Fix Densenet module keys (#474)

torchvision/models/densenet.py

+import re
 import torch
 import torch.nn as nn
 import torch.nn.functional as F
@@ -25,7 +26,20 @@ def densenet121(pretrained=False, **kwargs):
     model = DenseNet(num_init_features=64, growth_rate=32, block_config=(6, 12, 24, 16),
                      **kwargs)
     if pretrained:
-        model.load_state_dict(model_zoo.load_url(model_urls['densenet121']))
+        # '.'s are no longer allowed in module names, but pervious _DenseLayer
+        # has keys 'norm.1', 'relu.1', 'conv.1', 'norm.2', 'relu.2', 'conv.2'.
+        # They are also in the checkpoints in model_urls. This pattern is used
+        # to find such keys.
+        pattern = re.compile(
+            r'^(.*denselayer\d+\.(?:norm|relu|conv))\.((?:[12])\.(?:weight|bias|running_mean|running_var))$')
+        state_dict = model_zoo.load_url(model_urls['densenet121'])
+        for key in list(state_dict.keys()):
+            res = pattern.match(key)
+            if res:
+                new_key = res.group(1) + res.group(2)
+                state_dict[new_key] = state_dict[key]
+                del state_dict[key]
+        model.load_state_dict(state_dict)
     return model
 
 
@@ -39,7 +53,20 @@ def densenet169(pretrained=False, **kwargs):
     model = DenseNet(num_init_features=64, growth_rate=32, block_config=(6, 12, 32, 32),
                      **kwargs)
     if pretrained:
-        model.load_state_dict(model_zoo.load_url(model_urls['densenet169']))
+        # '.'s are no longer allowed in module names, but pervious _DenseLayer
+        # has keys 'norm.1', 'relu.1', 'conv.1', 'norm.2', 'relu.2', 'conv.2'.
+        # They are also in the checkpoints in model_urls. This pattern is used
+        # to find such keys.
+        pattern = re.compile(
+            r'^(.*denselayer\d+\.(?:norm|relu|conv))\.((?:[12])\.(?:weight|bias|running_mean|running_var))$')
+        state_dict = model_zoo.load_url(model_urls['densenet169'])
+        for key in list(state_dict.keys()):
+            res = pattern.match(key)
+            if res:
+                new_key = res.group(1) + res.group(2)
+                state_dict[new_key] = state_dict[key]
+                del state_dict[key]
+        model.load_state_dict(state_dict)
     return model
 
 
@@ -53,7 +80,20 @@ def densenet201(pretrained=False, **kwargs):
     model = DenseNet(num_init_features=64, growth_rate=32, block_config=(6, 12, 48, 32),
                      **kwargs)
     if pretrained:
-        model.load_state_dict(model_zoo.load_url(model_urls['densenet201']))
+        # '.'s are no longer allowed in module names, but pervious _DenseLayer
+        # has keys 'norm.1', 'relu.1', 'conv.1', 'norm.2', 'relu.2', 'conv.2'.
+        # They are also in the checkpoints in model_urls. This pattern is used
+        # to find such keys.
+        pattern = re.compile(
+            r'^(.*denselayer\d+\.(?:norm|relu|conv))\.((?:[12])\.(?:weight|bias|running_mean|running_var))$')
+        state_dict = model_zoo.load_url(model_urls['densenet201'])
+        for key in list(state_dict.keys()):
+            res = pattern.match(key)
+            if res:
+                new_key = res.group(1) + res.group(2)
+                state_dict[new_key] = state_dict[key]
+                del state_dict[key]
+        model.load_state_dict(state_dict)
     return model
 
 
@@ -67,20 +107,33 @@ def densenet161(pretrained=False, **kwargs):
     model = DenseNet(num_init_features=96, growth_rate=48, block_config=(6, 12, 36, 24),
                      **kwargs)
     if pretrained:
-        model.load_state_dict(model_zoo.load_url(model_urls['densenet161']))
+        # '.'s are no longer allowed in module names, but pervious _DenseLayer
+        # has keys 'norm.1', 'relu.1', 'conv.1', 'norm.2', 'relu.2', 'conv.2'.
+        # They are also in the checkpoints in model_urls. This pattern is used
+        # to find such keys.
+        pattern = re.compile(
+            r'^(.*denselayer\d+\.(?:norm|relu|conv))\.((?:[12])\.(?:weight|bias|running_mean|running_var))$')
+        state_dict = model_zoo.load_url(model_urls['densenet161'])
+        for key in list(state_dict.keys()):
+            res = pattern.match(key)
+            if res:
+                new_key = res.group(1) + res.group(2)
+                state_dict[new_key] = state_dict[key]
+                del state_dict[key]
+        model.load_state_dict(state_dict)
     return model
 
 
 class _DenseLayer(nn.Sequential):
     def __init__(self, num_input_features, growth_rate, bn_size, drop_rate):
         super(_DenseLayer, self).__init__()
-        self.add_module('norm.1', nn.BatchNorm2d(num_input_features)),
-        self.add_module('relu.1', nn.ReLU(inplace=True)),
-        self.add_module('conv.1', nn.Conv2d(num_input_features, bn_size *
+        self.add_module('norm1', nn.BatchNorm2d(num_input_features)),
+        self.add_module('relu1', nn.ReLU(inplace=True)),
+        self.add_module('conv1', nn.Conv2d(num_input_features, bn_size *
                         growth_rate, kernel_size=1, stride=1, bias=False)),
-        self.add_module('norm.2', nn.BatchNorm2d(bn_size * growth_rate)),
-        self.add_module('relu.2', nn.ReLU(inplace=True)),
-        self.add_module('conv.2', nn.Conv2d(bn_size * growth_rate, growth_rate,
+        self.add_module('norm2', nn.BatchNorm2d(bn_size * growth_rate)),
+        self.add_module('relu2', nn.ReLU(inplace=True)),
+        self.add_module('conv2', nn.Conv2d(bn_size * growth_rate, growth_rate,
                         kernel_size=3, stride=1, padding=1, bias=False)),
         self.drop_rate = drop_rate