-
Notifications
You must be signed in to change notification settings - Fork 7
/
vits.py
143 lines (120 loc) · 5.71 KB
/
vits.py
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
# Copyright (c) Facebook, Inc. and its 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.
import math
import torch
import torch.nn as nn
from functools import partial, reduce
from operator import mul
from timm.models.vision_transformer import VisionTransformer, _cfg
from timm.models.layers.helpers import to_2tuple
from timm.models.layers import PatchEmbed
__all__ = [
'vit_small',
'vit_base',
'vit_conv_small',
'vit_conv_base',
]
class VisionTransformerMoCo(VisionTransformer):
def __init__(self, stop_grad_conv1=False, **kwargs):
super().__init__(**kwargs)
# Use fixed 2D sin-cos position embedding
self.build_2d_sincos_position_embedding()
# weight initialization
for name, m in self.named_modules():
if isinstance(m, nn.Linear):
if 'qkv' in name:
# treat the weights of Q, K, V separately
val = math.sqrt(6. / float(m.weight.shape[0] // 3 + m.weight.shape[1]))
nn.init.uniform_(m.weight, -val, val)
else:
nn.init.xavier_uniform_(m.weight)
nn.init.zeros_(m.bias)
nn.init.normal_(self.cls_token, std=1e-6)
if isinstance(self.patch_embed, PatchEmbed):
# xavier_uniform initialization
val = math.sqrt(6. / float(3 * reduce(mul, self.patch_embed.patch_size, 1) + self.embed_dim))
nn.init.uniform_(self.patch_embed.proj.weight, -val, val)
nn.init.zeros_(self.patch_embed.proj.bias)
if stop_grad_conv1:
self.patch_embed.proj.weight.requires_grad = False
self.patch_embed.proj.bias.requires_grad = False
def build_2d_sincos_position_embedding(self, temperature=10000.):
h, w = self.patch_embed.grid_size
grid_w = torch.arange(w, dtype=torch.float32)
grid_h = torch.arange(h, dtype=torch.float32)
grid_w, grid_h = torch.meshgrid(grid_w, grid_h)
assert self.embed_dim % 4 == 0, 'Embed dimension must be divisible by 4 for 2D sin-cos position embedding'
pos_dim = self.embed_dim // 4
omega = torch.arange(pos_dim, dtype=torch.float32) / pos_dim
omega = 1. / (temperature**omega)
out_w = torch.einsum('m,d->md', [grid_w.flatten(), omega])
out_h = torch.einsum('m,d->md', [grid_h.flatten(), omega])
pos_emb = torch.cat([torch.sin(out_w), torch.cos(out_w), torch.sin(out_h), torch.cos(out_h)], dim=1)[None, :, :]
assert self.num_tokens == 1, 'Assuming one and only one token, [cls]'
pe_token = torch.zeros([1, 1, self.embed_dim], dtype=torch.float32)
self.pos_embed = nn.Parameter(torch.cat([pe_token, pos_emb], dim=1))
self.pos_embed.requires_grad = False
class ConvStem(nn.Module):
"""
ConvStem, from Early Convolutions Help Transformers See Better, Tete et al. https://arxiv.org/abs/2106.14881
"""
def __init__(self, img_size=224, patch_size=16, in_chans=3, embed_dim=768, norm_layer=None, flatten=True):
super().__init__()
assert patch_size == 16, 'ConvStem only supports patch size of 16'
assert embed_dim % 8 == 0, 'Embed dimension must be divisible by 8 for ConvStem'
img_size = to_2tuple(img_size)
patch_size = to_2tuple(patch_size)
self.img_size = img_size
self.patch_size = patch_size
self.grid_size = (img_size[0] // patch_size[0], img_size[1] // patch_size[1])
self.num_patches = self.grid_size[0] * self.grid_size[1]
self.flatten = flatten
# build stem, similar to the design in https://arxiv.org/abs/2106.14881
stem = []
input_dim, output_dim = 3, embed_dim // 8
for l in range(4):
stem.append(nn.Conv2d(input_dim, output_dim, kernel_size=3, stride=2, padding=1, bias=False))
stem.append(nn.BatchNorm2d(output_dim))
stem.append(nn.ReLU(inplace=True))
input_dim = output_dim
output_dim *= 2
stem.append(nn.Conv2d(input_dim, embed_dim, kernel_size=1))
self.proj = nn.Sequential(*stem)
self.norm = norm_layer(embed_dim) if norm_layer else nn.Identity()
def forward(self, x):
B, C, H, W = x.shape
assert H == self.img_size[0] and W == self.img_size[1], \
f"Input image size ({H}*{W}) doesn't match model ({self.img_size[0]}*{self.img_size[1]})."
x = self.proj(x)
if self.flatten:
x = x.flatten(2).transpose(1, 2) # BCHW -> BNC
x = self.norm(x)
return x
def vit_small(**kwargs):
model = VisionTransformerMoCo(
patch_size=16, embed_dim=384, depth=12, num_heads=12, mlp_ratio=4, qkv_bias=True,
norm_layer=partial(nn.LayerNorm, eps=1e-6), **kwargs)
model.default_cfg = _cfg()
return model
def vit_base(**kwargs):
model = VisionTransformerMoCo(
patch_size=16, embed_dim=768, depth=12, num_heads=12, mlp_ratio=4, qkv_bias=True,
norm_layer=partial(nn.LayerNorm, eps=1e-6), **kwargs)
model.default_cfg = _cfg()
return model
def vit_conv_small(**kwargs):
# minus one ViT block
model = VisionTransformerMoCo(
patch_size=16, embed_dim=384, depth=11, num_heads=12, mlp_ratio=4, qkv_bias=True,
norm_layer=partial(nn.LayerNorm, eps=1e-6), embed_layer=ConvStem, **kwargs)
model.default_cfg = _cfg()
return model
def vit_conv_base(**kwargs):
# minus one ViT block
model = VisionTransformerMoCo(
patch_size=16, embed_dim=768, depth=11, num_heads=12, mlp_ratio=4, qkv_bias=True,
norm_layer=partial(nn.LayerNorm, eps=1e-6), embed_layer=ConvStem, **kwargs)
model.default_cfg = _cfg()
return model