Add MobileNetV3 architecture for Classification (#3252)

* Add MobileNetV3 Architecture in TorchVision (#3182)

* Adding implementation of network architecture

* Adding rmsprop support on the train.py

* Adding auto-augment and random-erase in the training scripts.

* Adding support for reduced tail on MobileNetV3.

* Tagging blocks with comments.

* Adding documentation, pre-trained model URL and a minor refactoring.

* Handling better untrained supported models.

docs/source/models.rst

@@ -22,7 +22,8 @@ architectures for image classification:
 -  `Inception`_ v3
 -  `GoogLeNet`_
 -  `ShuffleNet`_ v2
--  `MobileNet`_ v2
+-  `MobileNetV2`_
+-  `MobileNetV3`_
 -  `ResNeXt`_
 -  `Wide ResNet`_
 -  `MNASNet`_
@@ -40,7 +41,9 @@ You can construct a model with random weights by calling its constructor:
     inception = models.inception_v3()
     googlenet = models.googlenet()
     shufflenet = models.shufflenet_v2_x1_0()
-    mobilenet = models.mobilenet_v2()
+    mobilenet_v2 = models.mobilenet_v2()
+    mobilenet_v3_large = models.mobilenet_v3_large()
+    mobilenet_v3_small = models.mobilenet_v3_small()
     resnext50_32x4d = models.resnext50_32x4d()
     wide_resnet50_2 = models.wide_resnet50_2()
     mnasnet = models.mnasnet1_0()
@@ -59,7 +62,8 @@ These can be constructed by passing ``pretrained=True``:
     inception = models.inception_v3(pretrained=True)
     googlenet = models.googlenet(pretrained=True)
     shufflenet = models.shufflenet_v2_x1_0(pretrained=True)
-    mobilenet = models.mobilenet_v2(pretrained=True)
+    mobilenet_v2 = models.mobilenet_v2(pretrained=True)
+    mobilenet_v3_large = models.mobilenet_v3_large(pretrained=True)
     resnext50_32x4d = models.resnext50_32x4d(pretrained=True)
     wide_resnet50_2 = models.wide_resnet50_2(pretrained=True)
     mnasnet = models.mnasnet1_0(pretrained=True)
@@ -137,6 +141,7 @@ Inception v3                      22.55           6.44
 GoogleNet                         30.22           10.47
 ShuffleNet V2                     30.64           11.68
 MobileNet V2                      28.12           9.71
+MobileNet V3 Large                25.96           8.66
 ResNeXt-50-32x4d                  22.38           6.30
 ResNeXt-101-32x8d                 20.69           5.47
 Wide ResNet-50-2                  21.49           5.91
@@ -153,7 +158,8 @@ MNASNet 1.0                       26.49           8.456
 .. _Inception: https://arxiv.org/abs/1512.00567
 .. _GoogLeNet: https://arxiv.org/abs/1409.4842
 .. _ShuffleNet: https://arxiv.org/abs/1807.11164
-.. _MobileNet: https://arxiv.org/abs/1801.04381
+.. _MobileNetV2: https://arxiv.org/abs/1801.04381
+.. _MobileNetV3: https://arxiv.org/abs/1905.02244
 .. _ResNeXt: https://arxiv.org/abs/1611.05431
 .. _MNASNet: https://arxiv.org/abs/1807.11626
 
@@ -231,6 +237,12 @@ MobileNet v2
 
 .. autofunction:: mobilenet_v2
 
+MobileNet v3
+-------------
+
+.. autofunction:: mobilenet_v3_large
+.. autofunction:: mobilenet_v3_small
+
 ResNext
 -------
 

hubconf.py

@@ -11,7 +11,8 @@ from torchvision.models.squeezenet import squeezenet1_0, squeezenet1_1
 from torchvision.models.vgg import vgg11, vgg13, vgg16, vgg19, vgg11_bn, vgg13_bn, vgg16_bn, vgg19_bn
 from torchvision.models.googlenet import googlenet
 from torchvision.models.shufflenetv2 import shufflenet_v2_x0_5, shufflenet_v2_x1_0
-from torchvision.models.mobilenet import mobilenet_v2
+from torchvision.models.mobilenetv2 import mobilenet_v2
+from torchvision.models.mobilenetv3 import mobilenet_v3_large, mobilenet_v3_small
 from torchvision.models.mnasnet import mnasnet0_5, mnasnet0_75, mnasnet1_0, \
     mnasnet1_3
 

