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import os
import sys
import torch
import torch.nn as nn
import math
try:
from lib.nn import SynchronizedBatchNorm2d
except ImportError:
from torch.nn import BatchNorm2d as SynchronizedBatchNorm2d
try:
from urllib import urlretrieve
except ImportError:
from urllib.request import urlretrieve
__all__ = ['ResNeXt', 'resnext101'] # support resnext 101
model_urls = {
#'resnext50': 'http://sceneparsing.csail.mit.edu/model/pretrained_resnet/resnext50-imagenet.pth',
'resnext101': 'http://sceneparsing.csail.mit.edu/model/pretrained_resnet/resnext101-imagenet.pth'
}
def conv3x3(in_planes, out_planes, stride=1):
"3x3 convolution with padding"
return nn.Conv2d(in_planes, out_planes, kernel_size=3, stride=stride,
padding=1, bias=False)
class GroupBottleneck(nn.Module):
expansion = 2
def __init__(self, inplanes, planes, stride=1, groups=1, downsample=None):
super(GroupBottleneck, self).__init__()
self.conv1 = nn.Conv2d(inplanes, planes, kernel_size=1, bias=False)
self.bn1 = SynchronizedBatchNorm2d(planes)
self.conv2 = nn.Conv2d(planes, planes, kernel_size=3, stride=stride,
padding=1, groups=groups, bias=False)
self.bn2 = SynchronizedBatchNorm2d(planes)
self.conv3 = nn.Conv2d(planes, planes * 2, kernel_size=1, bias=False)
self.bn3 = SynchronizedBatchNorm2d(planes * 2)
self.relu = nn.ReLU(inplace=True)
self.downsample = downsample
self.stride = stride
def forward(self, x):
residual = x
out = self.conv1(x)
out = self.bn1(out)
out = self.relu(out)
out = self.conv2(out)
out = self.bn2(out)
out = self.relu(out)
out = self.conv3(out)
out = self.bn3(out)
if self.downsample is not None:
residual = self.downsample(x)
out += residual
out = self.relu(out)
return out
class ResNeXt(nn.Module):
def __init__(self, block, layers, groups=32, num_classes=1000):
self.inplanes = 128
super(ResNeXt, self).__init__()
self.conv1 = conv3x3(3, 64, stride=2)
self.bn1 = SynchronizedBatchNorm2d(64)
self.relu1 = nn.ReLU(inplace=True)
self.conv2 = conv3x3(64, 64)
self.bn2 = SynchronizedBatchNorm2d(64)
self.relu2 = nn.ReLU(inplace=True)
self.conv3 = conv3x3(64, 128)
self.bn3 = SynchronizedBatchNorm2d(128)
self.relu3 = nn.ReLU(inplace=True)
self.maxpool = nn.MaxPool2d(kernel_size=3, stride=2, padding=1)
self.layer1 = self._make_layer(block, 128, layers[0], groups=groups)
self.layer2 = self._make_layer(block, 256, layers[1], stride=2, groups=groups)
self.layer3 = self._make_layer(block, 512, layers[2], stride=2, groups=groups)
self.layer4 = self._make_layer(block, 1024, layers[3], stride=2, groups=groups)
self.avgpool = nn.AvgPool2d(7, stride=1)
self.fc = nn.Linear(1024 * block.expansion, num_classes)
for m in self.modules():
if isinstance(m, nn.Conv2d):
n = m.kernel_size[0] * m.kernel_size[1] * m.out_channels // m.groups
m.weight.data.normal_(0, math.sqrt(2. / n))
elif isinstance(m, SynchronizedBatchNorm2d):
m.weight.data.fill_(1)
m.bias.data.zero_()
def _make_layer(self, block, planes, blocks, stride=1, groups=1):
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),
SynchronizedBatchNorm2d(planes * block.expansion),
)
layers = []
layers.append(block(self.inplanes, planes, stride, groups, downsample))
self.inplanes = planes * block.expansion
for i in range(1, blocks):
layers.append(block(self.inplanes, planes, groups=groups))
return nn.Sequential(*layers)
def forward(self, x):
x = self.relu1(self.bn1(self.conv1(x)))
x = self.relu2(self.bn2(self.conv2(x)))
x = self.relu3(self.bn3(self.conv3(x)))
x = self.maxpool(x)
x = self.layer1(x)
x = self.layer2(x)
x = self.layer3(x)
x = self.layer4(x)
x = self.avgpool(x)
x = x.view(x.size(0), -1)
x = self.fc(x)
return x
'''
def resnext50(pretrained=False, **kwargs):
"""Constructs a ResNet-50 model.
Args:
pretrained (bool): If True, returns a model pre-trained on Places
"""
model = ResNeXt(GroupBottleneck, [3, 4, 6, 3], **kwargs)
if pretrained:
model.load_state_dict(load_url(model_urls['resnext50']), strict=False)
return model
'''
def resnext101(pretrained=False, **kwargs):
"""Constructs a ResNet-101 model.
Args:
pretrained (bool): If True, returns a model pre-trained on Places
"""
model = ResNeXt(GroupBottleneck, [3, 4, 23, 3], **kwargs)
if pretrained:
model.load_state_dict(load_url(model_urls['resnext101']), strict=False)
return model
# def resnext152(pretrained=False, **kwargs):
# """Constructs a ResNeXt-152 model.
#
# Args:
# pretrained (bool): If True, returns a model pre-trained on Places
# """
# model = ResNeXt(GroupBottleneck, [3, 8, 36, 3], **kwargs)
# if pretrained:
# model.load_state_dict(load_url(model_urls['resnext152']))
# return model
def load_url(url, model_dir='./pretrained', map_location=None):
if not os.path.exists(model_dir):
os.makedirs(model_dir)
filename = url.split('/')[-1]
cached_file = os.path.join(model_dir, filename)
if not os.path.exists(cached_file):
sys.stderr.write('Downloading: "{}" to {}\n'.format(url, cached_file))
urlretrieve(url, cached_file)
return torch.load(cached_file, map_location=map_location)
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