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mmpretrain.models.necks.mixmim_neck 源代码

# Copyright (c) OpenMMLab. All rights reserved.
from typing import List, Optional, Union

import torch
import torch.nn as nn

from mmpretrain.registry import MODELS
from ..utils import build_2d_sincos_position_embedding
from .mae_neck import MAEPretrainDecoder


[文档]@MODELS.register_module() class MixMIMPretrainDecoder(MAEPretrainDecoder): """Decoder for MixMIM Pretraining. Some of the code is borrowed from `https://github.com/Sense-X/MixMIM`. # noqa Args: num_patches (int): The number of total patches. Defaults to 196. patch_size (int): Image patch size. Defaults to 16. in_chans (int): The channel of input image. Defaults to 3. embed_dim (int): Encoder's embedding dimension. Defaults to 1024. encoder_stride (int): The output stride of MixMIM backbone. Defaults to 32. decoder_embed_dim (int): Decoder's embedding dimension. Defaults to 512. decoder_depth (int): The depth of decoder. Defaults to 8. decoder_num_heads (int): Number of attention heads of decoder. Defaults to 16. mlp_ratio (int): Ratio of mlp hidden dim to decoder's embedding dim. Defaults to 4. norm_cfg (dict): Normalization layer. Defaults to LayerNorm. init_cfg (Union[List[dict], dict], optional): Initialization config dict. Defaults to None. """ def __init__(self, num_patches: int = 196, patch_size: int = 16, in_chans: int = 3, embed_dim: int = 1024, encoder_stride: int = 32, decoder_embed_dim: int = 512, decoder_depth: int = 8, decoder_num_heads: int = 16, mlp_ratio: int = 4, norm_cfg: dict = dict(type='LN', eps=1e-6), init_cfg: Optional[Union[List[dict], dict]] = None) -> None: super().__init__( num_patches=num_patches, patch_size=patch_size, in_chans=in_chans, embed_dim=embed_dim, decoder_embed_dim=decoder_embed_dim, decoder_depth=decoder_depth, decoder_num_heads=decoder_num_heads, mlp_ratio=mlp_ratio, norm_cfg=norm_cfg, init_cfg=init_cfg) self.decoder_pos_embed = nn.Parameter( torch.zeros(1, num_patches, decoder_embed_dim), requires_grad=False) self.decoder_pred = nn.Linear(decoder_embed_dim, encoder_stride**2 * 3)
[文档] def init_weights(self) -> None: """Initialize position embedding and mask token of MixMIM decoder.""" super(MAEPretrainDecoder, self).init_weights() decoder_pos_embed = build_2d_sincos_position_embedding( int(self.num_patches**.5), self.decoder_pos_embed.shape[-1], cls_token=False) self.decoder_pos_embed.data.copy_(decoder_pos_embed.float()) torch.nn.init.normal_(self.mask_token, std=.02)
[文档] def forward(self, x: torch.Tensor, mask: torch.Tensor) -> torch.Tensor: """Forward function. Args: x (torch.Tensor): The input features, which is of shape (N, L, C). mask (torch.Tensor): The tensor to indicate which tokens a re masked. Returns: torch.Tensor: The reconstructed features, which is of shape (N, L, C). """ x = self.decoder_embed(x) B, L, C = x.shape mask_tokens = self.mask_token.expand(B, L, -1) x1 = x * (1 - mask) + mask_tokens * mask x2 = x * mask + mask_tokens * (1 - mask) x = torch.cat([x1, x2], dim=0) # add pos embed x = x + self.decoder_pos_embed # apply Transformer blocks for idx, blk in enumerate(self.decoder_blocks): x = blk(x) x = self.decoder_norm(x) # predictor projection x = self.decoder_pred(x) return x
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