"""PyTorch CspNet A PyTorch implementation of Cross Stage Partial Networks including: * CSPResNet50 * CSPResNeXt50 * CSPDarkNet53 * and DarkNet53 for good measure Based on paper `CSPNet: A New Backbone that can Enhance Learning Capability of CNN` - https://arxiv.org/abs/1911.11929 Reference impl via darknet cfg files at https://github.com/WongKinYiu/CrossStagePartialNetworks Hacked together by / Copyright 2020 Ross Wightman """ import torch import torch.nn as nn import torch.nn.functional as F from timm.data import IMAGENET_DEFAULT_MEAN, IMAGENET_DEFAULT_STD from .helpers import build_model_with_cfg from .layers import ClassifierHead, ConvBnAct, DropPath, create_attn, get_norm_act_layer from .registry import register_model __all__ = ['CspNet'] # model_registry will add each entrypoint fn to this def _cfg(url='', **kwargs): return { 'url': url, 'num_classes': 1000, 'input_size': (3, 256, 256), 'pool_size': (8, 8), 'crop_pct': 0.887, 'interpolation': 'bilinear', 'mean': IMAGENET_DEFAULT_MEAN, 'std': IMAGENET_DEFAULT_STD, 'first_conv': 'stem.conv1.conv', 'classifier': 'head.fc', **kwargs } default_cfgs = { 'cspresnet50': _cfg( url='https://github.com/rwightman/pytorch-image-models/releases/download/v0.1-weights/cspresnet50_ra-d3e8d487.pth'), 'cspresnet50d': _cfg(url=''), 'cspresnet50w': _cfg(url=''), 'cspresnext50': _cfg( url='https://github.com/rwightman/pytorch-image-models/releases/download/v0.1-weights/cspresnext50_ra_224-648b4713.pth', input_size=(3, 224, 224), pool_size=(7, 7), crop_pct=0.875 # FIXME I trained this at 224x224, not 256 like ref impl ), 'cspresnext50_iabn': _cfg(url=''), 'cspdarknet53': _cfg( url='https://github.com/rwightman/pytorch-image-models/releases/download/v0.1-weights/cspdarknet53_ra_256-d05c7c21.pth'), 'cspdarknet53_iabn': _cfg(url=''), 'darknet53': _cfg(url=''), } model_cfgs = dict( cspresnet50=dict( stem=dict(out_chs=64, kernel_size=7, stride=2, pool='max'), stage=dict( out_chs=(128, 256, 512, 1024), depth=(3, 3, 5, 2), stride=(1,) + (2,) * 3, exp_ratio=(2.,) * 4, bottle_ratio=(0.5,) * 4, block_ratio=(1.,) * 4, cross_linear=True, ) ), cspresnet50d=dict( stem=dict(out_chs=[32, 32, 64], kernel_size=3, stride=2, pool='max'), stage=dict( out_chs=(128, 256, 512, 1024), depth=(3, 3, 5, 2), stride=(1,) + (2,) * 3, exp_ratio=(2.,) * 4, bottle_ratio=(0.5,) * 4, block_ratio=(1.,) * 4, cross_linear=True, ) ), cspresnet50w=dict( stem=dict(out_chs=[32, 32, 64], kernel_size=3, stride=2, pool='max'), stage=dict( out_chs=(256, 512, 1024, 2048), depth=(3, 3, 5, 2), stride=(1,) + (2,) * 3, exp_ratio=(1.,) * 4, bottle_ratio=(0.25,) * 4, block_ratio=(0.5,) * 4, cross_linear=True, ) ), cspresnext50=dict( stem=dict(out_chs=64, kernel_size=7, stride=2, pool='max'), stage=dict( out_chs=(256, 512, 1024, 2048), depth=(3, 3, 5, 2), stride=(1,) + (2,) * 3, groups=(32,) * 4, exp_ratio=(1.,) * 4, bottle_ratio=(1.,) * 4, block_ratio=(0.5,) * 4, cross_linear=True, ) ), cspdarknet53=dict( stem=dict(out_chs=32, kernel_size=3, stride=1, pool=''), stage=dict( out_chs=(64, 128, 256, 512, 1024), depth=(1, 2, 8, 8, 4), stride=(2,) * 5, exp_ratio=(2.,) + (1.,) * 4, bottle_ratio=(0.5,) + (1.0,) * 4, block_ratio=(1.,) + (0.5,) * 4, down_growth=True, ) ), darknet53=dict( stem=dict(out_chs=32, kernel_size=3, stride=1, pool=''), stage=dict( out_chs=(64, 128, 256, 512, 1024), depth=(1, 2, 8, 8, 4), stride=(2,) * 5, bottle_ratio=(0.5,) * 5, block_ratio=(1.,) * 5, ) ) ) def create_stem( in_chans=3, out_chs=32, kernel_size=3, stride=2, pool='', act_layer=None, norm_layer=None, aa_layer=None): stem = nn.Sequential() if not isinstance(out_chs, (tuple, list)): out_chs = [out_chs] assert len(out_chs) in_c = in_chans for i, out_c in enumerate(out_chs): conv_name = f'conv{i + 1}' stem.add_module(conv_name, ConvBnAct( in_c, out_c, kernel_size, stride=stride if i == 0 else 1, act_layer=act_layer, norm_layer=norm_layer)) in_c = out_c last_conv = conv_name if pool: if aa_layer is not None: stem.add_module('pool', nn.MaxPool2d(kernel_size=3, stride=1, padding=1)) stem.add_module('aa', aa_layer(channels=in_c, stride=2)) else: stem.add_module('pool', nn.MaxPool2d(kernel_size=3, stride=2, padding=1)) return stem, dict(num_chs=in_c, reduction=stride, module='.'