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			281 lines
		
	
	
		
			11 KiB
		
	
	
	
		
			Python
		
	
	
	
	
	
			
		
		
	
	
			281 lines
		
	
	
		
			11 KiB
		
	
	
	
		
			Python
		
	
	
	
	
	
# copyright (c) 2022 PaddlePaddle Authors. All Rights Reserve.
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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#    http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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"""
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This code is refer from:
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https://github.com/PaddlePaddle/PaddleDetection/blob/release/2.3/ppdet/modeling/necks/fpn.py
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"""
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import paddle.nn as nn
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import paddle.nn.functional as F
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from paddle import ParamAttr
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from paddle.nn.initializer import XavierUniform
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from paddle.nn.initializer import Normal
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from paddle.regularizer import L2Decay
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__all__ = ['FCEFPN']
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class ConvNormLayer(nn.Layer):
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    def __init__(self,
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                 ch_in,
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                 ch_out,
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                 filter_size,
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                 stride,
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                 groups=1,
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                 norm_type='bn',
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                 norm_decay=0.,
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                 norm_groups=32,
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                 lr_scale=1.,
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                 freeze_norm=False,
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                 initializer=Normal(
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                     mean=0., std=0.01)):
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        super(ConvNormLayer, self).__init__()
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        assert norm_type in ['bn', 'sync_bn', 'gn']
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        bias_attr = False
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        self.conv = nn.Conv2D(
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            in_channels=ch_in,
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            out_channels=ch_out,
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            kernel_size=filter_size,
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            stride=stride,
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            padding=(filter_size - 1) // 2,
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            groups=groups,
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            weight_attr=ParamAttr(
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                initializer=initializer, learning_rate=1.),
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            bias_attr=bias_attr)
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        norm_lr = 0. if freeze_norm else 1.
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        param_attr = ParamAttr(
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            learning_rate=norm_lr,
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            regularizer=L2Decay(norm_decay) if norm_decay is not None else None)
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        bias_attr = ParamAttr(
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            learning_rate=norm_lr,
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            regularizer=L2Decay(norm_decay) if norm_decay is not None else None)
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        if norm_type == 'bn':
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            self.norm = nn.BatchNorm2D(
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                ch_out, weight_attr=param_attr, bias_attr=bias_attr)
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        elif norm_type == 'sync_bn':
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            self.norm = nn.SyncBatchNorm(
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                ch_out, weight_attr=param_attr, bias_attr=bias_attr)
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        elif norm_type == 'gn':
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            self.norm = nn.GroupNorm(
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                num_groups=norm_groups,
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                num_channels=ch_out,
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                weight_attr=param_attr,
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                bias_attr=bias_attr)
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    def forward(self, inputs):
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        out = self.conv(inputs)
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        out = self.norm(out)
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        return out
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class FCEFPN(nn.Layer):
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    """
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    Feature Pyramid Network, see https://arxiv.org/abs/1612.03144
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    Args:
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        in_channels (list[int]): input channels of each level which can be 
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            derived from the output shape of backbone by from_config
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        out_channels (list[int]): output channel of each level
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        spatial_scales (list[float]): the spatial scales between input feature
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            maps and original input image which can be derived from the output 
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            shape of backbone by from_config
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        has_extra_convs (bool): whether to add extra conv to the last level.
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            default False
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        extra_stage (int): the number of extra stages added to the last level.
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            default 1
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        use_c5 (bool): Whether to use c5 as the input of extra stage, 
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            otherwise p5 is used. default True
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        norm_type (string|None): The normalization type in FPN module. If 
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            norm_type is None, norm will not be used after conv and if 
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            norm_type is string, bn, gn, sync_bn are available. default None
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        norm_decay (float): weight decay for normalization layer weights.
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            default 0.
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        freeze_norm (bool): whether to freeze normalization layer.  
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            default False
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        relu_before_extra_convs (bool): whether to add relu before extra convs.
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            default False
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    """
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    def __init__(self,
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                 in_channels,
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                 out_channels,
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                 spatial_scales=[0.25, 0.125, 0.0625, 0.03125],
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                 has_extra_convs=False,
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                 extra_stage=1,
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                 use_c5=True,
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                 norm_type=None,
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                 norm_decay=0.,
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                 freeze_norm=False,
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                 relu_before_extra_convs=True):
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        super(FCEFPN, self).__init__()
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        self.out_channels = out_channels
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        for s in range(extra_stage):
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            spatial_scales = spatial_scales + [spatial_scales[-1] / 2.]
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        self.spatial_scales = spatial_scales
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        self.has_extra_convs = has_extra_convs
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        self.extra_stage = extra_stage
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        self.use_c5 = use_c5
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        self.relu_before_extra_convs = relu_before_extra_convs
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        self.norm_type = norm_type
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        self.norm_decay = norm_decay
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        self.freeze_norm = freeze_norm
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        self.lateral_convs = []
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        self.fpn_convs = []
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        fan = out_channels * 3 * 3
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        # stage index 0,1,2,3 stands for res2,res3,res4,res5 on ResNet Backbone
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        # 0 <= st_stage < ed_stage <= 3
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        st_stage = 4 - len(in_channels)
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        ed_stage = st_stage + len(in_channels) - 1
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        for i in range(st_stage, ed_stage + 1):
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            if i == 3:
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                lateral_name = 'fpn_inner_res5_sum'
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            else:
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                lateral_name = 'fpn_inner_res{}_sum_lateral'.format(i + 2)
