# Copyright (c) 2021 PaddlePaddle Authors. All Rights Reserved. # # Licensed under the Apache License, Version 2.0 (the "License"); # you may not use this file except in compliance with the License. # You may obtain a copy of the License at # # http://www.apache.org/licenses/LICENSE-2.0 # # Unless required by applicable law or agreed to in writing, software # distributed under the License is distributed on an "AS IS" BASIS, # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. # See the License for the specific language governing permissions and # limitations under the License. """ This code is based on https://github.com/HRNet/Lite-HRNet/blob/hrnet/models/backbones/litehrnet.py """ import paddle import paddle.nn as nn import paddle.nn.functional as F from numbers import Integral from paddle import ParamAttr from paddle.regularizer import L2Decay from paddle.nn.initializer import Normal, Constant from ppdet.core.workspace import register from ppdet.modeling.shape_spec import ShapeSpec from ppdet.modeling.ops import channel_shuffle from .. import layers as L __all__ = ['LiteHRNet'] class ConvNormLayer(nn.Layer): def __init__(self, ch_in, ch_out, filter_size, stride=1, groups=1, norm_type=None, norm_groups=32, norm_decay=0., freeze_norm=False, act=None): super(ConvNormLayer, self).__init__() self.act = act norm_lr = 0. if freeze_norm else 1. if norm_type is not None: assert ( norm_type in ['bn', 'sync_bn', 'gn'], "norm_type should be one of ['bn', 'sync_bn', 'gn'], but got {}". format(norm_type)) param_attr = ParamAttr( initializer=Constant(1.0), learning_rate=norm_lr, regularizer=L2Decay(norm_decay), ) bias_attr = ParamAttr( learning_rate=norm_lr, regularizer=L2Decay(norm_decay)) global_stats = True if freeze_norm else False if norm_type in ['bn', 'sync_bn']: self.norm = nn.BatchNorm( ch_out, param_attr=param_attr, bias_attr=bias_attr, use_global_stats=global_stats, ) elif norm_type == 'gn': self.norm = nn.GroupNorm( num_groups=norm_groups, num_channels=ch_out, weight_attr=param_attr, bias_attr=bias_attr) norm_params = self.norm.parameters() if freeze_norm: for param in norm_params: param.stop_gradient = True conv_bias_attr = False else: conv_bias_attr = True self.norm = None self.conv = nn.Conv2D( in_channels=ch_in, out_channels=ch_out, kernel_size=filter_size, stride=stride, padding=(filter_size - 1) // 2, groups=groups, weight_attr=ParamAttr(initializer=Normal( mean=0., std=0.001)), bias_attr=conv_bias_attr) def forward(self, inputs): out = self.conv(inputs) if self.norm is not None: out = self.norm(out) if self.act == 'relu': out = F.relu(out) elif self.act == 'sigmoid': out = F.sigmoid(out) return out class DepthWiseSeparableConvNormLayer(nn.Layer): def __init__(self, ch_in, ch_out, filter_size, stride=1, dw_norm_type=None, pw_norm_type=None, norm_decay=0., freeze_norm=False, dw_act=None, pw_act=None): super(DepthWiseSeparableConvNormLayer, self).__init__() self.depthwise_conv = ConvNormLayer( ch_in=ch_in, ch_out=ch_in, filter_size=filter_size, stride=stride, groups=ch_in, norm_type=dw_norm_type, act=dw_act, norm_decay=norm_decay, freeze_norm=freeze_norm, ) self.pointwise_conv = ConvNormLayer( ch_in=ch_in, ch_out=ch_out, filter_size=1, stride=1, norm_type=pw_norm_type, act=pw_act, norm_decay=norm_decay, freeze_norm=freeze_norm, ) def forward(self, x): x = self.depthwise_conv(x) x = self.pointwise_conv(x) return x class CrossResolutionWeightingModule(nn.Layer): def __init__(self, channels, ratio=16, norm_type='bn', freeze_norm=False, norm_decay=0.): super(CrossResolutionWeightingModule, self).