File size: 18,806 Bytes
cc0dd3c
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
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
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
# Copyright (c) OpenMMLab. All rights reserved.
from typing import Optional, Tuple

import torch
import torch.nn as nn
from mmcv.cnn import build_conv_layer
from mmengine.model import BaseModule

from mmpretrain.registry import MODELS
from .base_backbone import BaseBackbone


class BasicConv2d(BaseModule):
    """A basic convolution block including convolution, batch norm and ReLU.

    Args:
        in_channels (int): The number of input channels.
        out_channels (int): The number of output channels.
        conv_cfg (dict, optional): The config of convolution layer.
            Defaults to None, which means to use ``nn.Conv2d``.
        init_cfg (dict, optional): The config of initialization.
            Defaults to None.
        **kwargs: Other keyword arguments of the convolution layer.
    """

    def __init__(self,
                 in_channels: int,
                 out_channels: int,
                 conv_cfg: Optional[dict] = None,
                 init_cfg: Optional[dict] = None,
                 **kwargs) -> None:
        super().__init__(init_cfg=init_cfg)
        self.conv = build_conv_layer(
            conv_cfg, in_channels, out_channels, bias=False, **kwargs)
        self.bn = nn.BatchNorm2d(out_channels, eps=0.001)
        self.relu = nn.ReLU(inplace=True)

    def forward(self, x: torch.Tensor) -> torch.Tensor:
        """Forward function."""
        x = self.conv(x)
        x = self.bn(x)
        return self.relu(x)


class InceptionA(BaseModule):
    """Type-A Inception block.

    Args:
        in_channels (int): The number of input channels.
        pool_features (int): The number of channels in pooling branch.
        conv_cfg (dict, optional): The convolution layer config in the
            :class:`BasicConv2d` block. Defaults to None.
        init_cfg (dict, optional): The config of initialization.
            Defaults to None.
    """

    def __init__(self,
                 in_channels: int,
                 pool_features: int,
                 conv_cfg: Optional[dict] = None,
                 init_cfg: Optional[dict] = None):
        super().__init__(init_cfg=init_cfg)
        self.branch1x1 = BasicConv2d(
            in_channels, 64, kernel_size=1, conv_cfg=conv_cfg)

        self.branch5x5_1 = BasicConv2d(
            in_channels, 48, kernel_size=1, conv_cfg=conv_cfg)
        self.branch5x5_2 = BasicConv2d(
            48, 64, kernel_size=5, padding=2, conv_cfg=conv_cfg)

        self.branch3x3dbl_1 = BasicConv2d(
            in_channels, 64, kernel_size=1, conv_cfg=conv_cfg)
        self.branch3x3dbl_2 = BasicConv2d(
            64, 96, kernel_size=3, padding=1, conv_cfg=conv_cfg)
        self.branch3x3dbl_3 = BasicConv2d(
            96, 96, kernel_size=3, padding=1, conv_cfg=conv_cfg)

        self.branch_pool_downsample = nn.AvgPool2d(
            kernel_size=3, stride=1, padding=1)
        self.branch_pool = BasicConv2d(
            in_channels, pool_features, kernel_size=1, conv_cfg=conv_cfg)

    def forward(self, x: torch.Tensor) -> torch.Tensor:
        """Forward function."""
        branch1x1 = self.branch1x1(x)

        branch5x5 = self.branch5x5_1(x)
        branch5x5 = self.branch5x5_2(branch5x5)

        branch3x3dbl = self.branch3x3dbl_1(x)
        branch3x3dbl = self.branch3x3dbl_2(branch3x3dbl)
        branch3x3dbl = self.branch3x3dbl_3(branch3x3dbl)

        branch_pool = self.branch_pool_downsample(x)
        branch_pool = self.branch_pool(branch_pool)

        outputs = [branch1x1, branch5x5, branch3x3dbl, branch_pool]
        return torch.cat(outputs, 1)


class InceptionB(BaseModule):
    """Type-B Inception block.

