape(2, 2, 3, 257)
q, k, v = make_tensor(size), make_tensor(size), make_tensor(size)
self.assertRaises(RuntimeError, lambda: torch.nn.functional.scaled_dot_product_attention(
q, k, v, None, 0.0, False))
@onlyCUDA
@unittest.skipIf(not PLATFORM_SUPPORTS_FUSED_ATTENTION, "Does not support fused scaled dot product attention")
@parametrize(
"kernel",
[SDPBackend.FLASH_ATTENTION, SDPBackend.EFFICIENT_ATTENTION]
if PLATFORM_SUPPORTS_FLASH_ATTENTION
else [SDPBackend.EFFICIENT_ATTENTION],
)
def test_invalid_fused_inputs_invalid_dtype(self, device, kernel: SDPBackend):
with sdp_kernel(**backend_map[kernel]):
# Invalid dtype for both Flash Attention and Mem Efficient Attention
size = SdpaShape(2, 2, 3, 16)
make_tensor = partial(torch.rand, device=device, dtype=torch.float64)
q, k, v = make_tensor(size), make_tensor(size), make_tensor(size)
self.assertRaises(RuntimeError, lambda: torch.nn.functional.scaled_dot_product_attention(
q, k, v, None, 0.0, False))
@onlyCUDA
@unittest.skipIf(not PLATFORM_SUPPORTS_FLASH_ATTENTION, "Does not support flash attention")
@parametrize("kernel", [SDPBackend.FLASH_ATTENTION])
def test_invalid_fused_inputs_attn_mask_present(self, device, kernel: SDPBackend):
with sdp_kernel(**backend_map[kernel]):
# Failures for unsupported SDP args
size = SdpaShape(2, 2, 3, 16)
make_tensor = partial(torch.rand, size, device=device, dtype=torch.float16)
q, k, v = make_tensor(), make_tensor(), make_tensor()
# Non-None attention mask
mask = torch.ones((2, 2, 3, 3), device=device, dtype=q.dtype)
self.assertRaises(RuntimeError, lambda: torch.nn.functional.scaled_dot_product_attention(
q, k, v, mask, 0.0, False))
@onlyCUDA
@unittest.skipIf(not PLATFORM_SUPPORTS_FLASH_ATTENTION, "Does not support fused SDPA or pre-SM80 hardware")
def test_unaligned_tensors(self, device):
# The alignment is depdent on arch so we specifiy SM80OrLater
dtype = torch.float16
size = SdpaShape(2, 2, 8, 5)
make_tensor = partial(torch.rand, size, device=device, dtype=dtype)
q, k, v = make_tensor(), make_tensor(), make_tensor()
with sdp_kernel(enable_flash=False, enable_mem_efficient=True, enable_math=False):
self.assertRaises(RuntimeError, lambda: torch.nn.functional.scaled_dot_product_attention(
q, k, v, None, 0.0, False))
@onlyCUDA
@unittest.skipIf(not PLATFORM_SUPPORTS_FLASH_ATTENTION, "Does not support fused SDPA or pre-SM80 hardware")
def test_flash_fail_fp32(self, device):
dtype = torch.float
size = SdpaShape(16, 16, 32, 32)
make_tensor = partial(torch.rand, size, device=device, dtype=dtype)
q, k, v = make_tensor(), make_tensor(), make_tensor()
with sdp_kernel(enable_flash=True, enable_mem_efficient=False, enable_math=False):
with self.assertWarnsRegex(UserWarning, "Expected query, key and value to all be of dtype: {Half, BFloat16}"):
self.assertRaises(RuntimeError, lambda: torch.nn.functional.scaled_dot_product_attention(
q, k, v, None, 0.0, False))
@onlyCUDA
@unittest.skipIf(not PLATFORM_SUPPORTS_FLASH_ATTENTION, "Does not support SDPA or pre-SM80 hardware")
def test_flash_autocast_fp32_float16(self, device):
dtype = torch.float
size = SdpaShape(16, 16, 32, 32)
make_tensor = partial(torch.rand, size, device=device, dtype=dtype)
q, k, v = make_tensor(), make_tensor(), make_tensor()
with torch.autocast(device_type='cuda', dtype=torch.float16):
with sdp_kernel(enable_flash=True, enable_mem_efficient=False, enable_math=False):
_ = torch.nn.functional.scaled_dot_product_attention(
q, k, v, None, 0.0, False)
@onlyCUDA
@unittest.skipIf(not PLATFORM_SUPPORTS_FLASH_ATTENTION, "Does not support SDPA or pre-SM80 hardware")
def test_flash_autocast_fp32_bfloat16(self, device):
dtype = torch.float
size = SdpaShape(16, 16, 32, 32)
make_tensor = partial(torch.rand, size, device=device, dtype=dtype)
q, k, v = make_tensor(), make_tensor(), make_tensor()
with torch.autocast(device_type='cuda', dtype=torch.bfloat16):
with sdp_kernel(enable_flash=True, enable_mem_efficient=False, enable_math=False):
_ = torch.nn.functional.scaled_dot_product_attention(
q, k, v, None, 0.0, False)
@parametrize("kernel", [SDPBackend.MATH, SDPBackend.FLASH_ATTENTION, SDPBackend.EFFICIENT_ATTENTION])
def test_invalid_inputs_different_datatypes(self, device, kernel: SDPBackend):
with sdp_kernel(**backend_map[kernel]):
# Different datatypes
shape = (1, 4, 8, 16)
query = torch.randn(shape, dtype=torch.float32, device=device)
key = torch.randn(shape, dtype=torch.float16, device=device)
value = torch.randn(shape, dtype=torch.float16, device=device)
self.assertRaises(RuntimeError, lambda: F.scaled_dot_product_attention(query, key, value))
@onlyCUDA
@parametrize("kernel", [SDPBackend.MATH, SDPBackend.FLASH_ATTENTION, SDPBackend.EFFICIENT_ATTENTION])
def test_invalid_inputs_different_devices(self, device, kernel: SDPBackend):
# Different devices
shape = (1, 4, 8, 16)
query = torch.randn(shape, dtype=torch.float32, device=device)
key = torch.randn(shape, dtype=torch.float16, device='cpu')
value = torch.randn(shape, dtype=torch.float16, device='cpu')
self.assertRaises(RuntimeError, lambda: F.scaled_dot_product_attention(query, key, value))
@parametrize("kernel", [SDPBackend.MATH, SDPBackend.FLASH_ATTENTION, SDPBackend.EFFICIENT_ATTENTION])
def test_invalid_inputs_1_dimensional_inputs(self, device, kernel: SDPBackend):
with sdp_kernel(**backend_map[kernel]):
# 1 dimensional input
shape = (1, 4)
query = torch.randn(4, dtype=torch.float16, device=device)
key = torch.randn(shape, dtype=torch.float16, device=device)
value = torch.randn(shape, dtype=torch.float16, device=device)
self.assertRaises(RuntimeError, lambda: F.scaled_dot_product_attention(query, key, value))
@onlyCUDA
@unittest.skipIf(not PLATFORM_SUPPORTS_FUSED_ATTENTION, "Fused SDPA was not built for this system")
def test_fused_kernels_nested_broadcasting_error_cases(self, device):
# one of k,v needs to be broadcasted and other has non consistent seq_len dim
rand_nested_tensor = partial(rand_sdpa_tensor, type="nested", device=device, dtype=torch.float32)
batch, num_heads, head_dim = 32, 8, 64
seq_lens_q = torch.randint(low=1, high=32, size=(batch,)).tolist()
seq_lens_v = torch.randint(low=1, high=32, size=(batch,)).tolist()
q_shape = SdpaShape(batch, num_heads, seq_lens_q, head_dim)
k_shape = SdpaShape(1, num_heads, 1, head_dim)
v_shape = SdpaShape(batch, num_heads, seq_lens_v, head_dim)
query = rand_nested_tensor(q_shape).transpose(1, 2)
key = rand_nested_tensor(k_shape).transpose(1, 2)
value = rand_nested_tensor(v_shape).transpose(1, 2)
with sdp_kernel(enable_flash=False, enable_math=False, enable_mem_efficient=True):
with self.assertRaisesRegex(RuntimeError, "No available kernel"):
torch.nn.functional.scaled_dot_product_attention(
query, key, value, attn_mask=None, dropout_p=0.0, is_causal=False)
@onlyCUDA
@unittest.skipIf(not PLATFORM_SUPPORTS_FLASH_ATTENTION, "Fused SDPA was not built for this system")
def test_nested_fails_on_padding_head_dim(self, device):
dtype = torch.bfloat16
seq_len_list = [2, 4, 5, 6, 7]
shape = SdpaShape(5, 8, seq_len_list, 57)
make_tensor = partial(rand_sdpa_tensor, shape=shape, type="nested", device=device, dtype=dtype)
q, k, v = make_tensor(), make_tensor(), make_tensor()
with torch.backends.cuda.sdp_kernel(enable_math=False, enable_flash=True, enable_mem_efficient=False):
with self.assertWarnsRegex(UserWarning, "For NestedTensor inputs, Flash attention requires"):
self.assertRaises(RuntimeError, lambda: torch.nn.functional.scaled_dot_product_attention(
q, k, v, None, 0.0, False))
@onlyCUDA
@unittest.skipIf(not PLATFORM_SUPPORTS_FUSED_ATTENTION or not isSM5xDevice, "Does not support fused SDPA or not SM50 hardware")
def test_mem_efficient_fail_bfloat16_sm50(self, device):
dtype = torch.bfloat16
size = SdpaShape(16, 16, 32, 32)
make_tensor = partial(torch.rand, size, device=device, dtype=dtype)
q, k, v = make_tensor(), make_tensor(), make_tensor()
with sdp_kernel(**backend_map[SDPBackend.EFFICIENT_ATTENTION]):
with self.assertWarnsRegex(UserWarning, "Expected query, key and value to all be of dtype: {Half, Float}"):
self.assertRaises(RuntimeError, lambda: torch.nn.functional.scaled_dot_product_attention(
q, k, v, None, 0.0, False))
@onlyCUDA
@unittest.skipIf(not PLATFORM_SUPPORTS_FUSED_ATTENTION, "Fused SDPA was not built for this system")
@parametrize("fused_kernel", [SDPBackend.FLASH_ATTENTION, SDPBackend.EFFICIENT_ATTENTION] if
PLATFORM_SUPPORTS_FLASH_ATTENTION else [SDPBackend.EFFICIENT_ATTENTION])
def test_fused_kernels_seq_len_0_inputs(self, device, fused_kernel):
rand_nested_tensor = partial(rand_sdpa_tensor, type="nested", device=device, dtype=torch.float16)
batch, num_heads, head_dim = 32, 16, 64
seq_lens = torch.randint(low=1, high=32, size=(batch,))
# make sure some seq_lens are 0
num_zeros = 10
indices = torch.randint(low=0, high=batch, size=(num_zeros,))
seq_lens.scatter_(0, indices, 0)
shape = SdpaShape(batch, num_heads, seq_lens.tolist(), head_dim)
query = rand_nested_tensor(shape)
key = rand_nested_tensor(shape)
value = rand_nested_tensor(shape)
query = query.transpose(1, 2)
key = key.transpose(1, 2)
value = value.transpose(1, 2)
with sdp_kernel(**backend_map[fused_kernel]):
with self.assertRaisesRegex(RuntimeError, "No available kernel"):
torch.nn.functional.scaled_dot_product_attention(
query, key, value, attn_mask=None, dropout_p=0.0, is_causal=False)
@onlyCUDA
@unittest.skipIf(not PLATFORM_SUPPORTS_FLASH_ATTENTION, "Fused SDPA was not built for this system")
def test_fused_kernels_nested_broadcasting_requires_grad_failure(self, device):
rand_nested_tensor = partial(rand_sdpa_tensor, type="nested", device=device, dtype=torch.float16, requires_grad=True)
batch, num_heads, head_dim, head_dim_v = 32, 16, 64, 64
seq_lens = torch.randint(low=1, high=32, size=(batch,)).tolist()
q_shape = SdpaShape(1, num_heads, 1, head_dim)
k_shape = SdpaShape(batch, num_heads, seq_lens, head_dim)
v_shape = SdpaShape(batch, 1, seq_lens, head_dim_v)
# create a dense query
query = torch.randn(q_shape, device=device, dtype=torch.float16, requires_grad=True)
key = rand_nested_tensor(k_shape)
value = rand_nested_tensor(v_shape)
query = query.transpose(1, 2)
key = key.transpose(1, 2)
value = value.transpose(1, 2)
with sdp_kernel(**backend_map[SDPBackend.FLASH_ATTENTION]):
with self.assertWarnsRegex(UserWarning, "Both fused kernels do not support training with broadcasted NT inputs"):
with self.assertRaisesRegex(RuntimeError, "No available kernel"):
out = torch.nn.functional.scaled_dot_product_attention(
query, key, value, attn_mask=None, dropout_p=0.0, is_causal=False)
@onlyCUDA
@unittest.skipIf(not PLATFORM_SUPPORTS_FLASH_ATTENTION, "Does not support flash attention")
def test_flash_attention_fail_with_non_square_causal_attention(self, device):
dtype = torch.bfloat16
q_shape = SdpaShape(1, 1, 8, 16)
kv_shape = SdpaShape(1, 1, 12, 16)
make_q = partial(torch.rand, q_shape, device=device, dtype=dtype)
make_kv = partial(torch.rand, kv_shape, device=device, dtype=dtype)
q, k, v = make_q(), make_kv(), make_kv()
warning_str = "Flash attention does not support the is_causal flag when seqlen_q != seqlen_k."
