RESA/models/resa.py

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

from models.registry import NET
from .resnet import ResNetWrapper 
from .decoder import BUSD, PlainDecoder 


class RESA(nn.Module):
    def __init__(self, cfg):
        super(RESA, self).__init__()
        self.iter = cfg.resa.iter
        chan = cfg.resa.input_channel
        fea_stride = cfg.backbone.fea_stride
        self.height = cfg.img_height // fea_stride
        self.width = cfg.img_width // fea_stride
        self.alpha = cfg.resa.alpha
        conv_stride = cfg.resa.conv_stride

        for i in range(self.iter):
            conv_vert1 = nn.Conv2d(
                chan, chan, (1, conv_stride),
                padding=(0, conv_stride//2), groups=1, bias=False)
            conv_vert2 = nn.Conv2d(
                chan, chan, (1, conv_stride),
                padding=(0, conv_stride//2), groups=1, bias=False)

            setattr(self, 'conv_d'+str(i), conv_vert1)
            setattr(self, 'conv_u'+str(i), conv_vert2)

            conv_hori1 = nn.Conv2d(
                chan, chan, (conv_stride, 1),
                padding=(conv_stride//2, 0), groups=1, bias=False)
            conv_hori2 = nn.Conv2d(
                chan, chan, (conv_stride, 1),
                padding=(conv_stride//2, 0), groups=1, bias=False)

            setattr(self, 'conv_r'+str(i), conv_hori1)
            setattr(self, 'conv_l'+str(i), conv_hori2)

            idx_d = (torch.arange(self.height) + self.height //
                     2**(self.iter - i)) % self.height
            setattr(self, 'idx_d'+str(i), idx_d)

            idx_u = (torch.arange(self.height) - self.height //
                     2**(self.iter - i)) % self.height
            setattr(self, 'idx_u'+str(i), idx_u)

            idx_r = (torch.arange(self.width) + self.width //
                     2**(self.iter - i)) % self.width
            setattr(self, 'idx_r'+str(i), idx_r)

            idx_l = (torch.arange(self.width) - self.width //
                     2**(self.iter - i)) % self.width
            setattr(self, 'idx_l'+str(i), idx_l)

    def forward(self, x):
        x = x.clone()

        for direction in ['d', 'u']:
            for i in range(self.iter):
                conv = getattr(self, 'conv_' + direction + str(i))
                idx = getattr(self, 'idx_' + direction + str(i))
                x.add_(self.alpha * F.relu(conv(x[..., idx, :])))

        for direction in ['r', 'l']:
            for i in range(self.iter):
                conv = getattr(self, 'conv_' + direction + str(i))
                idx = getattr(self, 'idx_' + direction + str(i))
                x.add_(self.alpha * F.relu(conv(x[..., idx])))

        return x



class ExistHead(nn.Module):
    def __init__(self, cfg=None):
        super(ExistHead, self).__init__()
        self.cfg = cfg

        self.dropout = nn.Dropout2d(0.1)  # ???
        self.conv8 = nn.Conv2d(128, cfg.num_classes, 1)

        stride = cfg.backbone.fea_stride * 2
        self.fc9 = nn.Linear(
            int(cfg.num_classes * cfg.img_width / stride * cfg.img_height / stride), 128)
        self.fc10 = nn.Linear(128, cfg.num_classes-1)

    def forward(self, x):
        x = self.dropout(x)
        x = self.conv8(x)

        x = F.softmax(x, dim=1)
        x = F.avg_pool2d(x, 2, stride=2, padding=0)
        x = x.view(-1, x.numel() // x.shape[0])
        x = self.fc9(x)
        x = F.relu(x)
        x = self.fc10(x)
        x = torch.sigmoid(x)

        return x


@NET.register_module
class RESANet(nn.Module):
    def __init__(self, cfg):
        super(RESANet, self).__init__()
        self.cfg = cfg
        self.backbone = ResNetWrapper(cfg)
        self.resa = RESA(cfg)
        self.decoder = eval(cfg.decoder)(cfg)
        self.heads = ExistHead(cfg) 

    def forward(self, batch):
        fea = self.backbone(batch)
        fea = self.resa(fea)
        seg = self.decoder(fea)
        exist = self.heads(fea)

        output = {'seg': seg, 'exist': exist}

        return output