__init__() self.channels = channels total_channel = sum(channels) self.conv1 = ConvNormLayer( ch_in=total_channel, ch_out=total_channel // ratio, filter_size=1, stride=1, norm_type=norm_type, act='relu', freeze_norm=freeze_norm, norm_decay=norm_decay) self.conv2 = ConvNormLayer( ch_in=total_channel // ratio, ch_out=total_channel, filter_size=1, stride=1, norm_type=norm_type, act='sigmoid', freeze_norm=freeze_norm, norm_decay=norm_decay) def forward(self, x): mini_size = x[-1].shape[-2:] out = [F.adaptive_avg_pool2d(s, mini_size) for s in x[:-1]] + [x[-1]] out = paddle.concat(out, 1) out = self.conv1(out) out = self.conv2(out) out = paddle.split(out, self.channels, 1) out = [ s * F.interpolate( a, s.shape[-2:], mode='nearest') for s, a in zip(x, out) ] return out class SpatialWeightingModule(nn.Layer): def __init__(self, in_channel, ratio=16, freeze_norm=False, norm_decay=0.): super(SpatialWeightingModule, self).__init__() self.global_avgpooling = nn.AdaptiveAvgPool2D(1) self.conv1 = ConvNormLayer( ch_in=in_channel, ch_out=in_channel // ratio, filter_size=1, stride=1, act='relu', freeze_norm=freeze_norm, norm_decay=norm_decay) self.conv2 = ConvNormLayer( ch_in=in_channel // ratio, ch_out=in_channel, filter_size=1, stride=1, act='sigmoid', freeze_norm=freeze_norm, norm_decay=norm_decay) def forward(self, x): out = self.global_avgpooling(x) out = self.conv1(out) out = self.conv2(out) return x * out class ConditionalChannelWeightingBlock(nn.Layer): def __init__(self, in_channels, stride, reduce_ratio, norm_type='bn', freeze_norm=False, norm_decay=0.): super(ConditionalChannelWeightingBlock, self).__init__() assert stride in [1, 2] branch_channels = [channel // 2 for channel in in_channels] self.cross_resolution_weighting = CrossResolutionWeightingModule( branch_channels, ratio=reduce_ratio, norm_type=norm_type, freeze_norm=freeze_norm, norm_decay=norm_decay) self.depthwise_convs = nn.LayerList([ ConvNormLayer( channel, channel, filter_size=3, stride=stride, groups=channel, norm_type=norm_type, freeze_norm=freeze_norm, norm_decay=norm_decay) for channel in branch_channels ]) self.spatial_weighting = nn.LayerList([ SpatialWeightingModule( channel, ratio=4, freeze_norm=freeze_norm, norm_decay=norm_decay) for channel in branch_channels ]) def forward(self, x): x = [s.chunk(2, axis=1) for s in x] x1 = [s[0] for s in x] x2 = [s[1] for s in x] x2 = self.cross_resolution_weighting(x2) x2 = [dw(s) for s, dw in zip(x2, self.depthwise_convs)] x2 = [sw(s) for s, sw in zip(x2, self.spatial_weighting)] out = [paddle.concat([s1, s2], axis=1) for s1, s2 in zip(x1, x2)] out = [channel_shuffle(s, groups=2) for s in out] return out class ShuffleUnit(nn.Layer): def __init__(self, in_channel, out_channel, stride, norm_type='bn', freeze_norm=False, norm_decay=0.): super(ShuffleUnit, self).__init__() branch_channel = out_channel // 2 self.stride = stride if self.stride == 1: assert ( in_channel == branch_channel * 2, "when stride=1, in_channel {} should equal to branch_channel*2 {}" .format(in_channel, branch_channel * 2)) if stride > 1: self.branch1 = nn.Sequential( ConvNormLayer( ch_in=in_channel, ch_out=in_channel, filter_size=3, stride=self.stride, groups=in_channel, norm_type=norm_type, freeze_norm=freeze_norm, norm_decay=norm_decay), ConvNormLayer( ch_in=in_channel, ch_out=branch_channel, filter_size=1, stride=1, norm_type=norm_type, act='relu', freeze_norm=freeze_norm, norm_decay=norm_decay), ) self.branch2 = nn.Sequential( ConvNormLayer( ch_in=branch_channel if stride == 1 else in_channel, ch_out=branch_channel, filter_size=1, stride=1, norm_type=norm_type, act='relu', freeze_norm=freeze_norm, norm_decay=norm_decay), ConvNormLayer( ch_in=branch_channel, ch_out=branch_channel, filter_size=3, stride=self.stride, groups=branch_channel, norm_type=norm_type, freeze_norm=freeze_norm, norm_decay=norm_decay), ConvNormLayer( ch_in=branch_channel, ch_out=branch_channel, filter_size=1, stride=1, norm_type=norm_type, act='relu', freeze_norm=freeze_norm, norm_decay=norm_decay), ) def forward(self, x): if self.stride > 1: x1 = self.branch1(x) x2 = self.branch2(x) else: x1, x2 = x.chunk(2, axis=1) x2 = self.branch2(x2) out = paddle.concat([x1, x2], axis=1) out = channel_shuffle(out, groups=2) return out class IterativeHead(nn.Layer): def __init__(self, in_channels, norm_type='bn', freeze_norm=False, norm_decay=0.): super(IterativeHead, self).__init__() num_branches = len(in_channels) self.in_channels = in_channels[::-1] projects = [] for i in range(num_branches): if i != num_branches - 1: projects.append( DepthWiseSeparableConvNormLayer( ch_in=self.in_channels[i], ch_out=self.in_channels[i + 1], filter_size=3, stride=1, dw_act=None, pw_act='relu', dw_norm_type=norm_type, pw_norm_type=norm_type, freeze_norm=freeze_norm, norm_decay=norm_decay)) else: projects.append( DepthWiseSeparableConvNormLayer( ch_in=self.in_channels[i], ch_out=self.in_channels[i], filter_size=3, stride=1, dw_act=None, pw_act='relu', dw_norm_type=norm_type, pw_norm_type=norm_type, freeze_norm=freeze_norm, norm_decay=norm_decay)) self.projects = nn.LayerList(projects) def forward(self, x): x = x[::-1] y = [] last_x = None for i, s in enumerate(x): if last_x is not None: last_x = F.interpolate( last_x, size=s.shape[-2:], mode='bilinear', align_corners=True) s = s + last_x s = self.projects[i](s) y.append(s) last_x = s return y[::-1] class Stem(nn.Layer): def __init__(self, in_channel, stem_channel, out_channel, expand_ratio, norm_type='bn', freeze_norm=False, norm_decay=0.): super(Stem, self).__init__() self.conv1 = ConvNormLayer( in_channel, stem_channel, filter_size=3, stride=2, norm_type=norm_type, act='relu', freeze_norm=freeze_norm, norm_decay=norm_decay) mid_channel = int(round(stem_channel * expand_ratio)) branch_channel = stem_channel // 2 if stem_channel == out_channel: inc_channel = out_channel - branch_channel else: inc_channel = out_channel - stem_channel self.branch1 = nn.Sequential( ConvNormLayer( ch_in=branch_channel, ch_out=branch_channel, filter_size=3, stride=2, groups=branch_channel, norm_type=norm_type, freeze_norm=freeze_norm, norm_decay=norm_decay), ConvNormLayer( ch_in=branch_channel, ch_out=inc_channel, filter_size=1, stride=1, norm_type=norm_type, act='relu', freeze_norm=freeze_norm, norm_decay=norm_decay), ) self.expand_conv = ConvNormLayer( ch_in=branch_channel, ch_out=mid_channel, filter_size=1, stride=1, norm_type=norm_type, act='relu', freeze_norm=freeze_norm, norm_decay=norm_decay) self.depthwise_conv = ConvNormLayer( ch_in=mid_channel, ch_out=mid_channel, filter_size=3, stride=2, groups=mid_channel, norm_type=norm_type, freeze_norm=freeze_norm, norm_decay=norm_decay) self.linear_conv = ConvNormLayer( ch_in=mid_channel, ch_out=branch_channel if stem_channel == out_channel else stem_channel, filter_size=1, stride=1, norm_type=norm_type, act='relu', freeze_norm=freeze_norm, norm_decay=norm_decay) def