with sdp_kernel(**backend_map[SDPBackend.FLASH_ATTENTION]):
with self.assertWarnsRegex(UserWarning, warning_str):
self.assertRaises(RuntimeError, lambda: torch.nn.functional.scaled_dot_product_attention(
q, k, v, None, 0.0, is_causal=True))
def _get_block_size(device, head_dim, is_causal):
# This should match the block sizes in the CUDA kernel
# Mask is only interesting when we are setting dropout
is_dropout = True
assert head_dim <= 256
major, minor = torch.cuda.get_device_capability(device)
is_sm8x = major == 8 and minor > 0 # Only include sm86 and sm89, exclude sm80 (A100)
is_sm80 = major == 8 and minor == 0
is_sm90 = major == 9 and minor == 0
if head_dim <= 32:
return 128, 128
if head_dim <= 64:
return (128, 128) if not is_dropout else (128, 64)
elif head_dim <= 96:
return (64, 64) if (is_sm8x and is_causal) else (128, 64)
elif head_dim <= 128:
if is_sm8x:
return (64, 64) if (not is_dropout and is_causal) else (128, 32)
else:
return 128, (64 if not is_dropout else 32)
elif head_dim <= 160:
if is_sm8x:
return (128, 64) if not is_causal else (64, 64)
else:
return 128, 32
elif head_dim <= 192:
return (128, 64) if not is_dropout else (64, 64)
elif head_dim <= 224:
return (128, 64) if (is_sm80 or is_sm90) else (64, 64)
elif head_dim <= 256:
return (128, 64) if is_sm80 else (64, 64)
def pad_last_dim(input_tensor, alignment_size, slice: bool = False):
last_dim_size = input_tensor.size(-1)
if (last_dim_size % alignment_size == 0):
return input_tensor, last_dim_size
pad_count = alignment_size - (last_dim_size % alignment_size)
padded_tensor = F.pad(input_tensor, (0, pad_count))
if slice:
return padded_tensor[..., :last_dim_size], last_dim_size
return padded_tensor, last_dim_size
class TestSDPA(NNTestCase):
""" Used to test generic functionality of scaled_dot_product_attention
Summary:
If you are adding a new test to this class, make sure that it runs
for both cpu and cuda. If you're test is only applicable to cuda,
add it to TestSDPACudaOnly.
"""
@parametrize("contiguous_inputs", [True, False])
def test_sdp_math_gradcheck(self, device, contiguous_inputs: bool):
batch_size, seq_len, num_heads, head_dim = 4, 4, 2, 16
shape = SdpaShape(batch_size, num_heads, seq_len, head_dim)
make_tensor = partial(rand_sdpa_tensor, type="dense", device=device,
dtype=torch.float64, requires_grad=True, packed=True)
qkv = make_tensor(shape)
query, key, value = qkv.chunk(3, dim=-1)
query = query.view(batch_size, -1, num_heads, head_dim).transpose(1, 2)
key = key.view(batch_size, -1, num_heads, head_dim).transpose(1, 2)
value = value.view(batch_size, -1, num_heads, head_dim).transpose(1, 2)
if contiguous_inputs:
query = query.contiguous()
key = key.contiguous()
value = value.contiguous()
with sdp_kernel(enable_math=True, enable_mem_efficient=False, enable_flash=False):
assert gradcheck(lambda *args, **kwargs:
wrapper_set_seed(torch.nn.functional.scaled_dot_product_attention, *args, **kwargs),
(query, key, value, None, 0.0, False)
)
@onlyCPU
@parametrize("type", ["dense", "nested"])
@parametrize("dropout", [0.0, 0.7])
@parametrize("dtype", [torch.float64, torch.float32, torch.bfloat16, torch.half])
def test_fused_sdp_choice_cpu(self, device, type: str, dropout: float, dtype: torch.dtype):
# Test that cpu and nestedtensor cpu return MATH backend
make_tensor = partial(rand_sdpa_tensor, type=type, device=device, dtype=dtype)
size = SdpaShape(2, 8, 128, 64)
q, k, v = make_tensor(size), make_tensor(size), make_tensor(size)
if type == "nested" \
or dropout > 0.0 \
or dtype not in [torch.float32, torch.float64, torch.bfloat16]:
assert torch._fused_sdp_choice(q, k, v, dropout_p=dropout) == SDPBackend.MATH.value
else:
assert torch._fused_sdp_choice(q, k, v, dropout_p=dropout) == SDPBackend.FLASH_ATTENTION.value
@onlyCPU
@parametrize("fused_kernel", [SDPBackend.FLASH_ATTENTION])
@parametrize("dtype", [torch.float64, torch.float32, torch.bfloat16])
@parametrize("batch_size", [2, 12])
@parametrize("seq_len", [267, 1030])
@parametrize("n_head", [1, 3])
@parametrize("head_dim", [8, 16])
@parametrize("causal", [True, False])
@parametrize("train", [True, False])
def test_scaled_dot_product_fused_attention_vs_math_cpu(
self,
device,
fused_kernel,
dtype,
batch_size,
seq_len,
n_head,
head_dim,
causal,
train,
):
atol = 1e-5
rtol = 5e-6
if dtype is torch.bfloat16:
atol = 2e-2
rtol = 2e-2
n_embd = n_head * head_dim
make_tensor = partial(rand_sdpa_tensor, type="dense", device=device, dtype=dtype, packed=True, requires_grad=False)
shape = SdpaShape(batch_size, n_head, seq_len, head_dim)
x = make_tensor(shape)
x2 = x.clone()
if train:
x.requires_grad_(True)
x2.requires_grad_(True)
q, k, v = x.split(n_embd, dim=2)
q2, k2, v2 = x2.split(n_embd, dim=2)
if dtype is torch.bfloat16:
q2 = q2.float()
k2 = k2.float()
v2 = v2.float()
# (B, nh, T, hs)
k = k.view(batch_size, seq_len, n_head, head_dim).transpose(1, 2)
q = q.view(batch_size, seq_len, n_head, head_dim).transpose(1, 2)
v = v.view(batch_size, seq_len, n_head, head_dim).transpose(1, 2)
k2 = k2.view(batch_size, seq_len, n_head, head_dim).transpose(1, 2)
q2 = q2.view(batch_size, seq_len, n_head, head_dim).transpose(1, 2)
v2 = v2.view(batch_size, seq_len, n_head, head_dim).transpose(1, 2)
with sdp_kernel(**backend_map[fused_kernel]):
actual = torch.nn.functional.scaled_dot_product_attention(
q, k, v, attn_mask=None, dropout_p=0.0, is_causal=causal)
with sdp_kernel(enable_flash=False, enable_math=True, enable_mem_efficient=False):
math_ref = torch.nn.functional.scaled_dot_product_attention(
q2, k2, v2, attn_mask=None, dropout_p=0.0, is_causal=causal)
if dtype is torch.bfloat16:
math_ref = math_ref.bfloat16()
self.assertEqual(actual, math_ref, atol=atol, rtol=rtol)
if train:
actual.sum().backward()
math_ref.sum().backward()
grad_x, grad_x2 = x.grad, x2.grad
grad_q_actual, grad_k_actual, grad_v_actual = grad_x.split(n_embd, dim=2)
grad_q_ref, grad_k_ref, grad_v_ref = grad_x2.split(n_embd, dim=2)
self.assertEqual(grad_q_actual, grad_q_ref, atol=atol, rtol=rtol)
self.assertEqual(grad_k_actual, grad_k_ref, atol=atol, rtol=rtol)
self.assertEqual(grad_v_actual, grad_v_ref, atol=atol, rtol=rtol)
@parametrize("kernel", [SDPBackend.MATH])
def test_scaled_dot_product_attention_math_with_negative_scale(self, device, kernel: SDPBackend):
# https://github.com/pytorch/pytorch/issues/105190.
def ref(x):
v1 = torch.matmul(x, x.transpose(-1, -2))
v2 = v1 / -0.0001
v3 = v2.softmax(dim=-1)
v4 = torch.matmul(v3, x)
return v4
x = torch.randn(1, 3, 64, 64, device=device)
ref_result = ref(x)
with sdp_kernel(**backend_map[kernel]):
sdp_math = torch.nn.functional.scaled_dot_product_attention(x, x, x, scale=-1.0 / 0.0001)
self.assertEqual(ref_result, sdp_math)
class TestSDPACudaOnly(NNTestCase):
""" Used to test CUDA only functionality of scaled_dot_product_attention
Quarks:
There is some trickiness with this function. It's runtime behavior
is dependent on the CUDA architecture you are testing it on. See
`PLATFORM_SUPPORTS_FUSED_ATTENTION` at the top of the file.
Summary:
Math: always supported
FlashAttention: Supported on sm80 or newer hardware
MemEfficientAttention: Supported on sm50 or newer hardware
"""
_do_cuda_memory_leak_check = True
_do_cuda_non_default_stream = True
def convert_flash_attn_S_to_softmax(self, S, query_padding_mask, key_padding_mask, head_dim, causal=False):
"""FlashAttention stores the S matrix in a different way.
Arguments:
S: (batch_size, nheads, seqlen_q, seqlen_k)
query_padding_mask: (batch_size, seqlen_q)
key_padding_mask: (batch_size, seqlen_k)
"""
b, h, seqlen_q, seqlen_k = S.shape
warps_n = 4
blocksize_m, blocksize_n = _get_block_size(S.device, head_dim, causal)
nblocks_m = (seqlen_q + blocksize_m - 1) // blocksize_m
nblocks_n = (seqlen_k + blocksize_n - 1) // blocksize_n
mmas_n = (blocksize_n + 16 - 1) // 16
# Reshape S using PyTorch native functions
S_flat = S.view(b, h, nblocks_m, blocksize_m, nblocks_n, blocksize_n)
S_flat = S_flat.permute(0, 1, 2, 4, 3, 5)
S_flat = S_flat.reshape(b, h, nblocks_m, nblocks_n, (blocksize_m * blocksize_n))
S_converted = S_flat.view(b, h, nblocks_m, nblocks_n, mmas_n, -1, warps_n, 8, 4, 2, 2, 2)
S_converted = S_converted.permute(0, 1, 2, 5, 6, 10, 7, 3, 4, 9, 8, 11)
S_converted = S_converted.reshape(b, h, (nblocks_m * S_converted.size(3) *
warps_n * 2 * 8), (nblocks_n * mmas_n * 2 * 4 * 2))
if causal:
causal_mask = torch.triu(torch.ones(seqlen_q, seqlen_k, dtype=torch.bool, device=S.device), 1)
S_converted.masked_fill_(causal_mask, 0.0)