    Args:
        in_channels (int): The number of input channels.
        conv_cfg (dict, optional): The convolution layer config in the
            :class:`BasicConv2d` block. Defaults to None.
        init_cfg (dict, optional): The config of initialization.
            Defaults to None.
    """

    def __init__(self,
                 in_channels: int,
                 conv_cfg: Optional[dict] = None,
                 init_cfg: Optional[dict] = None):
        super().__init__(init_cfg=init_cfg)
        self.branch3x3 = BasicConv2d(
            in_channels, 384, kernel_size=3, stride=2, conv_cfg=conv_cfg)

        self.branch3x3dbl_1 = BasicConv2d(
            in_channels, 64, kernel_size=1, conv_cfg=conv_cfg)
        self.branch3x3dbl_2 = BasicConv2d(
            64, 96, kernel_size=3, padding=1, conv_cfg=conv_cfg)
        self.branch3x3dbl_3 = BasicConv2d(
            96, 96, kernel_size=3, stride=2, conv_cfg=conv_cfg)

        self.branch_pool = nn.MaxPool2d(kernel_size=3, stride=2)

    def forward(self, x: torch.Tensor) -> torch.Tensor:
        """Forward function."""
        branch3x3 = self.branch3x3(x)

        branch3x3dbl = self.branch3x3dbl_1(x)
        branch3x3dbl = self.branch3x3dbl_2(branch3x3dbl)
        branch3x3dbl = self.branch3x3dbl_3(branch3x3dbl)

        branch_pool = self.branch_pool(x)

        outputs = [branch3x3, branch3x3dbl, branch_pool]
        return torch.cat(outputs, 1)


class InceptionC(BaseModule):
    """Type-C Inception block.

    Args:
        in_channels (int): The number of input channels.
        channels_7x7 (int): The number of channels in 7x7 convolution branch.
        conv_cfg (dict, optional): The convolution layer config in the
            :class:`BasicConv2d` block. Defaults to None.
        init_cfg (dict, optional): The config of initialization.
            Defaults to None.
    """

    def __init__(self,
                 in_channels: int,
                 channels_7x7: int,
                 conv_cfg: Optional[dict] = None,
                 init_cfg=None):
        super().__init__(init_cfg=init_cfg)
        self.branch1x1 = BasicConv2d(
            in_channels, 192, kernel_size=1, conv_cfg=conv_cfg)

        c7 = channels_7x7
        self.branch7x7_1 = BasicConv2d(
            in_channels, c7, kernel_size=1, conv_cfg=conv_cfg)
        self.branch7x7_2 = BasicConv2d(
            c7, c7, kernel_size=(1, 7), padding=(0, 3), conv_cfg=conv_cfg)
        self.branch7x7_3 = BasicConv2d(
            c7, 192, kernel_size=(7, 1), padding=(3, 0), conv_cfg=conv_cfg)

        self.branch7x7dbl_1 = BasicConv2d(
            in_channels, c7, kernel_size=1, conv_cfg=conv_cfg)
        self.branch7x7dbl_2 = BasicConv2d(
            c7, c7, kernel_size=(7, 1), padding=(3, 0), conv_cfg=conv_cfg)
        self.branch7x7dbl_3 = BasicConv2d(
            c7, c7, kernel_size=(1, 7), padding=(0, 3), conv_cfg=conv_cfg)
        self.branch7x7dbl_4 = BasicConv2d(
            c7, c7, kernel_size=(7, 1), padding=(3, 0), conv_cfg=conv_cfg)
        self.branch7x7dbl_5 = BasicConv2d(
            c7, 192, kernel_size=(1, 7), padding=(0, 3), conv_cfg=conv_cfg)

        self.branch_pool_downsample = nn.AvgPool2d(
            kernel_size=3, stride=1, padding=1)
        self.branch_pool = BasicConv2d(
            in_channels, 192, kernel_size=1, conv_cfg=conv_cfg)

    def forward(self, x: torch.Tensor) -> torch.Tensor:
        """Forward function."""
        branch1x1 = self.branch1x1(x)

        branch7x7 = self.branch7x7_1(x)
        branch7x7 = self.branch7x7_2(branch7x7)
        branch7x7 = self.branch7x7_3(branch7x7)

        branch7x7dbl = self.branch7x7dbl_1(x)
        branch7x7dbl = self.branch7x7dbl_2(branch7x7dbl)
        branch7x7dbl = self.branch7x7dbl_3(branch7x7dbl)
        branch7x7dbl = self.branch7x7dbl_4(branch7x7dbl)
        branch7x7dbl = self.branch7x7dbl_5(branch7x7dbl)

        branch_pool = self.branch_pool_downsample(x)
        branch_pool = self.branch_pool(branch_pool)

        outputs = [branch1x1, branch7x7, branch7x7dbl, branch_pool]
        return torch.cat(outputs, 1)


class InceptionD(BaseModule):
    """Type-D Inception block.

