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""" Sequencer
Paper: `Sequencer: Deep LSTM for Image Classification` - https://arxiv.org/pdf/2205.01972.pdf
"""
# Copyright (c) 2022. Yuki Tatsunami
# Licensed under the Apache License, Version 2.0 (the "License");
import math
from functools import partial
from itertools import accumulate
from typing import Tuple
import torch
import torch.nn as nn
from timm.data import IMAGENET_DEFAULT_MEAN, IMAGENET_DEFAULT_STD, DEFAULT_CROP_PCT
from timm.layers import lecun_normal_, DropPath, Mlp, PatchEmbed, ClassifierHead
from ._builder import build_model_with_cfg
from ._manipulate import named_apply
from ._registry import register_model, generate_default_cfgs
__all__ = ['Sequencer2d'] # model_registry will add each entrypoint fn to this
def _init_weights(module: nn.Module, name: str, head_bias: float = 0., flax=False):
if isinstance(module, nn.Linear):
if name.startswith('head'):
nn.init.zeros_(module.weight)
nn.init.constant_(module.bias, head_bias)
else:
if flax:
# Flax defaults
lecun_normal_(module.weight)
if module.bias is not None:
nn.init.zeros_(module.bias)
else:
nn.init.xavier_uniform_(module.weight)
if module.bias is not None:
if 'mlp' in name:
nn.init.normal_(module.bias, std=1e-6)
else:
nn.init.zeros_(module.bias)
elif isinstance(module, nn.Conv2d):
lecun_normal_(module.weight)
if module.bias is not None:
nn.init.zeros_(module.bias)
elif isinstance(module, (nn.LayerNorm, nn.BatchNorm2d, nn.GroupNorm)):
nn.init.ones_(module.weight)
nn.init.zeros_(module.bias)
elif isinstance(module, (nn.RNN, nn.GRU, nn.LSTM)):
stdv = 1.0 / math.sqrt(module.hidden_size)
for weight in module.parameters():
nn.init.uniform_(weight, -stdv, stdv)
elif hasattr(module, 'init_weights'):
module.init_weights()
class RNNIdentity(nn.Module):
def __init__(self, *args, **kwargs):
super(RNNIdentity, self).__init__()
def forward(self, x: torch.Tensor) -> Tuple[torch.Tensor, None]:
return x, None
class RNN2dBase(nn.Module):
def __init__(
self,
input_size: int,
hidden_size: int,
num_layers: int = 1,
bias: bool = True,
bidirectional: bool = True,
union="cat",
with_fc=True,
):
super().__init__()
self.input_size = input_size
self.hidden_size = hidden_size
self.output_size = 2 * hidden_size if bidirectional else hidden_size
self.union = union
self.with_vertical = True
self.with_horizontal = True
self.with_fc = with_fc
self.fc = None
if with_fc:
if union == "cat":
self.fc = nn.Linear(2 * self.output_size, input_size)
elif union == "add":
self.fc = nn.Linear(self.output_size, input_size)
elif union == "vertical":
self.fc = nn.Linear(self.output_size, input_size)
self.with_horizontal = False
elif union == "horizontal":
self.fc = nn.Linear(self.output_size, input_size)
self.with_vertical = False
else:
raise ValueError("Unrecognized union: " + union)
elif union == "cat":
pass
if 2 * self.output_size != input_size:
raise ValueError(f"The output channel {2 * self.output_size} is different from the input channel {input_size}.")
elif union == "add":
pass
if self.output_size != input_size:
raise ValueError(f"The output channel {self.output_size} is different from the input channel {input_size}.")
elif union == "vertical":
if self.output_size != input_size:
raise ValueError(f"The output channel {self.output_size} is different from the input channel {input_size}.")
self.with_horizontal = False
elif union == "horizontal":
if self.output_size != input_size:
raise ValueError(f"The output channel {self.output_size} is different from the input channel {input_size}.")
