preface
MobileNet V1
class MobileNet(nn.Module):
def __init__(self):
super(MobileNet, self).__init__()
def conv_bn(inp, oup, stride):
return nn.Sequential(
nn.Conv2d(inp, oup, 3, stride, 1, bias=False),
nn.BatchNorm2d(oup),
nn.ReLU(inplace=True)
)
def conv_dw(inp, oup, stride):
return nn.Sequential(
nn.Conv2d(inp, inp, 3, stride, 1, groups=inp, bias=False),
nn.BatchNorm2d(inp),
nn.ReLU(inplace=True),
nn.Conv2d(inp, oup, 1, 1, 0, bias=False),
nn.BatchNorm2d(oup),
nn.ReLU(inplace=True),
)
self.model = nn.Sequential(
conv_bn( 3, 32, 2),
conv_dw( 32, 64, 1),
conv_dw( 64, 128, 2),
conv_dw(128, 128, 1),
conv_dw(128, 256, 2),
conv_dw(256, 256, 1),
conv_dw(256, 512, 2),
conv_dw(512, 512, 1),
conv_dw(512, 512, 1),
conv_dw(512, 512, 1),
conv_dw(512, 512, 1),
conv_dw(512, 512, 1),
conv_dw(512, 1024, 2),
conv_dw(1024, 1024, 1),
nn.AvgPool2d(7),
)
self.fc = nn.Linear(1024, 1000)
def forward(self, x):
x = self.model(x)
x = x.view(-1, 1024)
x = self.fc(x)
return x
MobileNet V2
class ConvBNReLU(nn.Sequential):
def __init__(self, in_planes, out_planes, kernel_size=3, stride=1, groups=1):
padding = (kernel_size - 1) // 2
super(ConvBNReLU, self).__init__(
nn.Conv2d(in_planes, out_planes, kernel_size, stride, padding, groups=groups, bias=False),
nn.BatchNorm2d(out_planes),
nn.ReLU6(inplace=True)
)
class InvertedResidual(nn.Module):
def __init__(self, inp, oup, stride, expand_ratio):
super(InvertedResidual, self).__init__()
self.stride = stride
assert stride in [1, 2]
hidden_dim = int(round(inp * expand_ratio))
self.use_res_connect = self.stride == 1 and inp == oup
layers = []
if expand_ratio != 1:
# pw
layers.append(ConvBNReLU(inp, hidden_dim, kernel_size=1))
layers.extend([
# dw
ConvBNReLU(hidden_dim, hidden_dim, stride=stride, groups=hidden_dim),
# pw-linear
nn.Conv2d(hidden_dim, oup, 1, 1, 0, bias=False),
nn.BatchNorm2d(oup),
])
self.conv = nn.Sequential(*layers)
def forward(self, x):
if self.use_res_connect:
return x + self.conv(x)
else:
return self.conv(x)
class MobileNetV2(nn.Module):
def __init__(self, num_classes=1000, width_mult=1.0):
super(MobileNetV2, self).__init__()
block = InvertedResidual
input_channel = 32
last_channel = 1280
inverted_residual_setting = [
# t, c, n, s
[1, 16, 1, 1],
[6, 24, 2, 2],
[6, 32, 3, 2],
[6, 64, 4, 2],
[6, 96, 3, 1],
[6, 160, 3, 2],
[6, 320, 1, 1],
]
# building first layer
input_channel = int(input_channel * width_mult)
self.last_channel = int(last_channel * max(1.0, width_mult))
features = [ConvBNReLU(3, input_channel, stride=2)]
# building inverted residual blocks
for t, c, n, s in inverted_residual_setting:
output_channel = int(c * width_mult)
for i in range(n):
stride = s if i == 0 else 1
features.append(block(input_channel, output_channel, stride, expand_ratio=t))
input_channel = output_channel
# building last several layers
features.append(ConvBNReLU(input_channel, self.last_channel, kernel_size=1))
# make it nn.Sequential
self.features = nn.Sequential(*features)
# building classifier
self.classifier = nn.Sequential(
nn.Dropout(0.2),
nn.Linear(self.last_channel, num_classes),
