import torch import torch.nn as nn import torch.utils.checkpoint as cp from mmcv.cnn import (ConvModule, build_activation_layer, build_conv_layer, constant_init, kaiming_init) from torch.nn.modules.batchnorm import _BatchNorm from .base_backbone import BaseBackbone def channel_shuffle(x, groups): """ Channel Shuffle operation. This function enables cross-group information flow for multiple groups convolution layers. Args: x (Tensor): The input tensor. groups (int): The number of groups to divide the input tensor in the channel dimension. Returns: Tensor: The output tensor after channel shuffle operation. """ batchsize, num_channels, height, width = x.size() assert (num_channels % groups == 0), ('num_channels should be ' 'divisible by groups') channels_per_group = num_channels // groups x = x.view(batchsize, groups, channels_per_group, height, width) x = torch.transpose(x, 1, 2).contiguous() x = x.view(batchsize, -1, height, width) return x def make_divisible(value, divisor, min_value=None): """ Make divisible function. This function ensures that all layers have a channel number that is divisible by divisor. Args: value (int): The original channel number. divisor (int): The divisor to fully divide the channel number. min_value (int, optional): the minimum value of the output channel. Returns: int: The modified output channel number """ if min_value is None: min_value = divisor new_value = max(min_value, int(value + divisor / 2) // divisor * divisor) # Make sure that round down does not go down by more than 10%. if new_value < 0.9 * value: new_value += divisor return new_value class ShuffleUnit(nn.Module): """ShuffleUnit block. ShuffleNet unit with pointwise group convolution (GConv) and channel shuffle. Args: inplanes (int): The input channels of the ShuffleUnit. planes (int): The output channels of the ShuffleUnit. groups (int, optional): The number of groups to be used in grouped 1x1 convolutions in each ShuffleUnit. Default: 3 first_block (bool, optional): Whether it is the first ShuffleUnit of a sequential ShuffleUnits. Default: True, which means using the grouped 1x1 convolution. combine (str, optional): The ways to combine the input and output branches. Default: 'add'. conv_cfg (dict): Config dict for convolution layer. Default: None, which means using conv2d. norm_cfg (dict): Config dict for normalization layer. Default: dict(type='BN'). act_cfg (dict): Config dict for activation layer. Default: dict(type='ReLU'). with_cp (bool, optional): Use checkpoint or not. Using checkpoint will save some memory while slowing down the training speed. Default: False. Returns: Tensor: The output tensor. """ def __init__(self, inplanes, planes, groups=3, first_block=True, combine='add', conv_cfg=None, norm_cfg=dict(type='BN'), act_cfg=dict(type='ReLU'), with_cp=False): super(ShuffleUnit, self).__init__() self.inplanes = inplanes self.planes = planes self.first_block = first_block self.combine = combine self.groups = groups self.bottleneck_channels = self.planes // 4 self.with_cp = with_cp if self.combine == 'add': self.depthwise_stride = 1 self._combine_func = self._add assert inplanes == planes, ('inplanes must be equal to ' 'planes when combine is add') elif self.combine == 'concat': self.depthwise_stride = 2 self._combine_func = self._concat self.planes -= self.inplanes else: raise ValueError(f'Cannot combine tensors with {self.combine}. ' 'Only "add" and "concat" are supported') self.first_1x1_groups = self.groups if first_block else 1 self.g_conv_1x1_compress = ConvModule( in_channels=self.inplanes, out_channels=self.bottleneck_channels, kernel_size=1, groups=self.first_1x1_groups, conv_cfg=conv_cfg, norm_cfg=norm_cfg, act_cfg=act_cfg) self.depthwise_conv3x3_bn = ConvModule( in_channels=self.bottleneck_channels, out_channels=self.bottleneck_channels, kernel_size=3, stride=self.depthwise_stride, padding=1, groups=self.bottleneck_channels, conv_cfg=conv_cfg, norm_cfg=norm_cfg, act_cfg=None) self.g_conv_1x1_expand = ConvModule( in_channels=self.bottleneck_channels, out_channels=self.planes, kernel_size=1, groups=self.groups, conv_cfg=conv_cfg, norm_cfg=norm_cfg, act_cfg=None) self.avgpool = nn.AvgPool2d(kernel_size=3, stride=2, padding=1) self.act = build_activation_layer(act_cfg) @staticmethod def _add(x, out): # residual connection return x + out @staticmethod def _concat(x, out): # concatenate along channel axis return torch.cat((x, out), 1) def forward(self, x): def _inner_forward(x): residual = x if self.combine == 'concat': residual = self.avgpool(residual) out = self.g_conv_1x1_compress(x) out = channel_shuffle(out, self.groups) out = self.depthwise_conv3x3_bn(out) out = self.g_conv_1x1_expand(out) out = self._combine_func(residual, out) out = self.act(out) return out if self.with_cp and x.requires_grad: out = cp.checkpoint(_inner_forward, x) else: out = _inner_forward(x) return out class ShuffleNetv1(BaseBackbone): """ShuffleNetv1 backbone. Args: groups (int, optional): The number of groups to be used in grouped 1x1 convolutions in each ShuffleUnit. Default: 3. widen_factor (float, optional): Width multiplier - adjusts the number of channels in each layer by this amount. Default: 1.0. out_indices (Sequence[int]): Output from which stages. Default: (0, 1, 2, 3) frozen_stages (int): Stages to be frozen (all param fixed). Default: -1, which means not freezing any parameters. conv_cfg (dict): Config dict for convolution layer. Default: None, which means using conv2d. norm_cfg (dict): Config dict for normalization layer. Default: dict(type='BN'). act_cfg (dict): Config dict for activation layer. Default: dict(type='ReLU'). norm_eval (bool): Whether to set norm layers to eval mode, namely, freeze running stats (mean and var). Note: Effect on Batch Norm and its variants only. Default: False. with_cp (bool): Use checkpoint or not. Using checkpoint will save some memory while slowing down the training speed. Default: False. """ def __init__(self, groups=3, widen_factor=1.0, out_indices=(0, 1, 2, 3), frozen_stages=-1, conv_cfg=None, norm_cfg=dict(type='BN'), act_cfg=dict(type='ReLU'), norm_eval=False, with_cp=False): super(ShuffleNetv1, self).__init__() self.stage_blocks = [3, 7, 3] self.groups = groups for indice in out_indices: if indice not in range(0, 4): raise ValueError('the item in out_indices must in ' f'range(0, 4). But received {indice}') if frozen_stages not in range(-1, 4): raise ValueError('frozen_stages must be in range(-1, 4). ' f'But received {frozen_stages}') self.out_indices = out_indices self.frozen_stages = frozen_stages self.conv_cfg = conv_cfg self.norm_cfg = norm_cfg self.act_cfg = act_cfg self.norm_eval = norm_eval self.with_cp = with_cp if groups == 1: channels = (144, 288, 576) elif groups == 2: channels = (200, 400, 800) elif groups == 3: channels = (240, 480, 960) elif groups == 4: channels = (272, 544, 1088) elif groups == 8: channels = (384, 768, 1536) else: raise ValueError(f'{groups} groups is not supported for 1x1 ' 'Grouped Convolutions') channels = [make_divisible(ch * widen_factor, 8) for ch in channels] self.inplanes = int(24 * widen_factor) self.conv1 = build_conv_layer( self.conv_cfg, in_channels=3, out_channels=self.inplanes, kernel_size=3, stride=2, padding=1, bias=False) self.maxpool = nn.MaxPool2d(kernel_size=3, stride=2, padding=1) self.layers = [] for i, num_blocks in enumerate(self.stage_blocks): first_block = False if i == 0 else True layer = self.make_layer(channels[i], num_blocks, first_block) layer_name = f'layer{i + 1}' self.add_module(layer_name, layer) self.layers.append(layer_name) def _freeze_stages(self): if self.frozen_stages >= 0: for param in self.conv1.parameters(): param.requires_grad = False for i in range(1, self.frozen_stages + 1): layer = getattr(self, f'layer{i}') layer.eval() for param in layer.parameters(): param.requires_grad = False def init_weights(self, pretrained=None): if pretrained is None: for m in self.modules(): if isinstance(m, nn.Conv2d): kaiming_init(m) elif isinstance(m, (_BatchNorm, nn.GroupNorm)): constant_init(m, 1) else: raise TypeError('pretrained must be a str or None. But received ' f'{type(pretrained)}') def make_layer(self, planes, num_blocks, first_block=True): """ Stack ShuffleUnit blocks to make a layer. Args: planes (int): Planes of the block. num_blocks (int): Number of blocks. first_block (bool, optional): Whether is the first ShuffleUnit of a sequential ShuffleUnits. Default: True, which means using the grouped 1x1 convolution. """ layers = [] for i in range(num_blocks): first_block = first_block if i == 0 else True combine_mode = 'concat' if i == 0 else 'add' layers.append( ShuffleUnit( self.inplanes, planes, groups=self.groups, first_block=first_block, combine=combine_mode, conv_cfg=self.conv_cfg, norm_cfg=self.norm_cfg, act_cfg=self.act_cfg, with_cp=self.with_cp)) self.inplanes = planes return nn.Sequential(*layers) def forward(self, x): x = self.conv1(x) x = self.maxpool(x) outs = [] for i, layer_name in enumerate(self.layers): layer = getattr(self, layer_name) x = layer(x) if i in self.out_indices: outs.append(x) if len(outs) == 1: return outs[0] else: return tuple(outs) def train(self, mode=True): super(ShuffleNetv1, self).train(mode) self._freeze_stages() if mode and self.norm_eval: for m in self.modules(): if isinstance(m, _BatchNorm): m.eval()