File size: 8,712 Bytes
3d2142b
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
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
# ------------------------------------------------------------------------
# Copyright (c) 2023-present, BAAI. All Rights Reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#    http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
# ------------------------------------------------------------------------
"""Image decoder."""

try:
    from flash_attn import flash_attn_func
except ImportError:
    flash_attn_func = None

import torch
from torch import nn


class TransposedLayerNorm(nn.LayerNorm):
    """LayerNorm with pre-transposed spatial axes."""

    def forward(self, input):
        return super().forward(input.permute(0, 2, 3, 1)).permute(0, 3, 1, 2)


class MLP(nn.Module):
    """Two layers MLP."""

    def __init__(self, dim, mlp_dim, activation_type="ReLU"):
        super(MLP, self).__init__()
        self.fc1 = nn.Linear(dim, mlp_dim)
        self.fc2 = nn.Linear(mlp_dim, dim)
        self.activation = getattr(nn, activation_type)()
        self.activation.inplace = True

    def forward(self, x):
        return self.fc2(self.activation(self.fc1(x)))


class Attention(nn.Module):
    """Multi-head attention."""

    def __init__(self, dim=256, num_heads=8, attn_ratio=1):
        super(Attention, self).__init__()
        qkv_dim = int(dim * attn_ratio)
        self.num_heads = num_heads
        self.head_dim = qkv_dim // num_heads
        self.q_proj = nn.Linear(dim, qkv_dim)
        self.k_proj = nn.Linear(dim, qkv_dim)
        self.v_proj = nn.Linear(dim, qkv_dim)
        self.proj = nn.Linear(qkv_dim, dim)
        self.scale = self.head_dim**-0.5

    def forward(self, q, k, v):
        q = self.q_proj(q).view((-1, q.size(1), self.num_heads, self.head_dim))
        k = self.k_proj(k).view((-1, k.size(1), self.num_heads, self.head_dim))
        v = self.v_proj(v).view((-1, v.size(1), self.num_heads, self.head_dim))
        o = flash_attn_func(q, k, v, softmax_scale=self.scale)
        return self.proj(o.flatten(2))


class Block(nn.Module):
    """Transformer block."""

    def __init__(
        self,
        dim=256,
        num_heads=8,
        attn_ratio=0.5,
        mlp_dim=2048,
        dropout=0.1,
        activation_type="ReLU",
        skip_first_query_pos=False,
    ):
        super(Block, self).__init__()
        self.self_attn = Attention(dim, num_heads)
        self.norm1 = nn.LayerNorm(dim)
        self.cross_attn_token_to_image = Attention(dim, num_heads, attn_ratio)
        self.norm2 = nn.LayerNorm(dim)
        self.mlp = MLP(dim, mlp_dim, activation_type)
        self.norm3 = nn.LayerNorm(dim)
        self.cross_attn_image_to_token = Attention(dim, num_heads, attn_ratio)
        self.norm4 = nn.LayerNorm(dim)
        self.dropout = nn.Dropout(dropout, inplace=True)
        self.skip_first_query_pos = skip_first_query_pos

    def forward(self, query, key, query_pos, key_pos):
        if self.skip_first_query_pos:
            query = self.norm1(self.self_attn(query, query, query))
        else:
            q = query + query_pos
            query = self.norm1(self.dropout(self.self_attn(q, q, query)).add_(query))
        q, k = query + query_pos, key + key_pos
        query = self.norm2(self.dropout(self.cross_attn_token_to_image(q, k, key)).add_(query))
        query = self.norm3(self.dropout(self.mlp(query)).add_(query))
        q = query + query_pos
        key = self.norm4(self.cross_attn_image_to_token(k, q, query).add_(key))
        return query, key


class Transformer(nn.Module):
    """Two-way transformer decoder."""

    def __init__(
        self,
        embed_dim=256,
        num_heads=8,
        attn_ratio=0.5,
        mlp_dim=2048,
        dropout=0.1,
        activation_type="ReLU",
        depth=2,
    ):
        super(Transformer, self).__init__()
        self.blocks = nn.ModuleList(
            Block(
                embed_dim,
                num_heads,
                attn_ratio=attn_ratio,
                mlp_dim=mlp_dim,
                dropout=dropout,
                activation_type=activation_type,
                skip_first_query_pos=i == 0,
            )
            for i in range(depth)
        )
        self.final_attn_token_to_image = Attention(embed_dim, num_heads, attn_ratio)
        self.norm = nn.LayerNorm(embed_dim)
        self.dropout = nn.Dropout(dropout, inplace=True)

    def forward(self, query, key, query_pos, key_pos):
        for blk in self.blocks:
            query, key = blk(query, key, query_pos, key_pos)
        q, k = query + query_pos, key + key_pos
        query = self.dropout(self.final_attn_token_to_image(q, k, key)).add_(query)
        query = self.norm(query)
        return query, key


class Predictor(nn.Module):
    """MLP predictor."""

