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""" PoolFormer implementation
Paper: `PoolFormer: MetaFormer is Actually What You Need for Vision` - https://arxiv.org/abs/2111.11418
Code adapted from official impl at https://github.com/sail-sg/poolformer, original copyright in comment below
Modifications and additions for timm by / Copyright 2022, Ross Wightman
"""
# Copyright 2021 Garena Online Private Limited
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
import os
import copy
import torch
import torch.nn as nn
from timm.data import IMAGENET_DEFAULT_MEAN, IMAGENET_DEFAULT_STD
from .helpers import build_model_with_cfg, checkpoint_seq
from .layers import DropPath, trunc_normal_, to_2tuple, ConvMlp, GroupNorm1
from .registry import register_model
def _cfg(url='', **kwargs):
return {
'url': url,
'num_classes': 1000, 'input_size': (3, 224, 224), 'pool_size': None,
'crop_pct': .95, 'interpolation': 'bicubic',
'mean': IMAGENET_DEFAULT_MEAN, 'std': IMAGENET_DEFAULT_STD,
'first_conv': 'patch_embed.proj', 'classifier': 'head',
**kwargs
}
default_cfgs = dict(
poolformer_s12=_cfg(
url='https://github.com/sail-sg/poolformer/releases/download/v1.0/poolformer_s12.pth.tar',
crop_pct=0.9),
poolformer_s24=_cfg(
url='https://github.com/sail-sg/poolformer/releases/download/v1.0/poolformer_s24.pth.tar',
crop_pct=0.9),
poolformer_s36=_cfg(
url='https://github.com/sail-sg/poolformer/releases/download/v1.0/poolformer_s36.pth.tar',
crop_pct=0.9),
poolformer_m36=_cfg(
url='https://github.com/sail-sg/poolformer/releases/download/v1.0/poolformer_m36.pth.tar',
crop_pct=0.95),
poolformer_m48=_cfg(
url='https://github.com/sail-sg/poolformer/releases/download/v1.0/poolformer_m48.pth.tar',
crop_pct=0.95),
)
class PatchEmbed(nn.Module):
""" Patch Embedding that is implemented by a layer of conv.
Input: tensor in shape [B, C, H, W]
Output: tensor in shape [B, C, H/stride, W/stride]
"""
def __init__(self, in_chs=3, embed_dim=768, patch_size=16, stride=16, padding=0, norm_layer=None):
super().__init__()
patch_size = to_2tuple(patch_size)
stride = to_2tuple(stride)
padding = to_2tuple(padding)
self.proj = nn.Conv2d(in_chs, embed_dim, kernel_size=patch_size, stride=stride, padding=padding)
self.norm = norm_layer(embed_dim) if norm_layer else nn.Identity()
def forward(self, x):
x = self.proj(x)
x = self.norm(x)
return x
class Pooling(nn.Module):
def __init__(self, pool_size=3):
super().__init__()
self.pool = nn.AvgPool2d(pool_size, stride=1, padding=pool_size // 2, count_include_pad=False)
def forward(self, x):
return self.pool(x) - x
class PoolFormerBlock(nn.Module):
"""
Args:
dim: embedding dim
pool_size: pooling size
mlp_ratio: mlp expansion ratio
act_layer: activation
norm_layer: normalization
drop: dropout rate
drop path: Stochastic Depth, refer to https://arxiv.org/abs/1603.09382
use_layer_scale, --layer_scale_init_value: LayerScale, refer to https://arxiv.org/abs/2103.17239
"""
def __init__(
self, dim, pool_size=3, mlp_ratio=4.,
act_layer=nn.GELU, norm_layer=GroupNorm1,
drop=0., drop_path=0., layer_scale_init_value=1e-5):
super().__init__()
self.norm1 = norm_layer(dim)
self.token_mixer = Pooling(pool_size=pool_size)
self.drop_path1 = DropPath(drop_path) if drop_path > 0. else nn.Identity()
self.norm2 = norm_layer(dim)
self.mlp = ConvMlp(dim, hidden_features=int(dim * mlp_ratio), act_layer=act_layer, drop=drop)
self.drop_path2 = DropPath(drop_path) if drop_path > 0. else nn.Identity()
if layer_scale_init_value:
self.layer_scale_1 = nn.Parameter(layer_scale_init_value * torch.ones(dim))
self.layer_scale_2 = nn.Parameter(layer_scale_init_value * torch.ones(dim))
else:
self.layer_scale_1 = None
self.layer_scale_2 = None
def forward(self, x):
if self.layer_scale_1 is not None:
x = x + self.drop_path1(self.layer_scale_1.unsqueeze(-1).unsqueeze(-1) * self.token_mixer(self.norm1(x)))
x = x + self.drop_path2(self.layer_scale_2.unsqueeze(-1).unsqueeze(-1) * self.mlp(self.norm2(x)))
else:
x = x + self.drop_path1(self.token_mixer(self.norm1(x)))
x = x + self.drop_path2(self.mlp(self.norm2(x)))
return x
def basic_blocks(
dim, index, layers,
pool_size=3, mlp_ratio=4.,
act_layer=nn.GELU, norm_layer=GroupNorm1,
drop_rate=.0, drop_path_rate=0.,
layer_scale_init_value=1e-5,
):
""" generate PoolFormer blocks for a stage """
blocks = []
for block_idx in range(layers[index]):
block_dpr = drop_path_rate * (block_idx + sum(layers[:index])) / (sum(layers) - 1)
blocks.append(PoolFormerBlock(
dim, pool_size=pool_size, mlp_ratio=mlp_ratio,