# Need to zero out things not in attention_mask in case S was initialized with random values
# and some of those values aren't overwritten.
seqlen_q_og = query_padding_mask.shape[-1] if query_padding_mask is not None else seqlen_q
if query_padding_mask is not None:
if seqlen_q_og < seqlen_q:
query_padding_mask = F.pad(query_padding_mask, (0, seqlen_q - seqlen_q_og))
else:
query_padding_mask = query_padding_mask[:, :seqlen_q]
q_mask_fill = ~query_padding_mask.view(query_padding_mask.shape[0], 1, query_padding_mask.shape[1], 1)
S_converted = S_converted.masked_fill(q_mask_fill, 0.0)
seqlen_k_og = key_padding_mask.shape[-1] if key_padding_mask is not None else seqlen_k
if key_padding_mask is not None:
if seqlen_k_og < seqlen_k:
key_padding_mask = F.pad(key_padding_mask, (0, seqlen_k - seqlen_k_og))
else:
key_padding_mask = key_padding_mask[:, :seqlen_k]
k_mask_fill = ~key_padding_mask.view(key_padding_mask.shape[0], 1, 1, key_padding_mask.shape[1])
S_converted = S_converted.masked_fill(k_mask_fill, 0.0)
if seqlen_q_og < seqlen_q:
S_converted = S_converted[:, :, :seqlen_q_og, :]
else:
S_converted = F.pad(S_converted, (0, 0, 0, seqlen_q_og - seqlen_q))
if seqlen_k_og < seqlen_k:
S_converted = S_converted[:, :, :, :seqlen_k_og]
else:
S_converted = F.pad(S_converted, (0, seqlen_k_og - seqlen_k))
return S_converted
@unittest.skipIf(not PLATFORM_SUPPORTS_MEM_EFF_ATTENTION, "Fused SDPA was not built for this system")
@parametrize("mask_dim", [1, 2, 3, 4])
def test_mem_efficient_attetntion_mask_variants(self, device, mask_dim: List[int]):
dtype = torch.float16
make_tensor = partial(torch.rand, device=device, dtype=dtype, requires_grad=True)
batch, num_heads, head_dim = 8, 8, 64
seq_len_q, seq_len_kv = 64, 32
query = make_tensor(SdpaShape(batch, num_heads, seq_len_q, head_dim))
kv_shape = SdpaShape(batch, num_heads, seq_len_kv, head_dim)
key, value = make_tensor(kv_shape), make_tensor(kv_shape)
if mask_dim == 1:
mask = torch.randn((seq_len_kv,), device=device, dtype=dtype)
elif mask_dim == 2:
mask = torch.randn((seq_len_q, seq_len_kv), device=device, dtype=dtype)
elif mask_dim == 3:
mask = torch.randn((num_heads, seq_len_q, seq_len_kv), device=device, dtype=dtype)
elif mask_dim == 4:
mask = torch.randn((batch, num_heads, seq_len_q, seq_len_kv), device=device, dtype=dtype)
with sdp_kernel(**backend_map[SDPBackend.EFFICIENT_ATTENTION]):
out = F.scaled_dot_product_attention(query, key, value, mask)
out.sum().backward()
@unittest.skipIf(not PLATFORM_SUPPORTS_MEM_EFF_ATTENTION, "Fused SDPA was not built for this system")
@parametrize("dtype", [torch.float, torch.float16])
def test_mem_eff_attention_pad_mask(self, device, dtype):
make_tensor = partial(torch.rand, device=device, dtype=dtype, requires_grad=True)
batch, num_heads, head_dim = 8, 8, 64
seq_len_q, seq_len_kv = 64, 15
query = make_tensor(SdpaShape(batch, num_heads, seq_len_q, head_dim))
kv_shape = SdpaShape(batch, num_heads, seq_len_kv, head_dim)
key, value = make_tensor(kv_shape), make_tensor(kv_shape)
mask = torch.randn((batch, num_heads, seq_len_q, seq_len_kv), device=device, dtype=dtype)
with sdp_kernel(**backend_map[SDPBackend.EFFICIENT_ATTENTION]):
out = F.scaled_dot_product_attention(query, key, value, mask)
out.sum().backward()
@unittest.skipIf(not PLATFORM_SUPPORTS_MEM_EFF_ATTENTION, "Fused SDPA was not built for this system")
@parametrize("dtype", [torch.float, torch.float16])
def test_mem_eff_attention_non_contiguous_mask(self, device, dtype):
make_tensor = partial(torch.rand, device=device, dtype=dtype, requires_grad=True)
batch, num_heads, head_dim = 8, 8, 64
seq_len_q, seq_len_kv = 64, 16
query = make_tensor(SdpaShape(batch, num_heads, seq_len_q, head_dim))
kv_shape = SdpaShape(batch, num_heads, seq_len_kv, head_dim)
key, value = make_tensor(kv_shape), make_tensor(kv_shape)
mask = torch.randn((batch, num_heads, seq_len_q, seq_len_kv), device=device, dtype=dtype)
mask = torch.as_strided(mask, (batch, num_heads, seq_len_q, seq_len_kv), (0, 0, 0, 1))
with sdp_kernel(**backend_map[SDPBackend.EFFICIENT_ATTENTION]):
out = F.scaled_dot_product_attention(query, key, value, mask)
out.sum().backward()
@unittest.skipIf(not PLATFORM_SUPPORTS_MEM_EFF_ATTENTION, "Fused SDPA was not built for this system")
@parametrize("dtype", [torch.float, torch.float16])
def test_mem_eff_attention_long_sequence_mask(self, device, dtype):
if torch.cuda.get_device_properties('cuda').total_memory < 80 * 2**30:
unittest.skip("This test requires substatnial GPU memory.")
return
make_tensor = partial(torch.rand, device=device, dtype=dtype, requires_grad=True)
batch, num_heads, head_dim = 1, 32, 64
seq_len_q, seq_len_kv = 8192, 8192
query = make_tensor(SdpaShape(batch, num_heads, seq_len_q, head_dim))
kv_shape = SdpaShape(batch, num_heads, seq_len_kv, head_dim)
key, value = make_tensor(kv_shape), make_tensor(kv_shape)
mask = torch.randn((batch, num_heads, seq_len_q, seq_len_kv), device=device, dtype=dtype)
with sdp_kernel(**backend_map[SDPBackend.EFFICIENT_ATTENTION]):
out = F.scaled_dot_product_attention(query, key, value, mask)
out.sum().backward()
@unittest.skipIf(not PLATFORM_SUPPORTS_MEM_EFF_ATTENTION, "Fused SDPA was not built for this system")
def test_mem_eff_attention_non_contig_mask_bug(self, device):
dtype = torch.float32
make_tensor = partial(torch.rand, device=device, dtype=dtype, requires_grad=True)
batch, num_heads, head_dim = 1, 16, 128
seq_len_q, seq_len_kv = 1, 16
query = make_tensor(batch, seq_len_q, num_heads * head_dim).view(batch, seq_len_q, num_heads, head_dim).transpose(1, 2)
kv_shape = (batch, seq_len_kv, head_dim)
key, value = make_tensor(kv_shape).unsqueeze(1), make_tensor(kv_shape).unsqueeze(1)
key = key.expand(-1, num_heads, -1, -1)
value = value.expand(-1, num_heads, -1, -1)
mask = torch.ones((1, 1, seq_len_q, seq_len_kv), device=device, dtype=torch.bool)
with sdp_kernel(**backend_map[SDPBackend.EFFICIENT_ATTENTION]):
out = F.scaled_dot_product_attention(query, key, value, mask)
out_no_mask = F.scaled_dot_product_attention(query, key, value, None)
max_diff = (out - out_no_mask).abs().mean()
assert max_diff.item() < 1e-9
@unittest.skipIf(not PLATFORM_SUPPORTS_MEM_EFF_ATTENTION, "Fused SDPA was not built for this system")
@parametrize("type", ["dense", "nested"])
@parametrize("is_contiguous", [True, False])
def test_scaled_dot_product_attention_fused_kernels_packed(self, device, type: str, is_contiguous: bool):
make_tensor = partial(rand_sdpa_tensor, type=type, device=device, dtype=torch.float16, packed=True)
batch_size, seq_len, num_heads, head_dim = 32, 64, 16, 64
shape = SdpaShape(batch_size, num_heads, seq_len, head_dim)
# Test Packed
qkv = make_tensor(shape)
query, key, value = qkv.chunk(3, dim=-1)
query = query.view(batch_size, -1, num_heads, head_dim).transpose(1, 2)
value = value.view(batch_size, -1, num_heads, head_dim).transpose(1, 2)
key = key.view(batch_size, -1, num_heads, head_dim).transpose(1, 2)
if is_contiguous:
query = query.contiguous()
key = key.contiguous()
value = value.contiguous()
with sdp_kernel(enable_flash=False, enable_math=False, enable_mem_efficient=True):
actual = torch.nn.functional.scaled_dot_product_attention(
query, key, value, attn_mask=None, dropout_p=0.0, is_causal=False)
with sdp_kernel(enable_flash=False, enable_math=True, enable_mem_efficient=False):
math_ref = torch.nn.functional.scaled_dot_product_attention(
query.contiguous(), key.contiguous(), value.contiguous(),
attn_mask=None, dropout_p=0.0, is_causal=False)
self.assertEqual(actual.contiguous(), math_ref.contiguous(), atol=2e-3, rtol=1e-2)
@unittest.skipIf(not PLATFORM_SUPPORTS_FUSED_ATTENTION, "Fused SDPA was not built for this system")
@parametrize("type", ["dense", "nested"])
@parametrize("fused_kernel", [SDPBackend.FLASH_ATTENTION, SDPBackend.EFFICIENT_ATTENTION] if
PLATFORM_SUPPORTS_FLASH_ATTENTION else [SDPBackend.EFFICIENT_ATTENTION])
def test_scaled_dot_product_attention_fused_kernels_packed_accuracy(self, device, type: str, fused_kernel: str):
def rand_nt(shape):
batch, seq_len, num_heads, head_dim = shape
tensors = [6 * torch.rand((seq_len, 3 * num_heads * head_dim), device=device, dtype=torch.float32) - 3
for _ in range(batch)]
return (torch.nested.nested_tensor(tensors, device=device, dtype=torch.float32),
torch.nested.nested_tensor(tensors, device=device, dtype=torch.float16))
def rand_tensor(shape):
batch, seq_len, num_heads, head_dim = shape
tensor = 6 * torch.rand((batch, seq_len, 3 * num_heads * head_dim), device=device, dtype=torch.float32) - 3
return tensor, tensor.to(dtype=torch.float16)
batch_size, seq_len, num_heads, head_dim = 16, 8, 4, 64
shape = (batch_size, seq_len, num_heads, head_dim)
# Test Packed
qkv, qkv_low_precision = rand_tensor(shape) if type == "dense" else rand_nt(shape)
query, key, value = qkv.chunk(3, dim=-1)
query_lp, key_lp, value_lp = qkv_low_precision.chunk(3, dim=-1)
query = query.view(batch_size, -1, num_heads, head_dim).transpose(1, 2)
key = key.view(batch_size, -1, num_heads, head_dim).transpose(1, 2)
value = value.view(batch_size, -1, num_heads, head_dim).transpose(1, 2)
query_lp = query_lp.view(batch_size, -1, num_heads, head_dim).transpose(1, 2)
key_lp = key_lp.view(batch_size, -1, num_heads, head_dim).transpose(1, 2)
value_lp = value_lp.view(batch_size, -1, num_heads, head_dim).transpose(1, 2)
with sdp_kernel(**backend_map[fused_kernel]):
actual = torch.nn.functional.scaled_dot_product_attention(
query_lp, key_lp, value_lp, attn_mask=None, dropout_p=0.0, is_causal=False)
with sdp_kernel(**backend_map[SDPBackend.MATH]):
math_ref_lp = torch.nn.functional.scaled_dot_product_attention(
query_lp.contiguous(), key_lp.contiguous(), value_lp.contiguous(),
attn_mask=None, dropout_p=0.0, is_causal=False)
math_query = query.contiguous()
math_key = key.contiguous()
math_value = value.contiguous()
math_ref = torch.nn.functional.scaled_dot_product_attention(
math_query, math_key, math_value, attn_mask=None, dropout_p=0.0, is_causal=False)
actual_test = actual
math_ref_test = math_ref
math_ref_lp_test = math_ref_lp
if actual_test.is_nested:
actual_test = torch.nested.to_padded_tensor(actual_test.contiguous(), padding=0.0)
math_ref_test = torch.nested.to_padded_tensor(math_ref_test, padding=0.0)
math_ref_lp_test = torch.nested.to_padded_tensor(math_ref_lp_test, padding=0.0)
actual_test = actual_test.to(dtype=torch.float32).contiguous()
math_ref_test = math_ref_test.to(dtype=torch.float32).contiguous()
math_ref_lp_test = math_ref_lp_test.to(dtype=torch.float32).contiguous()
self.assertEqual(math_ref_test, math_ref_lp_test, atol=7e-3, rtol=7e-3)
self.assertEqual(actual_test, math_ref_test, atol=5e-3, rtol=5e-3)
@unittest.skipIf(not PLATFORM_SUPPORTS_MEM_EFF_ATTENTION, "Flash Attention was not built for this system")
@parametrize("contiguous_inputs", [True, False])
@parametrize("is_causal", [True, False])
def test_sdp_mem_efficient_grad_against_math(self, device, contiguous_inputs: bool, is_causal: bool):
batch_size, seq_len, num_heads, head_dim = 4, 4, 2, 16
make_tensor = partial(rand_sdpa_tensor, type="dense", device=device,
dtype=torch.float64, requires_grad=True, packed=True)
qkv = make_tensor(SdpaShape(batch_size, num_heads, seq_len, head_dim))
qkv_lp = qkv.detach().clone().to(torch.float32).requires_grad_()
query, key, value = qkv.chunk(3, dim=-1)
query_lp, key_lp, value_lp = qkv_lp.chunk(3, dim=-1)
query = query.view(batch_size, -1, num_heads, head_dim).transpose(1, 2)
