File size: 9,332 Bytes
d90ba79 |
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 |
# Copyright (c) Meta Platforms, Inc. and affiliates.
# All rights reserved.
#
# This source code is licensed under the license found in the
# LICENSE file in the root directory of this source tree.
# References:
# https://github.com/facebookresearch/dino/blob/master/vision_transformer.py
# https://github.com/rwightman/pytorch-image-models/tree/master/timm/layers/patch_embed.py
import logging
from typing import Callable, List, Any, Tuple, Dict
import torch
from torch import nn, Tensor
from .attention import Attention, MemEffAttention
from .drop_path import DropPath
from .layer_scale import LayerScale
from .mlp import Mlp
logger = logging.getLogger("dinov2")
try:
from xformers.ops import fmha
from xformers.ops import scaled_index_add, index_select_cat
XFORMERS_AVAILABLE = True
except ImportError:
logger.warning("xFormers not available")
XFORMERS_AVAILABLE = False
class Block(nn.Module):
def __init__(
self,
dim: int,
num_heads: int,
mlp_ratio: float = 4.0,
qkv_bias: bool = False,
proj_bias: bool = True,
ffn_bias: bool = True,
drop: float = 0.0,
attn_drop: float = 0.0,
init_values=None,
drop_path: float = 0.0,
act_layer: Callable[..., nn.Module] = nn.GELU,
norm_layer: Callable[..., nn.Module] = nn.LayerNorm,
attn_class: Callable[..., nn.Module] = Attention,
ffn_layer: Callable[..., nn.Module] = Mlp,
) -> None:
super().__init__()
# print(f"biases: qkv: {qkv_bias}, proj: {proj_bias}, ffn: {ffn_bias}")
self.norm1 = norm_layer(dim)
self.attn = attn_class(
dim,
num_heads=num_heads,
qkv_bias=qkv_bias,
proj_bias=proj_bias,
attn_drop=attn_drop,
proj_drop=drop,
)
self.ls1 = LayerScale(dim, init_values=init_values) if init_values else nn.Identity()
self.drop_path1 = DropPath(drop_path) if drop_path > 0.0 else nn.Identity()
self.norm2 = norm_layer(dim)
mlp_hidden_dim = int(dim * mlp_ratio)
self.mlp = ffn_layer(
in_features=dim,
hidden_features=mlp_hidden_dim,
act_layer=act_layer,
drop=drop,
bias=ffn_bias,
)
self.ls2 = LayerScale(dim, init_values=init_values) if init_values else nn.Identity()
self.drop_path2 = DropPath(drop_path) if drop_path > 0.0 else nn.Identity()
self.sample_drop_ratio = drop_path
def forward(self, x: Tensor) -> Tensor:
def attn_residual_func(x: Tensor) -> Tensor:
return self.ls1(self.attn(self.norm1(x)))
def ffn_residual_func(x: Tensor) -> Tensor:
return self.ls2(self.mlp(self.norm2(x)))
if self.training and self.sample_drop_ratio > 0.1:
# the overhead is compensated only for a drop path rate larger than 0.1
x = drop_add_residual_stochastic_depth(
x,
residual_func=attn_residual_func,
sample_drop_ratio=self.sample_drop_ratio,
)
x = drop_add_residual_stochastic_depth(
x,
residual_func=ffn_residual_func,
sample_drop_ratio=self.sample_drop_ratio,
)
elif self.training and self.sample_drop_ratio > 0.0:
x = x + self.drop_path1(attn_residual_func(x))
x = x + self.drop_path1(ffn_residual_func(x)) # FIXME: drop_path2
else:
x = x + attn_residual_func(x)
x = x + ffn_residual_func(x)
return x
def drop_add_residual_stochastic_depth(
x: Tensor,
residual_func: Callable[[Tensor], Tensor],
sample_drop_ratio: float = 0.0,
) -> Tensor:
# 1) extract subset using permutation
b, n, d = x.shape
sample_subset_size = max(int(b * (1 - sample_drop_ratio)), 1)
brange = (torch.randperm(b, device=x.device))[:sample_subset_size]
x_subset = x[brange]
# 2) apply residual_func to get residual
residual = residual_func(x_subset)
x_flat = x.flatten(1)
residual = residual.flatten(1)
residual_scale_factor = b / sample_subset_size
# 3) add the residual
x_plus_residual = torch.index_add(x_flat, 0, brange, residual.to(dtype=x.dtype), alpha=residual_scale_factor)
return x_plus_residual.view_as(x)
def get_branges_scales(x, sample_drop_ratio=0.0):
b, n, d = x.shape
sample_subset_size = max(int(b * (1 - sample_drop_ratio)), 1)
brange = (torch.randperm(b, device=x.device))[:sample_subset_size]
residual_scale_factor = b / sample_subset_size
