"""
An implementation of GhostNet Model as defined in:
GhostNet: More Features from Cheap Operations. https://arxiv.org/abs/1911.11907
The train script of the model is similar to that of MobileNetV3
Original model: https://github.com/huawei-noah/CV-backbones/tree/master/ghostnet_pytorch
"""
import math
from functools import partial
import torch
import torch.nn as nn
import torch.nn.functional as F
from timm.data import IMAGENET_DEFAULT_MEAN, IMAGENET_DEFAULT_STD
from .layers import SelectAdaptivePool2d, Linear, make_divisible
from .efficientnet_blocks import SqueezeExcite, ConvBnAct
from .helpers import build_model_with_cfg
from .registry import register_model
__all__ = ['GhostNet']
def _cfg(url='', **kwargs):
return {
'url': url, 'num_classes': 1000, 'input_size': (3, 224, 224), 'pool_size': (1, 1),
'crop_pct': 0.875, 'interpolation': 'bilinear',
'mean': IMAGENET_DEFAULT_MEAN, 'std': IMAGENET_DEFAULT_STD,
'first_conv': 'conv_stem', 'classifier': 'classifier',
**kwargs
}
default_cfgs = {
'ghostnet_050': _cfg(url=''),
'ghostnet_100': _cfg(
url='https://github.com/huawei-noah/CV-backbones/releases/download/ghostnet_pth/ghostnet_1x.pth'),
'ghostnet_130': _cfg(url=''),
}
_SE_LAYER = partial(SqueezeExcite, gate_layer='hard_sigmoid', rd_round_fn=partial(make_divisible, divisor=4))
class GhostModule(nn.Module):
def __init__(self, inp, oup, kernel_size=1, ratio=2, dw_size=3, stride=1, relu=True):
super(GhostModule, self).__init__()
self.oup = oup
init_channels = math.ceil(oup / ratio)
new_channels = init_channels * (ratio - 1)
self.primary_conv = nn.Sequential(
nn.Conv2d(inp, init_channels, kernel_size, stride, kernel_size//2, bias=False),
nn.BatchNorm2d(init_channels),
nn.ReLU(inplace=True) if relu else nn.Sequential(),
)
self.cheap_operation = nn.Sequential(
nn.Conv2d(init_channels, new_channels, dw_size, 1, dw_size//2, groups=init_channels, bias=False),
nn.BatchNorm2d(new_channels),
nn.ReLU(inplace=True) if relu else nn.Sequential(),
)
def forward(self, x):
x1 = self.primary_conv(x)
x2 = self.cheap_operation(x1)
out = torch.cat([x1, x2], dim=1)
return out[:, :self.oup, :, :]
class GhostBottleneck(nn.Module):
""" Ghost bottleneck w/ optional SE"""
def __init__(self, in_chs, mid_chs, out_chs, dw_kernel_size=3,
stride=1, act_layer=nn.ReLU, se_ratio=0.):
super(GhostBottleneck, self).__init__()
has_se = se_ratio is not None and se_ratio > 0.
self.stride = stride
# Point-wise expansion
self.ghost1 = GhostModule(in_chs, mid_chs, relu=True)
# Depth-wise convolution
if self.stride > 1:
self.conv_dw = nn.Conv2d(
mid_chs, mid_chs, dw_kernel_size, stride=stride,
padding=(dw_kernel_size-1)//2, groups=mid_chs, bias=False)
self.bn_dw = nn.BatchNorm2d(mid_chs)
else:
self.conv_dw = None
self.bn_dw = None
# Squeeze-and-excitation
self.se = _SE_LAYER(mid_chs, rd_ratio=se_ratio) if has_se else None
# Point-wise linear projection
self.ghost2 = GhostModule(mid_chs, out_chs, relu=False)
# shortcut
if in_chs == out_chs and self.stride == 1:
self.shortcut = nn.Sequential()
else:
self.shortcut = nn.Sequential(
nn.Conv2d(
in_chs, in_chs, dw_kernel_size, stride=stride,
padding=(dw_kernel_size-1)//2, groups=in_chs, bias=False),
nn.BatchNorm2d(in_chs),
nn.Conv2d(in_chs, out_chs, 1, stride=1, padding=0, bias=False),
nn.BatchNorm2d(out_chs),
)
def forward(self, x):
shortcut = x
# 1st ghost bottleneck
x = self.ghost1(x)
# Depth-wise convolution
if self.conv_dw is not None:
x = self.conv_dw(x)
x = self.bn_dw(x)
# Squeeze-and-excitation
if self.se is not None:
x = self.se(x)
# 2nd ghost bottleneck
x = self.ghost2(x)
x += self.shortcut(shortcut)
return x
class GhostNet(nn.Module):
def __init__(self, cfgs, num_classes=1000, width=1.0, dropout=0.2, in_chans=3, output_stride=32, global_pool='avg'):
super(GhostNet, self).__init__()
