Source code for torchvision.models.regnet
# Modified from
# https://github.com/facebookresearch/ClassyVision/blob/main/classy_vision/models/anynet.py
# https://github.com/facebookresearch/ClassyVision/blob/main/classy_vision/models/regnet.py
import math
import torch
from collections import OrderedDict
from functools import partial
from typing import Any, Callable, List, Optional, Tuple
from torch import nn, Tensor
from .._internally_replaced_utils import load_state_dict_from_url
from ..ops.misc import ConvNormActivation, SqueezeExcitation
from ._utils import _make_divisible
__all__ = ["RegNet", "regnet_y_400mf", "regnet_y_800mf", "regnet_y_1_6gf",
"regnet_y_3_2gf", "regnet_y_8gf", "regnet_y_16gf", "regnet_y_32gf",
"regnet_x_400mf", "regnet_x_800mf", "regnet_x_1_6gf", "regnet_x_3_2gf",
"regnet_x_8gf", "regnet_x_16gf", "regnet_x_32gf"]
model_urls = {
"regnet_y_400mf": "https://download.pytorch.org/models/regnet_y_400mf-c65dace8.pth",
"regnet_y_800mf": "https://download.pytorch.org/models/regnet_y_800mf-1b27b58c.pth",
"regnet_y_1_6gf": "https://download.pytorch.org/models/regnet_y_1_6gf-b11a554e.pth",
"regnet_y_3_2gf": "https://download.pytorch.org/models/regnet_y_3_2gf-b5a9779c.pth",
"regnet_y_8gf": "https://download.pytorch.org/models/regnet_y_8gf-d0d0e4a8.pth",
"regnet_y_16gf": "https://download.pytorch.org/models/regnet_y_16gf-9e6ed7dd.pth",
"regnet_y_32gf": "https://download.pytorch.org/models/regnet_y_32gf-4dee3f7a.pth",
"regnet_x_400mf": "https://download.pytorch.org/models/regnet_x_400mf-adf1edd5.pth",
"regnet_x_800mf": "https://download.pytorch.org/models/regnet_x_800mf-ad17e45c.pth",
"regnet_x_1_6gf": "https://download.pytorch.org/models/regnet_x_1_6gf-e3633e7f.pth",
"regnet_x_3_2gf": "https://download.pytorch.org/models/regnet_x_3_2gf-f342aeae.pth",
"regnet_x_8gf": "https://download.pytorch.org/models/regnet_x_8gf-03ceed89.pth",
"regnet_x_16gf": "https://download.pytorch.org/models/regnet_x_16gf-2007eb11.pth",
"regnet_x_32gf": "https://download.pytorch.org/models/regnet_x_32gf-9d47f8d0.pth",
}
class SimpleStemIN(ConvNormActivation):
"""Simple stem for ImageNet: 3x3, BN, ReLU."""
def __init__(
self,
width_in: int,
width_out: int,
norm_layer: Callable[..., nn.Module],
activation_layer: Callable[..., nn.Module],
) -> None:
super().__init__(width_in, width_out, kernel_size=3, stride=2,
norm_layer=norm_layer, activation_layer=activation_layer)
class BottleneckTransform(nn.Sequential):
"""Bottleneck transformation: 1x1, 3x3 [+SE], 1x1."""
def __init__(
self,
width_in: int,
width_out: int,
stride: int,
norm_layer: Callable[..., nn.Module],
activation_layer: Callable[..., nn.Module],
group_width: int,
bottleneck_multiplier: float,
se_ratio: Optional[float],
) -> None:
layers: OrderedDict[str, nn.Module] = OrderedDict()
w_b = int(round(width_out * bottleneck_multiplier))
g = w_b // group_width
layers["a"] = ConvNormActivation(width_in, w_b, kernel_size=1, stride=1,
norm_layer=norm_layer, activation_layer=activation_layer)
layers["b"] = ConvNormActivation(w_b, w_b, kernel_size=3, stride=stride, groups=g,
norm_layer=norm_layer, activation_layer=activation_layer)
if se_ratio:
# The SE reduction ratio is defined with respect to the
# beginning of the block
width_se_out = int(round(se_ratio * width_in))
layers["se"] = SqueezeExcitation(
input_channels=w_b,
squeeze_channels=width_se_out,
activation=activation_layer,
)
layers["c"] = ConvNormActivation(w_b, width_out, kernel_size=1, stride=1,
norm_layer=norm_layer, activation_layer=None)
super().__init__(layers)
class ResBottleneckBlock(nn.Module):
"""Residual bottleneck block: x + F(x), F = bottleneck transform."""