    Args:
        in_channels (int): The number of input channels.
        conv_cfg (dict, optional): The convolution layer config in the
            :class:`BasicConv2d` block. Defaults to None.
        init_cfg (dict, optional): The config of initialization.
            Defaults to None.
    """

    def __init__(self,
                 in_channels: int,
                 conv_cfg: Optional[dict] = None,
                 init_cfg: Optional[dict] = None):
        super().__init__(init_cfg=init_cfg)
        self.branch3x3_1 = BasicConv2d(
            in_channels, 192, kernel_size=1, conv_cfg=conv_cfg)
        self.branch3x3_2 = BasicConv2d(
            192, 320, kernel_size=3, stride=2, conv_cfg=conv_cfg)

        self.branch7x7x3_1 = BasicConv2d(
            in_channels, 192, kernel_size=1, conv_cfg=conv_cfg)
        self.branch7x7x3_2 = BasicConv2d(
            192, 192, kernel_size=(1, 7), padding=(0, 3), conv_cfg=conv_cfg)
        self.branch7x7x3_3 = BasicConv2d(
            192, 192, kernel_size=(7, 1), padding=(3, 0), conv_cfg=conv_cfg)
        self.branch7x7x3_4 = BasicConv2d(
            192, 192, kernel_size=3, stride=2, conv_cfg=conv_cfg)

        self.branch_pool = nn.MaxPool2d(kernel_size=3, stride=2)

    def forward(self, x: torch.Tensor) -> torch.Tensor:
        """Forward function."""
        branch3x3 = self.branch3x3_1(x)
        branch3x3 = self.branch3x3_2(branch3x3)

        branch7x7x3 = self.branch7x7x3_1(x)
        branch7x7x3 = self.branch7x7x3_2(branch7x7x3)
        branch7x7x3 = self.branch7x7x3_3(branch7x7x3)
        branch7x7x3 = self.branch7x7x3_4(branch7x7x3)

        branch_pool = self.branch_pool(x)
        outputs = [branch3x3, branch7x7x3, branch_pool]
        return torch.cat(outputs, 1)


class InceptionE(BaseModule):
    """Type-E Inception block.

    Args:
        in_channels (int): The number of input channels.
        conv_cfg (dict, optional): The convolution layer config in the
            :class:`BasicConv2d` block. Defaults to None.
        init_cfg (dict, optional): The config of initialization.
            Defaults to None.
    """

    def __init__(self,
                 in_channels: int,
                 conv_cfg: Optional[dict] = None,
                 init_cfg=None):
        super().__init__(init_cfg=init_cfg)
        self.branch1x1 = BasicConv2d(
            in_channels, 320, kernel_size=1, conv_cfg=conv_cfg)

        self.branch3x3_1 = BasicConv2d(
            in_channels, 384, kernel_size=1, conv_cfg=conv_cfg)
        self.branch3x3_2a = BasicConv2d(
            384, 384, kernel_size=(1, 3), padding=(0, 1), conv_cfg=conv_cfg)
        self.branch3x3_2b = BasicConv2d(
            384, 384, kernel_size=(3, 1), padding=(1, 0), conv_cfg=conv_cfg)

        self.branch3x3dbl_1 = BasicConv2d(
            in_channels, 448, kernel_size=1, conv_cfg=conv_cfg)
        self.branch3x3dbl_2 = BasicConv2d(
            448, 384, kernel_size=3, padding=1, conv_cfg=conv_cfg)
        self.branch3x3dbl_3a = BasicConv2d(
            384, 384, kernel_size=(1, 3), padding=(0, 1), conv_cfg=conv_cfg)
        self.branch3x3dbl_3b = BasicConv2d(
            384, 384, kernel_size=(3, 1), padding=(1, 0), conv_cfg=conv_cfg)

        self.branch_pool_downsample = nn.AvgPool2d(
            kernel_size=3, stride=1, padding=1)
        self.branch_pool = BasicConv2d(
            in_channels, 192, kernel_size=1, conv_cfg=conv_cfg)

    def forward(self, x: torch.Tensor) -> torch.Tensor:
        """Forward function."""
        branch1x1 = self.branch1x1(x)