act_layer=act_layer, norm_layer=norm_layer,
drop=drop_rate, drop_path=block_dpr,
layer_scale_init_value=layer_scale_init_value,
))
blocks = nn.Sequential(*blocks)
return blocks
class PoolFormer(nn.Module):
""" PoolFormer
"""
def __init__(
self,
layers,
embed_dims=(64, 128, 320, 512),
mlp_ratios=(4, 4, 4, 4),
downsamples=(True, True, True, True),
pool_size=3,
in_chans=3,
num_classes=1000,
global_pool='avg',
norm_layer=GroupNorm1,
act_layer=nn.GELU,
in_patch_size=7,
in_stride=4,
in_pad=2,
down_patch_size=3,
down_stride=2,
down_pad=1,
drop_rate=0., drop_path_rate=0.,
layer_scale_init_value=1e-5,
**kwargs):
super().__init__()
self.num_classes = num_classes
self.global_pool = global_pool
self.num_features = embed_dims[-1]
self.grad_checkpointing = False
self.patch_embed = PatchEmbed(
patch_size=in_patch_size, stride=in_stride, padding=in_pad,
in_chs=in_chans, embed_dim=embed_dims[0])
# set the main block in network
network = []
for i in range(len(layers)):
network.append(basic_blocks(
embed_dims[i], i, layers,
pool_size=pool_size, mlp_ratio=mlp_ratios[i],
act_layer=act_layer, norm_layer=norm_layer,
drop_rate=drop_rate, drop_path_rate=drop_path_rate,
layer_scale_init_value=layer_scale_init_value)
)
if i < len(layers) - 1 and (downsamples[i] or embed_dims[i] != embed_dims[i + 1]):
# downsampling between stages
network.append(PatchEmbed(
in_chs=embed_dims[i], embed_dim=embed_dims[i + 1],
patch_size=down_patch_size, stride=down_stride, padding=down_pad)
)
self.network = nn.Sequential(*network)
self.norm = norm_layer(self.num_features)
self.head = nn.Linear(self.num_features, num_classes) if num_classes > 0 else nn.Identity()
self.apply(self._init_weights)
# init for classification
def _init_weights(self, m):
if isinstance(m, nn.Linear):
trunc_normal_(m.weight, std=.02)
if isinstance(m, nn.Linear) and m.bias is not None:
nn.init.constant_(m.bias, 0)
@torch.jit.ignore
def group_matcher(self, coarse=False):
return dict(
stem=r'^patch_embed', # stem and embed
blocks=[
(r'^network\.(\d+).*\.proj', (99999,)),
(r'^network\.(\d+)', None) if coarse else (r'^network\.(\d+)\.(\d+)', None),
(r'^norm', (99999,))
],
)
@torch.jit.ignore
def set_grad_checkpointing(self, enable=True):
self.grad_checkpointing = enable
@torch.jit.ignore
def get_classifier(self):
return self.head
def reset_classifier(self, num_classes, global_pool=None):
self.num_classes = num_classes
if global_pool is not None:
self.global_pool = global_pool
self.head = nn.Linear(self.num_features, num_classes) if num_classes > 0 else nn.Identity()
def forward_features(self, x):
x = self.patch_embed(x)
x = self.network(x)
x = self.norm(x)
return x
def forward_head(self, x, pre_logits: bool = False):
if self.global_pool == 'avg':
x = x.mean([-2, -1])
return x if pre_logits else self.head(x)
def forward(self, x):
x = self.forward_features(x)
x = self.forward_head(x)
return x
def _create_poolformer(variant, pretrained=False, **kwargs):
if kwargs.get('features_only', None):
raise RuntimeError('features_only not implemented for Vision Transformer models.')
model = build_model_with_cfg(PoolFormer, variant, pretrained, **kwargs)
return model
@register_model
def poolformer_s12(pretrained=False, **kwargs):
""" PoolFormer-S12 model, Params: 12M """
model = _create_poolformer('poolformer_s12', pretrained=pretrained, layers=(2, 2, 6, 2), **kwargs)
return model
@register_model
def poolformer_s24(pretrained=False, **kwargs):
""" PoolFormer-S24 model, Params: 21M """
model = _create_poolformer('poolformer_s24', pretrained=pretrained, layers=(4, 4, 12, 4), **kwargs)
return model
@register_model
def poolformer_s36(pretrained=False, **kwargs):
""" PoolFormer-S36 model, Params: 31M """
model = _create_poolformer(
'poolformer_s36', pretrained=pretrained, layers=(6, 6, 18, 6), layer_scale_init_value=1e-6, **kwargs)
return model
@register_model
def poolformer_m36(pretrained=False, **kwargs):
""" PoolFormer-M36 model, Params: 56M """
layers = (6, 6, 18, 6)
embed_dims = (96, 192, 384, 768)
model = _create_poolformer(
'poolformer_m36', pretrained=pretrained, layers=layers, embed_dims=embed_dims,
layer_scale_init_value=1e-6, **kwargs)
return model
@register_model
def poolformer_m48(pretrained=False, **kwargs):
""" PoolFormer-M48 model, Params: 73M """
layers = (8, 8, 24, 8)
embed_dims = (96, 192, 384, 768)
model = _create_poolformer(
'poolformer_m48', pretrained=pretrained, layers=layers, embed_dims=embed_dims,
layer_scale_init_value=1e-6, **kwargs)
return model
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