def __init__(
self,
width_in: int,
width_out: int,
stride: int,
norm_layer: Callable[..., nn.Module],
activation_layer: Callable[..., nn.Module],
group_width: int = 1,
bottleneck_multiplier: float = 1.0,
se_ratio: Optional[float] = None,
) -> None:
super().__init__()
# Use skip connection with projection if shape changes
self.proj = None
should_proj = (width_in != width_out) or (stride != 1)
if should_proj:
self.proj = ConvNormActivation(width_in, width_out, kernel_size=1,
stride=stride, norm_layer=norm_layer, activation_layer=None)
self.f = BottleneckTransform(
width_in,
width_out,
stride,
norm_layer,
activation_layer,
group_width,
bottleneck_multiplier,
se_ratio,
)
self.activation = activation_layer(inplace=True)
def forward(self, x: Tensor) -> Tensor:
if self.proj is not None:
x = self.proj(x) + self.f(x)
else:
x = x + self.f(x)
return self.activation(x)
class AnyStage(nn.Sequential):
"""AnyNet stage (sequence of blocks w/ the same output shape)."""
def __init__(
self,
width_in: int,
width_out: int,
stride: int,
depth: int,
block_constructor: Callable[..., nn.Module],
norm_layer: Callable[..., nn.Module],
activation_layer: Callable[..., nn.Module],
group_width: int,
bottleneck_multiplier: float,
se_ratio: Optional[float] = None,
stage_index: int = 0,
) -> None:
super().__init__()
for i in range(depth):
block = block_constructor(
width_in if i == 0 else width_out,
width_out,
stride if i == 0 else 1,
norm_layer,
activation_layer,
group_width,
bottleneck_multiplier,
se_ratio,
)
self.add_module(f"block{stage_index}-{i}", block)
class BlockParams:
def __init__(
self,
depths: List[int],
widths: List[int],
group_widths: List[int],
bottleneck_multipliers: List[float],
strides: List[int],
se_ratio: Optional[float] = None,
) -> None:
self.depths = depths
self.widths = widths
self.group_widths = group_widths
self.bottleneck_multipliers = bottleneck_multipliers
self.strides = strides
self.se_ratio = se_ratio
@classmethod
def from_init_params(
cls,
depth: int,
w_0: int,
w_a: float,
w_m: float,
group_width: int,
bottleneck_multiplier: float = 1.0,
se_ratio: Optional[float] = None,
**kwargs: Any,
) -> "BlockParams":
"""
Programatically compute all the per-block settings,
given the RegNet parameters.
The first step is to compute the quantized linear block parameters,
in log space. Key parameters are:
- `w_a` is the width progression slope
- `w_0` is the initial width
- `w_m` is the width stepping in the log space
In other terms
`log(block_width) = log(w_0) + w_m * block_capacity`,
with `bock_capacity` ramping up following the w_0 and w_a params.
This block width is finally quantized to multiples of 8.
The second step is to compute the parameters per stage,
taking into account the skip connection and the final 1x1 convolutions.
We use the fact that the output width is constant within a stage.
"""
QUANT = 8
STRIDE = 2
if w_a < 0 or w_0 <= 0 or w_m <= 1 or w_0 % 8 != 0:
raise ValueError("Invalid RegNet settings")
# Compute the block widths. Each stage has one unique block width
widths_cont = torch.arange(depth) * w_a + w_0
block_capacity = torch.round(torch.log(widths_cont / w_0) / math.log(w_m))
block_widths = (
torch.round(torch.divide(w_0 * torch.pow(w_m, block_capacity), QUANT))
* QUANT
).int().tolist()
num_stages = len(set(block_widths))
# Convert to per stage parameters
split_helper = zip(
block_widths + [0],
[0] + block_widths,
block_widths + [0],
[0] + block_widths,
)
splits = [w != wp or r != rp for w, wp, r, rp in split_helper]
stage_widths = [w for w, t in zip(block_widths, splits[:-1]) if t]
stage_depths = torch.diff(torch.tensor([d for d, t in enumerate(splits) if t])).int().tolist()
strides = [STRIDE] * num_stages
bottleneck_multipliers = [bottleneck_multiplier] * num_stages
group_widths = [group_width] * num_stages
# Adjust the compatibility of stage widths and group widths
stage_widths, group_widths = cls._adjust_widths_groups_compatibilty(
stage_widths, bottleneck_multipliers, group_widths
)
return cls(
depths=stage_depths,
widths=stage_widths,
group_widths=group_widths,
bottleneck_multipliers=bottleneck_multipliers,
strides=strides,
se_ratio=se_ratio,
)
def _get_expanded_params(self):
return zip(
self.widths, self.strides, self.depths, self.group_widths, self.bottleneck_multipliers
)
@staticmethod
def _adjust_widths_groups_compatibilty(
stage_widths: List[int], bottleneck_ratios: List[float],
group_widths: List[int]) -> Tuple[List[int], List[int]]:
"""
Adjusts the compatibility of widths and groups,
depending on the bottleneck ratio.