forward(self, x): x = self.conv1(x) x1, x2 = x.chunk(2, axis=1) x1 = self.branch1(x1) x2 = self.expand_conv(x2) x2 = self.depthwise_conv(x2) x2 = self.linear_conv(x2) out = paddle.concat([x1, x2], axis=1) out = channel_shuffle(out, groups=2) return out class LiteHRNetModule(nn.Layer): def __init__(self, num_branches, num_blocks, in_channels, reduce_ratio, module_type, multiscale_output=False, with_fuse=True, norm_type='bn', freeze_norm=False, norm_decay=0.): super(LiteHRNetModule, self).__init__() assert (num_branches == len(in_channels), "num_branches {} should equal to num_in_channels {}" .format(num_branches, len(in_channels))) assert (module_type in ['LITE', 'NAIVE'], "module_type should be one of ['LITE', 'NAIVE']") self.num_branches = num_branches self.in_channels = in_channels self.multiscale_output = multiscale_output self.with_fuse = with_fuse self.norm_type = 'bn' self.module_type = module_type if self.module_type == 'LITE': self.layers = self._make_weighting_blocks( num_blocks, reduce_ratio, freeze_norm=freeze_norm, norm_decay=norm_decay) elif self.module_type == 'NAIVE': self.layers = self._make_naive_branches( num_branches, num_blocks, freeze_norm=freeze_norm, norm_decay=norm_decay) if self.with_fuse: self.fuse_layers = self._make_fuse_layers( freeze_norm=freeze_norm, norm_decay=norm_decay) self.relu = nn.ReLU() def _make_weighting_blocks(self, num_blocks, reduce_ratio, stride=1, freeze_norm=False, norm_decay=0.): layers = [] for i in range(num_blocks): layers.append( ConditionalChannelWeightingBlock( self.in_channels, stride=stride, reduce_ratio=reduce_ratio, norm_type=self.norm_type, freeze_norm=freeze_norm, norm_decay=norm_decay)) return nn.Sequential(*layers) def _make_naive_branches(self, num_branches, num_blocks, freeze_norm=False, norm_decay=0.): branches = [] for branch_idx in range(num_branches): layers = [] for i in range(num_blocks): layers.append( ShuffleUnit( self.in_channels[branch_idx], self.in_channels[branch_idx], stride=1, norm_type=self.norm_type, freeze_norm=freeze_norm, norm_decay=norm_decay)) branches.append(nn.Sequential(*layers)) return nn.LayerList(branches) def _make_fuse_layers(self, freeze_norm=False, norm_decay=0.): if self.num_branches == 1: return None fuse_layers = [] num_out_branches = self.num_branches if self.multiscale_output else 1 for i in range(num_out_branches): fuse_layer = [] for j in range(self.num_branches): if j > i: fuse_layer.append( nn.Sequential( L.Conv2d( self.in_channels[j], self.in_channels[i], kernel_size=1, stride=1, padding=0, bias=False, ), nn.BatchNorm(self.in_channels[i]), nn.Upsample( scale_factor=2**(j - i), mode='nearest'))) elif j == i: fuse_layer.append(None) else: conv_downsamples = [] for k in range(i - j): if k == i - j - 1: conv_downsamples.append( nn.Sequential( L.Conv2d( self.in_channels[j], self.in_channels[j], kernel_size=3, stride=2, padding=1, groups=self.in_channels[j], bias=False, ), nn.BatchNorm(self.in_channels[j]), L.Conv2d( self.in_channels[j], self.in_channels[i], kernel_size=1, stride=1, padding=0, bias=False, ), nn.BatchNorm(self.in_channels[i]))) else: conv_downsamples.append( nn.Sequential( L.Conv2d( self.in_channels[j], self.in_channels[j], kernel_size=3, stride=2, padding=1, groups=self.in_channels[j], bias=False, ), nn.BatchNorm(self.in_channels[j]), L.Conv2d( self.in_channels[j], self.in_channels[j], kernel_size=1, stride=1, padding=0, bias=False, ), nn.BatchNorm(self.in_channels[j]), nn.ReLU())) fuse_layer.append(nn.Sequential(*conv_downsamples)) fuse_layers.append(nn.LayerList(fuse_layer)) return