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# ------------------------------------------------------------------------
# Copyright (c) 2022 megvii-model. All Rights Reserved.
# ------------------------------------------------------------------------
# Modified from DETR3D (https://github.com/WangYueFt/detr3d)
# Copyright (c) 2021 Wang, Yue
# ------------------------------------------------------------------------
# Modified from mmdetection3d (https://github.com/open-mmlab/mmdetection3d)
# Copyright (c) OpenMMLab. All rights reserved.
# ------------------------------------------------------------------------
import warnings
import torch
import torch.nn as nn
import torch.utils.checkpoint as cp
from mmcv.cnn import build_norm_layer
from mmcv.cnn.bricks.transformer import (BaseTransformerLayer,
TransformerLayerSequence)
from mmengine.model import BaseModule
from mmengine.model.weight_init import xavier_init
# from mmcv.utils import deprecated_api_warning
from mmdet3d.registry import MODELS, TASK_UTILS
@MODELS.register_module()
class PETRTransformer(BaseModule):
"""Implements the DETR transformer. Following the official DETR
implementation, this module copy-paste from torch.nn.Transformer with
modifications:
* positional encodings are passed in MultiheadAttention
* extra LN at the end of encoder is removed
* decoder returns a stack of activations from all decoding layers
See `paper: End-to-End Object Detection with Transformers
<https://arxiv.org/pdf/2005.12872>`_ for details.
Args:
encoder (`mmcv.ConfigDict` | Dict): Config of
TransformerEncoder. Defaults to None.
decoder ((`mmcv.ConfigDict` | Dict)): Config of
TransformerDecoder. Defaults to None
init_cfg (obj:`mmcv.ConfigDict`): The Config for initialization.
Defaults to None.
"""
def __init__(self, encoder=None, decoder=None, init_cfg=None, cross=False):
super(PETRTransformer, self).__init__(init_cfg=init_cfg)
if encoder is not None:
self.encoder = MODELS.build(encoder)
else:
self.encoder = None
self.decoder = MODELS.build(decoder)
self.embed_dims = self.decoder.embed_dims
self.cross = cross
def init_weights(self):
# follow the official DETR to init parameters
for m in self.modules():
if hasattr(m, 'weight') and m.weight.dim() > 1:
xavier_init(m, distribution='uniform')
self._is_init = True
def forward(self, x, mask, query_embed, pos_embed, reg_branch=None):
"""Forward function for `Transformer`.
Args:
x (Tensor): Input query with shape [bs, c, h, w] where
c = embed_dims.
mask (Tensor): The key_padding_mask used for encoder and decoder,
with shape [bs, h, w].
query_embed (Tensor): The query embedding for decoder, with shape
[num_query, c].
pos_embed (Tensor): The positional encoding for encoder and
decoder, with the same shape as `x`.
Returns:
tuple[Tensor]: results of decoder containing the following tensor.
- out_dec: Output from decoder. If return_intermediate_dec \
is True output has shape [num_dec_layers, bs,
num_query, embed_dims], else has shape [1, bs, \
num_query, embed_dims].
- memory: Output results from encoder, with shape \
[bs, embed_dims, h, w].
"""
bs, n, c, h, w = x.shape
memory = x.permute(1, 3, 4, 0,
2).reshape(-1, bs,
c) # [bs, n, c, h, w] -> [n*h*w, bs, c]
pos_embed = pos_embed.permute(1, 3, 4, 0, 2).reshape(
-1, bs, c) # [bs, n, c, h, w] -> [n*h*w, bs, c]
query_embed = query_embed.unsqueeze(1).repeat(
1, bs, 1) # [num_query, dim] -> [num_query, bs, dim]
mask = mask.view(bs, -1) # [bs, n, h, w] -> [bs, n*h*w]
target = torch.zeros_like(query_embed)
# out_dec: [num_layers, num_query, bs, dim]
out_dec = self.decoder(
query=target,
key=memory,
value=memory,
key_pos=pos_embed,
query_pos=query_embed,
key_padding_mask=mask,
reg_branch=reg_branch,
)
out_dec = out_dec.transpose(1, 2)
memory = memory.reshape(n, h, w, bs, c).permute(3, 0, 4, 1, 2)
return out_dec, memory
@MODELS.register_module()
class PETRDNTransformer(BaseModule):
"""Implements the DETR transformer. Following the official DETR
implementation, this module copy-paste from torch.nn.Transformer with
modifications:
* positional encodings are passed in MultiheadAttention
* extra LN at the end of encoder is removed
* decoder returns a stack of activations from all decoding layers
See `paper: End-to-End Object Detection with Transformers
<https://arxiv.org/pdf/2005.12872>`_ for details.