"""
# Compute all widths for the current settings
widths = [int(w * b) for w, b in zip(stage_widths, bottleneck_ratios)]
group_widths_min = [min(g, w_bot) for g, w_bot in zip(group_widths, widths)]
# Compute the adjusted widths so that stage and group widths fit
ws_bot = [_make_divisible(w_bot, g) for w_bot, g in zip(widths, group_widths_min)]
stage_widths = [int(w_bot / b) for w_bot, b in zip(ws_bot, bottleneck_ratios)]
return stage_widths, group_widths_min
class RegNet(nn.Module):
def __init__(
self,
block_params: BlockParams,
num_classes: int = 1000,
stem_width: int = 32,
stem_type: Optional[Callable[..., nn.Module]] = None,
block_type: Optional[Callable[..., nn.Module]] = None,
norm_layer: Optional[Callable[..., nn.Module]] = None,
activation: Optional[Callable[..., nn.Module]] = None,
) -> None:
super().__init__()
if stem_type is None:
stem_type = SimpleStemIN
if norm_layer is None:
norm_layer = nn.BatchNorm2d
if block_type is None:
block_type = ResBottleneckBlock
if activation is None:
activation = nn.ReLU
# Ad hoc stem
self.stem = stem_type(
3, # width_in
stem_width,
norm_layer,
activation,
)
current_width = stem_width
blocks = []
for i, (
width_out,
stride,
depth,
group_width,
bottleneck_multiplier,
) in enumerate(block_params._get_expanded_params()):
blocks.append(
(
f"block{i+1}",
AnyStage(
current_width,
width_out,
stride,
depth,
block_type,
norm_layer,
activation,
group_width,
bottleneck_multiplier,
block_params.se_ratio,
stage_index=i + 1,
),
)
)
current_width = width_out
self.trunk_output = nn.Sequential(OrderedDict(blocks))
self.avgpool = nn.AdaptiveAvgPool2d((1, 1))
self.fc = nn.Linear(in_features=current_width, out_features=num_classes)
# Init weights and good to go
self._reset_parameters()
def forward(self, x: Tensor) -> Tensor:
x = self.stem(x)
x = self.trunk_output(x)
x = self.avgpool(x)
x = x.flatten(start_dim=1)
x = self.fc(x)
return x
def _reset_parameters(self) -> None:
# Performs ResNet-style weight initialization
for m in self.modules():
if isinstance(m, nn.Conv2d):
# Note that there is no bias due to BN
fan_out = m.kernel_size[0] * m.kernel_size[1] * m.out_channels
nn.init.normal_(m.weight, mean=0.0, std=math.sqrt(2.0 / fan_out))
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, mean=0.0, std=0.01)
nn.init.zeros_(m.bias)
def _regnet(arch: str, block_params: BlockParams, pretrained: bool, progress: bool, **kwargs: Any) -> RegNet:
model = RegNet(block_params, norm_layer=partial(nn.BatchNorm2d, eps=1e-05, momentum=0.1), **kwargs)
if pretrained:
if arch not in model_urls:
raise ValueError(f"No checkpoint is available for model type {arch}")
state_dict = load_state_dict_from_url(model_urls[arch], progress=progress)
model.load_state_dict(state_dict)
return model
[docs]def regnet_y_400mf(pretrained: bool = False, progress: bool = True, **kwargs: Any) -> RegNet:
"""
Constructs a RegNetY_400MF architecture from
`"Designing Network Design Spaces" <https://arxiv.org/abs/2003.13678>`_.
