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mixnet.py
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"""
MixNet for ImageNet-1K, implemented in PyTorch.
Original paper: 'MixConv: Mixed Depthwise Convolutional Kernels,' https://arxiv.org/abs/1907.09595.
"""
__all__ = ['MixNet', 'mixnet_s', 'mixnet_m', 'mixnet_l']
import os
import torch
import torch.nn as nn
import torch.nn.init as init
from .common import round_channels, get_activation_layer, conv1x1_block, conv3x3_block, dwconv3x3_block, SEBlock
class MixConv(nn.Module):
"""
Mixed convolution layer from 'MixConv: Mixed Depthwise Convolutional Kernels,' https://arxiv.org/abs/1907.09595.
Parameters:
----------
in_channels : int
Number of input channels.
out_channels : int
Number of output channels.
kernel_size : int or tuple/list of int, or tuple/list of tuple/list of 2 int
Convolution window size.
stride : int or tuple/list of 2 int
Strides of the convolution.
padding : int or tuple/list of int, or tuple/list of tuple/list of 2 int
Padding value for convolution layer.
dilation : int or tuple/list of 2 int, default 1
Dilation value for convolution layer.
groups : int, default 1
Number of groups.
bias : bool, default False
Whether the layer uses a bias vector.
axis : int, default 1
The axis on which to concatenate the outputs.
"""
def __init__(self,
in_channels,
out_channels,
kernel_size,
stride,
padding,
dilation=1,
groups=1,
bias=False,
axis=1):
super(MixConv, self).__init__()
kernel_size = kernel_size if isinstance(kernel_size, list) else [kernel_size]
padding = padding if isinstance(padding, list) else [padding]
kernel_count = len(kernel_size)
self.splitted_in_channels = self.split_channels(in_channels, kernel_count)
splitted_out_channels = self.split_channels(out_channels, kernel_count)
for i, kernel_size_i in enumerate(kernel_size):
in_channels_i = self.splitted_in_channels[i]
out_channels_i = splitted_out_channels[i]
padding_i = padding[i]
self.add_module(
name=str(i),
module=nn.Conv2d(
in_channels=in_channels_i,
out_channels=out_channels_i,
kernel_size=kernel_size_i,
stride=stride,
padding=padding_i,
dilation=dilation,
groups=(out_channels_i if out_channels == groups else groups),
bias=bias))
self.axis = axis
def forward(self, x):
xx = torch.split(x, self.splitted_in_channels, dim=self.axis)
out = [conv_i(x_i) for x_i, conv_i in zip(xx, self._modules.values())]
x = torch.cat(tuple(out), dim=self.axis)
return x
@staticmethod
def split_channels(channels, kernel_count):
splitted_channels = [channels // kernel_count] * kernel_count
splitted_channels[0] += channels - sum(splitted_channels)
return splitted_channels
class MixConvBlock(nn.Module):
"""
Mixed convolution block with Batch normalization and activation.
Parameters:
----------
in_channels : int
Number of input channels.
out_channels : int
Number of output channels.
kernel_size : int or tuple/list of int, or tuple/list of tuple/list of 2 int
Convolution window size.
stride : int or tuple/list of 2 int
Strides of the convolution.
padding : int or tuple/list of int, or tuple/list of tuple/list of 2 int
Padding value for convolution layer.
dilation : int or tuple/list of 2 int, default 1
Dilation value for convolution layer.
groups : int, default 1
Number of groups.
bias : bool, default False
Whether the layer uses a bias vector.
use_bn : bool, default True
Whether to use BatchNorm layer.
bn_eps : float, default 1e-5
Small float added to variance in Batch norm.
activation : function or str or None, default nn.ReLU(inplace=True)
Activation function or name of activation function.
activate : bool, default True
Whether activate the convolution block.
"""
def __init__(self,
in_channels,
out_channels,
kernel_size,
stride,
padding,
dilation=1,
groups=1,
bias=False,
use_bn=True,
bn_eps=1e-5,
activation=(lambda: nn.ReLU(inplace=True))):
super(MixConvBlock, self).__init__()
self.activate = (activation is not None)
self.use_bn = use_bn
self.conv = MixConv(
in_channels=in_channels,
out_channels=out_channels,
kernel_size=kernel_size,
stride=stride,
padding=padding,
dilation=dilation,
groups=groups,
bias=bias)
if self.use_bn:
self.bn = nn.BatchNorm2d(
num_features=out_channels,
eps=bn_eps)
if self.activate:
self.activ = get_activation_layer(activation)
def forward(self, x):
x = self.conv(x)
if self.use_bn:
x = self.bn(x)
if self.activate:
x = self.activ(x)
return x
def mixconv1x1_block(in_channels,
out_channels,
kernel_count,
stride=1,
groups=1,
bias=False,
use_bn=True,
bn_eps=1e-5,
activation=(lambda: nn.ReLU(inplace=True))):
"""
1x1 version of the mixed convolution block.
