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| # Copyright (c) OpenMMLab. All rights reserved. | |
| import mmcv | |
| import torch | |
| import torch.nn as nn | |
| from mmcv.cnn import ConvModule | |
| from mmcv.runner import BaseModule | |
| class SELayer(BaseModule): | |
| """Squeeze-and-Excitation Module. | |
| Args: | |
| channels (int): The input (and output) channels of the SE layer. | |
| ratio (int): Squeeze ratio in SELayer, the intermediate channel will be | |
| ``int(channels/ratio)``. Default: 16. | |
| conv_cfg (None or dict): Config dict for convolution layer. | |
| Default: None, which means using conv2d. | |
| act_cfg (dict or Sequence[dict]): Config dict for activation layer. | |
| If act_cfg is a dict, two activation layers will be configurated | |
| by this dict. If act_cfg is a sequence of dicts, the first | |
| activation layer will be configurated by the first dict and the | |
| second activation layer will be configurated by the second dict. | |
| Default: (dict(type='ReLU'), dict(type='Sigmoid')) | |
| init_cfg (dict or list[dict], optional): Initialization config dict. | |
| Default: None | |
| """ | |
| def __init__(self, | |
| channels, | |
| ratio=16, | |
| conv_cfg=None, | |
| act_cfg=(dict(type='ReLU'), dict(type='Sigmoid')), | |
| init_cfg=None): | |
| super(SELayer, self).__init__(init_cfg) | |
| if isinstance(act_cfg, dict): | |
| act_cfg = (act_cfg, act_cfg) | |
| assert len(act_cfg) == 2 | |
| assert mmcv.is_tuple_of(act_cfg, dict) | |
| self.global_avgpool = nn.AdaptiveAvgPool2d(1) | |
| self.conv1 = ConvModule( | |
| in_channels=channels, | |
| out_channels=int(channels / ratio), | |
| kernel_size=1, | |
| stride=1, | |
| conv_cfg=conv_cfg, | |
| act_cfg=act_cfg[0]) | |
| self.conv2 = ConvModule( | |
| in_channels=int(channels / ratio), | |
| out_channels=channels, | |
| kernel_size=1, | |
| stride=1, | |
| conv_cfg=conv_cfg, | |
| act_cfg=act_cfg[1]) | |
| def forward(self, x): | |
| out = self.global_avgpool(x) | |
| out = self.conv1(out) | |
| out = self.conv2(out) | |
| return x * out | |
| class DyReLU(BaseModule): | |
| """Dynamic ReLU (DyReLU) module. | |
| See `Dynamic ReLU <https://arxiv.org/abs/2003.10027>`_ for details. | |
| Current implementation is specialized for task-aware attention in DyHead. | |
| HSigmoid arguments in default act_cfg follow DyHead official code. | |
| https://github.com/microsoft/DynamicHead/blob/master/dyhead/dyrelu.py | |
| Args: | |
| channels (int): The input (and output) channels of DyReLU module. | |
| ratio (int): Squeeze ratio in Squeeze-and-Excitation-like module, | |
| the intermediate channel will be ``int(channels/ratio)``. | |
| Default: 4. | |
| conv_cfg (None or dict): Config dict for convolution layer. | |
| Default: None, which means using conv2d. | |
| act_cfg (dict or Sequence[dict]): Config dict for activation layer. | |
| If act_cfg is a dict, two activation layers will be configurated | |
| by this dict. If act_cfg is a sequence of dicts, the first | |
| activation layer will be configurated by the first dict and the | |
| second activation layer will be configurated by the second dict. | |
| Default: (dict(type='ReLU'), dict(type='HSigmoid', bias=3.0, | |
| divisor=6.0)) | |
| init_cfg (dict or list[dict], optional): Initialization config dict. | |
| Default: None | |
| """ | |
| def __init__(self, | |
| channels, | |
| ratio=4, | |
| conv_cfg=None, | |
| act_cfg=(dict(type='ReLU'), | |
| dict(type='HSigmoid', bias=3.0, divisor=6.0)), | |
| init_cfg=None): | |
| super().__init__(init_cfg=init_cfg) | |
| if isinstance(act_cfg, dict): | |
| act_cfg = (act_cfg, act_cfg) | |
| assert len(act_cfg) == 2 | |
| assert mmcv.is_tuple_of(act_cfg, dict) | |
| self.channels = channels | |
| self.expansion = 4 # for a1, b1, a2, b2 | |
| self.global_avgpool = nn.AdaptiveAvgPool2d(1) | |
| self.conv1 = ConvModule( | |
| in_channels=channels, | |
| out_channels=int(channels / ratio), | |
| kernel_size=1, | |
| stride=1, | |
| conv_cfg=conv_cfg, | |
| act_cfg=act_cfg[0]) | |
| self.conv2 = ConvModule( | |
| in_channels=int(channels / ratio), | |
| out_channels=channels * self.expansion, | |
| kernel_size=1, | |
| stride=1, | |
| conv_cfg=conv_cfg, | |
| act_cfg=act_cfg[1]) | |
| def forward(self, x): | |
| """Forward function.""" | |
| coeffs = self.global_avgpool(x) | |
| coeffs = self.conv1(coeffs) | |
| coeffs = self.conv2(coeffs) - 0.5 # value range: [-0.5, 0.5] | |
| a1, b1, a2, b2 = torch.split(coeffs, self.channels, dim=1) | |
| a1 = a1 * 2.0 + 1.0 # [-1.0, 1.0] + 1.0 | |
| a2 = a2 * 2.0 # [-1.0, 1.0] | |
| out = torch.max(x * a1 + b1, x * a2 + b2) | |
| return out | |