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''' |
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This code is partially borrowed from RAFT (https://github.com/princeton-vl/RAFT). |
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''' |
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import torch |
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import torch.nn as nn |
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import torch.nn.functional as F |
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def resize(x, scale_factor): |
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return F.interpolate(x, scale_factor=scale_factor, mode="bilinear", align_corners=False) |
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def bilinear_sampler(img, coords, mask=False): |
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""" Wrapper for grid_sample, uses pixel coordinates """ |
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H, W = img.shape[-2:] |
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xgrid, ygrid = coords.split([1,1], dim=-1) |
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xgrid = 2*xgrid/(W-1) - 1 |
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ygrid = 2*ygrid/(H-1) - 1 |
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grid = torch.cat([xgrid, ygrid], dim=-1) |
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img = F.grid_sample(img, grid, align_corners=True) |
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if mask: |
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mask = (xgrid > -1) & (ygrid > -1) & (xgrid < 1) & (ygrid < 1) |
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return img, mask.float() |
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return img |
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def coords_grid(batch, ht, wd, device): |
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coords = torch.meshgrid(torch.arange(ht, device=device), |
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torch.arange(wd, device=device), |
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indexing='ij') |
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coords = torch.stack(coords[::-1], dim=0).float() |
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return coords[None].repeat(batch, 1, 1, 1) |
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class SmallUpdateBlock(nn.Module): |
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def __init__(self, cdim, hidden_dim, flow_dim, corr_dim, fc_dim, |
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corr_levels=4, radius=3, scale_factor=None): |
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super(SmallUpdateBlock, self).__init__() |
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cor_planes = corr_levels * (2 * radius + 1) **2 |
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self.scale_factor = scale_factor |
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self.convc1 = nn.Conv2d(2 * cor_planes, corr_dim, 1, padding=0) |
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self.convf1 = nn.Conv2d(4, flow_dim*2, 7, padding=3) |
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self.convf2 = nn.Conv2d(flow_dim*2, flow_dim, 3, padding=1) |
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self.conv = nn.Conv2d(corr_dim+flow_dim, fc_dim, 3, padding=1) |
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self.gru = nn.Sequential( |
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nn.Conv2d(fc_dim+4+cdim, hidden_dim, 3, padding=1), |
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nn.LeakyReLU(negative_slope=0.1, inplace=True), |
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nn.Conv2d(hidden_dim, hidden_dim, 3, padding=1), |
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) |
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self.feat_head = nn.Sequential( |
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nn.Conv2d(hidden_dim, hidden_dim, 3, padding=1), |
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nn.LeakyReLU(negative_slope=0.1, inplace=True), |
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nn.Conv2d(hidden_dim, cdim, 3, padding=1), |
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) |
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self.flow_head = nn.Sequential( |
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nn.Conv2d(hidden_dim, hidden_dim, 3, padding=1), |
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nn.LeakyReLU(negative_slope=0.1, inplace=True), |
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nn.Conv2d(hidden_dim, 4, 3, padding=1), |
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) |
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self.lrelu = nn.LeakyReLU(negative_slope=0.1, inplace=True) |
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def forward(self, net, flow, corr): |
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net = resize(net, 1 / self.scale_factor |
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) if self.scale_factor is not None else net |
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cor = self.lrelu(self.convc1(corr)) |
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flo = self.lrelu(self.convf1(flow)) |
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flo = self.lrelu(self.convf2(flo)) |
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cor_flo = torch.cat([cor, flo], dim=1) |
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inp = self.lrelu(self.conv(cor_flo)) |
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inp = torch.cat([inp, flow, net], dim=1) |
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out = self.gru(inp) |
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delta_net = self.feat_head(out) |
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delta_flow = self.flow_head(out) |
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if self.scale_factor is not None: |
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delta_net = resize(delta_net, scale_factor=self.scale_factor) |
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delta_flow = self.scale_factor * resize(delta_flow, scale_factor=self.scale_factor) |
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return delta_net, delta_flow |
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class BasicUpdateBlock(nn.Module): |
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def __init__(self, cdim, hidden_dim, flow_dim, corr_dim, corr_dim2, |
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fc_dim, corr_levels=4, radius=3, scale_factor=None, out_num=1): |
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super(BasicUpdateBlock, self).__init__() |
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cor_planes = corr_levels * (2 * radius + 1) **2 |
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self.scale_factor = scale_factor |
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self.convc1 = nn.Conv2d(2 * cor_planes, corr_dim, 1, padding=0) |
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self.convc2 = nn.Conv2d(corr_dim, corr_dim2, 3, padding=1) |
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self.convf1 = nn.Conv2d(4, flow_dim*2, 7, padding=3) |
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self.convf2 = nn.Conv2d(flow_dim*2, flow_dim, 3, padding=1) |
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self.conv = nn.Conv2d(flow_dim+corr_dim2, fc_dim, 3, padding=1) |
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self.gru = nn.Sequential( |
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nn.Conv2d(fc_dim+4+cdim, hidden_dim, 3, padding=1), |
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nn.LeakyReLU(negative_slope=0.1, inplace=True), |