nn.LayerList(fuse_layers) def forward(self, x): if self.num_branches == 1: return [self.layers[0](x[0])] if self.module_type == 'LITE': out = self.layers(x) elif self.module_type == 'NAIVE': for i in range(self.num_branches): x[i] = self.layers[i](x[i]) out = x if self.with_fuse: out_fuse = [] for i in range(len(self.fuse_layers)): y = out[0] if i == 0 else self.fuse_layers[i][0](out[0]) for j in range(self.num_branches): if j == 0: y += y elif i == j: y += out[j] else: y += self.fuse_layers[i][j](out[j]) if i == 0: out[i] = y out_fuse.append(self.relu(y)) out = out_fuse elif not self.multiscale_output: out = [out[0]] return out @register class LiteHRNet(nn.Layer): """ @inproceedings{Yulitehrnet21, title={Lite-HRNet: A Lightweight High-Resolution Network}, author={Yu, Changqian and Xiao, Bin and Gao, Changxin and Yuan, Lu and Zhang, Lei and Sang, Nong and Wang, Jingdong}, booktitle={CVPR},year={2021} } Args: network_type (str): the network_type should be one of ["lite_18", "lite_30", "naive", "wider_naive"], "naive": Simply combining the shuffle block in ShuffleNet and the highresolution design pattern in HRNet. "wider_naive": Naive network with wider channels in each block. "lite_18": Lite-HRNet-18, which replaces the pointwise convolution in a shuffle block by conditional channel weighting. "lite_30": Lite-HRNet-30, with more blocks compared with Lite-HRNet-18. freeze_at (int): the stage to freeze freeze_norm (bool): whether to freeze norm in HRNet norm_decay (float): weight decay for normalization layer weights return_idx (List): the stage to return """ def __init__(self, network_type, freeze_at=0, freeze_norm=True, norm_decay=0., return_idx=[0, 1, 2, 3]): super(LiteHRNet, self).__init__() if isinstance(return_idx, Integral): return_idx = [return_idx] assert ( network_type in ["lite_18", "lite_30", "naive", "wider_naive"], "the network_type should be one of [lite_18, lite_30, naive, wider_naive]" ) assert len(return_idx) > 0, "need one or more return index" self.freeze_at = freeze_at self.freeze_norm = freeze_norm self.norm_decay = norm_decay self.return_idx = return_idx self.norm_type = 'bn' self.module_configs = { "lite_18": { "num_modules": [2, 4, 2], "num_branches": [2, 3, 4], "num_blocks": [2, 2, 2], "module_type": ["LITE", "LITE", "LITE"], "reduce_ratios": [8, 8, 8], "num_channels": [[40, 80], [40, 80, 160], [40, 80, 160, 320]], }, "lite_30": { "num_modules": [3, 8, 3], "num_branches": [2, 3, 4], "num_blocks": [2, 2, 2], "module_type": ["LITE", "LITE", "LITE"], "reduce_ratios": [8, 8, 8], "num_channels": [[40, 80], [40, 80, 160], [40, 80, 160, 320]], }, "naive": { "num_modules": [2, 4, 2], "num_branches": [2, 3, 4], "num_blocks": [2, 2, 2], "module_type": ["NAIVE", "NAIVE", "NAIVE"], "reduce_ratios": [1, 1, 1], "num_channels": [[30, 60], [30, 60, 120], [30, 60, 120, 240]], }, "wider_naive": { "num_modules": [2, 4, 2], "num_branches": [2, 3, 4], "num_blocks": [2, 2, 2], "module_type": ["NAIVE", "NAIVE", "NAIVE"], "reduce_ratios": [1, 1, 1], "num_channels": [[40, 80], [40, 80, 160], [40, 80, 160, 320]], }, } self.stages_config = self.module_configs[network_type] self.stem = Stem(3, 32, 32, 1) num_channels_pre_layer = [32] for stage_idx in range(3): num_channels = self.stages_config["num_channels"][stage_idx] setattr(self, 