Args:
encoder (`mmcv.ConfigDict` | Dict): Config of
TransformerEncoder. Defaults to None.
decoder ((`mmcv.ConfigDict` | Dict)): Config of
TransformerDecoder. Defaults to None
init_cfg (obj:`mmcv.ConfigDict`): The Config for initialization.
Defaults to None.
"""
def __init__(self, encoder=None, decoder=None, init_cfg=None, cross=False):
super(PETRDNTransformer, self).__init__(init_cfg=init_cfg)
if encoder is not None:
self.encoder = MODELS.build(encoder)
else:
self.encoder = None
self.decoder = MODELS.build(decoder)
self.embed_dims = self.decoder.embed_dims
self.cross = cross
def init_weights(self):
# follow the official DETR to init parameters
for m in self.modules():
if hasattr(m, 'weight') and m.weight.dim() > 1:
xavier_init(m, distribution='uniform')
self._is_init = True
def forward(self,
x,
mask,
query_embed,
pos_embed,
attn_masks=None,
reg_branch=None):
"""Forward function for `Transformer`.
Args:
x (Tensor): Input query with shape [bs, c, h, w] where
c = embed_dims.
mask (Tensor): The key_padding_mask used for encoder and decoder,
with shape [bs, h, w].
query_embed (Tensor): The query embedding for decoder, with shape
[num_query, c].
pos_embed (Tensor): The positional encoding for encoder and
decoder, with the same shape as `x`.
Returns:
tuple[Tensor]: results of decoder containing the following tensor.
- out_dec: Output from decoder. If return_intermediate_dec \
is True output has shape [num_dec_layers, bs,
num_query, embed_dims], else has shape [1, bs, \
num_query, embed_dims].
- memory: Output results from encoder, with shape \
[bs, embed_dims, h, w].
"""
bs, n, c, h, w = x.shape
memory = x.permute(1, 3, 4, 0,
2).reshape(-1, bs,
c) # [bs, n, c, h, w] -> [n*h*w, bs, c]
pos_embed = pos_embed.permute(1, 3, 4, 0, 2).reshape(
-1, bs, c) # [bs, n, c, h, w] -> [n*h*w, bs, c]
query_embed = query_embed.transpose(
0, 1) # [num_query, dim] -> [num_query, bs, dim]
mask = mask.view(bs, -1) # [bs, n, h, w] -> [bs, n*h*w]
target = torch.zeros_like(query_embed)
# out_dec: [num_layers, num_query, bs, dim]
out_dec = self.decoder(
query=target,
key=memory,
value=memory,
key_pos=pos_embed,
query_pos=query_embed,
key_padding_mask=mask,
attn_masks=[attn_masks, None],
reg_branch=reg_branch,
)
out_dec = out_dec.transpose(1, 2)
memory = memory.reshape(n, h, w, bs, c).permute(3, 0, 4, 1, 2)
return out_dec, memory
@MODELS.register_module()
class PETRTransformerDecoderLayer(BaseTransformerLayer):
"""Implements decoder layer in DETR transformer.
Args:
attn_cfgs (list[`mmcv.ConfigDict`] | list[dict] | dict )):
Configs for self_attention or cross_attention, the order
should be consistent with it in `operation_order`. If it is
a dict, it would be expand to the number of attention in
`operation_order`.
feedforward_channels (int): The hidden dimension for FFNs.
ffn_dropout (float): Probability of an element to be zeroed
in ffn. Default 0.0.
operation_order (tuple[str]): The execution order of operation
in transformer. Such as ('self_attn', 'norm', 'ffn', 'norm').
Default：None
act_cfg (dict): The activation config for FFNs. Default: `LN`
norm_cfg (dict): Config dict for normalization layer.
Default: `LN`.
ffn_num_fcs (int): The number of fully-connected layers in FFNs.
Default：2.
"""
def __init__(self,
attn_cfgs,
feedforward_channels,
ffn_dropout=0.0,
operation_order=None,
act_cfg=dict(type='ReLU', inplace=True),
norm_cfg=dict(type='LN'),
ffn_num_fcs=2,
with_cp=True,
**kwargs):
super(PETRTransformerDecoderLayer, self).__init__(
attn_cfgs=attn_cfgs,
feedforward_channels=feedforward_channels,
ffn_dropout=ffn_dropout,
operation_order=operation_order,
act_cfg=act_cfg,
norm_cfg=norm_cfg,
ffn_num_fcs=ffn_num_fcs,
**kwargs)
assert len(operation_order) == 6
assert set(operation_order) == set(
['self_attn', 'norm', 'cross_attn', 'ffn'])
self.use_checkpoint = with_cp
def _forward(
self,
query,
key=None,
value=None,
query_pos=None,
key_pos=None,
attn_masks=None,
query_key_padding_mask=None,
key_padding_mask=None,
):
"""Forward function for `TransformerCoder`.
