from typing import Optional import torch from torch import nn, Tensor from torch.nn import functional as F from timm.models.layers import trunc_normal_ from detectron2.layers import Conv2d import fvcore.nn.weight_init as weight_init from ..utils import MultiheadAttention class SelfAttentionLayer(nn.Module): def __init__(self, d_model, nhead, dropout=0.0, activation="relu", normalize_before=False): super().__init__() self.self_attn = MultiheadAttention(d_model, nhead, dropout=dropout) self.norm = nn.LayerNorm(d_model) self.dropout = nn.Dropout(dropout) self.activation = _get_activation_fn(activation) self.normalize_before = normalize_before self._reset_parameters() def _reset_parameters(self): for p in self.parameters(): if p.dim() > 1: nn.init.xavier_uniform_(p) def with_pos_embed(self, tensor, pos: Optional[Tensor]): return tensor if pos is None else tensor + pos def forward_post(self, tgt, tgt_mask: Optional[Tensor] = None, tgt_key_padding_mask: Optional[Tensor] = None, query_pos: Optional[Tensor] = None): q = k = self.with_pos_embed(tgt, query_pos) tgt2 = self.self_attn(q, k, value=tgt, attn_mask=tgt_mask, key_padding_mask=tgt_key_padding_mask)[0] tgt = tgt + self.dropout(tgt2) tgt = self.norm(tgt) return tgt def forward_pre(self, tgt, tgt_mask: Optional[Tensor] = None, tgt_key_padding_mask: Optional[Tensor] = None, query_pos: Optional[Tensor] = None): tgt2 = self.norm(tgt) q = k = self.with_pos_embed(tgt2, query_pos) tgt2 = self.self_attn(q, k, value=tgt2, attn_mask=tgt_mask, key_padding_mask=tgt_key_padding_mask)[0] tgt = tgt + self.dropout(tgt2) return tgt def forward(self, tgt, tgt_mask: Optional[Tensor] = None, tgt_key_padding_mask: Optional[Tensor] = None, query_pos: Optional[Tensor] = None): if self.normalize_before: return self.forward_pre(tgt, tgt_mask, tgt_key_padding_mask, query_pos) return self.forward_post(tgt, tgt_mask, tgt_key_padding_mask, query_pos) class CrossAttentionLayer(nn.Module): def __init__(self, d_model, nhead, dropout=0.0, activation="relu", normalize_before=False): super().__init__() self.multihead_attn = nn.MultiheadAttention(d_model, nhead, dropout=dropout) self.norm = nn.LayerNorm(d_model) self.dropout = nn.Dropout(dropout) self.activation = _get_activation_fn(activation) self.normalize_before = normalize_before self._reset_parameters() def _reset_parameters(self): for p in self.parameters(): if p.dim() > 1: nn.init.xavier_uniform_(p) def with_pos_embed(self, tensor, pos: Optional[Tensor]): return tensor if pos is None else tensor + pos def forward_post(self, tgt, memory, memory_mask: Optional[Tensor] = None, memory_key_padding_mask: Optional[Tensor] = None, pos: Optional[Tensor] = None, query_pos: Optional[Tensor] = None): tgt2, avg_attn = self.multihead_attn(query=self.with_pos_embed(tgt, query_pos), key=self.with_pos_embed(memory, pos), value=memory, attn_mask=memory_mask, key_padding_mask=memory_key_padding_mask) tgt = tgt + self.dropout(tgt2) tgt = self.norm(tgt) return tgt, avg_attn def forward_pre(self, tgt, memory, memory_mask: Optional[Tensor] = None, memory_key_padding_mask: Optional[Tensor] = None, pos: Optional[Tensor] = None, query_pos: Optional[Tensor] = None): tgt2 = self.norm(tgt) tgt2, avg_attn = self.multihead_attn(query=self.with_pos_embed(tgt2, query_pos), key=self.with_pos_embed(memory, pos), value=memory, attn_mask=memory_mask, key_padding_mask=memory_key_padding_mask) tgt = tgt + self.dropout(tgt2) return tgt, avg_attn def forward(self, tgt, memory, memory_mask: Optional[Tensor] = None, memory_key_padding_mask: Optional[Tensor] = None, pos: Optional[Tensor] = None, query_pos: Optional[Tensor] = None): if self.normalize_before: return self.forward_pre(tgt, memory, memory_mask, memory_key_padding_mask, pos, query_pos) return self.forward_post(tgt, memory, memory_mask, memory_key_padding_mask, pos, query_pos) class FFNLayer(nn.Module): def __init__(self, d_model, dim_feedforward=2048, dropout=0.0, activation="relu", normalize_before=False): super().__init__() # Implementation of Feedforward model self.linear1 = nn.Linear(d_model, dim_feedforward) self.dropout = nn.Dropout(dropout) self.linear2 = nn.Linear(dim_feedforward, d_model) self.norm = nn.LayerNorm(d_model) self.activation = _get_activation_fn(activation) self.normalize_before = normalize_before self._reset_parameters() def _reset_parameters(self): for p in self.parameters(): if p.dim() > 1: nn.init.xavier_uniform_(p) def with_pos_embed(self, tensor, pos: Optional[Tensor]): return tensor if pos is None else tensor + pos def forward_post(self, tgt): tgt2 = self.linear2(self.dropout(self.activation(self.linear1(tgt)))) tgt = tgt + self.dropout(tgt2) tgt = self.norm(tgt) return tgt def forward_pre(self, tgt): tgt2 = self.norm(tgt) tgt2 = self.linear2(self.dropout(self.activation(self.linear1(tgt2)))) tgt = tgt + self.dropout(tgt2) return tgt def forward(self, tgt): if self.normalize_before: return self.forward_pre(tgt) return self.forward_post(tgt) def _get_activation_fn(activation): """Return an activation function given a string""" if activation == "relu": return F.relu if activation == "gelu": return F.gelu if activation == "glu": return F.glu raise RuntimeError(F"activation should be relu/gelu, not {activation}.") class MLP(nn.Module): """ Very simple multi-layer perceptron (also called FFN)""" def __init__(self, input_dim, hidden_dim, output_dim, num_layers): super().__init__() self.num_layers = num_layers h = [hidden_dim] * (num_layers - 1) self.layers = nn.ModuleList(nn.Linear(n, k) for n, k in zip([input_dim] + h, h + [output_dim])) def forward(self, x): for i, layer in enumerate(self.layers): x = F.relu(layer(x)) if i < self.num_layers - 1 else layer(x) return x