# 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. # Copyright (c) Meta Platforms, Inc. and affiliates. # All rights reserved. # This source code is licensed under the license found in the # LICENSE file in the root directory of this source tree. import os import logging import torch import torch.nn as nn import torch.nn.functional as F from typing import Optional, Tuple, Type from functools import partial from .common import LayerNorm2d, MLPBlock from detectron2.utils.file_io import PathManager from detectron2.modeling import BACKBONE_REGISTRY, Backbone, ShapeSpec from .build import register_backbone logger = logging.getLogger(__name__) # This class and its supporting functions below lightly adapted from the ViTDet backbone available at: https://github.com/facebookresearch/detectron2/blob/main/detectron2/modeling/backbone/vit.py # noqa class ImageEncoderViT(nn.Module): def __init__( self, img_size: int = 1024, patch_size: int = 16, in_chans: int = 3, embed_dim: int = 768, depth: int = 12, num_heads: int = 12, mlp_ratio: float = 4.0, out_chans: int = 256, qkv_bias: bool = True, norm_layer: Type[nn.Module] = nn.LayerNorm, act_layer: Type[nn.Module] = nn.GELU, use_abs_pos: bool = True, use_rel_pos: bool = False, rel_pos_zero_init: bool = True, window_size: int = 0, global_attn_indexes: Tuple[int, ...] = (), ) -> None: """ Args: img_size (int): Input image size. patch_size (int): Patch size. in_chans (int): Number of input image channels. embed_dim (int): Patch embedding dimension. depth (int): Depth of ViT. num_heads (int): Number of attention heads in each ViT block. mlp_ratio (float): Ratio of mlp hidden dim to embedding dim. qkv_bias (bool): If True, add a learnable bias to query, key, value. norm_layer (nn.Module): Normalization layer. act_layer (nn.Module): Activation layer. use_abs_pos (bool): If True, use absolute positional embeddings. use_rel_pos (bool): If True, add relative positional embeddings to the attention map. rel_pos_zero_init (bool): If True, zero initialize relative positional parameters. window_size (int): Window size for window attention blocks. global_attn_indexes (list): Indexes for blocks using global attention. """ super().__init__() self.img_size = img_size self.patch_embed = PatchEmbed( kernel_size=(patch_size, patch_size), stride=(patch_size, patch_size), in_chans=in_chans, embed_dim=embed_dim, ) self.pos_embed: Optional[nn.Parameter] = None if use_abs_pos: # Initialize absolute positional embedding with pretrain image size. self.pos_embed = nn.Parameter( torch.zeros(1, img_size // patch_size, img_size // patch_size, embed_dim) ) self.blocks = nn.ModuleList() for i in range(depth): block = Block( dim=embed_dim, num_heads=num_heads, mlp_ratio=mlp_ratio, qkv_bias=qkv_bias, norm_layer=norm_layer, act_layer=act_layer, use_rel_pos=use_rel_pos, rel_pos_zero_init=rel_pos_zero_init, window_size=window_size if i not in global_attn_indexes else 0, input_size=(img_size // patch_size, img_size // patch_size), ) self.blocks.append(block) self.neck = nn.Sequential( nn.Conv2d( embed_dim, out_chans, kernel_size=1, bias=False, ), LayerNorm2d(out_chans), nn.Conv2d( out_chans, out_chans, kernel_size=3, padding=1, bias=False, ), LayerNorm2d(out_chans), ) def forward(self, x: torch.Tensor) -> torch.Tensor: x = self.patch_embed(x) if self.pos_embed is not None: x = x + self.pos_embed for