Returns:
Tensor: forwarded results with shape [num_query, bs, embed_dims].
"""
x = super(PETRTransformerDecoderLayer, self).forward(
query,
key=key,
value=value,
query_pos=query_pos,
key_pos=key_pos,
attn_masks=attn_masks,
query_key_padding_mask=query_key_padding_mask,
key_padding_mask=key_padding_mask,
)
return x
def forward(self,
query,
key=None,
value=None,
query_pos=None,
key_pos=None,
attn_masks=None,
query_key_padding_mask=None,
key_padding_mask=None,
**kwargs):
"""Forward function for `TransformerCoder`.
Returns:
Tensor: forwarded results with shape [num_query, bs, embed_dims].
"""
if self.use_checkpoint and self.training:
x = cp.checkpoint(
self._forward,
query,
key,
value,
query_pos,
key_pos,
attn_masks,
query_key_padding_mask,
key_padding_mask,
)
else:
x = self._forward(
query,
key=key,
value=value,
query_pos=query_pos,
key_pos=key_pos,
attn_masks=attn_masks,
query_key_padding_mask=query_key_padding_mask,
key_padding_mask=key_padding_mask)
return x
@MODELS.register_module()
class PETRMultiheadAttention(BaseModule):
"""A wrapper for ``torch.nn.MultiheadAttention``.
This module implements MultiheadAttention with identity connection,
and positional encoding is also passed as input.
Args:
embed_dims (int): The embedding dimension.
num_heads (int): Parallel attention heads.
attn_drop (float): A Dropout layer on attn_output_weights.
Default: 0.0.
proj_drop (float): A Dropout layer after `nn.MultiheadAttention`.
Default: 0.0.
dropout_layer (obj:`ConfigDict`): The dropout_layer used
when adding the shortcut.
init_cfg (obj:`mmcv.ConfigDict`): The Config for initialization.
Default: None.
batch_first (bool): When it is True, Key, Query and Value are shape of
(batch, n, embed_dim), otherwise (n, batch, embed_dim).
Default to False.
"""
def __init__(self,
embed_dims,
num_heads,
attn_drop=0.,
proj_drop=0.,
dropout_layer=dict(type='Dropout', drop_prob=0.),
init_cfg=None,
batch_first=False,
**kwargs):
super(PETRMultiheadAttention, self).__init__(init_cfg)
if 'dropout' in kwargs:
warnings.warn(
'The arguments `dropout` in MultiheadAttention '
'has been deprecated, now you can separately '
'set `attn_drop`(float), proj_drop(float), '
'and `dropout_layer`(dict) ', DeprecationWarning)
attn_drop = kwargs['dropout']
dropout_layer['drop_prob'] = kwargs.pop('dropout')
self.embed_dims = embed_dims
self.num_heads = num_heads
self.batch_first = batch_first
self.attn = nn.MultiheadAttention(embed_dims, num_heads, attn_drop,
**kwargs)
self.proj_drop = nn.Dropout(proj_drop)
self.dropout_layer = MODELS.build(
dropout_layer) if dropout_layer else nn.Identity()
# @deprecated_api_warning({'residual': 'identity'},
# cls_name='MultiheadAttention')
def forward(self,
query,
key=None,
value=None,
identity=None,
query_pos=None,
key_pos=None,
attn_mask=None,
key_padding_mask=None,
**kwargs):
"""Forward function for `MultiheadAttention`.
**kwargs allow passing a more general data flow when combining
with other operations in `transformerlayer`.
Args:
query (Tensor): The input query with shape [num_queries, bs,
embed_dims] if self.batch_first is False, else
[bs, num_queries embed_dims].
key (Tensor): The key tensor with shape [num_keys, bs,
embed_dims] if self.batch_first is False, else
[bs, num_keys, embed_dims] .
If None, the ``query`` will be used. Defaults to None.
value (Tensor): The value tensor with same shape as `key`.
Same in `nn.MultiheadAttention.forward`. Defaults to None.
If None, the `key` will be used.
identity (Tensor): This tensor, with the same shape as x,
will be used for the identity link.
