72 lines
2.5 KiB
Python
72 lines
2.5 KiB
Python
# Copyright (c) OpenMMLab. All rights reserved.
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import copy
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from typing import Optional, Tuple, Union
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import torch
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import torch.nn as nn
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from mmcv.cnn import build_activation_layer, build_norm_layer
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from mmengine.model import BaseModule
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from mmpretrain.registry import MODELS
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@MODELS.register_module()
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class LinearReduction(BaseModule):
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"""Neck with Dimension reduction.
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Args:
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in_channels (int): Number of channels in the input.
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out_channels (int): Number of channels in the output.
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norm_cfg (dict, optional): dictionary to construct and
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config norm layer. Defaults to dict(type='BN1d').
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act_cfg (dict, optional): dictionary to construct and
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config activate layer. Defaults to None.
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init_cfg (dict, optional): dictionary to initialize weights.
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Defaults to None.
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"""
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def __init__(self,
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in_channels: int,
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out_channels: int,
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norm_cfg: Optional[dict] = dict(type='BN1d'),
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act_cfg: Optional[dict] = None,
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init_cfg: Optional[dict] = None):
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super(LinearReduction, self).__init__(init_cfg=init_cfg)
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self.in_channels = in_channels
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self.out_channels = out_channels
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self.norm_cfg = copy.deepcopy(norm_cfg)
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self.act_cfg = copy.deepcopy(act_cfg)
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self.reduction = nn.Linear(
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in_features=in_channels, out_features=out_channels)
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if norm_cfg:
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self.norm = build_norm_layer(norm_cfg, out_channels)[1]
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else:
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self.norm = nn.Identity()
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if act_cfg:
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self.act = build_activation_layer(act_cfg)
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else:
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self.act = nn.Identity()
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def forward(self, inputs: Union[Tuple,
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torch.Tensor]) -> Tuple[torch.Tensor]:
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"""forward function.
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Args:
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inputs (Union[Tuple, torch.Tensor]): The features extracted from
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the backbone. Multiple stage inputs are acceptable but only
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the last stage will be used.
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Returns:
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Tuple(torch.Tensor)): A tuple of reducted features.
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"""
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assert isinstance(inputs, (tuple, torch.Tensor)), (
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'The inputs of `LinearReduction` neck must be tuple or '
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f'`torch.Tensor`, but get {type(inputs)}.')
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if isinstance(inputs, tuple):
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inputs = inputs[-1]
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out = self.act(self.norm(self.reduction(inputs)))
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return (out, )
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