self.with_vertical = False
else:
raise ValueError("Unrecognized union: " + union)
self.rnn_v = RNNIdentity()
self.rnn_h = RNNIdentity()
def forward(self, x):
B, H, W, C = x.shape
if self.with_vertical:
v = x.permute(0, 2, 1, 3)
v = v.reshape(-1, H, C)
v, _ = self.rnn_v(v)
v = v.reshape(B, W, H, -1)
v = v.permute(0, 2, 1, 3)
else:
v = None
if self.with_horizontal:
h = x.reshape(-1, W, C)
h, _ = self.rnn_h(h)
h = h.reshape(B, H, W, -1)
else:
h = None
if v is not None and h is not None:
if self.union == "cat":
x = torch.cat([v, h], dim=-1)
else:
x = v + h
elif v is not None:
x = v
elif h is not None:
x = h
if self.fc is not None:
x = self.fc(x)
return x
class LSTM2d(RNN2dBase):
def __init__(
self,
input_size: int,
hidden_size: int,
num_layers: int = 1,
bias: bool = True,
bidirectional: bool = True,
union="cat",
with_fc=True,
):
super().__init__(input_size, hidden_size, num_layers, bias, bidirectional, union, with_fc)
if self.with_vertical:
self.rnn_v = nn.LSTM(
input_size,
hidden_size,
num_layers,
batch_first=True,
bias=bias,
bidirectional=bidirectional,
)
if self.with_horizontal:
self.rnn_h = nn.LSTM(
input_size,
hidden_size,
num_layers,
batch_first=True,
bias=bias,
bidirectional=bidirectional,
)
class Sequencer2dBlock(nn.Module):
def __init__(
self,
dim,
hidden_size,
mlp_ratio=3.0,
rnn_layer=LSTM2d,
mlp_layer=Mlp,
norm_layer=partial(nn.LayerNorm, eps=1e-6),
act_layer=nn.GELU,
num_layers=1,
bidirectional=True,
union="cat",
with_fc=True,
drop=0.,
drop_path=0.,
):
super().__init__()
channels_dim = int(mlp_ratio * dim)
self.norm1 = norm_layer(dim)
self.rnn_tokens = rnn_layer(
dim,
hidden_size,
num_layers=num_layers,
bidirectional=bidirectional,
union=union,
with_fc=with_fc,
)
self.drop_path = DropPath(drop_path) if drop_path > 0. else nn.Identity()
self.norm2 = norm_layer(dim)
self.mlp_channels = mlp_layer(dim, channels_dim, act_layer=act_layer, drop=drop)
def forward(self, x):
x = x + self.drop_path(self.rnn_tokens(self.norm1(x)))
x = x + self.drop_path(self.mlp_channels(self.norm2(x)))
return x
class Shuffle(nn.Module):
def __init__(self):
super().__init__()
def forward(self, x):
if self.training:
B, H, W, C = x.shape
r = torch.randperm(H * W)
x = x.reshape(B, -1, C)
x = x[:, r, :].reshape(B, H, W, -1)
return x
class Downsample2d(nn.Module):
def __init__(self, input_dim, output_dim, patch_size):
super().__init__()
self.down = nn.Conv2d(input_dim, output_dim, kernel_size=patch_size, stride=patch_size)
def forward(self, x):
x = x.permute(0, 3, 1, 2)
x = self.down(x)
x = x.permute(0, 2, 3, 1)
return x
class Sequencer2dStage(nn.Module):
def __init__(
self,
dim,
dim_out,
depth,
patch_size,
hidden_size,
mlp_ratio,
downsample=False,
block_layer=Sequencer2dBlock,
rnn_layer=LSTM2d,
mlp_layer=Mlp,
norm_layer=partial(nn.LayerNorm, eps=1e-6),
act_layer=nn.GELU,
num_layers=1,
bidirectional=True,
