init

finetune/mmseg/models/decode_heads/da_head.py

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