return brange, residual_scale_factor
def add_residual(x, brange, residual, residual_scale_factor, scaling_vector=None):
if scaling_vector is None:
x_flat = x.flatten(1)
residual = residual.flatten(1)
x_plus_residual = torch.index_add(x_flat, 0, brange, residual.to(dtype=x.dtype), alpha=residual_scale_factor)
else:
x_plus_residual = scaled_index_add(
x, brange, residual.to(dtype=x.dtype), scaling=scaling_vector, alpha=residual_scale_factor
)
return x_plus_residual
attn_bias_cache: Dict[Tuple, Any] = {}
def get_attn_bias_and_cat(x_list, branges=None):
"""
this will perform the index select, cat the tensors, and provide the attn_bias from cache
"""
batch_sizes = [b.shape[0] for b in branges] if branges is not None else [x.shape[0] for x in x_list]
all_shapes = tuple((b, x.shape[1]) for b, x in zip(batch_sizes, x_list))
if all_shapes not in attn_bias_cache.keys():
seqlens = []
for b, x in zip(batch_sizes, x_list):
for _ in range(b):
seqlens.append(x.shape[1])
attn_bias = fmha.BlockDiagonalMask.from_seqlens(seqlens)
attn_bias._batch_sizes = batch_sizes
attn_bias_cache[all_shapes] = attn_bias
if branges is not None:
cat_tensors = index_select_cat([x.flatten(1) for x in x_list], branges).view(1, -1, x_list[0].shape[-1])
else:
tensors_bs1 = tuple(x.reshape([1, -1, *x.shape[2:]]) for x in x_list)
cat_tensors = torch.cat(tensors_bs1, dim=1)
return attn_bias_cache[all_shapes], cat_tensors
def drop_add_residual_stochastic_depth_list(
x_list: List[Tensor],
residual_func: Callable[[Tensor, Any], Tensor],
sample_drop_ratio: float = 0.0,
scaling_vector=None,
) -> Tensor:
# 1) generate random set of indices for dropping samples in the batch
branges_scales = [get_branges_scales(x, sample_drop_ratio=sample_drop_ratio) for x in x_list]
branges = [s[0] for s in branges_scales]
residual_scale_factors = [s[1] for s in branges_scales]
# 2) get attention bias and index+concat the tensors
attn_bias, x_cat = get_attn_bias_and_cat(x_list, branges)
# 3) apply residual_func to get residual, and split the result
residual_list = attn_bias.split(residual_func(x_cat, attn_bias=attn_bias)) # type: ignore
outputs = []
for x, brange, residual, residual_scale_factor in zip(x_list, branges, residual_list, residual_scale_factors):
outputs.append(add_residual(x, brange, residual, residual_scale_factor, scaling_vector).view_as(x))
return outputs
class NestedTensorBlock(Block):
def forward_nested(self, x_list: List[Tensor]) -> List[Tensor]:
"""
x_list contains a list of tensors to nest together and run
"""
assert isinstance(self.attn, MemEffAttention)
if self.training and self.sample_drop_ratio > 0.0:
def attn_residual_func(x: Tensor, attn_bias=None) -> Tensor:
return self.attn(self.norm1(x), attn_bias=attn_bias)
def ffn_residual_func(x: Tensor, attn_bias=None) -> Tensor:
return self.mlp(self.norm2(x))
x_list = drop_add_residual_stochastic_depth_list(
x_list,
residual_func=attn_residual_func,
sample_drop_ratio=self.sample_drop_ratio,
scaling_vector=self.ls1.gamma if isinstance(self.ls1, LayerScale) else None,
)
x_list = drop_add_residual_stochastic_depth_list(
x_list,
residual_func=ffn_residual_func,
sample_drop_ratio=self.sample_drop_ratio,
scaling_vector=self.ls2.gamma if isinstance(self.ls1, LayerScale) else None,
)
return x_list
else:
def attn_residual_func(x: Tensor, attn_bias=None) -> Tensor:
return self.ls1(self.attn(self.norm1(x), attn_bias=attn_bias))
def ffn_residual_func(x: Tensor, attn_bias=None) -> Tensor:
return self.ls2(self.mlp(self.norm2(x)))
attn_bias, x = get_attn_bias_and_cat(x_list)
x = x + attn_residual_func(x, attn_bias=attn_bias)
x = x + ffn_residual_func(x)
return attn_bias.split(x)
def forward(self, x_or_x_list):
if isinstance(x_or_x_list, Tensor):
return super().forward(x_or_x_list)
elif isinstance(x_or_x_list, list):
assert XFORMERS_AVAILABLE, "Please install xFormers for nested tensors usage"
return self.forward_nested(x_or_x_list)
else:
raise AssertionError
|