.join(['stem', last_conv])) class ResBottleneck(nn.Module): """ ResNe(X)t Bottleneck Block """ def __init__(self, in_chs, out_chs, dilation=1, bottle_ratio=0.25, groups=1, act_layer=nn.ReLU, norm_layer=nn.BatchNorm2d, attn_last=False, attn_layer=None, aa_layer=None, drop_block=None, drop_path=None): super(ResBottleneck, self).__init__() mid_chs = int(round(out_chs * bottle_ratio)) ckwargs = dict(act_layer=act_layer, norm_layer=norm_layer, aa_layer=aa_layer, drop_block=drop_block) self.conv1 = ConvBnAct(in_chs, mid_chs, kernel_size=1, **ckwargs) self.conv2 = ConvBnAct(mid_chs, mid_chs, kernel_size=3, dilation=dilation, groups=groups, **ckwargs) self.attn2 = create_attn(attn_layer, channels=mid_chs) if not attn_last else None self.conv3 = ConvBnAct(mid_chs, out_chs, kernel_size=1, apply_act=False, **ckwargs) self.attn3 = create_attn(attn_layer, channels=out_chs) if attn_last else None self.drop_path = drop_path self.act3 = act_layer(inplace=True) def zero_init_last_bn(self): nn.init.zeros_(self.conv3.bn.weight) def forward(self, x): shortcut = x x = self.conv1(x) x = self.conv2(x) if self.attn2 is not None: x = self.attn2(x) x = self.conv3(x) if self.attn3 is not None: x = self.attn3(x) if self.drop_path is not None: x = self.drop_path(x) x = x + shortcut # FIXME partial shortcut needed if first block handled as per original, not used for my current impl #x[:, :shortcut.size(1)] += shortcut x = self.act3(x) return x class DarkBlock(nn.Module): """ DarkNet Block """ def __init__(self, in_chs, out_chs, dilation=1, bottle_ratio=0.5, groups=1, act_layer=nn.ReLU, norm_layer=nn.BatchNorm2d, attn_layer=None, aa_layer=None, drop_block=None, drop_path=None): super(DarkBlock, self).__init__() mid_chs = int(round(out_chs * bottle_ratio)) ckwargs = dict(act_layer=act_layer, norm_layer=norm_layer, aa_layer=aa_layer, drop_block=drop_block) self.conv1 = ConvBnAct(in_chs, mid_chs, kernel_size=1, **ckwargs) self.conv2 = ConvBnAct(mid_chs, out_chs, kernel_size=3, dilation=dilation, groups=groups, **ckwargs) self.attn = create_attn(attn_layer, channels=out_chs) self.drop_path = drop_path def zero_init_last_bn(self): nn.init.zeros_(self.conv2.bn.weight) def forward(self, x): shortcut = x x = self.conv1(x) x = self.conv2(x) if self.attn is not None: x = self.attn(x) if self.drop_path is not None: x = self.drop_path(x) x = x + shortcut return x class CrossStage(nn.Module): """Cross Stage.""" def __init__(self, in_chs, out_chs, stride, dilation, depth, block_ratio=1., bottle_ratio=1., exp_ratio=1., groups=1, first_dilation=None, down_growth=False, cross_linear=False, block_dpr=None, block_fn=ResBottleneck, **block_kwargs): super(CrossStage, self).__init__() first_dilation = first_dilation or dilation down_chs = out_chs if down_growth else in_chs # grow downsample channels to output channels exp_chs = int(round(out_chs * exp_ratio)) block_out_chs = int(round(out_chs * block_ratio)) conv_kwargs = dict(act_layer=block_kwargs.get('act_layer'), norm_layer=block_kwargs.get('norm_layer')) if stride != 1 or first_dilation != dilation: self.conv_down = ConvBnAct( in_chs, down_chs, kernel_size=3, stride=stride, dilation=first_dilation, groups=groups, aa_layer=block_kwargs.get('aa_layer', None), **conv_kwargs) prev_chs = down_chs else: self.conv_down = None prev_chs = in_chs # FIXME this 1x1 expansion is pushed down into the cross and block paths in the darknet cfgs. Also, # there