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from typing import Callable, List, Optional
import torch
from torch import Tensor
from .vision_transformer_utils import _log_api_usage_once
interpolate = torch.nn.functional.interpolate
# This is not in nn
class FrozenBatchNorm2d(torch.nn.Module):
"""
BatchNorm2d where the batch statistics and the affine parameters are fixed
Args:
num_features (int): Number of features ``C`` from an expected input of size ``(N, C, H, W)``
eps (float): a value added to the denominator for numerical stability. Default: 1e-5
"""
def __init__(
self,
num_features: int,
eps: float = 1e-5,
):
super().__init__()
_log_api_usage_once(self)
self.eps = eps
self.register_buffer("weight", torch.ones(num_features))
self.register_buffer("bias", torch.zeros(num_features))
self.register_buffer("running_mean", torch.zeros(num_features))
self.register_buffer("running_var", torch.ones(num_features))
def _load_from_state_dict(
self,
state_dict: dict,
prefix: str,
local_metadata: dict,
strict: bool,
missing_keys: List[str],
unexpected_keys: List[str],
error_msgs: List[str],
):
num_batches_tracked_key = prefix + "num_batches_tracked"
if num_batches_tracked_key in state_dict:
del state_dict[num_batches_tracked_key]
super()._load_from_state_dict(
state_dict, prefix, local_metadata, strict, missing_keys, unexpected_keys, error_msgs
)
def forward(self, x: Tensor) -> Tensor:
# move reshapes to the beginning
# to make it fuser-friendly
w = self.weight.reshape(1, -1, 1, 1)
b = self.bias.reshape(1, -1, 1, 1)
rv = self.running_var.reshape(1, -1, 1, 1)
rm = self.running_mean.reshape(1, -1, 1, 1)
scale = w * (rv + self.eps).rsqrt()
bias = b - rm * scale
return x * scale + bias
def __repr__(self) -> str:
return f"{self.__class__.__name__}({self.weight.shape[0]}, eps={self.eps})"
class ConvNormActivation(torch.nn.Sequential):
"""
Configurable block used for Convolution-Normalzation-Activation blocks.
Args:
in_channels (int): Number of channels in the input image
out_channels (int): Number of channels produced by the Convolution-Normalzation-Activation block
kernel_size: (int, optional): Size of the convolving kernel. Default: 3
stride (int, optional): Stride of the convolution. Default: 1
padding (int, tuple or str, optional): Padding added to all four sides of the input. Default: None, in wich case it will calculated as ``padding = (kernel_size - 1) // 2 * dilation``
groups (int, optional): Number of blocked connections from input channels to output channels. Default: 1
norm_layer (Callable[..., torch.nn.Module], optional): Norm layer that will be stacked on top of the convolutiuon layer. If ``None`` this layer wont be used. Default: ``torch.nn.BatchNorm2d``
activation_layer (Callable[..., torch.nn.Module], optinal): Activation function which will be stacked on top of the normalization layer (if not None), otherwise on top of the conv layer. If ``None`` this layer wont be used. Default: ``torch.nn.ReLU``
dilation (int): Spacing between kernel elements. Default: 1
inplace (bool): Parameter for the activation layer, which can optionally do the operation in-place. Default ``True``
bias (bool, optional): Whether to use bias in the convolution layer. By default, biases are included if ``norm_layer is None``.
"""
def __init__(
self,
in_channels: int,
out_channels: int,
kernel_size: int = 3,
stride: int = 1,
padding: Optional[int] = None,
groups: int = 1,
norm_layer: Optional[Callable[..., torch.nn.Module]] = torch.nn.BatchNorm2d,
activation_layer: Optional[Callable[..., torch.nn.Module]] = torch.nn.ReLU,
dilation: int = 1,
inplace: Optional[bool] = True,
bias: Optional[bool] = None,
) -> None:
if padding is None:
padding = (kernel_size - 1) // 2 * dilation
if bias is None:
bias = norm_layer is None
layers = [
torch.nn.Conv2d(
in_channels,
out_channels,
kernel_size,
stride,
padding,
dilation=dilation,
groups=groups,
bias=bias,
)
]
if norm_layer is not None:
layers.append(norm_layer(out_channels))
if activation_layer is not None:
params = {} if inplace is None else {"inplace": inplace}
layers.append(activation_layer(**params))
super().__init__(*layers)
_log_api_usage_once(self)
self.out_channels = out_channels
class SqueezeExcitation(torch.nn.Module):
"""
This block implements the Squeeze-and-Excitation block from https://arxiv.org/abs/1709.01507 (see Fig. 1).
Parameters ``activation``, and ``scale_activation`` correspond to ``delta`` and ``sigma`` in in eq. 3.
Args:
input_channels (int): Number of channels in the input image
squeeze_channels (int): Number of squeeze channels
activation (Callable[..., torch.nn.Module], optional): ``delta`` activation. Default: ``torch.nn.ReLU``
scale_activation (Callable[..., torch.nn.Module]): ``sigma`` activation. Default: ``torch.nn.Sigmoid``
"""
def __init__(
self,
input_channels: int,
squeeze_channels: int,
activation: Callable[..., torch.nn.Module] = torch.nn.ReLU,
scale_activation: Callable[..., torch.nn.Module] = torch.nn.Sigmoid,
) -> None:
super().__init__()
_log_api_usage_once(self)
self.avgpool = torch.nn.AdaptiveAvgPool2d(1)
self.fc1 = torch.nn.Conv2d(input_channels, squeeze_channels, 1)
self.fc2 = torch.nn.Conv2d(squeeze_channels, input_channels, 1)
self.activation = activation()
self.scale_activation = scale_activation()
def _scale(self, input: Tensor) -> Tensor:
scale = self.avgpool(input)
scale = self.fc1(scale)
scale = self.activation(scale)
scale = self.fc2(scale)
return self.scale_activation(scale)
def forward(self, input: Tensor) -> Tensor:
scale = self._scale(input)
return scale * input
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