references/classification/README.md

@@ -53,6 +53,16 @@ python -m torch.distributed.launch --nproc_per_node=8 --use_env train.py\
      --lr-step-size 1 --lr-gamma 0.98
 ```
 
+
+### MobileNetV3 Large
+```
+python -m torch.distributed.launch --nproc_per_node=8 --use_env train.py\
+     --model mobilenet_v3_large --epochs 600 --opt rmsprop --batch-size 128 --lr 0.064\ 
+     --wd 0.00001 --lr-step-size 2 --lr-gamma 0.973 --auto-augment imagenet --random-erase 0.2
+```
+
+Then we averaged the parameters of the last 3 checkpoints that improved the Acc@1. See [#3182](https://github.com/pytorch/vision/pull/3182) for details.
+
 ## Mixed precision training
 Automatic Mixed Precision (AMP) training on GPU for Pytorch can be enabled with the [NVIDIA Apex extension](https://github.com/NVIDIA/apex).
 

references/classification/train.py

@@ -79,7 +79,7 @@ def _get_cache_path(filepath):
     return cache_path
 
 
-def load_data(traindir, valdir, cache_dataset, distributed):
+def load_data(traindir, valdir, args):
     # Data loading code
     print("Loading data")
     normalize = transforms.Normalize(mean=[0.485, 0.456, 0.406],
@@ -88,20 +88,28 @@ def load_data(traindir, valdir, cache_dataset, distributed):
     print("Loading training data")
     st = time.time()
     cache_path = _get_cache_path(traindir)
-    if cache_dataset and os.path.exists(cache_path):
+    if args.cache_dataset and os.path.exists(cache_path):
         # Attention, as the transforms are also cached!
         print("Loading dataset_train from {}".format(cache_path))
         dataset, _ = torch.load(cache_path)
     else:
+        trans = [
+            transforms.RandomResizedCrop(224),
+            transforms.RandomHorizontalFlip(),
+        ]
+        if args.auto_augment is not None:
+            aa_policy = transforms.AutoAugmentPolicy(args.auto_augment)
+            trans.append(transforms.AutoAugment(policy=aa_policy))
+        trans.extend([
+            transforms.ToTensor(),
+            normalize,
+        ])
+        if args.random_erase > 0:
+            trans.append(transforms.RandomErasing(p=args.random_erase))
         dataset = torchvision.datasets.ImageFolder(
             traindir,
-            transforms.Compose([
-                transforms.RandomResizedCrop(224),
-                transforms.RandomHorizontalFlip(),
-                transforms.ToTensor(),
-                normalize,
-            ]))
-        if cache_dataset:
+            transforms.Compose(trans))
+        if args.cache_dataset:
             print("Saving dataset_train to {}".format(cache_path))
             utils.mkdir(os.path.dirname(cache_path))
             utils.save_on_master((dataset, traindir), cache_path)
@@ -109,7 +117,7 @@ def load_data(traindir, valdir, cache_dataset, distributed):
 
     print("Loading validation data")
     cache_path = _get_cache_path(valdir)
-    if cache_dataset and os.path.exists(cache_path):
+    if args.cache_dataset and os.path.exists(cache_path):
         # Attention, as the transforms are also cached!
         print("Loading dataset_test from {}".format(cache_path))
         dataset_test, _ = torch.load(cache_path)
@@ -122,13 +130,13 @@ def load_data(traindir, valdir, cache_dataset, distributed):
                 transforms.ToTensor(),
                 normalize,
             ]))
-        if cache_dataset:
+        if args.cache_dataset:
             print("Saving dataset_test to {}".format(cache_path))
             utils.mkdir(os.path.dirname(cache_path))
             utils.save_on_master((dataset_test, valdir), cache_path)
 
     print("Creating data loaders")
-    if distributed:
+    if args.distributed:
         train_sampler = torch.utils.data.distributed.DistributedSampler(dataset)
         test_sampler = torch.utils.data.distributed.DistributedSampler(dataset_test)
     else:
@@ -155,8 +163,7 @@ def main(args):
 
     train_dir = os.path.join(args.data_path, 'train')
     val_dir = os.path.join(args.data_path, 'val')
-    dataset, dataset_test, train_sampler, test_sampler = load_data(train_dir, val_dir,
-                                                                   args.cache_dataset, args.distributed)
+    dataset, dataset_test, train_sampler, test_sampler = load_data(train_dir, val_dir, args)
     data_loader = torch.utils.data.DataLoader(
         dataset, batch_size=args.batch_size,
         sampler=train_sampler, num_workers=args.workers, pin_memory=True)
@@ -173,8 +180,15 @@ def main(args):
 
     criterion = nn.CrossEntropyLoss()
 
-    optimizer = torch.optim.SGD(
-        model.parameters(), lr=args.lr, momentum=args.momentum, weight_decay=args.weight_decay)
+    opt_name = args.opt.lower()
+    if opt_name == 'sgd':
+        optimizer = torch.optim.SGD(
+            model.parameters(), lr=args.lr, momentum=args.momentum, weight_decay=args.weight_decay)
+    elif opt_name == 'rmsprop':