is also special case for the first stage for some of the model that results in uneven split # across the two paths. I did it this way for simplicity for now. self.conv_exp = ConvBnAct(prev_chs, exp_chs, kernel_size=1, apply_act=not cross_linear, **conv_kwargs) prev_chs = exp_chs // 2 # output of conv_exp is always split in two self.blocks = nn.Sequential() for i in range(depth): drop_path = DropPath(block_dpr[i]) if block_dpr and block_dpr[i] else None self.blocks.add_module(str(i), block_fn( prev_chs, block_out_chs, dilation, bottle_ratio, groups, drop_path=drop_path, **block_kwargs)) prev_chs = block_out_chs # transition convs self.conv_transition_b = ConvBnAct(prev_chs, exp_chs // 2, kernel_size=1, **conv_kwargs) self.conv_transition = ConvBnAct(exp_chs, out_chs, kernel_size=1, **conv_kwargs) def forward(self, x): if self.conv_down is not None: x = self.conv_down(x) x = self.conv_exp(x) split = x.shape[1] // 2 xs, xb = x[:, :split], x[:, split:] xb = self.blocks(xb) xb = self.conv_transition_b(xb).contiguous() out = self.conv_transition(torch.cat([xs, xb], dim=1)) return out class DarkStage(nn.Module): """DarkNet stage.""" def __init__(self, in_chs, out_chs, stride, dilation, depth, block_ratio=1., bottle_ratio=1., groups=1, first_dilation=None, block_fn=ResBottleneck, block_dpr=None, **block_kwargs): super(DarkStage, self).__init__() first_dilation = first_dilation or dilation self.conv_down = ConvBnAct( in_chs, out_chs, kernel_size=3, stride=stride, dilation=first_dilation, groups=groups, act_layer=block_kwargs.get('act_layer'), norm_layer=block_kwargs.get('norm_layer'), aa_layer=block_kwargs.get('aa_layer', None)) prev_chs = out_chs block_out_chs = int(round(out_chs * block_ratio)) self.blocks = nn.Sequential() for i in range(depth): drop_path = DropPath(block_dpr[i]) if block_dpr and block_dpr[i] else None self.blocks.add_module(str(i), block_fn( prev_chs, block_out_chs, dilation, bottle_ratio, groups, drop_path=drop_path, **block_kwargs)) prev_chs = block_out_chs def forward(self, x): x = self.conv_down(x) x = self.blocks(x) return x def _cfg_to_stage_args(cfg, curr_stride=2, output_stride=32, drop_path_rate=0.): # get per stage args for stage and containing blocks, calculate strides to meet target output_stride num_stages = len(cfg['depth']) if 'groups' not in cfg: cfg['groups'] = (1,) * num_stages if 'down_growth' in cfg and not isinstance(cfg['down_growth'], (list, tuple)): cfg['down_growth'] = (cfg['down_growth'],) * num_stages if 'cross_linear' in cfg and not isinstance(cfg['cross_linear'], (list, tuple)): cfg['cross_linear'] = (cfg['cross_linear'],) * num_stages cfg['block_dpr'] = [None] * num_stages if not drop_path_rate else \ [x.tolist() for x in torch.linspace(0, drop_path_rate, sum(cfg['depth'])).split(cfg['depth'])] stage_strides = [] stage_dilations = [] stage_first_dilations = [] dilation = 1 for cfg_stride in cfg['stride']: stage_first_dilations.append(dilation) if curr_stride >= output_stride: dilation *= cfg_stride stride = 1 else: stride = cfg_stride curr_stride *= stride stage_strides.append(stride) stage_dilations.append(dilation) cfg['stride'] = stage_strides cfg['dilation'] = stage_dilations cfg['first_dilation'] = stage_first_dilations stage_args = [dict(zip(cfg.keys(), values)) for values in zip(*cfg.values())] return stage_args class CspNet(nn.Module): """Cross Stage Partial base model. Paper: `CSPNet: A New Backbone that can Enhance Learning Capability of CNN` - https://arxiv.org/abs/1911.11929 Ref Impl: https://github.com/WongKinYiu/CrossStagePartialNetworks NOTE: There are differences in the way I handle the 1x1 'expansion' conv in this impl vs the darknet impl. I did it this way for simplicity and less special cases. """ def __init__(self, cfg, in_chans=3, num_classes=1000, output_stride=32, global_pool='avg', drop_rate=0., act_layer=nn.LeakyReLU, norm_layer=nn.BatchNorm2d, aa_layer=None, drop_path_rate=0., zero_init_last_bn=True, stage_fn=CrossStage, block_fn=ResBottleneck): super().