)
# weight initialization
for m in self.modules():
if isinstance(m, nn.Conv2d):
nn.init.kaiming_normal_(m.weight, mode='fan_out')
if m.bias is not None:
nn.init.zeros_(m.bias)
elif isinstance(m, nn.BatchNorm2d):
nn.init.ones_(m.weight)
nn.init.zeros_(m.bias)
elif isinstance(m, nn.Linear):
nn.init.normal_(m.weight, 0, 0.01)
nn.init.zeros_(m.bias)
def forward(self, x):
x = self.features(x)
x = x.mean([2, 3])
x = self.classifier(x)
return x
MobileNet V3
def conv_bn(inp, oup, stride, conv_layer=nn.Conv2d, norm_layer=nn.BatchNorm2d, nlin_layer=nn.ReLU):
return nn.Sequential(
conv_layer(inp, oup, 3, stride, 1, bias=False),
norm_layer(oup),
nlin_layer(inplace=True)
)
def conv_1x1_bn(inp, oup, conv_layer=nn.Conv2d, norm_layer=nn.BatchNorm2d, nlin_layer=nn.ReLU):
return nn.Sequential(
conv_layer(inp, oup, 1, 1, 0, bias=False),
norm_layer(oup),
nlin_layer(inplace=True)
)
class Hswish(nn.Module):
def __init__(self, inplace=True):
super(Hswish, self).__init__()
self.inplace = inplace
def forward(self, x):
return x * F.relu6(x + 3., inplace=self.inplace) / 6.
class Hsigmoid(nn.Module):
def __init__(self, inplace=True):
super(Hsigmoid, self).__init__()
self.inplace = inplace
def forward(self, x):
return F.relu6(x + 3., inplace=self.inplace) / 6.
class SEModule(nn.Module):
def __init__(self, channel, reduction=4):
super(SEModule, self).__init__()
self.avg_pool = nn.AdaptiveAvgPool2d(1)
self.fc = nn.Sequential(
nn.Linear(channel, channel // reduction, bias=False),
nn.ReLU(inplace=True),
nn.Linear(channel // reduction, channel, bias=False),
Hsigmoid()
# nn.Sigmoid()
)
def forward(self, x):
b, c, _, _ = x.size()
y = self.avg_pool(x).view(b, c)
y = self.fc(y).view(b, c, 1, 1)
return x * y.expand_as(x)
class Identity(nn.Module):
def __init__(self, channel):
super(Identity, self).__init__()
def forward(self, x):
return x
def make_divisible(x, divisible_by=8):
import numpy as np
return int(np.ceil(x * 1. / divisible_by) * divisible_by)
class MobileBottleneck(nn.Module):
def __init__(self, inp, oup, kernel, stride, exp, se=False, nl='RE'):
super(MobileBottleneck, self).__init__()
assert stride in [1, 2]
assert kernel in [3, 5]
padding = (kernel - 1) // 2
self.use_res_connect = stride == 1 and inp == oup
conv_layer = nn.Conv2d
norm_layer = nn.BatchNorm2d
if nl == 'RE':
nlin_layer = nn.ReLU # or ReLU6
elif nl == 'HS':
nlin_layer = Hswish
else:
raise NotImplementedError
if se:
SELayer = SEModule
else:
SELayer = Identity
self.conv = nn.Sequential(
# pw
conv_layer(inp, exp, 1, 1, 0, bias=False),
norm_layer(exp),
nlin_layer(inplace=True),
# dw
conv_layer(exp, exp, kernel, stride, padding, groups=exp, bias=False),
norm_layer(exp),
SELayer(exp),
nlin_layer(inplace=True),
# pw-linear
conv_layer(exp, oup, 1, 1, 0, bias=False),
norm_layer(oup),
)
def forward(self, x):
if self.use_res_connect:
return x + self.conv(x)
else:
return self.conv(x)
class MobileNetV3(nn.Module):
def __init__(self, n_class=1000, input_size=224, dropout=0.8, mode='small', width_mult=1.0):
super(MobileNetV3, self).__init__()