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            in_c = in_channels[i - st_stage]
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            if self.norm_type is not None:
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                lateral = self.add_sublayer(
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                    lateral_name,
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                    ConvNormLayer(
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                        ch_in=in_c,
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                        ch_out=out_channels,
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                        filter_size=1,
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                        stride=1,
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                        norm_type=self.norm_type,
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                        norm_decay=self.norm_decay,
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                        freeze_norm=self.freeze_norm,
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                        initializer=XavierUniform(fan_out=in_c)))
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            else:
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                lateral = self.add_sublayer(
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                    lateral_name,
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                    nn.Conv2D(
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                        in_channels=in_c,
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                        out_channels=out_channels,
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                        kernel_size=1,
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                        weight_attr=ParamAttr(
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                            initializer=XavierUniform(fan_out=in_c))))
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            self.lateral_convs.append(lateral)
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        for i in range(st_stage, ed_stage + 1):
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            fpn_name = 'fpn_res{}_sum'.format(i + 2)
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            if self.norm_type is not None:
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                fpn_conv = self.add_sublayer(
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                    fpn_name,
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                    ConvNormLayer(
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                        ch_in=out_channels,
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                        ch_out=out_channels,
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                        filter_size=3,
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                        stride=1,
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                        norm_type=self.norm_type,
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                        norm_decay=self.norm_decay,
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                        freeze_norm=self.freeze_norm,
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                        initializer=XavierUniform(fan_out=fan)))
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            else:
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                fpn_conv = self.add_sublayer(
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                    fpn_name,
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                    nn.Conv2D(
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                        in_channels=out_channels,
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                        out_channels=out_channels,
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                        kernel_size=3,
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                        padding=1,
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                        weight_attr=ParamAttr(
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                            initializer=XavierUniform(fan_out=fan))))
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            self.fpn_convs.append(fpn_conv)
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        # add extra conv levels for RetinaNet(use_c5)/FCOS(use_p5)
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        if self.has_extra_convs:
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            for i in range(self.extra_stage):
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                lvl = ed_stage + 1 + i
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                if i == 0 and self.use_c5:
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                    in_c = in_channels[-1]
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                else:
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                    in_c = out_channels
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                extra_fpn_name = 'fpn_{}'.format(lvl + 2)
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                if self.norm_type is not None:
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                    extra_fpn_conv = self.add_sublayer(
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                        extra_fpn_name,
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                        ConvNormLayer(
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                            ch_in=in_c,
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                            ch_out=out_channels,
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                            filter_size=3,
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                            stride=2,
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                            norm_type=self.norm_type,
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                            norm_decay=self.norm_decay,
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                            freeze_norm=self.freeze_norm,
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                            initializer=XavierUniform(fan_out=fan)))
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                else:
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                    extra_fpn_conv = self.add_sublayer(
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                        extra_fpn_name,
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                        nn.Conv2D(
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                            in_channels=in_c,
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                            out_channels=out_channels,
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                            kernel_size=3,
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                            stride=2,
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                            padding=1,
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                            weight_attr=ParamAttr(
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                                initializer=XavierUniform(fan_out=fan))))
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                self.fpn_convs.append(extra_fpn_conv)
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    @classmethod
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    def from_config(cls, cfg, input_shape):
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        return {
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            'in_channels': [i.channels for i in input_shape],
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            'spatial_scales': [1.0 / i.stride for i in input_shape],
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        }
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    def forward(self, body_feats):
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        laterals = []
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        num_levels = len(body_feats)
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        for i in range(num_levels):
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            laterals.append(self.lateral_convs[i](body_feats[i]))
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        for i in range(1, num_levels):
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            lvl = num_levels - i
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            upsample = F.interpolate(
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                laterals[lvl],
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                scale_factor=2.,
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                mode='nearest', )
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            laterals[lvl - 1] += upsample
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        fpn_output = []
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        for lvl in range(num_levels):
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            fpn_output.append(self.fpn_convs[lvl](laterals[lvl]))
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        if self.extra_stage > 0:
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            # use max pool to get more levels on top of outputs (Faster R-CNN, Mask R-CNN)
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            if not self.has_extra_convs:
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                assert self.extra_stage == 1, 'extra_stage should be 1 if FPN has not extra convs'
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                fpn_output.append(F.max_pool2d(fpn_output[-1], 1, stride=2))
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            # add extra conv levels for RetinaNet(use_c5)/FCOS(use_p5)
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            else:
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                if self.use_c5:
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                    extra_source = body_feats[-1]
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                else:
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                    extra_source = fpn_output[-1]
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                fpn_output.append(self.fpn_convs[num_levels](extra_source))
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                for i in range(1, self.extra_stage):
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                    if self.relu_before_extra_convs:
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                        fpn_output.append(self.fpn_convs[num_levels + i](F.relu(
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                            fpn_output[-1])))
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                    else:
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                        fpn_output.append(self.fpn_convs[num_levels + i](
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                            fpn_output[-1]))
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        return fpn_output
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