Parameters:
----------
in_channels : int
Number of input channels.
out_channels : int
Number of output channels.
kernel_count : int
Kernel count.
stride : int or tuple/list of 2 int, default 1
Strides of the convolution.
groups : int, default 1
Number of groups.
bias : bool, default False
Whether the layer uses a bias vector.
use_bn : bool, default True
Whether to use BatchNorm layer.
bn_eps : float, default 1e-5
Small float added to variance in Batch norm.
activation : function or str, or None, default nn.ReLU(inplace=True)
Activation function or name of activation function.
"""
return MixConvBlock(
in_channels=in_channels,
out_channels=out_channels,
kernel_size=([1] * kernel_count),
stride=stride,
padding=([0] * kernel_count),
groups=groups,
bias=bias,
use_bn=use_bn,
bn_eps=bn_eps,
activation=activation)
class MixUnit(nn.Module):
"""
MixNet unit.
Parameters:
----------
in_channels : int
Number of input channels.
out_channels : int
Number of output channels.
exp_channels : int
Number of middle (expanded) channels.
stride : int or tuple/list of 2 int
Strides of the second convolution layer.
exp_kernel_count : int
Expansion convolution kernel count for each unit.
conv1_kernel_count : int
Conv1 kernel count for each unit.
conv2_kernel_count : int
Conv2 kernel count for each unit.
exp_factor : int
Expansion factor for each unit.
se_factor : int
SE reduction factor for each unit.
activation : str
Activation function or name of activation function.
"""
def __init__(self,
in_channels,
out_channels,
stride,
exp_kernel_count,
conv1_kernel_count,
conv2_kernel_count,
exp_factor,
se_factor,
activation):
super(MixUnit, self).__init__()
assert (exp_factor >= 1)
assert (se_factor >= 0)
self.residual = (in_channels == out_channels) and (stride == 1)
self.use_se = se_factor > 0
mid_channels = exp_factor * in_channels
self.use_exp_conv = exp_factor > 1
if self.use_exp_conv:
if exp_kernel_count == 1:
self.exp_conv = conv1x1_block(
in_channels=in_channels,
out_channels=mid_channels,
activation=activation)
else:
self.exp_conv = mixconv1x1_block(
in_channels=in_channels,
out_channels=mid_channels,
kernel_count=exp_kernel_count,
activation=activation)
if conv1_kernel_count == 1:
self.conv1 = dwconv3x3_block(
in_channels=mid_channels,
out_channels=mid_channels,
stride=stride,
activation=activation)
else:
self.conv1 = MixConvBlock(
in_channels=mid_channels,
out_channels=mid_channels,
kernel_size=[3 + 2 * i for i in range(conv1_kernel_count)],
stride=stride,
padding=[1 + i for i in range(conv1_kernel_count)],
groups=mid_channels,
activation=activation)
if self.use_se:
self.se = SEBlock(
channels=mid_channels,
reduction=(exp_factor * se_factor),
round_mid=False,
mid_activation=activation)
if conv2_kernel_count == 1:
self.conv2 = conv1x1_block(
in_channels=mid_channels,
out_channels=out_channels,
activation=None)
else:
self.conv2 = mixconv1x1_block(
in_channels=mid_channels,
out_channels=out_channels,
kernel_count=conv2_kernel_count,
activation=None)
def forward(self, x):
if self.residual:
identity = x
if self.use_exp_conv:
x = self.exp_conv(x)
x = self.conv1(x)
if self.use_se:
x = self.se(x)
x = self.conv2(x)
if self.residual:
x = x + identity
return x
class MixInitBlock(nn.Module):
"""
MixNet specific initial block.
Parameters:
----------
in_channels : int
Number of input channels.
out_channels : int
Number of output channels.
