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xception.py
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"""
Creates an Xception Model as defined in:
Francois Chollet
Xception: Deep Learning with Depthwise Separable Convolutions
https://arxiv.org/pdf/1610.02357.pdf
This weights ported from the Keras implementation. Achieves the following performance on the validation set:
Loss:0.9173 Prec@1:78.892 Prec@5:94.292
REMEMBER to set your image size to 3x299x299 for both test and validation
normalize = transforms.Normalize(mean=[0.5, 0.5, 0.5],
std=[0.5, 0.5, 0.5])
The resize parameter of the validation transform should be 333, and make sure to center crop at 299x299
"""
import math
import torch.nn as nn
import torch.nn.functional as F
import torch.utils.model_zoo as model_zoo
from torch.nn import init
import torch
__all__ = ['xception']
model_urls = {
# 'xception':'https://www.dropbox.com/s/1hplpzet9d7dv29/xception-c0a72b38.pth.tar?dl=1'
'xception':'http://data.lip6.fr/cadene/pretrainedmodels/xception-43020ad28.pth'
}
class SeparableConv2d(nn.Module):
def __init__(self,in_channels,out_channels,kernel_size=1,stride=1,padding=0,dilation=1,bias=False):
super(SeparableConv2d,self).__init__()
self.conv1 = nn.Conv2d(in_channels,in_channels,kernel_size,stride,padding,dilation,groups=in_channels,bias=bias)
self.pointwise = nn.Conv2d(in_channels,out_channels,1,1,0,1,1,bias=bias)
def forward(self,x):
x = self.conv1(x)
x = self.pointwise(x)
return x
class Block(nn.Module):
def __init__(self,in_filters,out_filters,reps,strides=1,start_with_relu=True,grow_first=True):
super(Block, self).__init__()
if out_filters != in_filters or strides!=1:
self.skip = nn.Conv2d(in_filters,out_filters,1,stride=strides, bias=False)
self.skipbn = nn.BatchNorm2d(out_filters)
else:
self.skip=None
self.relu = nn.ReLU(inplace=True)
rep=[]
filters=in_filters
if grow_first:
rep.append(self.relu)
rep.append(SeparableConv2d(in_filters,out_filters,3,stride=1,padding=1,bias=False))
rep.append(nn.BatchNorm2d(out_filters))
filters = out_filters
for i in range(reps-1):
rep.append(self.relu)
rep.append(SeparableConv2d(filters,filters,3,stride=1,padding=1,bias=False))
rep.append(nn.BatchNorm2d(filters))
if not grow_first:
rep.append(self.relu)
rep.append(SeparableConv2d(in_filters,out_filters,3,stride=1,padding=1,bias=False))
rep.append(nn.BatchNorm2d(out_filters))
if not start_with_relu:
rep = rep[1:]
else:
rep[0] = nn.ReLU(inplace=False)
if strides != 1:
rep.append(nn.MaxPool2d(3,strides,1))
self.rep = nn.Sequential(*rep)
def forward(self,inp):
x = self.rep(inp)
if self.skip is not None:
skip = self.skip(inp)
skip = self.skipbn(skip)
else:
skip = inp
x+=skip
return x
class Xception(nn.Module):
"""
Xception optimized for the ImageNet dataset, as specified in
https://arxiv.org/pdf/1610.02357.pdf
"""
def __init__(self, num_classes=1000):
""" Constructor
Args:
num_classes: number of classes
"""
super(Xception, self).__init__()
self.num_classes = num_classes
self.conv1 = nn.Conv2d(3, 32, 3,2, 0, bias=False)
self.bn1 = nn.BatchNorm2d(32)
self.relu = nn.ReLU(inplace=True)
self.conv2 = nn.Conv2d(32,64,3,bias=False)
self.bn2 = nn.BatchNorm2d(64)
#do relu here
self.block1=Block(64,128,2,2,start_with_relu=False,grow_first=True)
self.block2=Block(128,256,2,2,start_with_relu=True,grow_first=True)
self.block3=Block(256,728,2,2,start_with_relu=True,grow_first=True)
self.block4=Block(728,728,3,1,start_with_relu=True,grow_first=True)
self.block5=Block(728,728,3,1,start_with_relu=True,grow_first=True)
self.block6=Block(728,728,3,1,start_with_relu=True,grow_first=True)
self.block7=Block(728,728,3,1,start_with_relu=True,grow_first=True)
self.block8=Block(728,728,3,1,start_with_relu=True,grow_first=True)
self.block9=Block(728,728,3,1,start_with_relu=True,grow_first=True)
self.block10=Block(728,728,3,1,start_with_relu=True,grow_first=True)
self.block11=Block(728,728,3,1,start_with_relu=True,grow_first=True)
self.block12=Block(728,1024,2,2,start_with_relu=True,grow_first=False)
self.conv3 = SeparableConv2d(1024,1536,3,1,1)
self.bn3 = nn.BatchNorm2d(1536)
#do relu here
self.conv4 = SeparableConv2d(1536,2048,3,1,1)
self.bn4 = nn.BatchNorm2d(2048)
self.fc = nn.Linear(2048, num_classes)
#------- init weights --------
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 forward(self, x):
x = self.conv1(x)
x = self.bn1(x)
x = self.relu(x)
x = self.conv2(x)
x = self.bn2(x)
x = self.relu(x)
x = self.block1(x)
x = self.block2(x)
x = self.block3(x)
x = self.block4(x)
x = self.block5(x)
x = self.block6(x)
x = self.block7(x)
x = self.block8(x)
x = self.block9(x)
x = self.block10(x)
x = self.block11(x)
x = self.block12(x)
x = self.conv3(x)
x = self.bn3(x)
x = self.relu(x)
x = self.conv4(x)
x = self.bn4(x)
x = self.relu(x)
x = F.adaptive_avg_pool2d(x, (1, 1))
x = x.view(x.size(0), -1)
x = self.fc(x)
return x
def xception(pretrained=False,**kwargs):
"""
Construct Xception.
"""
model = Xception(**kwargs)
if pretrained:
model.load_state_dict(model_zoo.load_url(model_urls['xception']))
return model