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nn.Conv2d(hidden_dim, hidden_dim, 3, padding=1), |
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) |
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self.feat_head = nn.Sequential( |
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nn.Conv2d(hidden_dim, hidden_dim, 3, padding=1), |
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nn.LeakyReLU(negative_slope=0.1, inplace=True), |
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nn.Conv2d(hidden_dim, cdim, 3, padding=1), |
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) |
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self.flow_head = nn.Sequential( |
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nn.Conv2d(hidden_dim, hidden_dim, 3, padding=1), |
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nn.LeakyReLU(negative_slope=0.1, inplace=True), |
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nn.Conv2d(hidden_dim, 4*out_num, 3, padding=1), |
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) |
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self.lrelu = nn.LeakyReLU(negative_slope=0.1, inplace=True) |
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def forward(self, net, flow, corr): |
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net = resize(net, 1 / self.scale_factor |
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) if self.scale_factor is not None else net |
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cor = self.lrelu(self.convc1(corr)) |
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cor = self.lrelu(self.convc2(cor)) |
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flo = self.lrelu(self.convf1(flow)) |
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flo = self.lrelu(self.convf2(flo)) |
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cor_flo = torch.cat([cor, flo], dim=1) |
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inp = self.lrelu(self.conv(cor_flo)) |
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inp = torch.cat([inp, flow, net], dim=1) |
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out = self.gru(inp) |
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delta_net = self.feat_head(out) |
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delta_flow = self.flow_head(out) |
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if self.scale_factor is not None: |
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delta_net = resize(delta_net, scale_factor=self.scale_factor) |
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delta_flow = self.scale_factor * resize(delta_flow, scale_factor=self.scale_factor) |
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return delta_net, delta_flow |
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class BidirCorrBlock: |
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def __init__(self, fmap1, fmap2, num_levels=4, radius=4): |
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self.num_levels = num_levels |
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self.radius = radius |
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self.corr_pyramid = [] |
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self.corr_pyramid_T = [] |
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corr = BidirCorrBlock.corr(fmap1, fmap2) |
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batch, h1, w1, dim, h2, w2 = corr.shape |
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corr_T = corr.clone().permute(0, 4, 5, 3, 1, 2) |
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corr = corr.reshape(batch*h1*w1, dim, h2, w2) |
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corr_T = corr_T.reshape(batch*h2*w2, dim, h1, w1) |
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self.corr_pyramid.append(corr) |
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self.corr_pyramid_T.append(corr_T) |
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for _ in range(self.num_levels-1): |
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corr = F.avg_pool2d(corr, 2, stride=2) |
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corr_T = F.avg_pool2d(corr_T, 2, stride=2) |
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self.corr_pyramid.append(corr) |
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self.corr_pyramid_T.append(corr_T) |
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def __call__(self, coords0, coords1): |
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r = self.radius |
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coords0 = coords0.permute(0, 2, 3, 1) |
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coords1 = coords1.permute(0, 2, 3, 1) |
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assert coords0.shape == coords1.shape, f"coords0 shape: [{coords0.shape}] is not equal to [{coords1.shape}]" |
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batch, h1, w1, _ = coords0.shape |
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out_pyramid = [] |
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out_pyramid_T = [] |
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for i in range(self.num_levels): |
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corr = self.corr_pyramid[i] |
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corr_T = self.corr_pyramid_T[i] |
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dx = torch.linspace(-r, r, 2*r+1, device=coords0.device) |
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dy = torch.linspace(-r, r, 2*r+1, device=coords0.device) |
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delta = torch.stack(torch.meshgrid(dy, dx, indexing='ij'), axis=-1) |
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delta_lvl = delta.view(1, 2*r+1, 2*r+1, 2) |
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centroid_lvl_0 = coords0.reshape(batch*h1*w1, 1, 1, 2) / 2**i |
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centroid_lvl_1 = coords1.reshape(batch*h1*w1, 1, 1, 2) / 2**i |
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coords_lvl_0 = centroid_lvl_0 + delta_lvl |
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coords_lvl_1 = centroid_lvl_1 + delta_lvl |
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corr = bilinear_sampler(corr, coords_lvl_0) |
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corr_T = bilinear_sampler(corr_T, coords_lvl_1) |
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corr = corr.view(batch, h1, w1, -1) |
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corr_T = corr_T.view(batch, h1, w1, -1) |
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out_pyramid.append(corr) |
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out_pyramid_T.append(corr_T) |
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out = torch.cat(out_pyramid, dim=-1) |
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out_T = torch.cat(out_pyramid_T, dim=-1) |
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return out.permute(0, 3, 1, 2).contiguous().float(), out_T.permute(0, 3, 1, 2).contiguous().float() |
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@staticmethod |
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def corr(fmap1, fmap2): |
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batch, dim, ht, wd = fmap1.shape |
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fmap1 = fmap1.view(batch, dim, ht*wd) |
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fmap2 = fmap2.view(batch, dim, ht*wd) |
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corr = torch.matmul(fmap1.transpose(1,2), fmap2) |
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corr = corr.view(batch, ht, wd, 1, ht, wd) |
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return corr / torch.sqrt(torch.tensor(dim).float()) |
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