Dilated Residual Networks

完整代码请见: https://github.com/fyu/drn

class DRN(nn.Module):

    def __init__(self, block, layers, num_classes=1000,
                 channels=(16, 32, 64, 128, 256, 512, 512, 512),
                 out_map=False, out_middle=False, pool_size=28, arch='D'):
        super(DRN, self).__init__()
        self.inplanes = channels[0]
        self.out_map = out_map
        self.out_dim = channels[-1]
        self.out_middle = out_middle
        self.arch = arch

        if arch == 'C':
            self.conv1 = nn.Conv2d(3, channels[0], kernel_size=7, stride=1,
                                   padding=3, bias=False)
            self.bn1 = BatchNorm(channels[0])
            self.relu = nn.ReLU(inplace=True)

            self.layer1 = self._make_layer(
                BasicBlock, channels[0], layers[0], stride=1)
            self.layer2 = self._make_layer(
                BasicBlock, channels[1], layers[1], stride=2)
        elif arch == 'D':
            self.layer0 = nn.Sequential(
                nn.Conv2d(3, channels[0], kernel_size=7, stride=1, padding=3,
                          bias=False),
                BatchNorm(channels[0]),
                nn.ReLU(inplace=True)
            )

            self.layer1 = self._make_conv_layers(
                channels[0], layers[0], stride=1)
            self.layer2 = self._make_conv_layers(
                channels[1], layers[1], stride=2)

        self.layer3 = self._make_layer(block, channels[2], layers[2], stride=2)
        self.layer4 = self._make_layer(block, channels[3], layers[3], stride=2)
        self.layer5 = self._make_layer(block, channels[4], layers[4],
                                       dilation=2, new_level=False)
        self.layer6 = None if layers[5] == 0 else \
            self._make_layer(block, channels[5], layers[5], dilation=4,
                             new_level=False)

        if arch == 'C':
            self.layer7 = None if layers[6] == 0 else \
                self._make_layer(BasicBlock, channels[6], layers[6], dilation=2,
                                 new_level=False, residual=False)
            self.layer8 = None if layers[7] == 0 else \
                self._make_layer(BasicBlock, channels[7], layers[7], dilation=1,
                                 new_level=False, residual=False)
        elif arch == 'D':
            self.layer7 = None if layers[6] == 0 else \
                self._make_conv_layers(channels[6], layers[6], dilation=2)
            self.layer8 = None if layers[7] == 0 else \
                self._make_conv_layers(channels[7], layers[7], dilation=1)

        if num_classes > 0:
            self.avgpool = nn.AvgPool2d(pool_size)
            self.fc = nn.Conv2d(self.out_dim, num_classes, kernel_size=1,
                                stride=1, padding=0, bias=True)
        for m in self.modules():
            if isinstance(m, nn.Conv2d):
                n = m.kernel_size[0] * m.kernel_size[1] * m.out_channels
                m.weight.data.normal_(0, math.sqrt(2. / n))
            elif isinstance(m, BatchNorm):
                m.weight.data.fill_(1)
                m.bias.data.zero_()

    def _make_layer(self, block, planes, blocks, stride=1, dilation=1,
                    new_level=True, residual=True):
        assert dilation == 1 or dilation % 2 == 0
        downsample = None
        if stride != 1 or self.inplanes != planes * block.expansion:
            downsample = nn.Sequential(
                nn.Conv2d(self.inplanes, planes * block.expansion,
                          kernel_size=1, stride=stride, bias=False),
                BatchNorm(planes * block.expansion),
            )

        layers = list()
        layers.append(block(
            self.inplanes, planes, stride, downsample,
            dilation=(1, 1) if dilation == 1 else (
                dilation // 2 if new_level else dilation, dilation),
            residual=residual))
        self.inplanes = planes * block.expansion
        for i in range(1, blocks):
            layers.append(block(self.inplanes, planes, residual=residual,
                                dilation=(dilation, dilation)))

        return nn.Sequential(*layers)

    def _make_conv_layers(self, channels, convs, stride=1, dilation=1):
        modules = []
        for i in range(convs):
            modules.extend([
                nn.Conv2d(self.inplanes, channels, kernel_size=3,
                          stride=stride if i == 0 else 1,
                          padding=dilation, bias=False, dilation=dilation),
                BatchNorm(channels),
                nn.ReLU(inplace=True)])
            self.inplanes = channels
        return nn.Sequential(*modules)