key = key.view(batch_size, -1, num_heads, head_dim).transpose(1, 2)
value = value.view(batch_size, -1, num_heads, head_dim).transpose(1, 2)
query_lp = query_lp.view(batch_size, -1, num_heads, head_dim).transpose(1, 2)
key_lp = key_lp.view(batch_size, -1, num_heads, head_dim).transpose(1, 2)
value_lp = value_lp.view(batch_size, -1, num_heads, head_dim).transpose(1, 2)
if contiguous_inputs:
query = query.contiguous()
key = key.contiguous()
value = value.contiguous()
query_lp = query_lp.contiguous()
key_lp = key_lp.contiguous()
value_lp = value_lp.contiguous()
with sdp_kernel(enable_math=True, enable_mem_efficient=False, enable_flash=False):
out = torch.nn.functional.scaled_dot_product_attention(query, key, value, None, 0.0, is_causal)
with sdp_kernel(enable_math=False, enable_mem_efficient=True, enable_flash=False):
out_lp = torch.nn.functional.scaled_dot_product_attention(
query_lp, key_lp, value_lp, None, 0.0, is_causal)
rand_upward = torch.rand_like(out)
rand_upward_lp = rand_upward.to(torch.float32)
out.backward(rand_upward)
out_lp.backward(rand_upward_lp)
# Cast up and compare
self.assertEqual(qkv.grad, qkv_lp.grad.to(torch.float64), atol=1e-5, rtol=1e-5)
@unittest.skipIf(not PLATFORM_SUPPORTS_FLASH_ATTENTION, "Flash Attention was not built for this system")
@parametrize("contiguous_inputs", [True, False])
@parametrize("is_causal", [True, False])
@parametrize("dtype", [torch.float16, torch.bfloat16])
def test_sdp_flash_attention_grad_against_math(self, device, contiguous_inputs: bool, is_causal: bool, dtype: torch.dtype):
batch_size, seq_len, num_heads, head_dim = 4, 4, 2, 16
make_tensor = partial(rand_sdpa_tensor, type="dense", device=device,
dtype=torch.float64, requires_grad=True, packed=True)
qkv = make_tensor(SdpaShape(batch_size, num_heads, seq_len, head_dim))
qkv_lp = qkv.detach().clone().to(dtype).requires_grad_()
query, key, value = qkv.chunk(3, dim=-1)
query_lp, key_lp, value_lp = qkv_lp.chunk(3, dim=-1)
query = query.view(batch_size, -1, num_heads, head_dim).transpose(1, 2)
key = key.view(batch_size, -1, num_heads, head_dim).transpose(1, 2)
value = value.view(batch_size, -1, num_heads, head_dim).transpose(1, 2)
query_lp = query_lp.view(batch_size, -1, num_heads, head_dim).transpose(1, 2)
key_lp = key_lp.view(batch_size, -1, num_heads, head_dim).transpose(1, 2)
value_lp = value_lp.view(batch_size, -1, num_heads, head_dim).transpose(1, 2)
if contiguous_inputs:
query = query.contiguous()
key = key.contiguous()
value = value.contiguous()
query_lp = query_lp.contiguous()
key_lp = key_lp.contiguous()
value_lp = value_lp.contiguous()
with sdp_kernel(enable_math=True, enable_mem_efficient=False, enable_flash=False):
out = torch.nn.functional.scaled_dot_product_attention(query, key, value, None, 0.0, is_causal)
with sdp_kernel(enable_math=False, enable_mem_efficient=False, enable_flash=True):
out_lp = torch.nn.functional.scaled_dot_product_attention(
query_lp, key_lp, value_lp, None, 0.0, is_causal)
rand_upward = torch.rand_like(out)
rand_upward_lp = rand_upward.to(dtype)
out.backward(rand_upward)
out_lp.backward(rand_upward_lp)
# Cast up and compare
# Since we are doing the compute on fp16 we have to bump the tolerance
# Bump down the tolearnce for blfoat16
atol = 7e-4 if dtype == torch.float16 else 7e-3
rtol = 7e-4 if dtype == torch.float16 else 7e-3
self.assertEqual(qkv.grad, qkv_lp.grad.to(torch.float64), atol=atol, rtol=rtol)
@unittest.skipIf(not PLATFORM_SUPPORTS_FUSED_ATTENTION, "Platform does not support fused SDPA")
@parametrize("type", ["dense", "nested"])
def test_fused_sdp_choice(self, device, type: str):
batch_size, seq_len, num_heads, head_dim = 2, 128, 8, 64
shape = SdpaShape(batch_size, num_heads, seq_len, head_dim)
make_tensor = partial(rand_sdpa_tensor, device=device, dtype=torch.float16, packed=True, requires_grad=True)
qkv = make_tensor(shape, type=type)
query, key, value = qkv.chunk(3, dim=-1)
query = query.view(batch_size, -1, num_heads, head_dim).transpose(1, 2)
value = value.view(batch_size, -1, num_heads, head_dim).transpose(1, 2)
key = key.view(batch_size, -1, num_heads, head_dim).transpose(1, 2)
if PLATFORM_SUPPORTS_FLASH_ATTENTION:
assert torch._fused_sdp_choice(query, key, value) == SDPBackend.FLASH_ATTENTION.value
else:
assert torch._fused_sdp_choice(query, key, value) == SDPBackend.EFFICIENT_ATTENTION.value
# Change dtype to float32 so that efficient attention should get chosen
make_tensor = partial(rand_sdpa_tensor, device=device, dtype=torch.float32, packed=True)
qkv = make_tensor(shape, type=type)
query, key, value = qkv.chunk(3, dim=-1)
query = query.view(batch_size, -1, num_heads, head_dim).transpose(1, 2)
value = value.view(batch_size, -1, num_heads, head_dim).transpose(1, 2)
key = key.view(batch_size, -1, num_heads, head_dim).transpose(1, 2)
assert torch._fused_sdp_choice(query, key, value) == SDPBackend.EFFICIENT_ATTENTION.value
@unittest.skipIf(not PLATFORM_SUPPORTS_MEM_EFF_ATTENTION, "Platform does not support fused SDPA")
@parametrize("warn_only", [True, False])
def test_sdp_choice_with_determinism(self, device, warn_only):
batch_size, seq_len, num_heads, head_dim = 1, 64, 8, 64
shape = SdpaShape(batch_size, num_heads, seq_len, head_dim)
make_tensor = partial(rand_sdpa_tensor, type="dense", device=device, dtype=torch.float32, packed=False)
query, key, value = make_tensor(shape), make_tensor(shape), make_tensor(shape)
with use_deterministic_algorithims(True, warn_only=warn_only):
with sdp_kernel(enable_flash=False, enable_math=True, enable_mem_efficient=True):
assert torch._fused_sdp_choice(query, key, value) == SDPBackend.EFFICIENT_ATTENTION.value
@unittest.skipIf(not PLATFORM_SUPPORTS_MEM_EFF_ATTENTION, "Platform does not support fused SDPA")
@parametrize("warn_only", [True, False])
def test_mem_eff_backwards_throws_determinism_warning(self, device, warn_only):
batch_size, seq_len, num_heads, head_dim = 1, 64, 8, 64
shape = SdpaShape(batch_size, num_heads, seq_len, head_dim)
make_tensor = partial(rand_sdpa_tensor, type="dense", device=device, dtype=torch.float32, packed=False, requires_grad=True)
query, key, value = make_tensor(shape), make_tensor(shape), make_tensor(shape)
warning_context = (
self.assertWarnsRegex(
UserWarning,
"Memory Efficient attention defaults to a non-deterministic algorithm.",
)
if warn_only
else contextlib.nullcontext()
)
with use_deterministic_algorithims(True, warn_only=warn_only):
with sdp_kernel(**backend_map[SDPBackend.EFFICIENT_ATTENTION]):
with warning_context:
torch.nn.functional.scaled_dot_product_attention(query, key, value).sum().backward()
@unittest.skip("This test is not behaving deterministaclly non-deterministaclly on CI/CD")
@unittest.skipIf(not PLATFORM_SUPPORTS_FLASH_ATTENTION, "Platform does not support fused SDPA")
def test_mem_eff_backwards_determinism(self, device):
# Need big seq_len to ensure that num_splits > 1
dtype = torch.float32
batch_size, seq_len, n_heads, head_dim = 1, 1024, 8, 64
query = torch.rand(batch_size, n_heads, seq_len, head_dim,
device=device, dtype=dtype, requires_grad=True)
key = torch.rand(batch_size, n_heads, seq_len, head_dim, device=device,
dtype=dtype, requires_grad=True)
value = torch.rand(batch_size, n_heads, seq_len, head_dim,
device=device, dtype=dtype, requires_grad=True)
with sdp_kernel(enable_mem_efficient=True, enable_math=False, enable_flash=False):
# Run once to establish baseline
out = F.scaled_dot_product_attention(query, key, value)
upward_grad = torch.rand_like(out)
out.backward(upward_grad)
intial_query_grad = query.grad
# Re-run the op with the same upward grad and check that the backward is
# not deterministic
diff_anwser_once = False
for _ in range(100):
query.grad = None
out = F.scaled_dot_product_attention(query, key, value)
out.backward(upward_grad)
if not torch.equal(intial_query_grad, query.grad):
diff_anwser_once = True
break
self.assertTrue(diff_anwser_once)
with use_deterministic_algorithims(True, warn_only=False):
query.grad = None
out = F.scaled_dot_product_attention(query, key, value)
upward_grad = torch.rand_like(out)
out.backward(upward_grad)
intial_query_grad = query.grad
# Re-run the op with the same upward grad and check that the backward is
# deterministic now that we have enforced it
diff_anwser_once = False
for _ in range(100):
query.grad = None
out = F.scaled_dot_product_attention(query, key, value)
out.backward(upward_grad)
if not torch.equal(intial_query_grad, query.grad):
diff_anwser_once = True
break
self.assertFalse(diff_anwser_once)
# verified passing successfully on H100
@unittest.skipIf(not PLATFORM_SUPPORTS_MEM_EFF_ATTENTION, "Does not support SDPA")
@parametrize("batch_size", [1, 8])
@parametrize("seq_len_q", [4, 8, 64, 128, 256, 512, 1024, 2048] if SM80OrLater else [4, 8, 64, 128, 256, 512])
@parametrize("seq_len_k", [4, 8, 64, 128, 256, 512, 1024, 2048] if SM80OrLater else [4, 8, 64, 128, 256, 512])
@parametrize("head_dim", [8, 16, 32, 64, 72, 96, 128] if SM80OrLater else [8, 16, 32, 64])
@parametrize("is_causal", [False, True])
@parametrize("dropout_p", [0.0, 0.22])
@parametrize("dtype", [torch.float16, torch.bfloat16, torch.float32] if
SM80OrLater else [torch.float16, torch.float32])
@parametrize("scale", [None, "l1"])
def test_mem_efficient_attention_vs_math_ref_grads(self, device, batch_size: int, seq_len_q: int, seq_len_k: int,
head_dim: int, is_causal: bool, dropout_p: float, dtype: torch.dtype,
scale: str):
def _get_mem_eff_drop_mask(batch_size, n_heads, q_len, kv_len, p, seed, offset, device=device):
mask = torch.empty((batch_size, n_heads, q_len, kv_len), device=device, dtype=torch.float32)
rand_uniform = torch._fill_mem_eff_dropout_mask_(mask, p, seed, offset)
mask = (rand_uniform > p).to(torch.float32)
return mask
if max(seq_len_q, seq_len_k) >= 2048 and torch.cuda.get_device_properties('cuda').total_memory < 40 * 2**30:
unittest.skip("Reference implementation OOM")
return
seed = 42
scale = scale if scale is None else (1 / head_dim)
n_heads = 4
query = torch.rand(batch_size, n_heads, seq_len_q, head_dim,
device=device, dtype=dtype, requires_grad=True)
key = torch.rand(batch_size, n_heads, seq_len_k, head_dim, device=device,
dtype=dtype, requires_grad=True)
value = torch.rand(batch_size, n_heads, seq_len_k, head_dim,
device=device, dtype=dtype, requires_grad=True)
# Run the math kernel on low precision references
query_ref_lp, key_ref_lp, value_ref_lp = query_key_value_clones(query, key, value, dtype=dtype)
higher_precision_dtype = torch.float64 if dtype == torch.float32 else torch.float32
query_ref, key_ref, value_ref = query_key_value_clones(query, key, value, dtype=higher_precision_dtype)
# Create real output
with sdp_kernel(enable_mem_efficient=True, enable_flash=False, enable_math=False):
# Set the seed and run the kernel
torch.manual_seed(seed)
out = F.scaled_dot_product_attention(query, key, value, dropout_p=dropout_p, is_causal=is_causal, scale=scale)
if dropout_p == 0.0:
with sdp_kernel(enable_math=True, enable_flash=False, enable_mem_efficient=False):
# High Precision Math Reference
out_ref = F.scaled_dot_product_attention(query_ref, key_ref, value_ref,
dropout_p=dropout_p, is_causal=is_causal, scale=scale)
# Low Precision Math Reference
out_lp_ref = F.scaled_dot_product_attention(query_ref_lp, key_ref_lp, value_ref_lp,
dropout_p=dropout_p, is_causal=is_causal, scale=scale)
else:
if seq_len_q > 1024:
self.skipTest("Will call _fill_mem_eff_dropout_mask with too many threads!")
