mmdet.models.necks.nasfcos_fpn 源代码

# Copyright (c) OpenMMLab. All rights reserved.
import torch.nn as nn
import torch.nn.functional as F
from mmcv.cnn import ConvModule, caffe2_xavier_init
from mmcv.ops.merge_cells import ConcatCell
from mmcv.runner import BaseModule

from ..builder import NECKS

[文档]@NECKS.register_module() class NASFCOS_FPN(BaseModule): """FPN structure in NASFPN. Implementation of paper `NAS-FCOS: Fast Neural Architecture Search for Object Detection <>`_ Args: in_channels (List[int]): Number of input channels per scale. out_channels (int): Number of output channels (used at each scale) num_outs (int): Number of output scales. start_level (int): Index of the start input backbone level used to build the feature pyramid. Default: 0. end_level (int): Index of the end input backbone level (exclusive) to build the feature pyramid. Default: -1, which means the last level. add_extra_convs (bool): It decides whether to add conv layers on top of the original feature maps. Default to False. If True, its actual mode is specified by `extra_convs_on_inputs`. conv_cfg (dict): dictionary to construct and config conv layer. norm_cfg (dict): dictionary to construct and config norm layer. init_cfg (dict or list[dict], optional): Initialization config dict. Default: None """ def __init__(self, in_channels, out_channels, num_outs, start_level=1, end_level=-1, add_extra_convs=False, conv_cfg=None, norm_cfg=None, init_cfg=None): assert init_cfg is None, 'To prevent abnormal initialization ' \ 'behavior, init_cfg is not allowed to be set' super(NASFCOS_FPN, self).__init__(init_cfg) assert isinstance(in_channels, list) self.in_channels = in_channels self.out_channels = out_channels self.num_ins = len(in_channels) self.num_outs = num_outs self.norm_cfg = norm_cfg self.conv_cfg = conv_cfg if end_level == -1: self.backbone_end_level = self.num_ins assert num_outs >= self.num_ins - start_level else: self.backbone_end_level = end_level assert end_level <= len(in_channels) assert num_outs == end_level - start_level self.start_level = start_level self.end_level = end_level self.add_extra_convs = add_extra_convs self.adapt_convs = nn.ModuleList() for i in range(self.start_level, self.backbone_end_level): adapt_conv = ConvModule( in_channels[i], out_channels, 1, stride=1, padding=0, bias=False, norm_cfg=dict(type='BN'), act_cfg=dict(type='ReLU', inplace=False)) self.adapt_convs.append(adapt_conv) # C2 is omitted according to the paper extra_levels = num_outs - self.backbone_end_level + self.start_level def build_concat_cell(with_input1_conv, with_input2_conv): cell_conv_cfg = dict( kernel_size=1, padding=0, bias=False, groups=out_channels) return ConcatCell( in_channels=out_channels, out_channels=out_channels, with_out_conv=True, out_conv_cfg=cell_conv_cfg, out_norm_cfg=dict(type='BN'), out_conv_order=('norm', 'act', 'conv'), with_input1_conv=with_input1_conv, with_input2_conv=with_input2_conv, input_conv_cfg=conv_cfg, input_norm_cfg=norm_cfg, upsample_mode='nearest') # Denote c3=f0, c4=f1, c5=f2 for convince self.fpn = nn.ModuleDict() self.fpn['c22_1'] = build_concat_cell(True, True) self.fpn['c22_2'] = build_concat_cell(True, True) self.fpn['c32'] = build_concat_cell(True, False) self.fpn['c02'] = build_concat_cell(True, False) self.fpn['c42'] = build_concat_cell(True, True) self.fpn['c36'] = build_concat_cell(True, True) self.fpn['c61'] = build_concat_cell(True, True) # f9 self.extra_downsamples = nn.ModuleList() for i in range(extra_levels): extra_act_cfg = None if i == 0 \ else dict(type='ReLU', inplace=False) self.extra_downsamples.append( ConvModule( out_channels, out_channels, 3, stride=2, padding=1, act_cfg=extra_act_cfg, order=('act', 'norm', 'conv')))
[文档] def forward(self, inputs): """Forward function.""" feats = [ adapt_conv(inputs[i + self.start_level]) for i, adapt_conv in enumerate(self.adapt_convs) ] for (i, module_name) in enumerate(self.fpn): idx_1, idx_2 = int(module_name[1]), int(module_name[2]) res = self.fpn[module_name](feats[idx_1], feats[idx_2]) feats.append(res) ret = [] for (idx, input_idx) in zip([9, 8, 7], [1, 2, 3]): # add P3, P4, P5 feats1, feats2 = feats[idx], feats[5] feats2_resize = F.interpolate( feats2, size=feats1.size()[2:], mode='bilinear', align_corners=False) feats_sum = feats1 + feats2_resize ret.append( F.interpolate( feats_sum, size=inputs[input_idx].size()[2:], mode='bilinear', align_corners=False)) for submodule in self.extra_downsamples: ret.append(submodule(ret[-1])) return tuple(ret)
[文档] def init_weights(self): """Initialize the weights of module.""" super(NASFCOS_FPN, self).init_weights() for module in self.fpn.values(): if hasattr(module, 'conv_out'): caffe2_xavier_init(module.out_conv.conv) for modules in [ self.adapt_convs.modules(), self.extra_downsamples.modules() ]: for module in modules: if isinstance(module, nn.Conv2d): caffe2_xavier_init(module)
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