init

finetune/mmseg/models/backbones/mobilenet_v2.py

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+# Copyright (c) OpenMMLab. All rights reserved.
+import warnings
+
+import torch.nn as nn
+from mmcv.cnn import ConvModule
+from mmengine.model import BaseModule
+from torch.nn.modules.batchnorm import _BatchNorm
+
+from mmseg.registry import MODELS
+from ..utils import InvertedResidual, make_divisible
+
+
+@MODELS.register_module()
+class MobileNetV2(BaseModule):
+    """MobileNetV2 backbone.
+
+    This backbone is the implementation of
+    `MobileNetV2: Inverted Residuals and Linear Bottlenecks
+    <https://arxiv.org/abs/1801.04381>`_.
+
+    Args:
+        widen_factor (float): Width multiplier, multiply number of
+            channels in each layer by this amount. Default: 1.0.
+        strides (Sequence[int], optional): Strides of the first block of each
+            layer. If not specified, default config in ``arch_setting`` will
+            be used.
+        dilations (Sequence[int]): Dilation of each layer.
+        out_indices (None or Sequence[int]): Output from which stages.
+            Default: (7, ).
+        frozen_stages (int): Stages to be frozen (all param fixed).
+            Default: -1, which means not freezing any parameters.
+        conv_cfg (dict): Config dict for convolution layer.
+            Default: None, which means using conv2d.
+        norm_cfg (dict): Config dict for normalization layer.
+            Default: dict(type='BN').
+        act_cfg (dict): Config dict for activation layer.
+            Default: dict(type='ReLU6').
+        norm_eval (bool): Whether to set norm layers to eval mode, namely,
+            freeze running stats (mean and var). Note: Effect on Batch Norm
+            and its variants only. Default: False.
+        with_cp (bool): Use checkpoint or not. Using checkpoint will save some
+            memory while slowing down the training speed. Default: False.
+        pretrained (str, optional): model pretrained path. Default: None
+        init_cfg (dict or list[dict], optional): Initialization config dict.
+            Default: None
+    """
+
+    # Parameters to build layers. 3 parameters are needed to construct a
+    # layer, from left to right: expand_ratio, channel, num_blocks.
+    arch_settings = [[1, 16, 1], [6, 24, 2], [6, 32, 3], [6, 64, 4],
+                     [6, 96, 3], [6, 160, 3], [6, 320, 1]]
+
+    def __init__(self,
+                 widen_factor=1.,
+                 strides=(1, 2, 2, 2, 1, 2, 1),
+                 dilations=(1, 1, 1, 1, 1, 1, 1),
+                 out_indices=(1, 2, 4, 6),
+                 frozen_stages=-1,
+                 conv_cfg=None,
+                 norm_cfg=dict(type='BN'),
+                 act_cfg=dict(type='ReLU6'),
+                 norm_eval=False,
+                 with_cp=False,
+                 pretrained=None,
+                 init_cfg=None):
+        super().__init__(init_cfg)
+
+        self.pretrained = pretrained
+        assert not (init_cfg and pretrained), \
+            'init_cfg and pretrained cannot be setting at the same time'
+        if isinstance(pretrained, str):
+            warnings.warn('DeprecationWarning: pretrained is a deprecated, '
+                          'please use "init_cfg" instead')
+            self.init_cfg = dict(type='Pretrained', checkpoint=pretrained)
+        elif pretrained is None:
+            if init_cfg is None:
+                self.init_cfg = [
+                    dict(type='Kaiming', layer='Conv2d'),
+                    dict(
+                        type='Constant',
+                        val=1,
+                        layer=['_BatchNorm', 'GroupNorm'])
+                ]
+        else:
+            raise TypeError('pretrained must be a str or None')
+
+        self.widen_factor = widen_factor
+        self.strides = strides
+        self.dilations = dilations
+        assert len(strides) == len(dilations) == len(self.arch_settings)
+        self.out_indices = out_indices
+        for index in out_indices:
+            if index not in range(0, 7):
+                raise ValueError('the item in out_indices must in '
+                                 f'range(0, 7). But received {index}')
+
+        if frozen_stages not in range(-1, 7):
+            raise ValueError('frozen_stages must be in range(-1, 7). '
+                             f'But received {frozen_stages}')
+        self.out_indices = out_indices
+        self.frozen_stages = frozen_stages
+        self.conv_cfg = conv_cfg
+        self.norm_cfg = norm_cfg
+        self.act_cfg = act_cfg
+        self.norm_eval = norm_eval
+        self.with_cp = with_cp
+
+        self.in_channels = make_divisible(32 * widen_factor, 8)
+
+        self.conv1 = ConvModule(
+            in_channels=3,
+            out_channels=self.in_channels,
+            kernel_size=3,
+            stride=2,
+            padding=1,
+            conv_cfg=self.conv_cfg,
+            norm_cfg=self.norm_cfg,
+            act_cfg=self.act_cfg)
+
+        self.layers = []
+
+        for i, layer_cfg in enumerate(self.arch_settings):
+            expand_ratio, channel, num_blocks = layer_cfg
+            stride = self.strides[i]
+            dilation = self.dilations[i]
+            out_channels = make_divisible(channel * widen_factor, 8)
+            inverted_res_layer = self.make_layer(
+                out_channels=out_channels,
+                num_blocks=num_blocks,
+                stride=stride,
+                dilation=dilation,
+                expand_ratio=expand_ratio)
+            layer_name = f'layer{i + 1}'
+            self.add_module(layer_name, inverted_res_layer)
+            self.layers.append(layer_name)
+
+    def make_layer(self, out_channels, num_blocks, stride, dilation,
+                   expand_ratio):
+        """Stack InvertedResidual blocks to build a layer for MobileNetV2.
+
+        Args:
+            out_channels (int): out_channels of block.
+            num_blocks (int): Number of blocks.
+            stride (int): Stride of the first block.
+            dilation (int): Dilation of the first block.
+            expand_ratio (int): Expand the number of channels of the
+                hidden layer in InvertedResidual by this ratio.
+        """
+        layers = []
+        for i in range(num_blocks):
+            layers.append(
+                InvertedResidual(
+                    self.in_channels,
+                    out_channels,
+                    stride if i == 0 else 1,
+                    expand_ratio=expand_ratio,
+                    dilation=dilation if i == 0 else 1,
+                    conv_cfg=self.conv_cfg,
+                    norm_cfg=self.norm_cfg,
+                    act_cfg=self.act_cfg,
+                    with_cp=self.with_cp))
+            self.in_channels = out_channels
+
+        return nn.Sequential(*layers)
+
+    def forward(self, x):
+        x = self.conv1(x)
+
+        outs = []
+        for i, layer_name in enumerate(self.layers):
+            layer = getattr(self, layer_name)
+            x = layer(x)
+            if i in self.out_indices:
+                outs.append(x)
+
+        if len(outs) == 1:
+            return outs[0]
+        else:
+            return tuple(outs)
+
+    def _freeze_stages(self):
+        if self.frozen_stages >= 0:
+            for param in self.conv1.parameters():
+                param.requires_grad = False
+        for i in range(1, self.frozen_stages + 1):
+            layer = getattr(self, f'layer{i}')
+            layer.eval()
+            for param in layer.parameters():
+                param.requires_grad = False
+
+    def train(self, mode=True):
+        super().train(mode)
+        self._freeze_stages()
+        if mode and self.norm_eval:
+            for m in self.modules():
+                if isinstance(m, _BatchNorm):
+                    m.eval()