If None, `x` will be used. Defaults to None.
query_pos (Tensor): The positional encoding for query, with
the same shape as `x`. If not None, it will
be added to `x` before forward function. Defaults to None.
key_pos (Tensor): The positional encoding for `key`, with the
same shape as `key`. Defaults to None. If not None, it will
be added to `key` before forward function. If None, and
`query_pos` has the same shape as `key`, then `query_pos`
will be used for `key_pos`. Defaults to None.
attn_mask (Tensor): ByteTensor mask with shape [num_queries,
num_keys]. Same in `nn.MultiheadAttention.forward`.
Defaults to None.
key_padding_mask (Tensor): ByteTensor with shape [bs, num_keys].
Defaults to None.
Returns:
Tensor: forwarded results with shape
[num_queries, bs, embed_dims]
if self.batch_first is False, else
[bs, num_queries embed_dims].
"""
if key is None:
key = query
if value is None:
value = key
if identity is None:
identity = query
if key_pos is None:
if query_pos is not None:
# use query_pos if key_pos is not available
if query_pos.shape == key.shape:
key_pos = query_pos
else:
warnings.warn(f'position encoding of key is'
f'missing in {self.__class__.__name__}.')
if query_pos is not None:
query = query + query_pos
if key_pos is not None:
key = key + key_pos
# Because the dataflow('key', 'query', 'value') of
# ``torch.nn.MultiheadAttention`` is (num_query, batch,
# embed_dims), We should adjust the shape of dataflow from
# batch_first (batch, num_query, embed_dims) to num_query_first
# (num_query ,batch, embed_dims), and recover ``attn_output``
# from num_query_first to batch_first.
if self.batch_first:
query = query.transpose(0, 1)
key = key.transpose(0, 1)
value = value.transpose(0, 1)
out = self.attn(
query=query,
key=key,
value=value,
attn_mask=attn_mask,
key_padding_mask=key_padding_mask)[0]
if self.batch_first:
out = out.transpose(0, 1)
return identity + self.dropout_layer(self.proj_drop(out))
@MODELS.register_module()
class PETRTransformerEncoder(TransformerLayerSequence):
"""TransformerEncoder of DETR.
Args:
post_norm_cfg (dict): Config of last normalization layer. Default：
`LN`. Only used when `self.pre_norm` is `True`
"""
def __init__(self, *args, post_norm_cfg=dict(type='LN'), **kwargs):
super(PETRTransformerEncoder, self).__init__(*args, **kwargs)
if post_norm_cfg is not None:
self.post_norm = TASK_UTILS.build(
post_norm_cfg, self.embed_dims)[1] if self.pre_norm else None
else:
assert not self.pre_norm, f'Use prenorm in ' \
f'{self.__class__.__name__},' \
f'Please specify post_norm_cfg'
self.post_norm = None
def forward(self, *args, **kwargs):
"""Forward function for `TransformerCoder`.
Returns:
Tensor: forwarded results with shape [num_query, bs, embed_dims].
"""
x = super(PETRTransformerEncoder, self).forward(*args, **kwargs)
if self.post_norm is not None:
x = self.post_norm(x)
return x
@MODELS.register_module()
class PETRTransformerDecoder(TransformerLayerSequence):
"""Implements the decoder in DETR transformer.
Args:
return_intermediate (bool): Whether to return intermediate outputs.
post_norm_cfg (dict): Config of last normalization layer. Default：
`LN`.
"""
def __init__(self,
*args,
post_norm_cfg=dict(type='LN'),
return_intermediate=False,
**kwargs):
super(PETRTransformerDecoder, self).__init__(*args, **kwargs)
self.return_intermediate = return_intermediate
if post_norm_cfg is not None:
self.post_norm = build_norm_layer(post_norm_cfg,
self.embed_dims)[1]
else:
self.post_norm = None
def forward(self, query, *args, **kwargs):
"""Forward function for `TransformerDecoder`.
Args:
query (Tensor): Input query with shape
`(num_query, bs, embed_dims)`.
Returns:
Tensor: Results with shape [1, num_query, bs, embed_dims] when
return_intermediate is `False`, otherwise it has shape
[num_layers, num_query, bs, embed_dims].
"""
if not self.return_intermediate:
x = super().forward(query, *args, **kwargs)
if self.post_norm:
x = self.post_norm(x)[None]
return x
intermediate = []
for layer in self.layers:
query = layer(query, *args, **kwargs)
if self.return_intermediate:
if self.post_norm is not None:
intermediate.append(self.post_norm(query))
else:
intermediate.append(query)
return torch.stack(intermediate)
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