init

finetune/mmseg/models/backbones/resnext.py

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+# Copyright (c) OpenMMLab. All rights reserved.
+import math
+
+from mmcv.cnn import build_conv_layer, build_norm_layer
+
+from mmseg.registry import MODELS
+from ..utils import ResLayer
+from .resnet import Bottleneck as _Bottleneck
+from .resnet import ResNet
+
+
+class Bottleneck(_Bottleneck):
+    """Bottleneck block for ResNeXt.
+
+    If style is "pytorch", the stride-two layer is the 3x3 conv layer, if it is
+    "caffe", the stride-two layer is the first 1x1 conv layer.
+    """
+
+    def __init__(self,
+                 inplanes,
+                 planes,
+                 groups=1,
+                 base_width=4,
+                 base_channels=64,
+                 **kwargs):
+        super().__init__(inplanes, planes, **kwargs)
+
+        if groups == 1:
+            width = self.planes
+        else:
+            width = math.floor(self.planes *
+                               (base_width / base_channels)) * groups
+
+        self.norm1_name, norm1 = build_norm_layer(
+            self.norm_cfg, width, postfix=1)
+        self.norm2_name, norm2 = build_norm_layer(
+            self.norm_cfg, width, postfix=2)
+        self.norm3_name, norm3 = build_norm_layer(
+            self.norm_cfg, self.planes * self.expansion, postfix=3)
+
+        self.conv1 = build_conv_layer(
+            self.conv_cfg,
+            self.inplanes,
+            width,
+            kernel_size=1,
+            stride=self.conv1_stride,
+            bias=False)
+        self.add_module(self.norm1_name, norm1)
+        fallback_on_stride = False
+        self.with_modulated_dcn = False
+        if self.with_dcn:
+            fallback_on_stride = self.dcn.pop('fallback_on_stride', False)
+        if not self.with_dcn or fallback_on_stride:
+            self.conv2 = build_conv_layer(
+                self.conv_cfg,
+                width,
+                width,
+                kernel_size=3,
+                stride=self.conv2_stride,
+                padding=self.dilation,
+                dilation=self.dilation,
+                groups=groups,
+                bias=False)
+        else:
+            assert self.conv_cfg is None, 'conv_cfg must be None for DCN'
+            self.conv2 = build_conv_layer(
+                self.dcn,
+                width,
+                width,
+                kernel_size=3,
+                stride=self.conv2_stride,
+                padding=self.dilation,
+                dilation=self.dilation,
+                groups=groups,
+                bias=False)
+
+        self.add_module(self.norm2_name, norm2)
+        self.conv3 = build_conv_layer(
+            self.conv_cfg,
+            width,
+            self.planes * self.expansion,
+            kernel_size=1,
+            bias=False)
+        self.add_module(self.norm3_name, norm3)
+
+
+@MODELS.register_module()
+class ResNeXt(ResNet):
+    """ResNeXt backbone.
+
+    This backbone is the implementation of `Aggregated
+    Residual Transformations for Deep Neural
+    Networks <https://arxiv.org/abs/1611.05431>`_.
+
+    Args:
+        depth (int): Depth of resnet, from {18, 34, 50, 101, 152}.
+        in_channels (int): Number of input image channels. Normally 3.
+        num_stages (int): Resnet stages, normally 4.
+        groups (int): Group of resnext.
+        base_width (int): Base width of resnext.
+        strides (Sequence[int]): Strides of the first block of each stage.
+        dilations (Sequence[int]): Dilation of each stage.
+        out_indices (Sequence[int]): Output from which stages.
+        style (str): `pytorch` or `caffe`. If set to "pytorch", the stride-two
+            layer is the 3x3 conv layer, otherwise the stride-two layer is
+            the first 1x1 conv layer.
+        frozen_stages (int): Stages to be frozen (all param fixed). -1 means
+            not freezing any parameters.
+        norm_cfg (dict): dictionary to construct and config norm layer.
+        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.
+        with_cp (bool): Use checkpoint or not. Using checkpoint will save some
+            memory while slowing down the training speed.
+        zero_init_residual (bool): whether to use zero init for last norm layer
+            in resblocks to let them behave as identity.
+
+    Example:
+        >>> from mmseg.models import ResNeXt
+        >>> import torch
+        >>> self = ResNeXt(depth=50)
+        >>> self.eval()
+        >>> inputs = torch.rand(1, 3, 32, 32)
+        >>> level_outputs = self.forward(inputs)
+        >>> for level_out in level_outputs:
+        ...     print(tuple(level_out.shape))
+        (1, 256, 8, 8)
+        (1, 512, 4, 4)
+        (1, 1024, 2, 2)
+        (1, 2048, 1, 1)
+    """
+
+    arch_settings = {
+        50: (Bottleneck, (3, 4, 6, 3)),
+        101: (Bottleneck, (3, 4, 23, 3)),
+        152: (Bottleneck, (3, 8, 36, 3))
+    }
+
+    def __init__(self, groups=1, base_width=4, **kwargs):
+        self.groups = groups
+        self.base_width = base_width
+        super().__init__(**kwargs)
+
+    def make_res_layer(self, **kwargs):
+        """Pack all blocks in a stage into a ``ResLayer``"""
+        return ResLayer(
+            groups=self.groups,
+            base_width=self.base_width,
+            base_channels=self.base_channels,
+            **kwargs)