    def __init__(self, in_dim, out_dim, mlp_dim=None, depth=3):
        super(Predictor, self).__init__()
        mlp_dims = [mlp_dim or in_dim] * (depth - 1)
        in_dims, out_dims = [in_dim] + mlp_dims, mlp_dims + [out_dim]
        self.layers = nn.ModuleList(nn.Linear(n, k) for n, k in zip(in_dims, out_dims))

    def forward(self, x):
        for fc in self.layers[:-1]:
            x = nn.functional.relu(fc(x), inplace=True)
        return self.layers[-1](x)


class ImageDecoder(nn.Module):
    """Module to decode region tokens and masks."""

    def __init__(self, depth, embed_dim, num_heads, num_mask_tokens=4, sem_embed_dim=1024):
        super(ImageDecoder, self).__init__()
        self.embed_dim = embed_dim
        self.num_mask_tokens = num_mask_tokens
        self.transformer = Transformer(embed_dim, num_heads=num_heads, depth=depth)
        self.iou_token = nn.Embedding(1, embed_dim)
        self.sem_tokens = nn.Embedding(self.num_mask_tokens, embed_dim)
        self.mask_tokens = nn.Embedding(self.num_mask_tokens, embed_dim)
        self.output_conv = nn.Sequential(
            nn.ConvTranspose2d(embed_dim, embed_dim // 4, 2, 2),
            TransposedLayerNorm(embed_dim // 4),
            nn.GELU(),
            nn.ConvTranspose2d(embed_dim // 4, embed_dim // 8, 2, 2),
            nn.GELU(),
        )
        self.mask_pred = nn.ModuleList(
            Predictor(embed_dim, embed_dim // 8) for _ in range(num_mask_tokens)
        )
        self.iou_pred = Predictor(embed_dim, self.num_mask_tokens)
        self.sem_pred = Predictor(embed_dim, sem_embed_dim, 1024)

    def get_outputs(self, inputs):
        img_embeds = inputs["img_embeds"]
        sparse_embeds = inputs["sparse_embeds"]
        ims_per_batch = img_embeds.size(0)
        prompts_per_batch = sparse_embeds.size(0)
        img_embed_size = img_embeds.shape[2:-1]
        # Prepare query.
        tokens = [self.sem_tokens.weight, self.iou_token.weight, self.mask_tokens.weight]
        query = torch.cat(tokens).unsqueeze_(0).expand(prompts_per_batch, -1, -1)
        query = torch.cat((query, sparse_embeds), dim=1)
        num_tokens = query.shape[1] - sparse_embeds.shape[1]
        # Prepare key.
        key = img_embeds.expand(-1, prompts_per_batch // ims_per_batch, -1, -1, -1)
        key = key.flatten(0, 1).flatten(1, 2)
        # Decode.
        query, key = self.transformer(query, key, query, inputs["img_pos"])
        # Upscale key.
        key = key.transpose(1, 2).view((-1, self.embed_dim) + img_embed_size)
        output_masks = self.output_conv(key).flatten(2)
        # Unpack query.
        tokens = query[:, :num_tokens].unbind(dim=1)
        iou_tokens = tokens[num_tokens - self.num_mask_tokens - 1]
        mask_tokens = tokens[num_tokens - self.num_mask_tokens :]
        sem_tokens = tokens[: self.num_mask_tokens]
        # Predict.
        mask_pred = [f(x) for f, x in zip(self.mask_pred, mask_tokens)]
        mask_pred = torch.stack(mask_pred, dim=1) @ output_masks
        mask_pred_size = list(4 * embed_size for embed_size in img_embed_size)
        mask_pred = mask_pred.view([-1, self.num_mask_tokens] + mask_pred_size)
        outputs = {"iou_pred": self.iou_pred(iou_tokens), "mask_pred": mask_pred}
        outputs["sem_tokens"] = torch.stack(sem_tokens, dim=1)
        outputs["sem_embeds"] = self.sem_pred(outputs["sem_tokens"])
        return outputs

    def forward(self, inputs):
        outputs = self.get_outputs(inputs)
        outputs["iou_pred"] = outputs["iou_pred"].float()
        return outputs