rscd/models/backbones/ChangeMamba_backbone.py

from rscd.models.backbones.vmamba import VSSM, LayerNorm2d

import torch
import torch.nn as nn


class Backbone_VSSM(VSSM):
    def __init__(self, out_indices=(0, 1, 2, 3), pretrained=None, norm_layer='ln2d', **kwargs):
        # norm_layer='ln'
        kwargs.update(norm_layer=norm_layer)
        super().__init__(**kwargs)
        self.channel_first = (norm_layer.lower() in ["bn", "ln2d"])
        _NORMLAYERS = dict(
            ln=nn.LayerNorm,
            ln2d=LayerNorm2d,
            bn=nn.BatchNorm2d,
        )
        norm_layer: nn.Module = _NORMLAYERS.get(norm_layer.lower(), None)        
        
        self.out_indices = out_indices
        for i in out_indices:
            layer = norm_layer(self.dims[i])
            layer_name = f'outnorm{i}'
            self.add_module(layer_name, layer)

        del self.classifier
        self.load_pretrained(pretrained)

    def load_pretrained(self, ckpt=None, key="model"):
        if ckpt is None:
            return
        
        try:
            _ckpt = torch.load(open(ckpt, "rb"), map_location=torch.device("cpu"))
            print(f"Successfully load ckpt {ckpt}")
            incompatibleKeys = self.load_state_dict(_ckpt[key], strict=False)
            print(incompatibleKeys)        
        except Exception as e:
            print(f"Failed loading checkpoint form {ckpt}: {e}")

    def forward(self, x):
        def layer_forward(l, x):
            x = l.blocks(x)
            y = l.downsample(x)
            return x, y

        x = self.patch_embed(x)
        outs = []
        for i, layer in enumerate(self.layers):
            o, x = layer_forward(layer, x) # (B, H, W, C)
            if i in self.out_indices:
                norm_layer = getattr(self, f'outnorm{i}')
                out = norm_layer(o)
                if not self.channel_first:
                    out = out.permute(0, 3, 1, 2).contiguous()
                outs.append(out)

        if len(self.out_indices) == 0:
            return x
        
        return outs
    
class CMBackbone(nn.Module):
    def __init__(self, pretrained, **kwargs):
        super(CMBackbone, self).__init__()
        self.encoder = Backbone_VSSM(out_indices=(0, 1, 2, 3), pretrained=pretrained, **kwargs)

    def forward(self, pre_data, post_data):
        # Encoder processing
        pre_features = self.encoder(pre_data)
        post_features = self.encoder(post_data)

        return [pre_features, post_features, pre_data.size()[-2:]]