union="cat",
with_fc=True,
drop=0.,
drop_path=0.,
):
super().__init__()
if downsample:
self.downsample = Downsample2d(dim, dim_out, patch_size)
else:
assert dim == dim_out
self.downsample = nn.Identity()
blocks = []
for block_idx in range(depth):
blocks.append(block_layer(
dim_out,
hidden_size,
mlp_ratio=mlp_ratio,
rnn_layer=rnn_layer,
mlp_layer=mlp_layer,
norm_layer=norm_layer,
act_layer=act_layer,
num_layers=num_layers,
bidirectional=bidirectional,
union=union,
with_fc=with_fc,
drop=drop,
drop_path=drop_path[block_idx] if isinstance(drop_path, (list, tuple)) else drop_path,
))
self.blocks = nn.Sequential(*blocks)
def forward(self, x):
x = self.downsample(x)
x = self.blocks(x)
return x
class Sequencer2d(nn.Module):
def __init__(
self,
num_classes=1000,
img_size=224,
in_chans=3,
global_pool='avg',
layers=(4, 3, 8, 3),
patch_sizes=(7, 2, 2, 1),
embed_dims=(192, 384, 384, 384),
hidden_sizes=(48, 96, 96, 96),
mlp_ratios=(3.0, 3.0, 3.0, 3.0),
block_layer=Sequencer2dBlock,
rnn_layer=LSTM2d,
mlp_layer=Mlp,
norm_layer=partial(nn.LayerNorm, eps=1e-6),
act_layer=nn.GELU,
num_rnn_layers=1,
bidirectional=True,
union="cat",
with_fc=True,
drop_rate=0.,
drop_path_rate=0.,
nlhb=False,
stem_norm=False,
):
super().__init__()
assert global_pool in ('', 'avg')
self.num_classes = num_classes
self.global_pool = global_pool
self.num_features = embed_dims[-1] # num_features for consistency with other models
self.feature_dim = -1 # channel dim index for feature outputs (rank 4, NHWC)
self.output_fmt = 'NHWC'
self.feature_info = []
self.stem = PatchEmbed(
img_size=None,
patch_size=patch_sizes[0],
in_chans=in_chans,
embed_dim=embed_dims[0],
norm_layer=norm_layer if stem_norm else None,
flatten=False,
output_fmt='NHWC',
)
assert len(layers) == len(patch_sizes) == len(embed_dims) == len(hidden_sizes) == len(mlp_ratios)
reductions = list(accumulate(patch_sizes, lambda x, y: x * y))
stages = []
prev_dim = embed_dims[0]
for i, _ in enumerate(embed_dims):
stages += [Sequencer2dStage(
prev_dim,
embed_dims[i],
depth=layers[i],
downsample=i > 0,
patch_size=patch_sizes[i],
hidden_size=hidden_sizes[i],
mlp_ratio=mlp_ratios[i],
block_layer=block_layer,
rnn_layer=rnn_layer,
mlp_layer=mlp_layer,
norm_layer=norm_layer,
act_layer=act_layer,
num_layers=num_rnn_layers,
bidirectional=bidirectional,
union=union,
with_fc=with_fc,
drop=drop_rate,
drop_path=drop_path_rate,
)]
prev_dim = embed_dims[i]
self.feature_info += [dict(num_chs=prev_dim, reduction=reductions[i], module=f'stages.{i}')]
self.stages = nn.Sequential(*stages)
self.norm = norm_layer(embed_dims[-1])
self.head = ClassifierHead(
self.num_features,
num_classes,
pool_type=global_pool,
drop_rate=drop_rate,
input_fmt=self.output_fmt,
)
self.init_weights(nlhb=nlhb)
def init_weights(self, nlhb=False):
head_bias = -math.log(self.num_classes) if nlhb else 0.