Args:
pretrained (bool): If True, returns a model pre-trained on ImageNet
progress (bool): If True, displays a progress bar of the download to stderr
"""
params = BlockParams.from_init_params(depth=16, w_0=48, w_a=27.89, w_m=2.09,
group_width=8, se_ratio=0.25, **kwargs)
return _regnet("regnet_y_400mf", params, pretrained, progress, **kwargs)
[docs]def regnet_y_800mf(pretrained: bool = False, progress: bool = True, **kwargs: Any) -> RegNet:
"""
Constructs a RegNetY_800MF architecture from
`"Designing Network Design Spaces" <https://arxiv.org/abs/2003.13678>`_.
Args:
pretrained (bool): If True, returns a model pre-trained on ImageNet
progress (bool): If True, displays a progress bar of the download to stderr
"""
params = BlockParams.from_init_params(depth=14, w_0=56, w_a=38.84, w_m=2.4,
group_width=16, se_ratio=0.25, **kwargs)
return _regnet("regnet_y_800mf", params, pretrained, progress, **kwargs)
[docs]def regnet_y_1_6gf(pretrained: bool = False, progress: bool = True, **kwargs: Any) -> RegNet:
"""
Constructs a RegNetY_1.6GF architecture from
`"Designing Network Design Spaces" <https://arxiv.org/abs/2003.13678>`_.
Args:
pretrained (bool): If True, returns a model pre-trained on ImageNet
progress (bool): If True, displays a progress bar of the download to stderr
"""
params = BlockParams.from_init_params(depth=27, w_0=48, w_a=20.71, w_m=2.65,
group_width=24, se_ratio=0.25, **kwargs)
return _regnet("regnet_y_1_6gf", params, pretrained, progress, **kwargs)
[docs]def regnet_y_3_2gf(pretrained: bool = False, progress: bool = True, **kwargs: Any) -> RegNet:
"""
Constructs a RegNetY_3.2GF architecture from
`"Designing Network Design Spaces" <https://arxiv.org/abs/2003.13678>`_.
Args:
pretrained (bool): If True, returns a model pre-trained on ImageNet
progress (bool): If True, displays a progress bar of the download to stderr
"""
params = BlockParams.from_init_params(depth=21, w_0=80, w_a=42.63, w_m=2.66,
group_width=24, se_ratio=0.25, **kwargs)
return _regnet("regnet_y_3_2gf", params, pretrained, progress, **kwargs)
[docs]def regnet_y_8gf(pretrained: bool = False, progress: bool = True, **kwargs: Any) -> RegNet:
"""
Constructs a RegNetY_8GF architecture from
`"Designing Network Design Spaces" <https://arxiv.org/abs/2003.13678>`_.
Args:
pretrained (bool): If True, returns a model pre-trained on ImageNet
progress (bool): If True, displays a progress bar of the download to stderr
"""
params = BlockParams.from_init_params(depth=17, w_0=192, w_a=76.82, w_m=2.19,
group_width=56, se_ratio=0.25, **kwargs)
return _regnet("regnet_y_8gf", params, pretrained, progress, **kwargs)
[docs]def regnet_y_16gf(pretrained: bool = False, progress: bool = True, **kwargs: Any) -> RegNet:
"""
Constructs a RegNetY_16GF architecture from
`"Designing Network Design Spaces" <https://arxiv.org/abs/2003.13678>`_.
Args:
pretrained (bool): If True, returns a model pre-trained on ImageNet
progress (bool): If True, displays a progress bar of the download to stderr
"""
params = BlockParams.from_init_params(depth=18, w_0=200, w_a=106.23, w_m=2.48,
group_width=112, se_ratio=0.25, **kwargs)
return _regnet("regnet_y_16gf", params, pretrained, progress, **kwargs)
[docs]def regnet_y_32gf(pretrained: bool = False, progress: bool = True, **kwargs: Any) -> RegNet:
"""
Constructs a RegNetY_32GF architecture from
`"Designing Network Design Spaces" <https://arxiv.org/abs/2003.13678>`_.
Args:
pretrained (bool): If True, returns a model pre-trained on ImageNet
progress (bool): If True, displays a progress bar of the download to stderr
"""
params = BlockParams.from_init_params(depth=20, w_0=232, w_a=115.89, w_m=2.53,
group_width=232, se_ratio=0.25, **kwargs)
return _regnet("regnet_y_32gf", params, pretrained, progress, **kwargs)
[docs]def regnet_x_400mf(pretrained: bool = False, progress: bool = True, **kwargs: Any) -> RegNet:
"""
Constructs a RegNetX_400MF architecture from
`"Designing Network Design Spaces" <https://arxiv.org/abs/2003.13678>`_.
