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mmpretrain.models.necks.milan_neck 源代码

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

import torch
from torch import nn

from mmpretrain.registry import MODELS
from ..backbones.vision_transformer import TransformerEncoderLayer
from ..utils import PromptMultiheadAttention
from .mae_neck import MAEPretrainDecoder


class PromptTransformerEncoderLayer(TransformerEncoderLayer):
    """Prompt Transformer Encoder Layer for MILAN.

    This module is specific for the prompt encoder in MILAN. It will not update
    the visible tokens from the encoder.

    Args:
        embed_dims (int): The feature dimension.
        num_heads (int): Parallel attention heads.
        feedforward_channels (int): The hidden dimension for FFNs.
        drop_rate (float): Probability of an element to be zeroed
            after the feed forward layer. Defaults to 0.0.
        attn_drop_rate (float): The drop out rate for attention layer.
            Defaults to 0.0.
        drop_path_rate (float): Stochastic depth rate. Defaults to 0.0.
        num_fcs (int): The number of fully-connected layers for FFNs.
            Defaults to 2.
        qkv_bias (bool): Enable bias for qkv if True. Defaults to True.
        act_cfg (dict): The activation config for FFNs.
            Defaults to ``dict(type='GELU')``.
        norm_cfg (dict): Config dict for normalization layer.
            Defaults to ``dict(type='LN')``.
        batch_first (bool): Key, Query and Value are shape of
            (batch, n, embed_dim)
            or (n, batch, embed_dim). Defaults to False.
        init_cfg (dict, optional): The Config for initialization.
            Defaults to None.
    """

    def __init__(self,
                 embed_dims: int,
                 num_heads: int,
                 feedforward_channels=int,
                 drop_rate: float = 0.,
                 attn_drop_rate: float = 0.,
                 drop_path_rate: float = 0.,
                 num_fcs: int = 2,
                 qkv_bias: bool = True,
                 act_cfg: dict = dict(type='GELU'),
                 norm_cfg: dict = dict(type='LN'),
                 init_cfg: Optional[Union[List[dict], dict]] = None) -> None:
        super().__init__(
            embed_dims=embed_dims,
            num_heads=num_heads,
            feedforward_channels=feedforward_channels,
            drop_rate=drop_rate,
            attn_drop_rate=attn_drop_rate,
            drop_path_rate=drop_path_rate,
            num_fcs=num_fcs,
            qkv_bias=qkv_bias,
            act_cfg=act_cfg,
            norm_cfg=norm_cfg,
            init_cfg=init_cfg)
        self.attn = PromptMultiheadAttention(
            embed_dims=embed_dims,
            num_heads=num_heads,
            attn_drop=attn_drop_rate,
            proj_drop=drop_rate,
            dropout_layer=dict(type='DropPath', drop_prob=drop_path_rate),
            qkv_bias=qkv_bias)

    def forward(self, x: torch.Tensor, visible_tokens: torch.Tensor,
                ids_restore: torch.Tensor) -> torch.Tensor:
        """Forward function for `PromptMultiheadAttention`.

        Args:
            x (torch.Tensor): Mask token features with shape N x L_m x C.
            visible_tokens (torch.Tensor): The visible tokens features from
                encoder with shape N x L_v x C.
            ids_restore (torch.Tensor): The ids of all tokens in the original
                image with shape N x L.

        Returns:
            torch Tensor: Output features with shape N x L x C.
        """
        x = x + self.attn(self.norm1(x), visible_tokens, ids_restore)
        x = self.ffn(self.norm2(x), identity=x)
        return x


[文档]@MODELS.register_module() class MILANPretrainDecoder(MAEPretrainDecoder): """Prompt decoder for MILAN. This decoder is used in MILAN pretraining, which will not update these visible tokens from the encoder. 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. 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. predict_feature_dim (int): The dimension of the feature to be predicted. Defaults to 512. 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, decoder_embed_dim: int = 512, decoder_depth: int = 8, decoder_num_heads: int = 16, predict_feature_dim: int = 512, 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) # map the dim of features from decoder to the dim compatible with # that of CLIP self.decoder_pred = nn.Linear( decoder_embed_dim, predict_feature_dim, bias=True) # use prompt transformer encoder layer, instead of the conventional # transformer encoder layer self.decoder_blocks = nn.ModuleList([ PromptTransformerEncoderLayer( decoder_embed_dim, decoder_num_heads, int(mlp_ratio * decoder_embed_dim), qkv_bias=True, norm_cfg=norm_cfg) for _ in range(decoder_depth) ])
[文档] def forward(self, x: torch.Tensor, ids_restore: torch.Tensor, ids_keep: torch.Tensor, ids_dump: torch.Tensor) -> torch.Tensor: """Forward function. Args: x (torch.Tensor): The input features, which is of shape (N, L, C). ids_restore (torch.Tensor): The indices to restore these tokens to the original image. ids_keep (torch.Tensor): The indices of tokens to be kept. ids_dump (torch.Tensor): The indices of tokens to be masked. Returns: torch.Tensor: The reconstructed features, which is of shape (N, L, C). """ # embed tokens x = self.decoder_embed(x) # append mask tokens to sequence mask_tokens = self.mask_token.repeat( x.shape[0], ids_restore.shape[1] + 1 - x.shape[1], 1) x_ = torch.cat([x[:, 1:, :], mask_tokens], dim=1) x_ = torch.gather( x_, dim=1, index=ids_restore.unsqueeze(-1).repeat(1, 1, x.shape[2])) x = torch.cat([x[:, :1, :], x_], dim=1) # add pos embed x = x + self.decoder_pos_embed # split mask tokens and visible tokens visible_tokens = torch.cat([ x[:, :1, :], torch.gather( x[:, 1:, :], dim=1, index=ids_keep.unsqueeze(-1).repeat(1, 1, x.shape[-1])) ], dim=1) x = torch.gather( x[:, 1:, :], dim=1, index=ids_dump.unsqueeze(-1).repeat(1, 1, x.shape[-1])) for blk in self.decoder_blocks: x = blk(x, visible_tokens, ids_restore) # full sequence recovery x_ = torch.cat([visible_tokens[:, 1:, :], x], dim=1) x_ = torch.gather( x_, dim=1, index=ids_restore.unsqueeze(-1).repeat(1, 1, x.shape[-1])) # unshuffle x = torch.cat([visible_tokens[:, :1, :], x_], dim=1) x = self.decoder_norm(x) # predictor projection x = self.decoder_pred(x) return x
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