input_channel = 16
last_channel = 1280
if mode == 'large':
# refer to Table 1 in paper
mobile_setting = [
# k, exp, c, se, nl, s,
[3, 16, 16, False, 'RE', 1],
[3, 64, 24, False, 'RE', 2],
[3, 72, 24, False, 'RE', 1],
[5, 72, 40, True, 'RE', 2],
[5, 120, 40, True, 'RE', 1],
[5, 120, 40, True, 'RE', 1],
[3, 240, 80, False, 'HS', 2],
[3, 200, 80, False, 'HS', 1],
[3, 184, 80, False, 'HS', 1],
[3, 184, 80, False, 'HS', 1],
[3, 480, 112, True, 'HS', 1],
[3, 672, 112, True, 'HS', 1],
[5, 672, 160, True, 'HS', 2],
[5, 960, 160, True, 'HS', 1],
[5, 960, 160, True, 'HS', 1],
]
elif mode == 'small':
# refer to Table 2 in paper
mobile_setting = [
# k, exp, c, se, nl, s,
[3, 16, 16, True, 'RE', 2],
[3, 72, 24, False, 'RE', 2],
[3, 88, 24, False, 'RE', 1],
[5, 96, 40, True, 'HS', 2],
[5, 240, 40, True, 'HS', 1],
[5, 240, 40, True, 'HS', 1],
[5, 120, 48, True, 'HS', 1],
[5, 144, 48, True, 'HS', 1],
[5, 288, 96, True, 'HS', 2],
[5, 576, 96, True, 'HS', 1],
[5, 576, 96, True, 'HS', 1],
]
else:
raise NotImplementedError
# building first layer
assert input_size % 32 == 0
last_channel = make_divisible(last_channel * width_mult) if width_mult > 1.0 else last_channel
self.features = [conv_bn(3, input_channel, 2, nlin_layer=Hswish)]
self.classifier = []
# building mobile blocks
for k, exp, c, se, nl, s in mobile_setting:
output_channel = make_divisible(c * width_mult)
exp_channel = make_divisible(exp * width_mult)
self.features.append(MobileBottleneck(input_channel, output_channel, k, s, exp_channel, se, nl))
input_channel = output_channel
# building last several layers
if mode == 'large':
last_conv = make_divisible(960 * width_mult)
self.features.append(conv_1x1_bn(input_channel, last_conv, nlin_layer=Hswish))
self.features.append(nn.AdaptiveAvgPool2d(1))
self.features.append(nn.Conv2d(last_conv, last_channel, 1, 1, 0))
self.features.append(Hswish(inplace=True))
elif mode == 'small':
last_conv = make_divisible(576 * width_mult)
self.features.append(conv_1x1_bn(input_channel, last_conv, nlin_layer=Hswish))
# self.features.append(SEModule(last_conv)) # refer to paper Table2, but I think this is a mistake
self.features.append(nn.AdaptiveAvgPool2d(1))
self.features.append(nn.Conv2d(last_conv, last_channel, 1, 1, 0))
self.features.append(Hswish(inplace=True))
else:
raise NotImplementedError
# make it nn.Sequential
self.features = nn.Sequential(*self.features)
# building classifier
self.classifier = nn.Sequential(
nn.Dropout(p=dropout), # refer to paper section 6
nn.Linear(last_channel, n_class),
)
self._initialize_weights()
def forward(self, x):
x = self.features(x)
x = x.mean(3).mean(2)
x = self.classifier(x)
return x
def _initialize_weights(self):
# weight initialization
for m in self.modules():
if isinstance(m, nn.Conv2d):
nn.init.kaiming_normal_(m.weight, mode='fan_out')
if m.bias is not None:
nn.init.zeros_(m.bias)
elif isinstance(m, nn.BatchNorm2d):
nn.init.ones_(m.weight)
nn.init.zeros_(m.bias)
elif isinstance(m, nn.Linear):
nn.init.normal_(m.weight, 0, 0.01)
if m.bias is not None:
nn.init.zeros_(m.bias)