Args:
pretrained (bool): If True, returns a model pre-trained on ImageNet
progress (bool): If True, displays a progress bar of the download to stderr
"""
params = BlockParams.from_init_params(depth=22, w_0=24, w_a=24.48, w_m=2.54,
group_width=16, **kwargs)
return _regnet("regnet_x_400mf", params, pretrained, progress, **kwargs)
[docs]def regnet_x_800mf(pretrained: bool = False, progress: bool = True, **kwargs: Any) -> RegNet:
"""
Constructs a RegNetX_800MF architecture from
`"Designing Network Design Spaces" <https://arxiv.org/abs/2003.13678>`_.
Args:
pretrained (bool): If True, returns a model pre-trained on ImageNet
progress (bool): If True, displays a progress bar of the download to stderr
"""
params = BlockParams.from_init_params(depth=16, w_0=56, w_a=35.73, w_m=2.28,
group_width=16, **kwargs)
return _regnet("regnet_x_800mf", params, pretrained, progress, **kwargs)
[docs]def regnet_x_1_6gf(pretrained: bool = False, progress: bool = True, **kwargs: Any) -> RegNet:
"""
Constructs a RegNetX_1.6GF architecture from
`"Designing Network Design Spaces" <https://arxiv.org/abs/2003.13678>`_.
Args:
pretrained (bool): If True, returns a model pre-trained on ImageNet
progress (bool): If True, displays a progress bar of the download to stderr
"""
params = BlockParams.from_init_params(depth=18, w_0=80, w_a=34.01, w_m=2.25,
group_width=24, **kwargs)
return _regnet("regnet_x_1_6gf", params, pretrained, progress, **kwargs)
[docs]def regnet_x_3_2gf(pretrained: bool = False, progress: bool = True, **kwargs: Any) -> RegNet:
"""
Constructs a RegNetX_3.2GF architecture from
`"Designing Network Design Spaces" <https://arxiv.org/abs/2003.13678>`_.
Args:
pretrained (bool): If True, returns a model pre-trained on ImageNet
progress (bool): If True, displays a progress bar of the download to stderr
"""
params = BlockParams.from_init_params(depth=25, w_0=88, w_a=26.31, w_m=2.25,
group_width=48, **kwargs)
return _regnet("regnet_x_3_2gf", params, pretrained, progress, **kwargs)
[docs]def regnet_x_8gf(pretrained: bool = False, progress: bool = True, **kwargs: Any) -> RegNet:
"""
Constructs a RegNetX_8GF architecture from
`"Designing Network Design Spaces" <https://arxiv.org/abs/2003.13678>`_.
Args:
pretrained (bool): If True, returns a model pre-trained on ImageNet
progress (bool): If True, displays a progress bar of the download to stderr
"""
params = BlockParams.from_init_params(depth=23, w_0=80, w_a=49.56, w_m=2.88,
group_width=120, **kwargs)
return _regnet("regnet_x_8gf", params, pretrained, progress, **kwargs)
[docs]def regnet_x_16gf(pretrained: bool = False, progress: bool = True, **kwargs: Any) -> RegNet:
"""
Constructs a RegNetX_16GF architecture from
`"Designing Network Design Spaces" <https://arxiv.org/abs/2003.13678>`_.
Args:
pretrained (bool): If True, returns a model pre-trained on ImageNet
progress (bool): If True, displays a progress bar of the download to stderr
"""
params = BlockParams.from_init_params(depth=22, w_0=216, w_a=55.59, w_m=2.1,
group_width=128, **kwargs)
return _regnet("regnet_x_16gf", params, pretrained, progress, **kwargs)
[docs]def regnet_x_32gf(pretrained: bool = False, progress: bool = True, **kwargs: Any) -> RegNet:
"""
Constructs a RegNetX_32GF architecture from
`"Designing Network Design Spaces" <https://arxiv.org/abs/2003.13678>`_.
Args:
pretrained (bool): If True, returns a model pre-trained on ImageNet
progress (bool): If True, displays a progress bar of the download to stderr
"""
params = BlockParams.from_init_params(depth=23, w_0=320, w_a=69.86, w_m=2.0,
group_width=168, **kwargs)
return _regnet("regnet_x_32gf", params, pretrained, progress, **kwargs)
# TODO(kazhang): Add RegNetZ_500MF and RegNetZ_4GF