__init__() self.num_classes = num_classes self.drop_rate = drop_rate assert output_stride in (8, 16, 32) layer_args = dict(act_layer=act_layer, norm_layer=norm_layer, aa_layer=aa_layer) # Construct the stem self.stem, stem_feat_info = create_stem(in_chans, **cfg['stem'], **layer_args) self.feature_info = [stem_feat_info] prev_chs = stem_feat_info['num_chs'] curr_stride = stem_feat_info['reduction'] # reduction does not include pool if cfg['stem']['pool']: curr_stride *= 2 # Construct the stages per_stage_args = _cfg_to_stage_args( cfg['stage'], curr_stride=curr_stride, output_stride=output_stride, drop_path_rate=drop_path_rate) self.stages = nn.Sequential() for i, sa in enumerate(per_stage_args): self.stages.add_module( str(i), stage_fn(prev_chs, **sa, **layer_args, block_fn=block_fn)) prev_chs = sa['out_chs'] curr_stride *= sa['stride'] self.feature_info += [dict(num_chs=prev_chs, reduction=curr_stride, module=f'stages.{i}')] # Construct the head self.num_features = prev_chs self.head = ClassifierHead( in_chs=prev_chs, num_classes=num_classes, pool_type=global_pool, drop_rate=drop_rate) for m in self.modules(): if isinstance(m, nn.Conv2d): nn.init.kaiming_normal_(m.weight, mode='fan_out', nonlinearity='relu') elif isinstance(m, nn.BatchNorm2d): nn.init.ones_(m.weight) nn.init.zeros_(m.bias) elif isinstance(m, nn.Linear): nn.init.normal_(m.weight, mean=0.0, std=0.01) nn.init.zeros_(m.bias) if zero_init_last_bn: for m in self.modules(): if hasattr(m, 'zero_init_last_bn'): m.zero_init_last_bn() def get_classifier(self): return self.head.fc def reset_classifier(self, num_classes, global_pool='avg'): self.head = ClassifierHead(self.num_features, num_classes, pool_type=global_pool, drop_rate=self.drop_rate) def forward_features(self, x): x = self.stem(x) x = self.stages(x) return x def forward(self, x): x = self.forward_features(x) x = self.head(x) return x def _create_cspnet(variant, pretrained=False, **kwargs): cfg_variant = variant.split('_')[0] if 'darknet' in variant: # NOTE: DarkNet is one of few models with stride==1 features w/ 6 out_indices [0..5] kwargs.setdefault('out_indices', (0, 1, 2, 3, 4, 5)) return build_model_with_cfg( CspNet, variant, pretrained, default_cfg=default_cfgs[variant], model_cfg=model_cfgs[cfg_variant], feature_cfg=dict(flatten_sequential=True), **kwargs) @register_model def cspresnet50(pretrained=False, **kwargs): return _create_cspnet('cspresnet50', pretrained=pretrained, **kwargs) @register_model def cspresnet50d(pretrained=False, **kwargs): return _create_cspnet('cspresnet50d', pretrained=pretrained, **kwargs) @register_model def cspresnet50w(pretrained=False, **kwargs): return _create_cspnet('cspresnet50w', pretrained=pretrained, **kwargs) @register_model def cspresnext50(pretrained=False, **kwargs): return _create_cspnet('cspresnext50', pretrained=pretrained, **kwargs) @register_model def cspresnext50_iabn(pretrained=False, **kwargs): norm_layer = get_norm_act_layer('iabn') return _create_cspnet('cspresnext50_iabn', pretrained=pretrained, norm_layer=norm_layer, **kwargs) @register_model def cspdarknet53(pretrained=False, **kwargs): return _create_cspnet('cspdarknet53', pretrained=pretrained, block_fn=DarkBlock, **kwargs) @register_model def cspdarknet53_iabn(pretrained=False, **kwargs): norm_layer = get_norm_act_layer('iabn') return _create_cspnet('cspdarknet53_iabn', pretrained=pretrained, block_fn=DarkBlock, norm_layer=norm_layer, **kwargs) @register_model def darknet53(pretrained=False, **kwargs): return _create_cspnet('darknet53', pretrained=pretrained, block_fn=DarkBlock, stage_fn=DarkStage, **kwargs)