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import copy
import math
from typing import Optional
import torch
import torch.nn.functional as F
from torch import Tensor, nn
# modified from https://github.com/microsoft/X-Decoder/blob/main/xdecoder/body/transformer_blocks.py # noqa
"""Transformer class.
Copy-paste from torch.nn.Transformer with modifications:
* positional encodings are passed in MHattention
* extra LN at the end of encoder is removed
* decoder returns a stack of activations from all decoding layers
"""
class Conv2d(torch.nn.Conv2d):
"""A wrapper around :class:`torch.nn.Conv2d` to support empty inputs and
more features."""
def __init__(self, *args, **kwargs):
"""Extra keyword arguments supported in addition to those in
`torch.nn.Conv2d`:
Args:
norm (nn.Module, optional): a normalization layer
activation (callable(Tensor) -> Tensor): a callable
activation function
It assumes that norm layer is used before activation.
"""
norm = kwargs.pop('norm', None)
activation = kwargs.pop('activation', None)
super().__init__(*args, **kwargs)
self.norm = norm
self.activation = activation
def forward(self, x):
x = F.conv2d(x, self.weight, self.bias, self.stride, self.padding,
self.dilation, self.groups)
if self.norm is not None:
x = self.norm(x)
if self.activation is not None:
x = self.activation(x)
return x
class PositionEmbeddingSine(nn.Module):
"""This is a more standard version of the position embedding, very similar
to the one used by the Attention is all you need paper, generalized to work
on images."""
def __init__(self,
num_pos_feats=64,
temperature=10000,
normalize=False,
scale=None):
super().__init__()
self.num_pos_feats = num_pos_feats
self.temperature = temperature
self.normalize = normalize
if scale is not None and normalize is False:
raise ValueError('normalize should be True if scale is passed')
if scale is None:
scale = 2 * math.pi
self.scale = scale
def forward(self, x, mask=None):
if mask is None:
mask = torch.zeros((x.size(0), x.size(2), x.size(3)),
device=x.device,
dtype=torch.bool)
not_mask = ~mask
y_embed = not_mask.cumsum(1, dtype=x.dtype)
x_embed = not_mask.cumsum(2, dtype=x.dtype)
if self.normalize:
eps = 1e-6
y_embed = y_embed / (y_embed[:, -1:, :] + eps) * self.scale
x_embed = x_embed / (x_embed[:, :, -1:] + eps) * self.scale
dim_t = torch.arange(
self.num_pos_feats, dtype=x.dtype, device=x.device)
dim_t = self.temperature**(2 * (dim_t // 2) / self.num_pos_feats)
pos_x = x_embed[:, :, :, None] / dim_t
pos_y = y_embed[:, :, :, None] / dim_t
pos_x = torch.stack(
(pos_x[:, :, :, 0::2].sin(), pos_x[:, :, :, 1::2].cos()),
dim=4).flatten(3)
pos_y = torch.stack(
(pos_y[:, :, :, 0::2].sin(), pos_y[:, :, :, 1::2].cos()),
dim=4).flatten(3)
pos = torch.cat((pos_y, pos_x), dim=3).permute(0, 3, 1, 2)
return pos
def __repr__(self, _repr_indent=4):
head = 'Positional encoding ' + self.__class__.__name__
body = [
'num_pos_feats: {}'.format(self.num_pos_feats),
'temperature: {}'.format(self.temperature),
'normalize: {}'.format(self.normalize),
'scale: {}'.format(self.scale),
]
# _repr_indent = 4
lines = [head] + [' ' * _repr_indent + line for line in body]
return '\n'.join(lines)
class TransformerEncoder(nn.Module):
def __init__(self, encoder_layer, num_layers, norm=None):
super().__init__()
self.layers = _get_clones(encoder_layer, num_layers)
self.num_layers = num_layers
self.norm = norm
def forward(
self,
src,
mask: Optional[Tensor] = None,
src_key_padding_mask: Optional[Tensor] = None,
pos: Optional[Tensor] = None,
):
output = src
for layer in self.layers:
output = layer(
output,
src_mask=mask,
src_key_padding_mask=src_key_padding_mask,
pos=pos)
if self.norm is not None:
output = self.norm(output)
return output
class TransformerEncoderLayer(nn.Module):
def __init__(
self,
d_model,
nhead,
dim_feedforward=2048,
dropout=0.1,
activation='relu',
normalize_before=False,
):
super().__init__()
self.self_attn = nn.MultiheadAttention(d_model, nhead, dropout=dropout)
# 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.norm1 = nn.LayerNorm(d_model)
self.norm2 = nn.LayerNorm(d_model)
self.dropout1 = nn.Dropout(dropout)
self.dropout2 = nn.Dropout(dropout)
self.activation = _get_activation_fn(activation)
self.normalize_before = normalize_before
def with_pos_embed(self, tensor, pos: Optional[Tensor]):
return tensor if pos is None else tensor + pos
def forward_post(
self,
src,
src_mask: Optional[Tensor] = None,
src_key_padding_mask: Optional[Tensor] = None,
pos: Optional[Tensor] = None,
):
q = k = self.with_pos_embed(src, pos)
src2 = self.self_attn(
q,
k,
value=src,
attn_mask=src_mask,
key_padding_mask=src_key_padding_mask)[0]
src = src + self.dropout1(src2)
src = self.norm1(src)
src2 = self.linear2(self.dropout(self.activation(self.linear1(src))))
src = src + self.dropout2(src2)
src = self.norm2(src)
return src
def forward_pre(
self,
src,
src_mask: Optional[Tensor] = None,
src_key_padding_mask: Optional[Tensor] = None,
pos: Optional[Tensor] = None,
):
src2 = self.norm1(src)
q = k = self.with_pos_embed(src2, pos)
src2 = self.self_attn(
q,
k,
value=src2,
attn_mask=src_mask,
key_padding_mask=src_key_padding_mask)[0]
src = src + self.dropout1(src2)
src2 = self.norm2(src)
src2 = self.linear2(self.dropout(self.activation(self.linear1(src2))))
src = src + self.dropout2(src2)
return src
def forward(
self,
src,
src_mask: Optional[Tensor] = None,
src_key_padding_mask: Optional[Tensor] = None,
pos: Optional[Tensor] = None,
):
if self.normalize_before:
return self.forward_pre(src, src_mask, src_key_padding_mask, pos)
return self.forward_post(src, src_mask, src_key_padding_mask, pos)
class SelfAttentionLayer(nn.Module):
def __init__(self,
d_model,
nhead,
dropout=0.0,
activation='relu',
normalize_before=False):
super().__init__()
self.self_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,
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)
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
def get_norm(norm, out_channels):
"""
Args:
norm (str or callable): either one of BN, SyncBN, FrozenBN, GN;
or a callable that takes a channel number and returns
the normalization layer as a nn.Module.
Returns:
nn.Module or None: the normalization layer
"""
if norm is None:
return None
if isinstance(norm, str):
if len(norm) == 0:
return None
norm = {
'BN': nn.BatchNorm2d,
'GN': lambda channels: nn.GroupNorm(32, channels),
}[norm]
return norm(out_channels)
def _get_clones(module, N):
return nn.ModuleList([copy.deepcopy(module) for i in range(N)])
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}.')
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