# Create the dropout_mask
torch.manual_seed(seed)
dropout_mask = _get_mem_eff_drop_mask(batch_size, n_heads, seq_len_q, seq_len_k, dropout_p, seed, 0, device=device)
# High Precision Math Reference
out_ref = torch.ops.aten._scaled_dot_product_attention_math(
query_ref, key_ref, value_ref, dropout_p=dropout_p, is_causal=is_causal, scale=scale, dropout_mask=dropout_mask)[0]
# Low Precision Math Reference
out_lp_ref = torch.ops.aten._scaled_dot_product_attention_math(
query_ref_lp, key_ref_lp, value_ref_lp, dropout_p=dropout_p, is_causal=is_causal, scale=scale,
dropout_mask=dropout_mask)[0]
upstream_grad = torch.rand_like(out, requires_grad=False)
out.backward(upstream_grad)
out_ref.backward(upstream_grad.to(out_ref.dtype))
out_lp_ref.backward(upstream_grad.to(out_lp_ref.dtype))
# [Note] Fused Tolerances
# Establish the numerical error between the "true" high precision math output
# and the low precision math reference. We use this reference for the atol
# And we use the default rtol for the low precision type.
# We then provide a fudge factor for gradients respectively to account
# for the use of the fused kernel rather than the eager implemntation.
output_ref_atol, output_ref_rtol = get_tolerances(out_ref, out_lp_ref)
# Fudge Factor when dropout is enabled
dropout_fudge_factor = 1.0 if dropout_p == 0.0 else 2.0
query_fudge_factor = dropout_fudge_factor
grad_q_ref_atol, grad_q_ref_rtol = get_tolerances(query_ref.grad, query_ref_lp.grad, query_fudge_factor)
# TODO: Investigate why grad_k needs larger tolerances
key_fudge_factor = 8 * dropout_fudge_factor
grad_k_ref_atol, grad_k_ref_rtol = get_tolerances(key_ref.grad, key_ref_lp.grad, key_fudge_factor)
value_fudge_factor = 7 if not SM80OrLater and dtype == torch.float16 else 1.0
grad_v_ref_atol, grad_v_ref_rtol = get_tolerances(value_ref.grad, value_ref_lp.grad, value_fudge_factor)
self.assertEqual(out, out_ref.to(out.dtype), atol=output_ref_atol, rtol=output_ref_rtol)
self.assertEqual(query.grad, query_ref.grad.to(query.grad.dtype),
atol=grad_q_ref_atol, rtol=grad_q_ref_rtol)
self.assertEqual(key.grad, key_ref.grad.to(key.grad.dtype),
atol=grad_k_ref_atol, rtol=grad_k_ref_rtol)
self.assertEqual(value.grad, value_ref.grad.to(value.grad.dtype),
atol=grad_v_ref_atol, rtol=grad_v_ref_rtol)
@unittest.skipIf(not PLATFORM_SUPPORTS_MEM_EFF_ATTENTION, "Does not support SDPA")
@parametrize("batch_size", [1, 8])
@parametrize("seq_len_q", [4, 8, 64, 128, 256, 312, 512, 1024, 2048] if SM80OrLater else [4, 8, 64, 128, 152, 256, 512])
@parametrize("seq_len_k", [4, 8, 64, 65, 128, 256, 408, 512, 1024, 2048] if SM80OrLater else [4, 8, 37, 64, 128, 256, 512])
@parametrize("head_dim", [8, 16, 32, 64, 72, 96, 128] if SM80OrLater else [8, 16, 32, 64])
@parametrize("is_causal", [False])
@parametrize("dropout_p", [0.0, 0.22])
@parametrize("dtype", [torch.float16, torch.bfloat16, torch.float32] if
SM80OrLater else [torch.float16, torch.float32])
@parametrize("scale", [None, "l1"])
def test_mem_efficient_attention_attn_mask_vs_math_ref_grads(self, device, batch_size: int, seq_len_q: int,
seq_len_k: int, head_dim: int, is_causal: bool,
dropout_p: float, dtype: torch.dtype,
scale: str):
def _get_mem_eff_drop_mask(batch_size, n_heads, q_len, kv_len, p, seed, offset, device=device):
mask = torch.empty((batch_size, n_heads, q_len, kv_len), device=device, dtype=torch.float32)
rand_uniform = torch._fill_mem_eff_dropout_mask_(mask, p, seed, offset)
mask = (rand_uniform > p).to(torch.float32)
return mask
if max(seq_len_q, seq_len_k) >= 2048 and torch.cuda.get_device_properties('cuda').total_memory < 40 * 2**30:
unittest.skip("Reference implementation OOM")
return
seed = 42
scale = scale if scale is None else (1 / head_dim)
n_heads = 4
query = torch.rand(batch_size, n_heads, seq_len_q, head_dim,
device=device, dtype=dtype, requires_grad=True)
key = torch.rand(batch_size, n_heads, seq_len_k, head_dim, device=device,
dtype=dtype, requires_grad=True)
value = torch.rand(batch_size, n_heads, seq_len_k, head_dim,
device=device, dtype=dtype, requires_grad=True)
attn_mask = torch.rand(seq_len_q, seq_len_k, device=device, dtype=dtype, requires_grad=True)
# Run the math kernel on low precision references
query_ref_lp, key_ref_lp, value_ref_lp = query_key_value_clones(query, key, value, dtype=dtype)
attn_mask_ref_lp = attn_mask.detach().to(dtype).requires_grad_(True)
higher_precision_dtype = torch.float64 if dtype == torch.float32 else torch.float32
query_ref, key_ref, value_ref = query_key_value_clones(query, key, value, dtype=higher_precision_dtype)
attn_mask_ref = attn_mask.detach().to(higher_precision_dtype).requires_grad_(True)
# Create real output
with sdp_kernel(enable_mem_efficient=True, enable_flash=False, enable_math=False):
# Set the seed and run the kernel
torch.manual_seed(seed)
out = F.scaled_dot_product_attention(query, key, value, attn_mask, dropout_p=dropout_p,
is_causal=is_causal, scale=scale)
if dropout_p == 0.0:
with sdp_kernel(enable_math=True, enable_flash=False, enable_mem_efficient=False):
# High Precision Math Reference
out_ref = F.scaled_dot_product_attention(query_ref, key_ref, value_ref, attn_mask_ref,
dropout_p=dropout_p, is_causal=is_causal, scale=scale)
# Low Precision Math Reference
out_lp_ref = F.scaled_dot_product_attention(query_ref_lp, key_ref_lp, value_ref_lp, attn_mask_ref_lp,
dropout_p=dropout_p, is_causal=is_causal, scale=scale)
else:
if seq_len_q > 1024:
self.skipTest("Will call _fill_mem_eff_dropout_mask with too many threads!")
# Create the dropout_mask
torch.manual_seed(seed)
dropout_mask = _get_mem_eff_drop_mask(batch_size, n_heads, seq_len_q,
seq_len_k, dropout_p, seed, 0, device=device)
# High Precision Math Reference
out_ref = torch.ops.aten._scaled_dot_product_attention_math(
query_ref, key_ref, value_ref, attn_mask_ref, dropout_p=dropout_p, is_causal=is_causal,
scale=scale, dropout_mask=dropout_mask)[0]
# Low Precision Math Reference
out_lp_ref = torch.ops.aten._scaled_dot_product_attention_math(
query_ref_lp, key_ref_lp, value_ref_lp, attn_mask_ref_lp,
dropout_p=dropout_p, is_causal=is_causal, scale=scale,
dropout_mask=dropout_mask)[0]
upstream_grad = torch.rand_like(out, requires_grad=False)
out.backward(upstream_grad)
out_ref.backward(upstream_grad.to(out_ref.dtype))
out_lp_ref.backward(upstream_grad.to(out_lp_ref.dtype))
