Question about ABF model

[a1248341036]

class ABF(nn.Module):

def __init__(self, in_channel, out_channel, mid_channel, is_fuse=True):
    super(ABF, self).__init__()

    self.conv_first = nn.Sequential(
        nn.Conv2d(in_channel, mid_channel, kernel_size=(1, 1), bias=False),
        nn.BatchNorm2d(mid_channel)
    )

    self.conv_last = nn.Sequential(
        nn.Conv2d(mid_channel, out_channel, kernel_size=(3, 3), stride=(1, 1), padding=(1, 1), bias=False),
        nn.BatchNorm2d(out_channel)
    )

    self.att_conv = None if not is_fuse else nn.Sequential(
        nn.Conv2d(mid_channel * 2, 2, kernel_size=(1, 1)),
        nn.Sigmoid()
    )

    self.__init_weights()

def __init_weights(self):
    nn.init.kaiming_uniform_(self.conv_first[0].weight, a=1)
    nn.init.kaiming_uniform_(self.conv_last[0].weight, a=1)

def forward(self, x, y=None, shape=None):
    assert len(x.shape) == 4
    N, _, H, W = x.shape[:4]

    x = self.conv_first(x)
    if self.att_conv is not None:
        # up sample residual features
        y = F.interpolate(y, shape, mode="nearest")
        # fusion
        z = torch.cat([x, y], dim=1)
        z = self.att_conv(z)

        x = (x * z[:, 0].view(N, 1, H, W) + y * z[:, 1].view(N, 1, H, W))
    y = self.conv_last(x)

    return y, x

In the 'forward' function, only the channel of y seems must be equal to mid_channel if self.att_conv could work.But the input y is res_features, the channel's number of res_features seem can't be guaranteed to be equal to mid_channel.

[a1248341036]

I'm sorry I misunderstood. Now I know what it means.