        branch3x3 = self.branch3x3_1(x)
        branch3x3 = [
            self.branch3x3_2a(branch3x3),
            self.branch3x3_2b(branch3x3),
        ]
        branch3x3 = torch.cat(branch3x3, 1)

        branch3x3dbl = self.branch3x3dbl_1(x)
        branch3x3dbl = self.branch3x3dbl_2(branch3x3dbl)
        branch3x3dbl = [
            self.branch3x3dbl_3a(branch3x3dbl),
            self.branch3x3dbl_3b(branch3x3dbl),
        ]
        branch3x3dbl = torch.cat(branch3x3dbl, 1)

        branch_pool = self.branch_pool_downsample(x)
        branch_pool = self.branch_pool(branch_pool)

        outputs = [branch1x1, branch3x3, branch3x3dbl, branch_pool]
        return torch.cat(outputs, 1)


class InceptionAux(BaseModule):
    """The Inception block for the auxiliary classification branch.

    Args:
        in_channels (int): The number of input channels.
        num_classes (int): The number of categroies.
        conv_cfg (dict, optional): The convolution layer config in the
            :class:`BasicConv2d` block. Defaults to None.
        init_cfg (dict, optional): The config of initialization.
            Defaults to use trunc normal with ``std=0.01`` for Conv2d layers
            and use trunc normal with ``std=0.001`` for Linear layers..
    """

    def __init__(self,
                 in_channels: int,
                 num_classes: int,
                 conv_cfg: Optional[dict] = None,
                 init_cfg: Optional[dict] = [
                     dict(type='TruncNormal', layer='Conv2d', std=0.01),
                     dict(type='TruncNormal', layer='Linear', std=0.001)
                 ]):
        super().__init__(init_cfg=init_cfg)
        self.downsample = nn.AvgPool2d(kernel_size=5, stride=3)
        self.conv0 = BasicConv2d(
            in_channels, 128, kernel_size=1, conv_cfg=conv_cfg)
        self.conv1 = BasicConv2d(128, 768, kernel_size=5, conv_cfg=conv_cfg)
        self.gap = nn.AdaptiveAvgPool2d((1, 1))
        self.fc = nn.Linear(768, num_classes)

    def forward(self, x: torch.Tensor) -> torch.Tensor:
        """Forward function."""
        # N x 768 x 17 x 17
        x = self.downsample(x)
        # N x 768 x 5 x 5
        x = self.conv0(x)
        # N x 128 x 5 x 5
        x = self.conv1(x)
        # N x 768 x 1 x 1
        # Adaptive average pooling
        x = self.gap(x)
        # N x 768 x 1 x 1
        x = torch.flatten(x, 1)
        # N x 768
        x = self.fc(x)
        # N x 1000
        return x


@MODELS.register_module()
class InceptionV3(BaseBackbone):
    """Inception V3 backbone.

    A PyTorch implementation of `Rethinking the Inception Architecture for
    Computer Vision <https://arxiv.org/abs/1512.00567>`_

    This implementation is modified from
    https://github.com/pytorch/vision/blob/main/torchvision/models/inception.py.
    Licensed under the BSD 3-Clause License.

    Args:
        num_classes (int): The number of categroies. Defaults to 1000.
        aux_logits (bool): Whether to enable the auxiliary branch. If False,
            the auxiliary logits output will be None. Defaults to False.
        dropout (float): Dropout rate. Defaults to 0.5.
        init_cfg (dict, optional): The config of initialization. Defaults
            to use trunc normal with ``std=0.1`` for all Conv2d and Linear
            layers and constant with ``val=1`` for all BatchNorm2d layers.

    Example:
        >>> import torch
        >>> from mmpretrain.models import build_backbone
        >>>
        >>> inputs = torch.rand(2, 3, 299, 299)
        >>> cfg = dict(type='InceptionV3', num_classes=100)
        >>> backbone = build_backbone(cfg)
        >>> aux_out, out = backbone(inputs)
        >>> # The auxiliary branch is disabled by default.
        >>> assert aux_out is None
        >>> print(out.shape)
        torch.Size([2, 100])
        >>> cfg = dict(type='InceptionV3', num_classes=100, aux_logits=True)
        >>> backbone = build_backbone(cfg)
        >>> aux_out, out = backbone(inputs)
        >>> print(aux_out.shape, out.shape)
        torch.Size([2, 100]) torch.Size([2, 100])
    """