# [Note] Fused Tolerances
# Establish the numerical error between the "true" high precision math output
# and the low precision math reference. We use this reference for the atol
# And we use the default rtol for the low precision type.
# We then provide a fudge factor for gradients respectively to account
# for the use of the fused kernel rather than the eager implemntation.
output_ref_atol, output_ref_rtol = get_tolerances(out_ref, out_lp_ref)
# Fudge Factor when dropout is enabled
dropout_fudge_factor = 1.0 if dropout_p == 0.0 else 1.5
mask_fudge_factor = 1.0 if attn_mask is None else 1.5
query_fudge_factor = dropout_fudge_factor
grad_q_ref_atol, grad_q_ref_rtol = get_tolerances(query_ref.grad, query_ref_lp.grad, query_fudge_factor)
# TODO: Investigate why grad_k needs larger tolerances
key_fudge_factor = 8 * dropout_fudge_factor * mask_fudge_factor
grad_k_ref_atol, grad_k_ref_rtol = get_tolerances(key_ref.grad, key_ref_lp.grad, key_fudge_factor)
value_fudge_factor = 7 if not SM80OrLater and dtype == torch.float16 else 1.0
grad_v_ref_atol, grad_v_ref_rtol = get_tolerances(value_ref.grad, value_ref_lp.grad, value_fudge_factor)
mask_fudge_factor = 12 if attn_mask.numel() > 512 else 22
grad_attn_mask_atol, grad_attn_mask_rtol = get_tolerances(
attn_mask_ref.grad, attn_mask_ref_lp.grad, mask_fudge_factor)
self.assertEqual(out, out_ref.to(out.dtype), atol=output_ref_atol, rtol=output_ref_rtol)
self.assertEqual(query.grad, query_ref.grad.to(query.grad.dtype),
atol=grad_q_ref_atol, rtol=grad_q_ref_rtol)
self.assertEqual(key.grad, key_ref.grad.to(key.grad.dtype),
atol=grad_k_ref_atol, rtol=grad_k_ref_rtol)
self.assertEqual(value.grad, value_ref.grad.to(value.grad.dtype),
atol=grad_v_ref_atol, rtol=grad_v_ref_rtol)
self.assertEqual(attn_mask.grad, attn_mask_ref.grad.to(attn_mask.grad.dtype),
atol=grad_attn_mask_atol, rtol=grad_attn_mask_rtol)
@unittest.skipIf(not PLATFORM_SUPPORTS_FLASH_ATTENTION, "Does not support SDPA or pre-SM80 hardware")
@parametrize("batch_size", [1, 8])
@parametrize("seq_len_q", [4, 8, 64, 143, 256, 512, 1024, 2048])
@parametrize("seq_len_k", [4, 8, 64, 128, 256, 587, 1024, 2048])
@parametrize("head_dim", [8, 16, 21, 32, 64, 72, 96, 128, 160, 192, 203, 256])
@parametrize("is_causal", [True, False])
@parametrize("dropout_p", [0.0, 0.22, 0.48])
@parametrize("dtype", [torch.float16, torch.bfloat16])
@parametrize("scale", [None, "l1"])
def test_flash_attention_vs_math_ref_grads(self, device, batch_size: int, seq_len_q: int, seq_len_k: int,
head_dim: int, is_causal: bool, dropout_p: float, dtype: torch.dtype,
scale: str):
if isSM86or89Device and head_dim in range(193, 256 + 1):
self.skipTest("Flash attention on sm86 and sm89 for headdim > 192 currently disabled")
if is_causal and seq_len_q != seq_len_k:
self.skipTest("Flash V2 does not accept is_casual when seq_len_q != seq_len_k")
scale = scale if scale is None else (1 / head_dim)
n_heads = 4
query = torch.rand(batch_size, n_heads, seq_len_q, head_dim,
device=device, dtype=dtype, requires_grad=True)
key = torch.rand(batch_size, n_heads, seq_len_k, head_dim, device=device,
dtype=dtype, requires_grad=True)
value = torch.rand(batch_size, n_heads, seq_len_k, head_dim,
device=device, dtype=dtype, requires_grad=True)
# Run the math kernel on low precision references
query_ref_lp, key_ref_lp, value_ref_lp = query_key_value_clones(query, key, value, dtype=dtype)
higher_precision_dtype = torch.float64 if dtype == torch.float32 else torch.float32
query_ref, key_ref, value_ref = query_key_value_clones(query, key, value, dtype=higher_precision_dtype)
is_dropout = dropout_p > 0.0
if not is_dropout:
# Problem: We pad sizes in the composite region of the top level SDPA. But we need the
# Debug mask when have dropout. So I am going to manualy pad up here when testing dropout
with sdp_kernel(enable_math=False, enable_flash=True, enable_mem_efficient=False):
out = F.scaled_dot_product_attention(query, key, value, dropout_p=dropout_p, is_causal=is_causal, scale=scale)
with sdp_kernel(enable_math=True, enable_flash=False, enable_mem_efficient=False):
# High Precision Math Reference
out_ref = F.scaled_dot_product_attention(
query_ref, key_ref, value_ref, is_causal=is_causal, scale=scale)
# Low Precision Math Reference
out_lp_ref = F.scaled_dot_product_attention(
query_ref_lp, key_ref_lp, value_ref_lp, is_causal=is_causal, scale=scale)
else:
q_padded, q_og_size = pad_last_dim(query, 8)
k_padded, k_og_size = pad_last_dim(key, 8)
v_padded, v_og_size = pad_last_dim(value, 8)
# scale needs to be calculated on the og head_size
if scale is None:
scale = 1 / math.sqrt(q_og_size)
output_tuple = torch.ops.aten._scaled_dot_product_flash_attention(
q_padded, k_padded, v_padded, dropout_p=dropout_p, is_causal=is_causal, scale=scale, return_debug_mask=is_dropout)
out = output_tuple[0]
out = out[..., :v_og_size]
# Build dropout_mask
dbug_mask = output_tuple[-1]
query_padding_mask = torch.ones(
batch_size, seq_len_q, device=device, dtype=torch.bool)
key_padding_mask = torch.ones(
batch_size, seq_len_k, device=device, dtype=torch.bool)
softmax_mask = self.convert_flash_attn_S_to_softmax(
dbug_mask, query_padding_mask, key_padding_mask, head_dim=head_dim,
causal=is_causal)[:, :, :seq_len_q, :seq_len_k]
dropout_mask = softmax_mask >= 0
# High Precision Math Reference
out_ref = torch.ops.aten._scaled_dot_product_attention_math(
query_ref, key_ref, value_ref, dropout_p=dropout_p, is_causal=is_causal, scale=scale, dropout_mask=dropout_mask)[0]
# Low Precision Math Reference
out_lp_ref = torch.ops.aten._scaled_dot_product_attention_math(
query_ref_lp, key_ref_lp, value_ref_lp, dropout_p=dropout_p, is_causal=is_causal, scale=scale,
dropout_mask=dropout_mask)[0]
upstream_grad = torch.rand_like(out, requires_grad=False)
# backward for flash attention on sm86 and sm89 for headdim > 64 currently disabled
if isSM86or89Device and head_dim in range(193, 256):
self.assertRaises(RuntimeError, lambda: out.backward(upstream_grad))
return
out.backward(upstream_grad)
out_ref.backward(upstream_grad.to(out_ref.dtype))
out_lp_ref.backward(upstream_grad.to(out_lp_ref.dtype))
# See [Note] Fused Tolerances above
output_fudge_factor = 3 if head_dim % 8 != 0 else 1
output_ref_atol, output_ref_rtol = get_tolerances(out_ref, out_lp_ref, output_fudge_factor)
# TODO: Investigate why grad_q needs larger tolerances
query_fudge_factor = 4
grad_q_ref_atol, grad_q_ref_rtol = get_tolerances(query_ref.grad, query_ref_lp.grad, query_fudge_factor)
grad_k_ref_atol, grad_k_ref_rtol = get_tolerances(key_ref.grad, key_ref_lp.grad)
value_fudge_factor = 2
grad_v_ref_atol, grad_v_ref_rtol = get_tolerances(value_ref.grad, value_ref_lp.grad, value_fudge_factor)
self.assertEqual(out, out_ref.to(out.dtype), atol=output_ref_atol, rtol=output_ref_rtol)
self.assertEqual(query.grad, query_ref.grad.to(query.grad.dtype),
atol=grad_q_ref_atol, rtol=grad_q_ref_rtol)
self.assertEqual(key.grad, key_ref.grad.to(key.grad.dtype),
atol=grad_k_ref_atol, rtol=grad_k_ref_rtol)
self.assertEqual(value.grad, value_ref.grad.to(value.grad.dtype),
atol=grad_v_ref_atol, rtol=grad_v_ref_rtol)
@unittest.skipIf(not PLATFORM_SUPPORTS_FLASH_ATTENTION, "Does not support SDPA or pre-SM80 hardware")
@parametrize("batch_size", [1, 8])
@parametrize("seq_len_q", [256, 512, 1024])
@parametrize("seq_len_k", [256, 512, 1024])
@parametrize("head_dim", [32, 64])
@parametrize("is_causal", [True, False])
@parametrize("dropout_p", [0.0, 0.22])
@parametrize("dtype", [torch.float16,])
@parametrize("scale", [None, "l1"])
@parametrize("fused_kernel", [SDPBackend.FLASH_ATTENTION, SDPBackend.EFFICIENT_ATTENTION])
def test_fused_attention_vs_math_ref_grads_cudagraph(self, device, batch_size: int, seq_len_q: int, seq_len_k: int,
head_dim: int,
is_causal: bool,
dropout_p: float,
dtype: torch.dtype,
scale: str,
fused_kernel: SDPBackend):
def _get_mem_eff_drop_mask(batch_size, n_heads, q_len, kv_len, dropout_p, seed, offset, device=device):
mask = torch.empty((batch_size, n_heads, q_len, kv_len), device=device, dtype=torch.float32)
rand_uniform = torch._fill_mem_eff_dropout_mask_(mask, dropout_p, seed, offset)
mask = (rand_uniform > dropout_p).to(torch.float32)
return mask
def get_dropout_mask(output, fused_kernel, batch_size, n_heads, q_len, kv_len, dropout_p, device=device):
if fused_kernel == SDPBackend.EFFICIENT_ATTENTION:
output_seed, output_offset = output_tuple[2], output_tuple[3]
output_seed = output_seed.item()
output_offset = output_offset.item()
return _get_mem_eff_drop_mask(batch_size, n_heads, q_len, kv_len,
dropout_p, output_seed, output_offset, device=device)
else:
# Build dropout_mask
dbug_mask = output_tuple[-1]
query_padding_mask = torch.ones(
batch_size, seq_len_q, device=device, dtype=torch.bool)
key_padding_mask = torch.ones(
batch_size, seq_len_k, device=device, dtype=torch.bool)
softmax_mask = self.convert_flash_attn_S_to_softmax(
dbug_mask, query_padding_mask, key_padding_mask, head_dim=head_dim, causal=is_causal)
dropout_mask = softmax_mask >= 0
return dropout_mask
if fused_kernel == SDPBackend.FLASH_ATTENTION and is_causal and seq_len_q != seq_len_k:
self.skipTest("Flash V2 does not accept is_casual when seq_len_q != seq_len_k")
seed = 42
scale = scale if scale is None else (1 / head_dim)
n_heads = 4
query = torch.rand(batch_size, n_heads, seq_len_q, head_dim,
device=device, dtype=dtype, requires_grad=True)
key = torch.rand(batch_size, n_heads, seq_len_k, head_dim, device=device,
dtype=dtype, requires_grad=True)
value = torch.rand(batch_size, n_heads, seq_len_k, head_dim,
device=device, dtype=dtype, requires_grad=True)
fused_op = (torch.ops.aten._scaled_dot_product_efficient_attention
if fused_kernel == SDPBackend.EFFICIENT_ATTENTION else torch.ops.aten._scaled_dot_product_flash_attention)
# Run the math kernel on low precision references
query_ref_lp, key_ref_lp, value_ref_lp = query_key_value_clones(query, key, value, dtype=dtype)
higher_precision_dtype = torch.float64 if dtype == torch.float32 else torch.float32
query_ref, key_ref, value_ref = query_key_value_clones(query, key, value, dtype=higher_precision_dtype)
# warmup
s = torch.cuda.Stream()
s.wait_stream(torch.cuda.current_stream())
# Set the global seed before capture
torch.manual_seed(seed)
kwargs = {"dropout_p": dropout_p, "is_causal": is_causal, "scale": scale}
if fused_kernel == SDPBackend.EFFICIENT_ATTENTION:
kwargs["compute_log_sumexp"] = True
kwargs["attn_bias"] = None
if fused_kernel == SDPBackend.FLASH_ATTENTION:
kwargs['return_debug_mask'] = dropout_p > 0.0
with torch.cuda.stream(s):
# Create real output
output_tuple = fused_op(query, key, value, **kwargs)
torch.cuda.current_stream().wait_stream(s)
out = output_tuple[0]
upstream_grad = torch.rand_like(out, requires_grad=False)
s.wait_stream(torch.cuda.current_stream())
with torch.cuda.stream(s):
out.backward(upstream_grad)
for x in (query, key, value):
x.grad = None
g = torch.cuda.CUDAGraph()
# Create real output
with torch.cuda.graph(g):
tmp = torch.rand_like(query, device=query.device) # test non-zero intragraph offset
# Create real output
output_tuple = fused_op(query, key, value, **kwargs)
assert all(not isinstance(o, torch.Tensor) or o.is_cuda for o in output_tuple)
g.replay()
out_first = output_tuple[0].clone()
g.replay()
out = output_tuple[0]
if dropout_p == 0.0:
self.assertEqual(out_first, out, atol=0, rtol=0)
else:
# replays produce different results
self.assertNotEqual(out_first, out)
with sdp_kernel(enable_math=True, enable_flash=False, enable_mem_efficient=False):
if dropout_p == 0.0:
# High Precision Math Reference
out_ref = F.scaled_dot_product_attention(query_ref, key_ref, value_ref,
dropout_p=dropout_p, is_causal=is_causal, scale=scale)
# Low Precision Math Reference
out_lp_ref = F.scaled_dot_product_attention(query_ref_lp, key_ref_lp, value_ref_lp,
dropout_p=dropout_p, is_causal=is_causal, scale=scale)
else:
# Create the dropout_mask
dropout_mask = get_dropout_mask(output_tuple, fused_kernel, batch_size,
n_heads, seq_len_q, seq_len_k, dropout_p, device)
# High Precision Math Reference
out_ref = torch.ops.aten._scaled_dot_product_attention_math(
query_ref, key_ref, value_ref, dropout_p=dropout_p, is_causal=is_causal,
scale=scale, dropout_mask=dropout_mask)[0]
# Low Precision Math Reference
out_lp_ref = torch.ops.aten._scaled_dot_product_attention_math(
query_ref_lp, key_ref_lp, value_ref_lp, dropout_p=dropout_p, is_causal=is_causal, scale=scale,
dropout_mask=dropout_mask)[0]
g1 = torch.cuda.CUDAGraph()
with torch.cuda.graph(g1):
out.backward(upstream_grad)
g1.replay()
out_ref.backward(upstream_grad.to(out_ref.dtype))
out_lp_ref.backward(upstream_grad.to(out_lp_ref.dtype))
