Implement Functional Blur on resnet.py

1. add ResNet argument blur=''
2. implement blur for maxpool and strided convs in downsampling blocks

timm/models/layers/__init__.py

@@ -15,3 +15,4 @@ from .adaptive_avgmax_pool import \
 from .drop import DropBlock2d, DropPath, drop_block_2d, drop_path
 from .test_time_pool import TestTimePoolHead, apply_test_time_pool
 from .split_batchnorm import SplitBatchNorm2d, convert_splitbn_model
+from .blurpool import BlurPool2d

timm/models/layers/blurpool.py

@@ -17,7 +17,7 @@ class BlurPool2d(nn.Module):
     Corresponds to the Downsample class, which does blurring and subsampling
     Args:
         channels = Number of input channels
-        blur_filter_size (int): binomial filter size for blurring. currently supports 3(default) and 5.
+        blur_filter_size (int): binomial filter size for blurring. currently supports 3 (default) and 5.
         stride (int): downsampling filter stride
     Shape:
     Returns:

timm/models/resnet.py

@@ -12,7 +12,7 @@ import torch.nn.functional as F
 
 from .registry import register_model
 from .helpers import load_pretrained
-from .layers import SelectAdaptivePool2d, DropBlock2d, DropPath, AvgPool2dSame, create_attn
+from .layers import SelectAdaptivePool2d, DropBlock2d, DropPath, AvgPool2dSame, create_attn, BlurPool2d
 from timm.data import IMAGENET_DEFAULT_MEAN, IMAGENET_DEFAULT_STD
 
 
@@ -104,6 +104,8 @@ default_cfgs = {
         interpolation='bicubic'),
     'ecaresnet18': _cfg(),
     'ecaresnet50': _cfg(),
+    'resnetblur18': _cfg(),
+    'resnetblur50': _cfg()
 }
 
 
@@ -117,7 +119,7 @@ class BasicBlock(nn.Module):
 
     def __init__(self, inplanes, planes, stride=1, downsample=None, cardinality=1, base_width=64,
                  reduce_first=1, dilation=1, first_dilation=None, act_layer=nn.ReLU, norm_layer=nn.BatchNorm2d,
-                 attn_layer=None, drop_block=None, drop_path=None):
+                 attn_layer=None, drop_block=None, drop_path=None, blur=False):
         super(BasicBlock, self).__init__()
 
         assert cardinality == 1, 'BasicBlock only supports cardinality of 1'
@@ -125,10 +127,19 @@ class BasicBlock(nn.Module):
         first_planes = planes // reduce_first
         outplanes = planes * self.expansion
         first_dilation = first_dilation or dilation
+        self.blur = blur
 
+        if blur and stride==2:
+            self.conv1 = nn.Conv2d(
+                inplanes, first_planes, kernel_size=3, stride=1, padding=first_dilation,
+                dilation=first_dilation, bias=False)
+            self.blurpool=BlurPool2d(channels=first_planes)
+        else:
             self.conv1 = nn.Conv2d(
             inplanes, first_planes, kernel_size=3, stride=stride, padding=first_dilation,
             dilation=first_dilation, bias=False)
+            self.blurpool = None
+        
         self.bn1 = norm_layer(first_planes)
         self.act1 = act_layer(inplace=True)
         self.conv2 = nn.Conv2d(
@@ -154,6 +165,10 @@ class BasicBlock(nn.Module):
         x = self.bn1(x)
         if self.drop_block is not None:
             x = self.drop_block(x)
+        if self.blurpool is not None:
+            x = self.act1(x)
+            x = self.blurpool(x)
+        else:
             x = self.act1(x)
 
         x = self.conv2(x)
@@ -181,20 +196,30 @@ class Bottleneck(nn.Module):
 
     def __init__(self, inplanes, planes, stride=1, downsample=None, cardinality=1, base_width=64,
                  reduce_first=1, dilation=1, first_dilation=None, act_layer=nn.ReLU, norm_layer=nn.BatchNorm2d,
-                 attn_layer=None, drop_block=None, drop_path=None):
+                 attn_layer=None, drop_block=None, drop_path=None, blur=False):
         super(Bottleneck, self).__init__()
 
         width = int(math.floor(planes * (base_width / 64)) * cardinality)
         first_planes = width // reduce_first
         outplanes = planes * self.expansion
         first_dilation = first_dilation or dilation
+        self.blur = blur
 
