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100 lines
3.6 KiB
100 lines
3.6 KiB
3 years ago
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import copy
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import torch
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import torch.nn as nn
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from .linear_attention import LinearAttention, FullAttention
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#Ref: https://github.com/zju3dv/LoFTR/blob/master/src/loftr/loftr_module/transformer.py
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class LoFTREncoderLayer(nn.Module):
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def __init__(self,
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d_model,
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nhead,
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attention='linear'):
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super(LoFTREncoderLayer, self).__init__()
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self.dim = d_model // nhead
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self.nhead = nhead
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# multi-head attention
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self.q_proj = nn.Linear(d_model, d_model, bias=False)
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self.k_proj = nn.Linear(d_model, d_model, bias=False)
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self.v_proj = nn.Linear(d_model, d_model, bias=False)
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self.attention = LinearAttention() if attention == 'linear' else FullAttention()
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self.merge = nn.Linear(d_model, d_model, bias=False)
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# feed-forward network
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self.mlp = nn.Sequential(
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nn.Linear(d_model*2, d_model*2, bias=False),
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nn.ReLU(True),
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nn.Linear(d_model*2, d_model, bias=False),
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)
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# norm and dropout
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self.norm1 = nn.LayerNorm(d_model)
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self.norm2 = nn.LayerNorm(d_model)
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def forward(self, x, source, x_mask=None, source_mask=None):
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"""
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Args:
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x (torch.Tensor): [N, L, C]
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source (torch.Tensor): [N, S, C]
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x_mask (torch.Tensor): [N, L] (optional)
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source_mask (torch.Tensor): [N, S] (optional)
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"""
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bs = x.size(0)
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query, key, value = x, source, source
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# multi-head attention
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query = self.q_proj(query).view(bs, -1, self.nhead, self.dim) # [N, L, (H, D)]
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key = self.k_proj(key).view(bs, -1, self.nhead, self.dim) # [N, S, (H, D)]
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value = self.v_proj(value).view(bs, -1, self.nhead, self.dim)
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message = self.attention(query, key, value, q_mask=x_mask, kv_mask=source_mask) # [N, L, (H, D)]
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message = self.merge(message.view(bs, -1, self.nhead*self.dim)) # [N, L, C]
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message = self.norm1(message)
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# feed-forward network
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message = self.mlp(torch.cat([x, message], dim=2))
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message = self.norm2(message)
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return x + message
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class LocalFeatureTransformer(nn.Module):
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"""A Local Feature Transformer (LoFTR) module."""
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def __init__(self, d_model, nhead, layer_names, attention):
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super(LocalFeatureTransformer, self).__init__()
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self.d_model = d_model
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self.nhead = nhead
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self.layer_names = layer_names
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encoder_layer = LoFTREncoderLayer(d_model, nhead, attention)
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self.layers = nn.ModuleList([copy.deepcopy(encoder_layer) for _ in range(len(self.layer_names))])
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self._reset_parameters()
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def _reset_parameters(self):
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for p in self.parameters():
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if p.dim() > 1:
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nn.init.xavier_uniform_(p)
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def forward(self, feat0, feat1, mask0=None, mask1=None):
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"""
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Args:
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feat0 (torch.Tensor): [N, L, C]
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feat1 (torch.Tensor): [N, S, C]
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mask0 (torch.Tensor): [N, L] (optional)
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mask1 (torch.Tensor): [N, S] (optional)
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"""
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assert self.d_model == feat0.size(2), "the feature number of src and transformer must be equal"
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for layer, name in zip(self.layers, self.layer_names):
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if name == 'self':
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feat0 = layer(feat0, feat0, mask0, mask0)
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feat1 = layer(feat1, feat1, mask1, mask1)
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elif name == 'cross':
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feat0 = layer(feat0, feat1, mask0, mask1)
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feat1 = layer(feat1, feat0, mask1, mask0)
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else:
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raise KeyError
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return feat0, feat1
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