# [Note] Fused Tolerances
# Establish the numerical error between the "true" high precision math output
# and the low precision math reference. We use this reference for the atol
# And we use the default rtol for the low precision type.
# We then provide a fudge factor for gradients respectively to account
# for the use of the fused kernel rather than the eager implemntation.
output_ref_atol, output_ref_rtol = get_tolerances(out_ref, out_lp_ref)
# Fudge Factor when dropout is enabled
dropout_fudge_factor = 1.0 if dropout_p == 0.0 else 1.5
query_fudge_factor = dropout_fudge_factor
grad_q_ref_atol, grad_q_ref_rtol = get_tolerances(query_ref.grad, query_ref_lp.grad, query_fudge_factor)
# TODO: Investigate why grad_k needs larger tolerances
key_fudge_factor = 8 * dropout_fudge_factor
grad_k_ref_atol, grad_k_ref_rtol = get_tolerances(key_ref.grad, key_ref_lp.grad, key_fudge_factor)
value_fudge_factor = 7 if not SM80OrLater and dtype == torch.float16 else 1.0
grad_v_ref_atol, grad_v_ref_rtol = get_tolerances(value_ref.grad, value_ref_lp.grad, value_fudge_factor)
self.assertEqual(out, out_ref.to(out.dtype), atol=output_ref_atol, rtol=output_ref_rtol)
self.assertEqual(query.grad, query_ref.grad.to(query.grad.dtype),
atol=grad_q_ref_atol, rtol=grad_q_ref_rtol)
self.assertEqual(key.grad, key_ref.grad.to(key.grad.dtype),
atol=grad_k_ref_atol, rtol=grad_k_ref_rtol)
self.assertEqual(value.grad, value_ref.grad.to(value.grad.dtype),
atol=grad_v_ref_atol, rtol=grad_v_ref_rtol)
@unittest.skipIf(not PLATFORM_SUPPORTS_FUSED_ATTENTION, "Fused SDPA was not built for this system")
@parametrize("fused_kernel", [SDPBackend.FLASH_ATTENTION, SDPBackend.EFFICIENT_ATTENTION] if
PLATFORM_SUPPORTS_FLASH_ATTENTION else [SDPBackend.EFFICIENT_ATTENTION])
def test_fused_kernels_seq_len_1_inputs(self, device, fused_kernel):
rand_nested_tensor = partial(rand_sdpa_tensor, type="nested", device=device, dtype=torch.float16)
batch, num_heads, head_dim = 32, 16, 64
seq_lens = torch.randint(low=1, high=32, size=(batch,))
# make sure some seq_lens are 1
num_ones = 10
indices = torch.randint(low=0, high=batch, size=(num_ones,))
seq_lens.scatter_(0, indices, 1)
shape = SdpaShape(batch, num_heads, seq_lens.tolist(), head_dim)
query = rand_nested_tensor(shape)
key = rand_nested_tensor(shape)
value = rand_nested_tensor(shape)
query = query.transpose(1, 2)
key = key.transpose(1, 2)
value = value.transpose(1, 2)
with sdp_kernel(**backend_map[fused_kernel]):
actual = torch.nn.functional.scaled_dot_product_attention(
query, key, value, attn_mask=None, dropout_p=0.0, is_causal=False)
with sdp_kernel(enable_flash=False, enable_math=True, enable_mem_efficient=False):
math_ref = torch.nn.functional.scaled_dot_product_attention(
query.contiguous().to(torch.float32),
key.contiguous().to(torch.float32),
value.contiguous().to(torch.float32),
attn_mask=None, dropout_p=0.0, is_causal=False)
self.assertEqual(actual.contiguous(), math_ref.contiguous().to(torch.float16), atol=1e-3, rtol=1e-2)
@unittest.skipIf(not PLATFORM_SUPPORTS_FUSED_ATTENTION, "Fused SDPA was not built for this system")
@parametrize("kernel", [SDPBackend.FLASH_ATTENTION, SDPBackend.EFFICIENT_ATTENTION] if
PLATFORM_SUPPORTS_FLASH_ATTENTION else [SDPBackend.EFFICIENT_ATTENTION])
@parametrize("expand_q_batch", [True, False])
@parametrize("expand_k_batch", [True, False])
@parametrize("expand_v_batch", [True, False])
@parametrize("expand_q_num_heads", [True, False])
@parametrize("expand_k_num_heads", [True, False])
@parametrize("expand_v_num_heads", [True, False])
def test_fused_kernels_nested_broadcasting(
self,
device,
kernel,
expand_q_batch,
expand_k_batch,
expand_v_batch,
expand_q_num_heads,
expand_k_num_heads,
expand_v_num_heads,
):
is_efficient = kernel == SDPBackend.EFFICIENT_ATTENTION
dtype = torch.float32 if is_efficient else torch.float16
rand_nested_tensor = partial(rand_sdpa_tensor, type="nested", device=device, dtype=dtype)
batch, num_heads, head_dim = 32, 8, 64
head_dim_v = 32 if is_efficient else head_dim
seq_lens_q = (torch.randint(low=1, high=5, size=(1,)).item()
if expand_q_batch
else torch.randint(low=1, high=32, size=(batch,)).tolist())
seq_lens_kv = (torch.randint(low=1, high=5, size=(1,)).item()
if (expand_k_batch or expand_v_batch)
else torch.randint(low=1, high=32, size=(batch,)).tolist())
batch_q = 1 if expand_q_batch else batch
batch_k = 1 if expand_k_batch else batch
batch_v = 1 if expand_v_batch else batch
# handle case where all batch_sizes are 1
batch = max(batch_q, batch_k, batch_v)
num_heads_q = 1 if expand_q_num_heads else num_heads
num_heads_k = 1 if expand_k_num_heads else num_heads
num_heads_v = 1 if expand_v_num_heads else num_heads
# handle case where all num_heads are 1
num_heads = max(num_heads_q, num_heads_k, num_heads_v)
q_shape = SdpaShape(batch_q, num_heads_q, seq_lens_q, head_dim)
k_shape = SdpaShape(batch_k, num_heads_k, seq_lens_kv, head_dim)
v_shape = SdpaShape(batch_v, num_heads_v, seq_lens_kv, head_dim_v)
query = rand_nested_tensor(q_shape)
key = rand_nested_tensor(k_shape)
value = rand_nested_tensor(v_shape)
def _broadcast(t, batch_broadcasted, num_heads_broadcasted):
if batch_broadcasted and num_heads_broadcasted:
# (1, seq_len, 1, head_dim) -> (batch, seq_len, num_heads, head_dim)
result = torch.nested.nested_tensor(
[t[0].expand(-1, num_heads, t.size(-1)) for _ in range(batch)], dtype=torch.float32)
elif batch_broadcasted:
# (1, seq_len, num_heads, head_dim) -> (batch, seq_len, num_heads, head_dim)
result = torch.nested.nested_tensor([t[0] for _ in range(batch)], dtype=torch.float32)
elif num_heads_broadcasted:
# (batch, seq_len, 1, head_dim) -> (batch, seq_len, num_heads, head_dim)
result = torch.nested.nested_tensor([x.expand(-1, num_heads, t.size(-1))
for x in t.unbind()], dtype=torch.float32)
else:
result = t.to(torch.float32)
return result
query_expanded = _broadcast(query, expand_q_batch, expand_q_num_heads).transpose(1, 2)
key_expanded = _broadcast(key, expand_k_batch, expand_k_num_heads).transpose(1, 2)
value_expanded = _broadcast(value, expand_v_batch, expand_v_num_heads).transpose(1, 2)
query = query.transpose(1, 2)
key = key.transpose(1, 2)
value = value.transpose(1, 2)
with sdp_kernel(**backend_map[kernel]):
actual = torch.nn.functional.scaled_dot_product_attention(
query, key, value, attn_mask=None, dropout_p=0.0, is_causal=False)
with sdp_kernel(enable_flash=False, enable_math=True, enable_mem_efficient=False):
math_ref = torch.nn.functional.scaled_dot_product_attention(
query_expanded.contiguous(), key_expanded.contiguous(), value_expanded.contiguous(),
attn_mask=None, dropout_p=0.0, is_causal=False)
self.assertEqual(actual.contiguous(), math_ref.contiguous().to(dtype), atol=1e-3, rtol=1e-2)
@unittest.skipIf(not PLATFORM_SUPPORTS_MEM_EFF_ATTENTION, "Fused SDPA was not built for this system")
def test_fused_kernels_nested_broadcasting_query_dense(self, device):
rand_nested_tensor = partial(rand_sdpa_tensor, type="nested", device=device, dtype=torch.float32)
batch, num_heads, head_dim, head_dim_v = 32, 16, 64, 96
seq_lens = torch.randint(low=1, high=32, size=(batch,)).tolist()
q_shape = (1, 1, num_heads, head_dim)
k_shape = SdpaShape(batch, num_heads, seq_lens, head_dim)
v_shape = SdpaShape(batch, 1, seq_lens, head_dim_v)
# create a dense query
query = torch.randn(q_shape, device=device, dtype=torch.float32)
key = rand_nested_tensor(k_shape)
value = rand_nested_tensor(v_shape)
# (1, 1, num_heads, head_dim) -> (batch, 1, num_heads, head_dim)
query_expanded = torch.nested.nested_tensor([query.squeeze(0) for _ in range(batch)]).transpose(1, 2)
# (batch, seq_lens, 1, head_dim) -> (batch, seq_lens, num_heads, head_dim)
value_expanded = torch.nested.nested_tensor(
[t.expand(-1, num_heads, head_dim_v) for t in value.unbind()]).transpose(1, 2)
query = query.transpose(1, 2)
key = key.transpose(1, 2)
value = value.transpose(1, 2)
with sdp_kernel(enable_flash=False, enable_math=False, enable_mem_efficient=True):
actual = torch.nn.functional.scaled_dot_product_attention(
query, key, value, attn_mask=None, dropout_p=0.0, is_causal=False)
with sdp_kernel(enable_flash=False, enable_math=True, enable_mem_efficient=False):
math_ref = torch.nn.functional.scaled_dot_product_attention(
query_expanded.contiguous(), key.contiguous(), value_expanded.contiguous(),
attn_mask=None, dropout_p=0.0, is_causal=False)
self.assertEqual(actual.contiguous(), math_ref.contiguous(), atol=1e-3, rtol=1e-2)
@onlyCUDA
@unittest.skipIf(not PLATFORM_SUPPORTS_FLASH_ATTENTION, "Does not support SDPA or pre-SM80 hardware")
@parametrize("batch_size", [8, 32])
@parametrize("max_seq_len_q", [32, 256])
@parametrize("max_seq_len_kv", [32, 256])
@parametrize("head_dim", [8, 64])
@parametrize("dropout_p", [0.0, 0.1])
@parametrize("dtype", [torch.float16])
@parametrize("scale", [None, "l1"])
@parametrize("is_causal", [True, False])
def test_flash_attention_vs_math_ref_grads_nestedtensor(self, device, batch_size: int, max_seq_len_q: int, max_seq_len_kv: int,
head_dim: int, dropout_p: float, dtype: torch.dtype,
scale: str, is_causal: bool):
if is_causal:
# TODO we should support this
self.assertRaisesRegex(RuntimeError, "Nested tensors for query / key are not supported when is_causal=True")
return
scale = scale if scale is None else (1 / head_dim)
n_heads = 4
seq_lens_q = torch.randint(low=1, high=max_seq_len_q, size=(batch_size,))
# Set one entry to max length
seq_lens_q[torch.randint(0, batch_size, size=(1,))] = max_seq_len_q
seq_lens_kv = torch.randint(low=1, high=max_seq_len_kv, size=(batch_size,))
seq_lens_kv[torch.randint(0, batch_size, size=(1,))] = max_seq_len_kv
def rand_nt(sequence_list, num_heads, head_dim):
tensors = [torch.rand((num_heads, seq_len, head_dim)) for seq_len in sequence_list]
return torch.nested.nested_tensor(tensors, requires_grad=True, device=device, dtype=dtype)