    def __init__(
        self,
        num_classes: int = 1000,
        aux_logits: bool = False,
        dropout: float = 0.5,
        init_cfg: Optional[dict] = [
            dict(type='TruncNormal', layer=['Conv2d', 'Linear'], std=0.1),
            dict(type='Constant', layer='BatchNorm2d', val=1)
        ],
    ) -> None:
        super().__init__(init_cfg=init_cfg)

        self.aux_logits = aux_logits
        self.Conv2d_1a_3x3 = BasicConv2d(3, 32, kernel_size=3, stride=2)
        self.Conv2d_2a_3x3 = BasicConv2d(32, 32, kernel_size=3)
        self.Conv2d_2b_3x3 = BasicConv2d(32, 64, kernel_size=3, padding=1)
        self.maxpool1 = nn.MaxPool2d(kernel_size=3, stride=2)
        self.Conv2d_3b_1x1 = BasicConv2d(64, 80, kernel_size=1)
        self.Conv2d_4a_3x3 = BasicConv2d(80, 192, kernel_size=3)
        self.maxpool2 = nn.MaxPool2d(kernel_size=3, stride=2)
        self.Mixed_5b = InceptionA(192, pool_features=32)
        self.Mixed_5c = InceptionA(256, pool_features=64)
        self.Mixed_5d = InceptionA(288, pool_features=64)
        self.Mixed_6a = InceptionB(288)
        self.Mixed_6b = InceptionC(768, channels_7x7=128)
        self.Mixed_6c = InceptionC(768, channels_7x7=160)
        self.Mixed_6d = InceptionC(768, channels_7x7=160)
        self.Mixed_6e = InceptionC(768, channels_7x7=192)
        self.AuxLogits: Optional[nn.Module] = None
        if aux_logits:
            self.AuxLogits = InceptionAux(768, num_classes)
        self.Mixed_7a = InceptionD(768)
        self.Mixed_7b = InceptionE(1280)
        self.Mixed_7c = InceptionE(2048)
        self.avgpool = nn.AdaptiveAvgPool2d((1, 1))
        self.dropout = nn.Dropout(p=dropout)
        self.fc = nn.Linear(2048, num_classes)

    def forward(
            self,
            x: torch.Tensor) -> Tuple[Optional[torch.Tensor], torch.Tensor]:
        """Forward function."""
        # N x 3 x 299 x 299
        x = self.Conv2d_1a_3x3(x)
        # N x 32 x 149 x 149
        x = self.Conv2d_2a_3x3(x)
        # N x 32 x 147 x 147
        x = self.Conv2d_2b_3x3(x)
        # N x 64 x 147 x 147
        x = self.maxpool1(x)
        # N x 64 x 73 x 73
        x = self.Conv2d_3b_1x1(x)
        # N x 80 x 73 x 73
        x = self.Conv2d_4a_3x3(x)
        # N x 192 x 71 x 71
        x = self.maxpool2(x)
        # N x 192 x 35 x 35
        x = self.Mixed_5b(x)
        # N x 256 x 35 x 35
        x = self.Mixed_5c(x)
        # N x 288 x 35 x 35
        x = self.Mixed_5d(x)
        # N x 288 x 35 x 35
        x = self.Mixed_6a(x)
        # N x 768 x 17 x 17
        x = self.Mixed_6b(x)
        # N x 768 x 17 x 17
        x = self.Mixed_6c(x)
        # N x 768 x 17 x 17
        x = self.Mixed_6d(x)
        # N x 768 x 17 x 17
        x = self.Mixed_6e(x)
        # N x 768 x 17 x 17
        aux: Optional[torch.Tensor] = None
        if self.aux_logits and self.training:
            aux = self.AuxLogits(x)
        # N x 768 x 17 x 17
        x = self.Mixed_7a(x)
        # N x 1280 x 8 x 8
        x = self.Mixed_7b(x)
        # N x 2048 x 8 x 8
        x = self.Mixed_7c(x)
        # N x 2048 x 8 x 8
        # Adaptive average pooling
        x = self.avgpool(x)
        # N x 2048 x 1 x 1
        x = self.dropout(x)
        # N x 2048 x 1 x 1
        x = torch.flatten(x, 1)
        # N x 2048
        x = self.fc(x)
        # N x 1000 (num_classes)
        return aux, x