wide_resnet.py

# based on https://github.com/meliketoy/wide-resnet.pytorch implementation
import torch
import torch.nn as nn
import torch.nn.functional as F

class wide_basic(nn.Module):
    def __init__(self, in_planes, planes, dropout_rate, stride=1):
        super(wide_basic, self).__init__()
        self.bn1 = nn.BatchNorm2d(in_planes)
        self.conv1 = nn.Conv2d(in_planes, planes, kernel_size=3, padding=1, bias=True)
        self.dropout = nn.Dropout(p=dropout_rate)
        self.bn2 = nn.BatchNorm2d(planes)
        self.conv2 = nn.Conv2d(planes, planes, kernel_size=3, stride=stride, padding=1, bias=True)

        self.shortcut = nn.Sequential()
        if stride != 1 or in_planes != planes:
            self.shortcut = nn.Sequential(
                nn.Conv2d(in_planes, planes, kernel_size=1, stride=stride, bias=True),
            )

    def forward(self, x):
        out = self.dropout(self.conv1(F.relu(self.bn1(x))))
        out = self.conv2(F.relu(self.bn2(out)))
        out += self.shortcut(x)

        return out

class WideResNet(nn.Module):
    def __init__(self, depth, widen_factor, dropout_rate, num_classes):
        super(WideResNet, self).__init__()
        self.in_planes = 16

        assert ((depth-4)%6 ==0), 'Wide-resnet depth should be 6n+4'
        n = (depth-4)//6
        k = widen_factor

        print('| Wide-Resnet %dx%d' %(depth, k))
        nStages = [16, int(round(16*k)), int(round(32*k)), int(round(64*k))]

        self.conv1 = nn.Conv2d(3,nStages[0], 3, 1, 1)
        self.layer1 = self._wide_layer(wide_basic, nStages[1], n, dropout_rate, stride=1)
        self.layer2 = self._wide_layer(wide_basic, nStages[2], n, dropout_rate, stride=2)
        self.layer3 = self._wide_layer(wide_basic, nStages[3], n, dropout_rate, stride=2)
        self.bn = nn.Sequential(nn.BatchNorm2d(nStages[3]), nn.ReLU())
        self.avgpool = nn.AdaptiveAvgPool2d((1, 1))
        self.linear = nn.Linear(nStages[3], num_classes)

    def _wide_layer(self, block, planes, num_blocks, dropout_rate, stride):
        strides = [stride] + [1]*int(num_blocks-1)
        layers = []

        for stride in strides:
            layers.append(block(self.in_planes, planes, dropout_rate, stride))
            self.in_planes = planes

        return nn.Sequential(*layers)

    def forward(self, x):
        out = self.conv1(x)
        out = self.layer1(out)
        out = self.layer2(out)
        out = self.layer3(out)
        out = self.bn(out)
        out = self.avgpool(out)
        out = out.view(out.size(0), -1)
        out = self.linear(out)

        return out