query = rand_nt(seq_lens_q, n_heads, head_dim)
key = rand_nt(seq_lens_kv, n_heads, head_dim)
value = rand_nt(seq_lens_kv, n_heads, head_dim)
# Run the math kernel on low precision references
query_ref_lp = query.clone().detach().requires_grad_(True)
key_ref_lp = key.clone().detach().requires_grad_(True)
value_ref_lp = value.clone().detach().requires_grad_(True)
query_ref = query.clone().detach().to(torch.float32).requires_grad_(True)
key_ref = key.clone().detach().to(torch.float32).requires_grad_(True)
value_ref = value.clone().detach().to(torch.float32).requires_grad_(True)
is_dropout = dropout_p > 0.0
if not is_dropout:
with sdp_kernel(enable_math=False, enable_flash=True, enable_mem_efficient=False):
out = F.scaled_dot_product_attention(query, key, value, dropout_p=dropout_p, is_causal=is_causal, scale=scale)
with sdp_kernel(enable_math=True, enable_flash=False, enable_mem_efficient=False):
# High Precision Math Reference
out_ref = F.scaled_dot_product_attention(
query_ref, key_ref, value_ref, is_causal=is_causal, scale=scale)
# Low Precision Math Reference
out_lp_ref = F.scaled_dot_product_attention(
query_ref_lp, key_ref_lp, value_ref_lp, is_causal=is_causal, scale=scale)
else:
# Create real output
output_tuple = torch.ops.aten._scaled_dot_product_flash_attention(
query, key, value, dropout_p=dropout_p, is_causal=is_causal,
scale=scale, return_debug_mask=is_dropout)
out = output_tuple[0]
dbug_mask = output_tuple[-1]
query_padding_mask = torch.arange(max_seq_len_q).unsqueeze(0).expand(
batch_size, max_seq_len_q
) < seq_lens_q.unsqueeze(-1)
query_padding_mask = query_padding_mask.to("cuda")
key_padding_mask = torch.arange(max_seq_len_kv).unsqueeze(0).expand(
batch_size, max_seq_len_kv
) < seq_lens_kv.unsqueeze(-1)
key_padding_mask = key_padding_mask.to("cuda")
softmax_mask = self.convert_flash_attn_S_to_softmax(
dbug_mask, query_padding_mask, key_padding_mask, head_dim=head_dim, causal=is_causal)
dropout_mask = softmax_mask >= 0
nt_stack = []
for tensor_component in range(batch_size):
batch_stack = []
for head in range(n_heads):
batch_stack.append(dropout_mask[tensor_component, head,
0:seq_lens_q[tensor_component],
0:seq_lens_kv[tensor_component]].unsqueeze(0))
nt_stack.append(torch.cat(batch_stack))
nested_dropout_mask = torch.nested.nested_tensor(nt_stack)
# High Precision Math Reference
out_ref = torch.ops.aten._scaled_dot_product_attention_math(
query_ref, key_ref, value_ref, dropout_p=dropout_p,
is_causal=is_causal, scale=scale, dropout_mask=nested_dropout_mask)[0]
# Low Precision Math Reference
out_lp_ref = torch.ops.aten._scaled_dot_product_attention_math(
query_ref_lp, key_ref_lp, value_ref_lp, dropout_p=dropout_p, is_causal=is_causal, scale=scale,
dropout_mask=nested_dropout_mask)[0]
upstream_grad = out.detach().clone().contiguous()
out.backward(upstream_grad)
out_ref.backward(upstream_grad.to(out_ref.dtype))
out_lp_ref.backward(upstream_grad.to(out_lp_ref.dtype))
# See [Note] Fused Tolerances above
output_ref_atol, output_ref_rtol = calculate_nt_tolerances(out_ref, out_lp_ref, out.dtype)
grad_q_ref_atol, grad_q_ref_rtol = calculate_nt_tolerances(query_ref.grad, query_ref_lp.grad,
query.grad.dtype, fudge_factor=4)
grad_k_ref_atol, grad_k_ref_rtol = calculate_nt_tolerances(key_ref.grad, key_ref_lp.grad, key.grad.dtype)
grad_v_ref_atol, grad_v_ref_rtol = calculate_nt_tolerances(value_ref.grad, value_ref_lp.grad, value.grad.dtype)
self.assertEqual(out, out_ref.to(out.dtype), atol=output_ref_atol, rtol=output_ref_rtol)
self.assertEqual(query.grad, query_ref.grad.to(query.grad.dtype),
atol=grad_q_ref_atol, rtol=grad_q_ref_rtol)
self.assertEqual(key.grad.contiguous(), key_ref.grad.contiguous().to(key.grad.dtype),
atol=grad_k_ref_atol, rtol=grad_k_ref_rtol)
self.assertEqual(value.grad, value_ref.grad.to(value.grad.dtype),
atol=grad_v_ref_atol, rtol=grad_v_ref_rtol)
class TestAttnMasks(NNTestCase):
def run_test(self, device, compile, make_q, make_kv, attn_bias=None,
forw_tolerances: Optional[Tolerances] = None, grad_tolerances: Optional[Tolerances] = None):
if compile:
torch._dynamo.reset()
query, key, value = make_q(), make_kv(), make_kv()
query_prototype, key_prototype, value_prototype = query_key_value_clones(query, key, value)
realized = attn_bias._materialize(device) if attn_bias is not None else None
pytorch_output = scaled_dot_product_attention(
query, key, value, attn_mask=realized, dropout_p=0.0, is_causal=False
)
sdpa_op = (
torch.compile(scaled_dot_product_attention, fullgraph=True)
if compile
else scaled_dot_product_attention
)
sdpa_output = sdpa_op(
query_prototype,
key_prototype,
value_prototype,
attn_mask=attn_bias,
dropout_p=0.0,
is_causal=False,
scale=None,
)
dOut = torch.randn_like(pytorch_output)
pytorch_output.backward(dOut)
sdpa_output.backward(dOut)
# Use default assert_close tolerances for dtypes
if forw_tolerances is None:
forw_tolerances = Tolerances(atol=None, rtol=None)
if grad_tolerances is None:
grad_tolerances = Tolerances(atol=None, rtol=None)
torch.testing.assert_close(pytorch_output, sdpa_output, rtol=forw_tolerances.rtol, atol=forw_tolerances.atol)
torch.testing.assert_close(query.grad, query_prototype.grad, rtol=grad_tolerances.rtol, atol=grad_tolerances.atol)
torch.testing.assert_close(key.grad, key_prototype.grad, rtol=grad_tolerances.rtol, atol=grad_tolerances.atol)
torch.testing.assert_close(value.grad, value_prototype.grad, rtol=grad_tolerances.rtol, atol=grad_tolerances.atol)
@parametrize("causal_variant", [CausalVariant.UPPER_LEFT, CausalVariant.LOWER_RIGHT])
@parametrize(
"shape",
[(16, 16, 128, 128, 16), (16, 16, 128, 256, 32), (16, 16, 256, 128, 32), (1, 1, 23, 56, 15)],
)
def test_causal_variants(self, device, causal_variant: CausalVariant, shape: List[Tuple[int]]):
make_tensor = partial(
torch.rand, device=device, dtype=torch.float16, requires_grad=True
)
bsz, num_heads, seq_len_q, seq_len_kv, head_dim = shape
make_q_tensor = partial(make_tensor, SdpaShape(bsz, num_heads, seq_len_q, head_dim))
make_kv_tensor = partial(make_tensor, SdpaShape(bsz, num_heads, seq_len_kv, head_dim))
if causal_variant == CausalVariant.LOWER_RIGHT and seq_len_q > seq_len_kv:
self.skipTest(
"Lower right causal mask will produce NaNs in the output when seq_len_q > seq_len_kv!"
)
forw_tol = Tolerances(1e-3, 1e-3)
grad_tol = Tolerances(5e-3, 5e-3)
if causal_variant == CausalVariant.UPPER_LEFT:
attn_bias = causal_upper_left(seq_len_q, seq_len_kv)
else:
attn_bias = causal_lower_right(seq_len_q, seq_len_kv)
self.run_test(device, False, make_q_tensor, make_kv_tensor, attn_bias, forw_tol, grad_tol)
@parametrize("causal_variant", [CausalVariant.UPPER_LEFT, CausalVariant.LOWER_RIGHT])
@parametrize(
"shape",
[(16, 16, 128, 128, 16), (16, 16, 128, 256, 32), (16, 16, 256, 128, 32), (1, 1, 23, 56, 15)],
)
@xfail
def test_causal_variants_compile(self, device, causal_variant: CausalVariant, shape: List[Tuple[int]]):
make_tensor = partial(
torch.rand, device=device, dtype=torch.float16, requires_grad=True
)
bsz, num_heads, seq_len_q, seq_len_kv, head_dim = shape
make_q_tensor = partial(make_tensor, SdpaShape(bsz, num_heads, seq_len_q, head_dim))
make_kv_tensor = partial(make_tensor, SdpaShape(bsz, num_heads, seq_len_kv, head_dim))
if causal_variant == CausalVariant.LOWER_RIGHT and seq_len_q > seq_len_kv:
self.skipTest(
"Lower right causal mask will produce NaNs in the output when seq_len_q > seq_len_kv!"
)
forw_tol = Tolerances(1e-3, 1e-3)
grad_tol = Tolerances(5e-3, 5e-3)
if causal_variant == CausalVariant.UPPER_LEFT:
attn_bias = causal_upper_left(seq_len_q, seq_len_kv)
else:
attn_bias = causal_lower_right(seq_len_q, seq_len_kv)
self.run_test(device, True, make_q_tensor, make_kv_tensor, attn_bias, forw_tol, grad_tol)
@parametrize("shape", [(16, 16, 128, 128, 16), (16, 16, 128, 256, 32), (16, 16, 256, 128, 32), (1, 1, 23, 56, 15)])
def test_is_causal_equals_upper_left(self, device, shape: List[Tuple[int]]):
make_tensor = partial(
torch.rand, device=device, dtype=torch.float16, requires_grad=True
)
bsz, num_heads, seq_len_q, seq_len_kv, head_dim = shape
make_q_tensor = partial(make_tensor, SdpaShape(bsz, num_heads, seq_len_q, head_dim))
make_kv_tensor = partial(make_tensor, SdpaShape(bsz, num_heads, seq_len_kv, head_dim))
forw_tol = Tolerances(1e-3, 1e-3)
grad_tol = Tolerances(5e-3, 5e-3)
query = make_q_tensor()
key = make_kv_tensor()
value = make_kv_tensor()
attn_bias = causal_upper_left(seq_len_q, seq_len_kv)
out_attn_bias = scaled_dot_product_attention(query, key, value, attn_mask=attn_bias, dropout_p=0.0)
out_is_causal = scaled_dot_product_attention(query, key, value, is_causal=True, dropout_p=0.0)
torch.testing.assert_close(out_attn_bias, out_is_causal, rtol=forw_tol.rtol, atol=forw_tol.atol)
def test_is_causal_and_mask_fails(self, device):
make_tensor = partial(
torch.rand, device=device, dtype=torch.float16, requires_grad=True
)
make_q_tensor = partial(make_tensor, SdpaShape(16, 16, 128, 16))
make_kv_tensor = partial(make_tensor, SdpaShape(16, 16, 128, 16))
query = make_q_tensor()
key = make_kv_tensor()
value = make_kv_tensor()
attn_bias = causal_upper_left(128, 128)
with self.assertRaisesRegex(ValueError, "CausalBias should not be used with causal=True"):
scaled_dot_product_attention(query, key, value, attn_mask=attn_bias, is_causal=True, dropout_p=0.0)
if NOTEST_CPU:
device_types = ("cuda", )
else:
device_types = ("cpu", "cuda")
instantiate_device_type_tests(TestTransformers, globals(), only_for=device_types)
instantiate_device_type_tests(TestSDPAFailureModes, globals(), only_for=device_types)
instantiate_device_type_tests(TestSDPA, globals(), only_for=device_types)
instantiate_device_type_tests(TestSDPACudaOnly, globals(), only_for=("cuda"))
instantiate_device_type_tests(TestAttnMasks, globals(), only_for=device_types)
if __name__ == '__main__':
run_tests()
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