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res2next.py
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res2next.py
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from __future__ import division
import math
import torch.nn as nn
import torch.nn.functional as F
from torch.nn import init
import torch
import torch.utils.model_zoo as model_zoo
__all__ = ['res2next50']
model_urls = {
'res2next50': 'https://shanghuagao.oss-cn-beijing.aliyuncs.com/res2net/res2next50_4s-6ef7e7bf.pth',
}
class Bottle2neckX(nn.Module):
expansion = 4
def __init__(self, inplanes, planes, baseWidth, cardinality, stride=1, downsample=None, scale = 4, stype='normal'):
""" Constructor
Args:
inplanes: input channel dimensionality
planes: output channel dimensionality
baseWidth: base width.
cardinality: num of convolution groups.
stride: conv stride. Replaces pooling layer.
scale: number of scale.
type: 'normal': normal set. 'stage': frist blokc of a new stage.
"""
super(Bottle2neckX, self).__init__()
D = int(math.floor(planes * (baseWidth/64.0)))
C = cardinality
self.conv1 = nn.Conv2d(inplanes, D*C*scale, kernel_size=1, stride=1, padding=0, bias=False)
self.bn1 = nn.BatchNorm2d(D*C*scale)
if scale == 1:
self.nums = 1
else:
self.nums = scale -1
if stype == 'stage':
self.pool = nn.AvgPool2d(kernel_size=3, stride = stride, padding=1)
convs = []
bns = []
for i in range(self.nums):
convs.append(nn.Conv2d(D*C, D*C, kernel_size=3, stride = stride, padding=1, groups=C, bias=False))
bns.append(nn.BatchNorm2d(D*C))
self.convs = nn.ModuleList(convs)
self.bns = nn.ModuleList(bns)
self.conv3 = nn.Conv2d(D*C*scale, planes * 4, kernel_size=1, stride=1, padding=0, bias=False)
self.bn3 = nn.BatchNorm2d(planes * 4)
self.relu = nn.ReLU(inplace=True)
self.downsample = downsample
self.width = D*C
self.stype = stype
self.scale = scale
def forward(self, x):
residual = x
out = self.conv1(x)
out = self.bn1(out)
out = self.relu(out)
spx = torch.split(out, self.width, 1)
for i in range(self.nums):
if i==0 or self.stype=='stage':
sp = spx[i]
else:
sp = sp + spx[i]
sp = self.convs[i](sp)
sp = self.relu(self.bns[i](sp))
if i==0:
out = sp
else:
out = torch.cat((out, sp), 1)
if self.scale != 1 and self.stype=='normal':
out = torch.cat((out, spx[self.nums]),1)
elif self.scale != 1 and self.stype=='stage':
out = torch.cat((out, self.pool(spx[self.nums])),1)
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 Res2NeXt(nn.Module):
def __init__(self, block, baseWidth, cardinality, layers, num_classes, scale=4):
""" Constructor
Args:
baseWidth: baseWidth for ResNeXt.
cardinality: number of convolution groups.
layers: config of layers, e.g., [3, 4, 6, 3]
num_classes: number of classes
scale: scale in res2net
"""
super(Res2NeXt, self).__init__()
self.cardinality = cardinality
self.baseWidth = baseWidth
self.num_classes = num_classes
self.inplanes = 64
self.output_size = 64
self.scale = scale
self.conv1 = nn.Conv2d(3, 64, 7, 2, 3, bias=False)
self.bn1 = nn.BatchNorm2d(64)
self.relu = nn.ReLU(inplace=True)
self.maxpool1 = nn.MaxPool2d(kernel_size=3, stride=2, padding=1)
self.layer1 = self._make_layer(block, 64, layers[0])
self.layer2 = self._make_layer(block, 128, layers[1], 2)
self.layer3 = self._make_layer(block, 256, layers[2], 2)
self.layer4 = self._make_layer(block, 512, layers[3], 2)
self.avgpool = nn.AdaptiveAvgPool2d(1)
self.fc = nn.Linear(512 * 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.weight.data.normal_(0, math.sqrt(2. / n))
elif isinstance(m, nn.BatchNorm2d):
m.weight.data.fill_(1)
m.bias.data.zero_()
def _make_layer(self, block, planes, blocks, stride=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),
nn.BatchNorm2d(planes * block.expansion),
)
layers = []
layers.append(block(self.inplanes, planes, self.baseWidth, self.cardinality, stride, downsample, scale=self.scale, stype='stage'))
self.inplanes = planes * block.expansion
for i in range(1, blocks):
layers.append(block(self.inplanes, planes, self.baseWidth, self.cardinality, scale=self.scale))
return nn.Sequential(*layers)
def forward(self, x):
x = self.conv1(x)
x = self.bn1(x)
x = self.relu(x)
x = self.maxpool1(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 res2next50(pretrained=False, **kwargs):
""" Construct Res2NeXt-50.
The default scale is 4.
Args:
pretrained (bool): If True, returns a model pre-trained on ImageNet
"""
model = Res2NeXt(Bottle2neckX, layers = [3, 4, 6, 3], baseWidth = 4, cardinality=8, scale = 4, num_classes=1000)
if pretrained:
model.load_state_dict(model_zoo.load_url(model_urls['res2next50']))
return model
if __name__ == '__main__':
images = torch.rand(1, 3, 224, 224).cuda(0)
model = res2next50(pretrained=True)
model = model.cuda(0)
print(model(images).size())