"""
def __init__(self,
in_channels,
out_channels):
super(MixInitBlock, self).__init__()
self.conv1 = conv3x3_block(
in_channels=in_channels,
out_channels=out_channels,
stride=2)
self.conv2 = MixUnit(
in_channels=out_channels,
out_channels=out_channels,
stride=1,
exp_kernel_count=1,
conv1_kernel_count=1,
conv2_kernel_count=1,
exp_factor=1,
se_factor=0,
activation="relu")
def forward(self, x):
x = self.conv1(x)
x = self.conv2(x)
return x
class MixNet(nn.Module):
"""
MixNet model from 'MixConv: Mixed Depthwise Convolutional Kernels,' https://arxiv.org/abs/1907.09595.
Parameters:
----------
channels : list of list of int
Number of output channels for each unit.
init_block_channels : int
Number of output channels for the initial unit.
final_block_channels : int
Number of output channels for the final block of the feature extractor.
exp_kernel_counts : list of list of int
Expansion convolution kernel count for each unit.
conv1_kernel_counts : list of list of int
Conv1 kernel count for each unit.
conv2_kernel_counts : list of list of int
Conv2 kernel count for each unit.
exp_factors : list of list of int
Expansion factor for each unit.
se_factors : list of list of int
SE reduction factor for each unit.
in_channels : int, default 3
Number of input channels.
in_size : tuple of two ints, default (224, 224)
Spatial size of the expected input image.
num_classes : int, default 1000
Number of classification classes.
"""
def __init__(self,
channels,
init_block_channels,
final_block_channels,
exp_kernel_counts,
conv1_kernel_counts,
conv2_kernel_counts,
exp_factors,
se_factors,
in_channels=3,
in_size=(224, 224),
num_classes=1000):
super(MixNet, self).__init__()
self.in_size = in_size
self.num_classes = num_classes
self.features = nn.Sequential()
self.features.add_module("init_block", MixInitBlock(
in_channels=in_channels,
out_channels=init_block_channels))
in_channels = init_block_channels
for i, channels_per_stage in enumerate(channels):
stage = nn.Sequential()
for j, out_channels in enumerate(channels_per_stage):
stride = 2 if ((j == 0) and (i != 3)) or ((j == len(channels_per_stage) // 2) and (i == 3)) else 1
exp_kernel_count = exp_kernel_counts[i][j]
conv1_kernel_count = conv1_kernel_counts[i][j]
conv2_kernel_count = conv2_kernel_counts[i][j]
exp_factor = exp_factors[i][j]
se_factor = se_factors[i][j]
activation = "relu" if i == 0 else "swish"
stage.add_module("unit{}".format(j + 1), MixUnit(
in_channels=in_channels,
out_channels=out_channels,
stride=stride,
exp_kernel_count=exp_kernel_count,
conv1_kernel_count=conv1_kernel_count,
conv2_kernel_count=conv2_kernel_count,
exp_factor=exp_factor,
se_factor=se_factor,
activation=activation))
in_channels = out_channels
self.features.add_module("stage{}".format(i + 1), stage)
self.features.add_module("final_block", conv1x1_block(
in_channels=in_channels,
out_channels=final_block_channels))
in_channels = final_block_channels
self.features.add_module("final_pool", nn.AvgPool2d(
kernel_size=7,
stride=1))
self.output = nn.Linear(
in_features=in_channels,
out_features=num_classes)
self._init_params()
def _init_params(self):
for name, module in self.named_modules():
if isinstance(module, nn.Conv2d):
init.kaiming_uniform_(module.weight)
if module.bias is not None:
init.constant_(module.bias, 0)
def forward(self, x):
x = self.features(x)
x = x.view(x.size(0), -1)
x = self.output(x)
return x
def get_mixnet(version,
width_scale,
model_name=None,
pretrained=False,
root=os.path.join("~", ".torch", "models"),
**kwargs):
"""
Create MixNet model with specific parameters.
Parameters:
----------
version : str
Version of MobileNetV3 ('s' or 'm').
width_scale : float
Scale factor for width of layers.
model_name : str or None, default None
Model name for loading pretrained model.
pretrained : bool, default False
Whether to load the pretrained weights for model.
root : str, default '~/.torch/models'
Location for keeping the model parameters.