# setting of inverted residual blocks
assert output_stride == 32, 'only output_stride==32 is valid, dilation not supported'
self.cfgs = cfgs
self.num_classes = num_classes
self.dropout = dropout
self.feature_info = []
# building first layer
stem_chs = make_divisible(16 * width, 4)
self.conv_stem = nn.Conv2d(in_chans, stem_chs, 3, 2, 1, bias=False)
self.feature_info.append(dict(num_chs=stem_chs, reduction=2, module=f'conv_stem'))
self.bn1 = nn.BatchNorm2d(stem_chs)
self.act1 = nn.ReLU(inplace=True)
prev_chs = stem_chs
# building inverted residual blocks
stages = nn.ModuleList([])
block = GhostBottleneck
stage_idx = 0
net_stride = 2
for cfg in self.cfgs:
layers = []
s = 1
for k, exp_size, c, se_ratio, s in cfg:
out_chs = make_divisible(c * width, 4)
mid_chs = make_divisible(exp_size * width, 4)
layers.append(block(prev_chs, mid_chs, out_chs, k, s, se_ratio=se_ratio))
prev_chs = out_chs
if s > 1:
net_stride *= 2
self.feature_info.append(dict(
num_chs=prev_chs, reduction=net_stride, module=f'blocks.{stage_idx}'))
stages.append(nn.Sequential(*layers))
stage_idx += 1
out_chs = make_divisible(exp_size * width, 4)
stages.append(nn.Sequential(ConvBnAct(prev_chs, out_chs, 1)))
self.pool_dim = prev_chs = out_chs
self.blocks = nn.Sequential(*stages)
# building last several layers
self.num_features = out_chs = 1280
self.global_pool = SelectAdaptivePool2d(pool_type=global_pool)
self.conv_head = nn.Conv2d(prev_chs, out_chs, 1, 1, 0, bias=True)
self.act2 = nn.ReLU(inplace=True)
self.flatten = nn.Flatten(1) if global_pool else nn.Identity() # don't flatten if pooling disabled
self.classifier = Linear(out_chs, num_classes) if num_classes > 0 else nn.Identity()
def get_classifier(self):
return self.classifier
def reset_classifier(self, num_classes, global_pool='avg'):
self.num_classes = num_classes
# cannot meaningfully change pooling of efficient head after creation
self.global_pool = SelectAdaptivePool2d(pool_type=global_pool)
self.flatten = nn.Flatten(1) if global_pool else nn.Identity() # don't flatten if pooling disabled
self.classifier = Linear(self.pool_dim, num_classes) if num_classes > 0 else nn.Identity()
def forward_features(self, x):
x = self.conv_stem(x)
x = self.bn1(x)
x = self.act1(x)
x = self.blocks(x)
x = self.global_pool(x)
x = self.conv_head(x)
x = self.act2(x)
return x
def forward(self, x):
x = self.forward_features(x)
x = self.flatten(x)
if self.dropout > 0.:
x = F.dropout(x, p=self.dropout, training=self.training)
x = self.classifier(x)
return x
def _create_ghostnet(variant, width=1.0, pretrained=False, **kwargs):
"""
Constructs a GhostNet model
"""
cfgs = [
# k, t, c, SE, s
# stage1
[[3, 16, 16, 0, 1]],
# stage2
[[3, 48, 24, 0, 2]],
[[3, 72, 24, 0, 1]],
# stage3
[[5, 72, 40, 0.25, 2]],
[[5, 120, 40, 0.25, 1]],
# stage4
[[3, 240, 80, 0, 2]],
[[3, 200, 80, 0, 1],
[3, 184, 80, 0, 1],
[3, 184, 80, 0, 1],
[3, 480, 112, 0.25, 1],
[3, 672, 112, 0.25, 1]
],
# stage5
[[5, 672, 160, 0.25, 2]],
[[5, 960, 160, 0, 1],
[5, 960, 160, 0.25, 1],
[5, 960, 160, 0, 1],
[5, 960, 160, 0.25, 1]
]
]
model_kwargs = dict(
cfgs=cfgs,
width=width,
**kwargs,
)
return build_model_with_cfg(
GhostNet, variant, pretrained,
default_cfg=default_cfgs[variant],
feature_cfg=dict(flatten_sequential=True),
**model_kwargs)
@register_model
def ghostnet_050(pretrained=False, **kwargs):
""" GhostNet-0.5x """
model = _create_ghostnet('ghostnet_050', width=0.5, pretrained=pretrained, **kwargs)
return model
@register_model
def ghostnet_100(pretrained=False, **kwargs):
""" GhostNet-1.0x """
model = _create_ghostnet('ghostnet_100', width=1.0, pretrained=pretrained, **kwargs)
return model
@register_model
def ghostnet_130(pretrained=False, **kwargs):
""" GhostNet-1.3x """
model = _create_ghostnet('ghostnet_130', width=1.3, pretrained=pretrained, **kwargs)
return model