         self.conv1 = nn.Conv2d(inplanes, first_planes, kernel_size=1, bias=False)
         self.bn1 = norm_layer(first_planes)
         self.act1 = act_layer(inplace=True)
+
+        if blur and stride==2:
+            self.conv2 = nn.Conv2d(
+                first_planes, width, kernel_size=3, stride=1,
+                padding=first_dilation, dilation=first_dilation, groups=cardinality, bias=False)
+            self.blurpool = BlurPool2d(channels=width)
+        else:
             self.conv2 = nn.Conv2d(
                 first_planes, width, kernel_size=3, stride=stride,
                 padding=first_dilation, dilation=first_dilation, groups=cardinality, bias=False)
+            self.blurpool = None
+
         self.bn2 = norm_layer(width)
         self.act2 = act_layer(inplace=True)
         self.conv3 = nn.Conv2d(width, outplanes, kernel_size=1, bias=False)
@@ -345,12 +370,19 @@ class ResNet(nn.Module):
         Dropout probability before classifier, for training
     global_pool : str, default 'avg'
         Global pooling type. One of 'avg', 'max', 'avgmax', 'catavgmax'
+    blur : str, default ''
+        Location of Blurring:
+        * '', default - Not applied
+        * 'max' - only stem layer MaxPool will be blurred
+        * 'strided' - only strided convolutions in the downsampling blocks (assembled-cnn style)
+        * 'max_strided' - on both stem MaxPool and strided convolutions (zhang2019shiftinvar style for ResNets)
+
     """
     def __init__(self, block, layers, num_classes=1000, in_chans=3,
                  cardinality=1, base_width=64, stem_width=64, stem_type='',
                  block_reduce_first=1, down_kernel_size=1, avg_down=False, output_stride=32,
                  act_layer=nn.ReLU, norm_layer=nn.BatchNorm2d, drop_rate=0.0, drop_path_rate=0.,
-                 drop_block_rate=0., global_pool='avg', zero_init_last_bn=True, block_args=None):
+                 drop_block_rate=0., global_pool='avg', blur='', zero_init_last_bn=True, block_args=None):
         block_args = block_args or dict()
         self.num_classes = num_classes
         deep_stem = 'deep' in stem_type
@@ -359,6 +391,7 @@ class ResNet(nn.Module):
         self.base_width = base_width
         self.drop_rate = drop_rate
         self.expansion = block.expansion
+        self.blur = 'strided' in blur
         super(ResNet, self).__init__()
 
         # Stem
@@ -379,6 +412,12 @@ class ResNet(nn.Module):
             self.conv1 = nn.Conv2d(in_chans, self.inplanes, kernel_size=7, stride=2, padding=3, bias=False)
         self.bn1 = norm_layer(self.inplanes)
         self.act1 = act_layer(inplace=True)
+        # Stem Blur
+        if 'max' in blur :
+            self.maxpool = nn.Sequential(*[
+            nn.MaxPool2d(kernel_size=3, stride=1, padding=1),
+            BlurPool2d(channels=self.inplanes)])
+        else :
             self.maxpool = nn.MaxPool2d(kernel_size=3, stride=2, padding=1)
 
         # Feature Blocks
@@ -432,7 +471,7 @@ class ResNet(nn.Module):
         block_kwargs = dict(
             cardinality=self.cardinality, base_width=self.base_width, reduce_first=reduce_first,
             dilation=dilation, **kwargs)
-        layers = [block(self.inplanes, planes, stride, downsample, first_dilation=first_dilation, **block_kwargs)]
+        layers = [block(self.inplanes, planes, stride, downsample, first_dilation=first_dilation, blur=self.blur, **block_kwargs)]
         self.inplanes = planes * block.expansion
         layers += [block(self.inplanes, planes, **block_kwargs) for _ in range(1, blocks)]
 
@@ -1022,3 +1061,21 @@ def ecaresnet50(pretrained=False, num_classes=1000, in_chans=3, **kwargs):
     if pretrained:
         load_pretrained(model, default_cfg, num_classes, in_chans)
     return model
+
+@register_model
+def resnetblur18(pretrained=False, num_classes=1000, in_chans=3, **kwargs):
+    """Constructs a ResNet-18 model. With original style blur
+    """
+    default_cfg = default_cfgs['resnetblur18']
+    model = ResNet(BasicBlock, [2, 2, 2, 2], num_classes=num_classes, in_chans=in_chans, blur='max_strided',**kwargs)
+    model.default_cfg = default_cfg
+    return model
+
+@register_model
+def resnetblur50(pretrained=False, num_classes=1000, in_chans=3, **kwargs):
+    """Constructs a ResNet-50 model. With assembled-cnn style blur
+    """
+    default_cfg = default_cfgs['resnetblur18']
+    model = ResNet(Bottleneck, [3, 4, 6, 3], num_classes=num_classes, in_chans=in_chans, blur='strided', **kwargs)
+    model.default_cfg = default_cfg
+    return model