"""
if version == "s":
init_block_channels = 16
channels = [[24, 24], [40, 40, 40, 40], [80, 80, 80], [120, 120, 120, 200, 200, 200]]
exp_kernel_counts = [[2, 2], [1, 2, 2, 2], [1, 1, 1], [2, 2, 2, 1, 1, 1]]
conv1_kernel_counts = [[1, 1], [3, 2, 2, 2], [3, 2, 2], [3, 4, 4, 5, 4, 4]]
conv2_kernel_counts = [[2, 2], [1, 2, 2, 2], [2, 2, 2], [2, 2, 2, 1, 2, 2]]
exp_factors = [[6, 3], [6, 6, 6, 6], [6, 6, 6], [6, 3, 3, 6, 6, 6]]
se_factors = [[0, 0], [2, 2, 2, 2], [4, 4, 4], [2, 2, 2, 2, 2, 2]]
elif version == "m":
init_block_channels = 24
channels = [[32, 32], [40, 40, 40, 40], [80, 80, 80, 80], [120, 120, 120, 120, 200, 200, 200, 200]]
exp_kernel_counts = [[2, 2], [1, 2, 2, 2], [1, 2, 2, 2], [1, 2, 2, 2, 1, 1, 1, 1]]
conv1_kernel_counts = [[3, 1], [4, 2, 2, 2], [3, 4, 4, 4], [1, 4, 4, 4, 4, 4, 4, 4]]
conv2_kernel_counts = [[2, 2], [1, 2, 2, 2], [1, 2, 2, 2], [1, 2, 2, 2, 1, 2, 2, 2]]
exp_factors = [[6, 3], [6, 6, 6, 6], [6, 6, 6, 6], [6, 3, 3, 3, 6, 6, 6, 6]]
se_factors = [[0, 0], [2, 2, 2, 2], [4, 4, 4, 4], [2, 2, 2, 2, 2, 2, 2, 2]]
else:
raise ValueError("Unsupported MixNet version {}".format(version))
final_block_channels = 1536
if width_scale != 1.0:
channels = [[round_channels(cij * width_scale) for cij in ci] for ci in channels]
init_block_channels = round_channels(init_block_channels * width_scale)
net = MixNet(
channels=channels,
init_block_channels=init_block_channels,
final_block_channels=final_block_channels,
exp_kernel_counts=exp_kernel_counts,
conv1_kernel_counts=conv1_kernel_counts,
conv2_kernel_counts=conv2_kernel_counts,
exp_factors=exp_factors,
se_factors=se_factors,
**kwargs)
if pretrained:
if (model_name is None) or (not model_name):
raise ValueError("Parameter `model_name` should be properly initialized for loading pretrained model.")
from .model_store import download_model
download_model(
net=net,
model_name=model_name,
local_model_store_dir_path=root)
return net
def mixnet_s(**kwargs):
"""
MixNet-S model from 'MixConv: Mixed Depthwise Convolutional Kernels,' https://arxiv.org/abs/1907.09595.
Parameters:
----------
pretrained : bool, default False
Whether to load the pretrained weights for model.
root : str, default '~/.torch/models'
Location for keeping the model parameters.
"""
return get_mixnet(version="s", width_scale=1.0, model_name="mixnet_s", **kwargs)
def mixnet_m(**kwargs):
"""
MixNet-M model from 'MixConv: Mixed Depthwise Convolutional Kernels,' https://arxiv.org/abs/1907.09595.
Parameters:
----------
pretrained : bool, default False
Whether to load the pretrained weights for model.
root : str, default '~/.torch/models'
Location for keeping the model parameters.
"""
return get_mixnet(version="m", width_scale=1.0, model_name="mixnet_m", **kwargs)
def mixnet_l(**kwargs):
"""
MixNet-L model from 'MixConv: Mixed Depthwise Convolutional Kernels,' https://arxiv.org/abs/1907.09595.
Parameters:
----------
pretrained : bool, default False
Whether to load the pretrained weights for model.
root : str, default '~/.torch/models'
Location for keeping the model parameters.
"""
return get_mixnet(version="m", width_scale=1.3, model_name="mixnet_l", **kwargs)
def _calc_width(net):
import numpy as np
net_params = filter(lambda p: p.requires_grad, net.parameters())
weight_count = 0
for param in net_params:
weight_count += np.prod(param.size())
return weight_count
def _test():
import torch
pretrained = False
models = [
mixnet_s,
mixnet_m,
mixnet_l,
]
for model in models:
net = model(pretrained=pretrained)
# net.train()
net.eval()
weight_count = _calc_width(net)
print("m={}, {}".format(model.__name__, weight_count))
assert (model != mixnet_s or weight_count == 4134606)
assert (model != mixnet_m or weight_count == 5014382)
assert (model != mixnet_l or weight_count == 7329252)
x = torch.randn(1, 3, 224, 224)
y = net(x)
y.sum().backward()
assert (tuple(y.size()) == (1, 1000))
if __name__ == "__main__":
_test()