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import torch |
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import torch.nn.functional as F |
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from mmcv.cnn import ConvModule, Scale |
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from torch import nn |
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from mmseg.core import add_prefix |
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from ..builder import HEADS |
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from ..utils import SelfAttentionBlock as _SelfAttentionBlock |
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from .decode_head import BaseDecodeHead |
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class PAM(_SelfAttentionBlock): |
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"""Position Attention Module (PAM) |
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Args: |
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in_channels (int): Input channels of key/query feature. |
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channels (int): Output channels of key/query transform. |
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""" |
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def __init__(self, in_channels, channels): |
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super(PAM, self).__init__( |
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key_in_channels=in_channels, |
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query_in_channels=in_channels, |
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channels=channels, |
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out_channels=in_channels, |
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share_key_query=False, |
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query_downsample=None, |
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key_downsample=None, |
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key_query_num_convs=1, |
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key_query_norm=False, |
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value_out_num_convs=1, |
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value_out_norm=False, |
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matmul_norm=False, |
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with_out=False, |
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conv_cfg=None, |
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norm_cfg=None, |
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act_cfg=None) |
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self.gamma = Scale(0) |
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def forward(self, x): |
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"""Forward function.""" |
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out = super(PAM, self).forward(x, x) |
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out = self.gamma(out) + x |
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return out |
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class CAM(nn.Module): |
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"""Channel Attention Module (CAM)""" |
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def __init__(self): |
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super(CAM, self).__init__() |
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self.gamma = Scale(0) |
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def forward(self, x): |
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"""Forward function.""" |
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batch_size, channels, height, width = x.size() |
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proj_query = x.view(batch_size, channels, -1) |
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proj_key = x.view(batch_size, channels, -1).permute(0, 2, 1) |
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energy = torch.bmm(proj_query, proj_key) |
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energy_new = torch.max( |
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energy, -1, keepdim=True)[0].expand_as(energy) - energy |
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attention = F.softmax(energy_new, dim=-1) |
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proj_value = x.view(batch_size, channels, -1) |
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out = torch.bmm(attention, proj_value) |
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out = out.view(batch_size, channels, height, width) |
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out = self.gamma(out) + x |
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return out |
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@HEADS.register_module() |
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class DAHead(BaseDecodeHead): |
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"""Dual Attention Network for Scene Segmentation. |
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This head is the implementation of `DANet |
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<https://arxiv.org/abs/1809.02983>`_. |
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Args: |
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pam_channels (int): The channels of Position Attention Module(PAM). |
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""" |
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def __init__(self, pam_channels, **kwargs): |
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super(DAHead, self).__init__(**kwargs) |
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self.pam_channels = pam_channels |
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self.pam_in_conv = ConvModule( |
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self.in_channels, |
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self.channels, |
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3, |
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padding=1, |
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conv_cfg=self.conv_cfg, |
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norm_cfg=self.norm_cfg, |
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act_cfg=self.act_cfg) |
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self.pam = PAM(self.channels, pam_channels) |
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self.pam_out_conv = ConvModule( |
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self.channels, |
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self.channels, |
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3, |
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padding=1, |
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conv_cfg=self.conv_cfg, |
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norm_cfg=self.norm_cfg, |
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act_cfg=self.act_cfg) |
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self.pam_conv_seg = nn.Conv2d( |
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self.channels, self.num_classes, kernel_size=1) |
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self.cam_in_conv = ConvModule( |
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self.in_channels, |
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self.channels, |
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3, |
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padding=1, |
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conv_cfg=self.conv_cfg, |
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norm_cfg=self.norm_cfg, |
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act_cfg=self.act_cfg) |
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self.cam = CAM() |
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self.cam_out_conv = ConvModule( |
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self.channels, |
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self.channels, |
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3, |
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padding=1, |
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conv_cfg=self.conv_cfg, |
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norm_cfg=self.norm_cfg, |
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act_cfg=self.act_cfg) |
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self.cam_conv_seg = nn.Conv2d( |
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self.channels, self.num_classes, kernel_size=1) |
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def pam_cls_seg(self, feat): |
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"""PAM feature classification.""" |
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if self.dropout is not None: |
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feat = self.dropout(feat) |
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output = self.pam_conv_seg(feat) |
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return output |
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def cam_cls_seg(self, feat): |
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"""CAM feature classification.""" |
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if self.dropout is not None: |
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feat = self.dropout(feat) |
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output = self.cam_conv_seg(feat) |
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return output |
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def forward(self, inputs): |
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"""Forward function.""" |
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x = self._transform_inputs(inputs) |
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pam_feat = self.pam_in_conv(x) |
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pam_feat = self.pam(pam_feat) |
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pam_feat = self.pam_out_conv(pam_feat) |
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pam_out = self.pam_cls_seg(pam_feat) |
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cam_feat = self.cam_in_conv(x) |
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cam_feat = self.cam(cam_feat) |
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cam_feat = self.cam_out_conv(cam_feat) |
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cam_out = self.cam_cls_seg(cam_feat) |
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feat_sum = pam_feat + cam_feat |
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pam_cam_out = self.cls_seg(feat_sum) |
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return pam_cam_out, pam_out, cam_out |
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def forward_test(self, inputs, img_metas, test_cfg): |
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"""Forward function for testing, only ``pam_cam`` is used.""" |
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return self.forward(inputs)[0] |
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def losses(self, seg_logit, seg_label): |
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"""Compute ``pam_cam``, ``pam``, ``cam`` loss.""" |
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pam_cam_seg_logit, pam_seg_logit, cam_seg_logit = seg_logit |
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loss = dict() |
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loss.update( |
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add_prefix( |
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super(DAHead, self).losses(pam_cam_seg_logit, seg_label), |
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'pam_cam')) |
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loss.update( |
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add_prefix( |
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super(DAHead, self).losses(pam_seg_logit, seg_label), 'pam')) |
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loss.update( |
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add_prefix( |
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super(DAHead, self).losses(cam_seg_logit, seg_label), 'cam')) |
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return loss |
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