named_apply(partial(_init_weights, head_bias=head_bias), module=self) # depth-first
@torch.jit.ignore
def group_matcher(self, coarse=False):
return dict(
stem=r'^stem',
blocks=[
(r'^stages\.(\d+)', None),
(r'^norm', (99999,))
] if coarse else [
(r'^stages\.(\d+)\.blocks\.(\d+)', None),
(r'^stages\.(\d+)\.downsample', (0,)),
(r'^norm', (99999,))
]
)
@torch.jit.ignore
def set_grad_checkpointing(self, enable=True):
assert not enable, 'gradient checkpointing not supported'
@torch.jit.ignore
def get_classifier(self):
return self.head
def reset_classifier(self, num_classes, global_pool=None):
self.num_classes = num_classes
self.head.reset(num_classes, pool_type=global_pool)
def forward_features(self, x):
x = self.stem(x)
x = self.stages(x)
x = self.norm(x)
return x
def forward_head(self, x, pre_logits: bool = False):
return self.head(x, pre_logits=True) if pre_logits else self.head(x)
def forward(self, x):
x = self.forward_features(x)
x = self.forward_head(x)
return x
def checkpoint_filter_fn(state_dict, model):
""" Remap original checkpoints -> timm """
if 'stages.0.blocks.0.norm1.weight' in state_dict:
return state_dict # already translated checkpoint
if 'model' in state_dict:
state_dict = state_dict['model']
import re
out_dict = {}
for k, v in state_dict.items():
k = re.sub(r'blocks.([0-9]+).([0-9]+).down', lambda x: f'stages.{int(x.group(1)) + 1}.downsample.down', k)
k = re.sub(r'blocks.([0-9]+).([0-9]+)', r'stages.\1.blocks.\2', k)
k = k.replace('head.', 'head.fc.')
out_dict[k] = v
return out_dict
def _create_sequencer2d(variant, pretrained=False, **kwargs):
default_out_indices = tuple(range(3))
out_indices = kwargs.pop('out_indices', default_out_indices)
model = build_model_with_cfg(
Sequencer2d,
variant,
pretrained,
pretrained_filter_fn=checkpoint_filter_fn,
feature_cfg=dict(flatten_sequential=True, out_indices=out_indices),
**kwargs,
)
return model
def _cfg(url='', **kwargs):
return {
'url': url,
'num_classes': 1000, 'input_size': (3, 224, 224), 'pool_size': None,
'crop_pct': DEFAULT_CROP_PCT, 'interpolation': 'bicubic', 'fixed_input_size': True,
'mean': IMAGENET_DEFAULT_MEAN, 'std': IMAGENET_DEFAULT_STD,
'first_conv': 'stem.proj', 'classifier': 'head.fc',
**kwargs
}
default_cfgs = generate_default_cfgs({
'sequencer2d_s.in1k': _cfg(hf_hub_id='timm/'),
'sequencer2d_m.in1k': _cfg(hf_hub_id='timm/'),
'sequencer2d_l.in1k': _cfg(hf_hub_id='timm/'),
})
@register_model
def sequencer2d_s(pretrained=False, **kwargs) -> Sequencer2d:
model_args = dict(
layers=[4, 3, 8, 3],
patch_sizes=[7, 2, 1, 1],
embed_dims=[192, 384, 384, 384],
hidden_sizes=[48, 96, 96, 96],
mlp_ratios=[3.0, 3.0, 3.0, 3.0],
rnn_layer=LSTM2d,
bidirectional=True,
union="cat",
with_fc=True,
)
model = _create_sequencer2d('sequencer2d_s', pretrained=pretrained, **dict(model_args, **kwargs))
return model
@register_model
def sequencer2d_m(pretrained=False, **kwargs) -> Sequencer2d:
model_args = dict(
layers=[4, 3, 14, 3],
patch_sizes=[7, 2, 1, 1],
embed_dims=[192, 384, 384, 384],
hidden_sizes=[48, 96, 96, 96],
mlp_ratios=[3.0, 3.0, 3.0, 3.0],
rnn_layer=LSTM2d,
bidirectional=True,
union="cat",
with_fc=True,
**kwargs)
model = _create_sequencer2d('sequencer2d_m', pretrained=pretrained, **dict(model_args, **kwargs))
return model
@register_model
def sequencer2d_l(pretrained=False, **kwargs) -> Sequencer2d:
model_args = dict(
layers=[8, 8, 16, 4],
patch_sizes=[7, 2, 1, 1],
embed_dims=[192, 384, 384, 384],
hidden_sizes=[48, 96, 96, 96],
mlp_ratios=[3.0, 3.0, 3.0, 3.0],
rnn_layer=LSTM2d,
bidirectional=True,
union="cat",
with_fc=True,
**kwargs)
model = _create_sequencer2d('sequencer2d_l', pretrained=pretrained, **dict(model_args, **kwargs))
return model
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