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| # Copyright (c) OpenMMLab. All rights reserved. | |
| # Modified from https://github.com/Kevinz-code/CSRA | |
| from typing import Tuple | |
| import torch | |
| import torch.nn as nn | |
| from mmengine.model import BaseModule, ModuleList | |
| from mmcls.registry import MODELS | |
| from .multi_label_cls_head import MultiLabelClsHead | |
| class CSRAClsHead(MultiLabelClsHead): | |
| """Class-specific residual attention classifier head. | |
| Please refer to the `Residual Attention: A Simple but Effective Method for | |
| Multi-Label Recognition (ICCV 2021) <https://arxiv.org/abs/2108.02456>`_ | |
| for details. | |
| Args: | |
| num_classes (int): Number of categories. | |
| in_channels (int): Number of channels in the input feature map. | |
| num_heads (int): Number of residual at tensor heads. | |
| loss (dict): Config of classification loss. | |
| lam (float): Lambda that combines global average and max pooling | |
| scores. | |
| init_cfg (dict, optional): The extra init config of layers. | |
| Defaults to use ``dict(type='Normal', layer='Linear', std=0.01)``. | |
| """ | |
| temperature_settings = { # softmax temperature settings | |
| 1: [1], | |
| 2: [1, 99], | |
| 4: [1, 2, 4, 99], | |
| 6: [1, 2, 3, 4, 5, 99], | |
| 8: [1, 2, 3, 4, 5, 6, 7, 99] | |
| } | |
| def __init__(self, | |
| num_classes: int, | |
| in_channels: int, | |
| num_heads: int, | |
| lam: float, | |
| init_cfg=dict(type='Normal', layer='Linear', std=0.01), | |
| **kwargs): | |
| assert num_heads in self.temperature_settings.keys( | |
| ), 'The num of heads is not in temperature setting.' | |
| assert lam > 0, 'Lambda should be between 0 and 1.' | |
| super(CSRAClsHead, self).__init__(init_cfg=init_cfg, **kwargs) | |
| self.temp_list = self.temperature_settings[num_heads] | |
| self.csra_heads = ModuleList([ | |
| CSRAModule(num_classes, in_channels, self.temp_list[i], lam) | |
| for i in range(num_heads) | |
| ]) | |
| def pre_logits(self, feats: Tuple[torch.Tensor]) -> torch.Tensor: | |
| """The process before the final classification head. | |
| The input ``feats`` is a tuple of tensor, and each tensor is the | |
| feature of a backbone stage. In ``CSRAClsHead``, we just obtain the | |
| feature of the last stage. | |
| """ | |
| # The CSRAClsHead doesn't have other module, just return after | |
| # unpacking. | |
| return feats[-1] | |
| def forward(self, feats: Tuple[torch.Tensor]) -> torch.Tensor: | |
| """The forward process.""" | |
| pre_logits = self.pre_logits(feats) | |
| logit = sum([head(pre_logits) for head in self.csra_heads]) | |
| return logit | |
| class CSRAModule(BaseModule): | |
| """Basic module of CSRA with different temperature. | |
| Args: | |
| num_classes (int): Number of categories. | |
| in_channels (int): Number of channels in the input feature map. | |
| T (int): Temperature setting. | |
| lam (float): Lambda that combines global average and max pooling | |
| scores. | |
| init_cfg (dict | optional): The extra init config of layers. | |
| Defaults to use dict(type='Normal', layer='Linear', std=0.01). | |
| """ | |
| def __init__(self, | |
| num_classes: int, | |
| in_channels: int, | |
| T: int, | |
| lam: float, | |
| init_cfg=None): | |
| super(CSRAModule, self).__init__(init_cfg=init_cfg) | |
| self.T = T # temperature | |
| self.lam = lam # Lambda | |
| self.head = nn.Conv2d(in_channels, num_classes, 1, bias=False) | |
| self.softmax = nn.Softmax(dim=2) | |
| def forward(self, x): | |
| score = self.head(x) / torch.norm( | |
| self.head.weight, dim=1, keepdim=True).transpose(0, 1) | |
| score = score.flatten(2) | |
| base_logit = torch.mean(score, dim=2) | |
| if self.T == 99: # max-pooling | |
| att_logit = torch.max(score, dim=2)[0] | |
| else: | |
| score_soft = self.softmax(score * self.T) | |
| att_logit = torch.sum(score * score_soft, dim=2) | |
| return base_logit + self.lam * att_logit | |