blk in self.blocks: x = blk(x) x = self.neck(x.permute(0, 3, 1, 2)) return x class Block(nn.Module): """Transformer blocks with support of window attention and residual propagation blocks""" def __init__( self, dim: int, num_heads: int, mlp_ratio: float = 4.0, qkv_bias: bool = True, norm_layer: Type[nn.Module] = nn.LayerNorm, act_layer: Type[nn.Module] = nn.GELU, use_rel_pos: bool = False, rel_pos_zero_init: bool = True, window_size: int = 0, input_size: Optional[Tuple[int, int]] = None, ) -> None: """ Args: dim (int): Number of input channels. num_heads (int): Number of attention heads in each ViT block. mlp_ratio (float): Ratio of mlp hidden dim to embedding dim. qkv_bias (bool): If True, add a learnable bias to query, key, value. norm_layer (nn.Module): Normalization layer. act_layer (nn.Module): Activation layer. use_rel_pos (bool): If True, add relative positional embeddings to the attention map. rel_pos_zero_init (bool): If True, zero initialize relative positional parameters. window_size (int): Window size for window attention blocks. If it equals 0, then use global attention. input_size (tuple(int, int) or None): Input resolution for calculating the relative positional parameter size. """ super().__init__() self.norm1 = norm_layer(dim) self.attn = Attention( dim, num_heads=num_heads, qkv_bias=qkv_bias, use_rel_pos=use_rel_pos, rel_pos_zero_init=rel_pos_zero_init, input_size=input_size if window_size == 0 else (window_size, window_size), ) self.norm2 = norm_layer(dim) self.mlp = MLPBlock(embedding_dim=dim, mlp_dim=int(dim * mlp_ratio), act=act_layer) self.window_size = window_size def forward(self, x: torch.Tensor) -> torch.Tensor: shortcut = x x = self.norm1(x) # Window partition if self.window_size > 0: H, W = x.shape[1], x.shape[2] x, pad_hw = window_partition(x, self.window_size) x = self.attn(x) # Reverse window partition if self.window_size > 0: x = window_unpartition(x, self.window_size, pad_hw, (H, W)) x = shortcut + x x = x + self.mlp(self.norm2(x)) return x class Attention(nn.Module): """Multi-head Attention block with relative position embeddings.""" def __init__( self, dim: int, num_heads: int = 8, qkv_bias: bool = True, use_rel_pos: bool = False, rel_pos_zero_init: bool = True, input_size: Optional[Tuple[int, int]] = None, ) -> None: """ Args: dim (int): Number of input channels. num_heads (int): Number of attention heads. qkv_bias (bool): If True, add a learnable bias to query, key, value. rel_pos (bool): If True, add relative positional embeddings to the attention map. rel_pos_zero_init (bool): If True, zero initialize relative positional parameters. input_size (tuple(int, int) or None): Input resolution for calculating the relative positional parameter size. """ super().__init__() self.num_heads = num_heads head_dim = dim // num_heads self.scale = head_dim**-0.5 self.qkv = nn.Linear(dim, dim * 3, bias=qkv_bias) self.proj = nn.Linear(dim, dim) self.use_rel_pos = use_rel_pos if self.use_rel_pos: assert ( input_size is not None ), "Input size must be provided if using relative positional encoding." # initialize relative positional embeddings self.rel_pos_h = nn.Parameter(torch.zeros(2 * input_size[0] - 1, head_dim)) self.rel_pos_w = nn.Parameter(torch.zeros(2 * input_size[1] - 1, head_dim)) def forward(self, x: torch.Tensor) -> torch.Tensor: B, H, W, _ = x.shape # qkv with shape (3, B, nHead, H * W, C) qkv = self.qkv(x).reshape(B, H * W, 3, self.num_heads, -1).permute(2, 0, 3, 1, 4) # q, k, v with shape (B * nHead, H * W, C) q, k, v = qkv.reshape(3, B * self.num_heads, H * W, -1).unbind(0) attn = (q * self.scale) @ k.transpose(-2, -1) if self.use_rel_pos: attn = add_decomposed_rel_pos(attn, q, self.rel_pos_h, self.rel_pos_w, (H, W), (H, W)) attn = attn.softmax(dim=-1) x = (attn @ v).view(B, self.num_heads, H, W, -1).permute(0, 2, 3, 1, 4).reshape(B, H, W, -1) x = self.proj(x) return x def window_partition(x: torch.Tensor, window_size: int) -> Tuple[torch.Tensor, Tuple[int, int]]: """ Partition into non-overlapping windows with padding if needed. Args: x (tensor): input tokens with [B, H, W, C]. window_size (int): window size. Returns: windows: windows after partition with [B * num_windows, window_size, window_size, C]. (Hp, Wp): padded height and width before partition """ B, H, W, C = x.shape pad_h = (window_size - H % window_size) % window_size pad_w = (window_size - W % window_size) % window_size if pad_h > 0 or pad_w > 0: x = F.pad(x, (0, 0, 0, pad_w, 0, pad_h)) Hp, Wp = H + pad_h, W + pad_w x = x.view(B, Hp // window_size, window_size, Wp // window_size, window_size, C) windows = x.permute(0, 1, 3, 2, 4, 5).contiguous().view(-1, window_size, window_size, C) return windows, (Hp, Wp) def window_unpartition( windows: torch.Tensor, window_size: int, pad_hw: Tuple[int, int], hw: Tuple[int, int] ) -> torch.Tensor: """ Window unpartition into original sequences and removing padding. Args: windows (tensor): input tokens with [B * num_windows, window_size, window_size, C]. window_size (int): window size. pad_hw (Tuple): padded height and width (Hp, Wp). hw (Tuple): original height and width (H, W) before padding. Returns: x: unpartitioned sequences with [B, H, W, C]. """ Hp, Wp = pad_hw H, W = hw B = windows.shape[0] // (Hp * Wp // window_size // window_size) x = windows.view(B, Hp // window_size, Wp // window_size, window_size, window_size, -1) x = x.permute(0, 1, 3, 2, 4, 5).contiguous().view(B, Hp, Wp, -1) if Hp > H or Wp > W: x = x[:, :H, :W, :].contiguous() return x def get_rel_pos(q_size: int, k_size: int, rel_pos: torch.Tensor) -> torch.Tensor: """ Get relative positional embeddings according to the relative positions of query and key sizes. Args: q_size (int): size of query q. k_size (int): size of key k. rel_pos (Tensor): relative position embeddings (L, C). Returns: Extracted positional embeddings according to relative positions. """ max_rel_dist = int(2 * max(q_size, k_size) - 1) # Interpolate rel pos if needed. if rel_pos.shape[0] != max_rel_dist: # Interpolate rel pos. rel_pos_resized = F.interpolate( rel_pos.reshape(1, rel_pos.shape[0], -1).permute(0, 2, 1), size=max_rel_dist, mode="linear", ) rel_pos_resized = rel_pos_resized.reshape(-1, max_rel_dist).permute(1, 0) else: rel_pos_resized = rel_pos # Scale the coords with short length if shapes for q and k are different. q_coords = torch.arange(q_size)[:, None] * max(k_size / q_size, 1.0) k_coords = torch.arange(k_size)[None, :] * max(q_size / k_size, 1.0) relative_coords = (q_coords - k_coords) + (k_size - 1) * max(q_size / k_size, 1.0) return rel_pos_resized[relative_coords.long()] def add_decomposed_rel_pos( attn: torch.Tensor, q: torch.Tensor, rel_pos_h: torch.Tensor, rel_pos_w: torch.Tensor, q_size: Tuple[int, int], k_size: Tuple[int, int], ) -> torch.Tensor: """ Calculate decomposed Relative Positional Embeddings from :paper:`mvitv2`. https://github.com/facebookresearch/mvit/blob/19786631e330df9f3622e5402b4a419a263a2c80/mvit/models/attention.py # noqa B950 Args: attn (Tensor): attention map. q (Tensor): query q in the attention layer with shape (B, q_h * q_w, C). rel_pos_h (Tensor): relative position embeddings (Lh, C) for height axis. rel_pos_w (Tensor): relative position embeddings (Lw, C) for width axis. q_size (Tuple): spatial sequence size of query q with (q_h, q_w). k_size (Tuple): spatial sequence size of key k with (k_h, k_w). Returns: attn (Tensor): attention map with added relative positional embeddings. """ q_h, q_w = q_size k_h, k_w = k_size Rh = get_rel_pos(q_h, k_h, rel_pos_h) Rw = get_rel_pos(q_w, k_w, rel_pos_w) B, _, dim = q.shape r_q = q.reshape(B, q_h, q_w, dim) rel_h = torch.einsum("bhwc,hkc->bhwk", r_q, Rh) rel_w = torch.einsum("bhwc,wkc->bhwk", r_q, Rw) attn = ( attn.view(B, q_h, q_w, k_h, k_w) + rel_h[:, :, :, :, None] + rel_w[:, :, :, None, :] ).view(B, q_h * q_w, k_h * k_w) return attn class PatchEmbed(nn.Module): """ Image to Patch Embedding. """ def __init__( self, kernel_size: Tuple[int, int] = (16, 16), stride: Tuple[int, int] = (16, 16), padding: Tuple[int, int] = (0, 0), in_chans: int = 3, embed_dim: int = 768, ) -> None: """ Args: kernel_size (Tuple): kernel size of the projection layer. stride (Tuple): stride of the projection layer. padding (Tuple): padding size of the projection layer. in_chans (int): Number of input image channels. embed_dim (int): Patch embedding dimension. """ super().__init__() self.proj = nn.Conv2d( in_chans, embed_dim, kernel_size=kernel_size, stride=stride, padding=padding ) def forward(self, x: torch.Tensor) -> torch.Tensor: x = self.proj(x) # B C H W -> B H W C x = x.permute(0, 2, 3, 1) return x class SimpleFPN(nn.Module): def __init__(self, in_dim=768, out_dims=[128, 256, 512, 1024]): super().__init__() self.down_4_chan = max(out_dims[0]*2, in_dim // 2) self.down_4 = nn.Sequential( nn.ConvTranspose2d(in_dim, self.down_4_chan, 2, stride=2), nn.GroupNorm(1, self.down_4_chan), nn.GELU(), nn.ConvTranspose2d(self.down_4_chan, self.down_4_chan // 2, 2, stride=2), nn.GroupNorm(1, self.down_4_chan // 2), nn.Conv2d(self.down_4_chan // 2, out_dims[0], 1), nn.GroupNorm(1, out_dims[0]), nn.GELU() ) self.down_8_chan = max(out_dims[1], in_dim // 2) self.down_8 = nn.Sequential( nn.ConvTranspose2d(in_dim, self.down_8_chan, 2, stride=2), nn.GroupNorm(1, self.down_8_chan), nn.Conv2d(self.down_8_chan, out_dims[1], 1), nn.GroupNorm(1, out_dims[1]), nn.GELU() ) self.down_16 = nn.Sequential( nn.Conv2d(in_dim, out_dims[2], 1), nn.GroupNorm(1, out_dims[2]), nn.GELU() ) self.down_32_chan = max(out_dims[3], in_dim * 2) self.down_32 = nn.Sequential( nn.Conv2d(in_dim, self.down_32_chan, 2, stride=2), nn.GroupNorm(1, self.down_32_chan), nn.Conv2d(self.down_32_chan, out_dims[3], 1), nn.GroupNorm(1, out_dims[3]), nn.GELU() ) self.init_weights() def init_weights(self): # TODO pass def forward(self, x): x_down_4 = self.down_4(x) x_down_8 = self.down_8(x) x_down_16 = self.down_16(x) x_down_32 = self.down_32(x) return { 'res2': x_down_4, 'res3': x_down_8, 'res4': x_down_16, 'res5': x_down_32 } class D2ViT(ImageEncoderViT, Backbone): def __init__(self, cfg, input_shape): size = cfg['BACKBONE']['VIT']['SIZE'] if size == "base": encoder_depth = 12 encoder_embed_dim = 768 encoder_num_heads = 12 encoder_global_attn_indexes = [2, 5, 8, 11] neck_in_dim=768 neck_out_dims=[128, 256, 512, 1024] elif size == "large": encoder_embed_dim = 1024 encoder_depth = 24 encoder_num_heads = 16 encoder_global_attn_indexes = [5, 11, 17, 23] neck_in_dim=1024 neck_out_dims=[128, 256, 512, 1024] elif size == "huge": encoder_embed_dim = 1280 encoder_depth = 32 encoder_num_heads = 16 encoder_global_attn_indexes = [7, 15, 23, 31] neck_in_dim=1280 neck_out_dims=[128, 256, 512, 1024] prompt_embed_dim = 256 image_size = 1024 vit_patch_size = 16 image_embedding_size = image_size // vit_patch_size super().__init__( depth=encoder_depth, embed_dim=encoder_embed_dim, img_size=image_size, mlp_ratio=4, norm_layer=partial(torch.nn.LayerNorm, eps=1e-6), num_heads=encoder_num_heads, patch_size=vit_patch_size, qkv_bias=True, use_rel_pos=True, global_attn_indexes=encoder_global_attn_indexes, window_size=14, out_chans=prompt_embed_dim, ) self.neck = SimpleFPN(in_dim=neck_in_dim, out_dims=neck_out_dims) self._out_features = cfg['BACKBONE']['VIT']['OUT_FEATURES'] self._out_feature_strides = { "res2": 4, "res3": 8, "res4": 16, "res5": 32, } self._out_feature_channels = { "res2": neck_out_dims[0], "res3": neck_out_dims[1], "res4": neck_out_dims[2], "res5": neck_out_dims[3], } def forward(self, x): """ Args: x: Tensor of shape (N,C,H,W). H, W must be a multiple of ``self.size_divisibility``. Returns: dict[str->Tensor]: names and the corresponding features """ assert ( x.dim() == 4 ), f"SwinTransformer takes an input of shape (N, C, H, W). Got {x.shape} instead!" outputs = {} y = super().forward(x) for k in y.keys(): if k in self._out_features: outputs[k] = y[k] return outputs def output_shape(self): return { name: ShapeSpec( channels=self._out_feature_channels[name], stride=self._out_feature_strides[name] ) for name in self._out_features } def load_weights(self, pretrained_dict=None, pretrained_layers=[], verbose=True): model_dict = self.state_dict() pretrained_dict = pretrained_dict['model'] if 'model' in pretrained_dict else pretrained_dict pretrained_dict = {k.replace('image_encoder.', ''):v for k,v in pretrained_dict.items()} pretrained_dict = { k: v for k, v in pretrained_dict.items() if k in model_dict.keys() } need_init_state_dict = {} for k, v in pretrained_dict.items(): need_init = ( ( k.split('.')[0] in pretrained_layers or pretrained_layers[0] == '*' ) and 'relative_position_index' not in k and 'attn_mask' not in k ) if need_init: need_init_state_dict[k] = v logger.info(f'=> loaded keys {need_init_state_dict.keys()}') unloaded_keys = set(model_dict.keys()) - set(need_init_state_dict.keys()) logger.info(f'=> unloaded keys {unloaded_keys}') self.load_state_dict(need_init_state_dict, strict=False) @property def size_divisibility(self): return 32 @register_backbone def get_vit_backbone(cfg): vit = D2ViT(cfg['MODEL'], 224) if cfg['MODEL']['BACKBONE']['LOAD_PRETRAINED'] is True: filename = cfg['MODEL']['BACKBONE']['PRETRAINED'] assert os.path.isfile(filename), f"=> no checkpoint found at '{filename}'" logger.info(f'=> init from {filename}') with PathManager.open(filename, "rb") as f: ckpt = torch.load(f) vit.load_weights(ckpt, cfg['MODEL']['BACKBONE']['VIT'].get('PRETRAINED_LAYERS', ['*']), cfg['VERBOSE']) return vit