web-demos/hugging_face/tracker/model/channel_attn.py

import math
import torch
import torch.nn as nn
import torch.nn.functional as F


class CAResBlock(nn.Module):
    def __init__(self, in_dim: int, out_dim: int, residual: bool = True):
        super().__init__()
        self.residual = residual
        self.conv1 = nn.Conv2d(in_dim, out_dim, kernel_size=3, padding=1)
        self.conv2 = nn.Conv2d(out_dim, out_dim, kernel_size=3, padding=1)

        t = int((abs(math.log2(out_dim)) + 1) // 2)
        k = t if t % 2 else t + 1
        self.pool = nn.AdaptiveAvgPool2d(1)
        self.conv = nn.Conv1d(1, 1, kernel_size=k, padding=(k - 1) // 2, bias=False)

        if self.residual:
            if in_dim == out_dim:
                self.downsample = nn.Identity()
            else:
                self.downsample = nn.Conv2d(in_dim, out_dim, kernel_size=1)

    def forward(self, x: torch.Tensor) -> torch.Tensor:
        r = x
        x = self.conv1(F.relu(x))
        x = self.conv2(F.relu(x))

        b, c = x.shape[:2]
        w = self.pool(x).view(b, 1, c)
        w = self.conv(w).transpose(-1, -2).unsqueeze(-1).sigmoid()  # B*C*1*1

        if self.residual:
            x = x * w + self.downsample(r)
        else:
            x = x * w

        return x