'transition{}'.format(stage_idx), self._make_transition_layer(num_channels_pre_layer, num_channels, self.freeze_norm, self.norm_decay)) stage, num_channels_pre_layer = self._make_stage( self.stages_config, stage_idx, num_channels, True, self.freeze_norm, self.norm_decay) setattr(self, 'stage{}'.format(stage_idx), stage) self.head_layer = IterativeHead(num_channels_pre_layer, 'bn', self.freeze_norm, self.norm_decay) def _make_transition_layer(self, num_channels_pre_layer, num_channels_cur_layer, freeze_norm=False, norm_decay=0.): num_branches_pre = len(num_channels_pre_layer) num_branches_cur = len(num_channels_cur_layer) transition_layers = [] for i in range(num_branches_cur): if i < num_branches_pre: if num_channels_cur_layer[i] != num_channels_pre_layer[i]: transition_layers.append( nn.Sequential( L.Conv2d( num_channels_pre_layer[i], num_channels_pre_layer[i], kernel_size=3, stride=1, padding=1, groups=num_channels_pre_layer[i], bias=False), nn.BatchNorm(num_channels_pre_layer[i]), L.Conv2d( num_channels_pre_layer[i], num_channels_cur_layer[i], kernel_size=1, stride=1, padding=0, bias=False, ), nn.BatchNorm(num_channels_cur_layer[i]), nn.ReLU())) else: transition_layers.append(None) else: conv_downsamples = [] for j in range(i + 1 - num_branches_pre): conv_downsamples.append( nn.Sequential( L.Conv2d( num_channels_pre_layer[-1], num_channels_pre_layer[-1], groups=num_channels_pre_layer[-1], kernel_size=3, stride=2, padding=1, bias=False, ), nn.BatchNorm(num_channels_pre_layer[-1]), L.Conv2d( num_channels_pre_layer[-1], num_channels_cur_layer[i] if j == i - num_branches_pre else num_channels_pre_layer[-1], kernel_size=1, stride=1, padding=0, bias=False, ), nn.BatchNorm(num_channels_cur_layer[i] if j == i - num_branches_pre else num_channels_pre_layer[-1]), nn.ReLU())) transition_layers.append(nn.Sequential(*conv_downsamples)) return nn.LayerList(transition_layers) def _make_stage(self, stages_config, stage_idx, in_channels, multiscale_output, freeze_norm=False, norm_decay=0.): num_modules = stages_config["num_modules"][stage_idx] num_branches = stages_config["num_branches"][stage_idx] num_blocks = stages_config["num_blocks"][stage_idx] reduce_ratio = stages_config['reduce_ratios'][stage_idx] module_type = stages_config['module_type'][stage_idx] modules = [] for i in range(num_modules): if not multiscale_output and i == num_modules - 1: reset_multiscale_output = False else: reset_multiscale_output = True modules.append( LiteHRNetModule( num_branches, num_blocks, in_channels, reduce_ratio, module_type, multiscale_output=reset_multiscale_output, with_fuse=True, freeze_norm=freeze_norm, norm_decay=norm_decay)) in_channels = modules[-1].in_channels return nn.Sequential(*modules), in_channels def forward(self, inputs): x = inputs['image'] x = self.stem(x) y_list = [x] for stage_idx in range(3): x_list = [] transition = getattr(self, 'transition{}'.format(stage_idx)) for j in range(self.stages_config["num_branches"][stage_idx]): if transition[j] is not None: if j >= len(y_list): x_list.append(transition[j](y_list[-1])) else: x_list.append(transition[j](y_list[j])) else: x_list.append(y_list[j]) y_list = getattr(self, 'stage{}'.format(stage_idx))(x_list) x = self.head_layer(y_list) res = [] for i, layer in enumerate(x): if i == self.freeze_at: layer.stop_gradient = True if i in self.return_idx: res.append(layer) return res @property def out_shape(self): return [ ShapeSpec( channels=self._out_channels[i], stride=self._out_strides[i]) for i in self.return_idx ]