+        optimizer = torch.optim.RMSprop(model.parameters(), lr=args.lr, momentum=args.momentum,
+                                        weight_decay=args.weight_decay, eps=0.0316, alpha=0.9)
+    else:
+        raise RuntimeError("Invalid optimizer {}. Only SGD and RMSprop are supported.".format(args.opt))
 
     if args.apex:
         model, optimizer = amp.initialize(model, optimizer,
@@ -238,6 +252,7 @@ def parse_args():
                         help='number of total epochs to run')
     parser.add_argument('-j', '--workers', default=16, type=int, metavar='N',
                         help='number of data loading workers (default: 16)')
+    parser.add_argument('--opt', default='sgd', type=str, help='optimizer')
     parser.add_argument('--lr', default=0.1, type=float, help='initial learning rate')
     parser.add_argument('--momentum', default=0.9, type=float, metavar='M',
                         help='momentum')
@@ -275,6 +290,8 @@ def parse_args():
         help="Use pre-trained models from the modelzoo",
         action="store_true",
     )
+    parser.add_argument('--auto-augment', default=None, help='auto augment policy (default: None)')
+    parser.add_argument('--random-erase', default=0.0, type=float, help='random erasing probability (default: 0.0)')
 
     # Mixed precision training parameters
     parser.add_argument('--apex', action='store_true',

test/test_models.py

@@ -275,16 +275,17 @@ class ModelTester(TestCase):
         out = model(x)
         self.assertEqual(out.shape[-1], 1000)
 
-    def test_mobilenetv2_norm_layer(self):
-        model = models.__dict__["mobilenet_v2"]()
-        self.assertTrue(any(isinstance(x, nn.BatchNorm2d) for x in model.modules()))
+    def test_mobilenet_norm_layer(self):
+        for name in ["mobilenet_v2", "mobilenet_v3_large", "mobilenet_v3_small"]:
+            model = models.__dict__[name]()
+            self.assertTrue(any(isinstance(x, nn.BatchNorm2d) for x in model.modules()))
 
-        def get_gn(num_channels):
-            return nn.GroupNorm(32, num_channels)
+            def get_gn(num_channels):
+                return nn.GroupNorm(32, num_channels)
 
-        model = models.__dict__["mobilenet_v2"](norm_layer=get_gn)
-        self.assertFalse(any(isinstance(x, nn.BatchNorm2d) for x in model.modules()))
-        self.assertTrue(any(isinstance(x, nn.GroupNorm) for x in model.modules()))
+            model = models.__dict__[name](norm_layer=get_gn)
+            self.assertFalse(any(isinstance(x, nn.BatchNorm2d) for x in model.modules()))
+            self.assertTrue(any(isinstance(x, nn.GroupNorm) for x in model.modules()))
 
     def test_inception_v3_eval(self):
         # replacement for models.inception_v3(pretrained=True) that does not download weights

torchvision/models/mobilenet.py

 from .mobilenetv2 import MobileNetV2, mobilenet_v2, __all__ as mv2_all
+from .mobilenetv3 import MobileNetV3, mobilenet_v3_large, mobilenet_v3_small, __all__ as mv3_all
 
-__all__ = mv2_all
+__all__ = mv2_all + mv3_all

torchvision/models/mobilenetv2.py

@@ -53,6 +53,7 @@ class ConvBNActivation(nn.Sequential):
             norm_layer(out_planes),
             activation_layer(inplace=True)
         )
+        self.out_channels = out_planes
 
 
 # necessary for backwards compatibility
@@ -90,6 +91,8 @@ class InvertedResidual(nn.Module):
             norm_layer(oup),
         ])
         self.conv = nn.Sequential(*layers)
+        self.out_channels = oup
+        self.is_strided = stride > 1
 
     def forward(self, x: Tensor) -> Tensor:
         if self.use_res_connect:

torchvision/models/mobilenetv3.py

+import torch
+
+from functools import partial
+from torch import nn, Tensor
+from torch.nn import functional as F
+from typing import Any, Callable, List, Optional, Sequence
+
+from torchvision.models.utils import load_state_dict_from_url
+from torchvision.models.mobilenetv2 import _make_divisible, ConvBNActivation
+
+
+__all__ = ["MobileNetV3", "mobilenet_v3_large", "mobilenet_v3_small"]
+
+
+model_urls = {
+    "mobilenet_v3_large": "https://download.pytorch.org/models/mobilenet_v3_large-8738ca79.pth",
+    "mobilenet_v3_small": None,
+}
+
+
+class Identity(nn.Module):
+
+    def __init__(self, inplace: bool = False):
+        super().__init__()
+        self.inplace = inplace
+
+    def forward(self, input: Tensor) -> Tensor:
+        return input
+
+
+class SqueezeExcitation(nn.Module):
+
+    def __init__(self, input_channels: int, squeeze_factor: int = 4):
+        super().__init__()
+        squeeze_channels = _make_divisible(input_channels // squeeze_factor, 8)
+        self.fc1 = nn.Conv2d(input_channels, squeeze_channels, 1)
+        self.fc2 = nn.Conv2d(squeeze_channels, input_channels, 1)
+
+    def forward(self, input: Tensor) -> Tensor:
+        scale = F.adaptive_avg_pool2d(input, 1)
+        scale = self.fc1(scale)
+        scale = F.relu(scale, inplace=True)
+        scale = self.fc2(scale)
+        scale = F.hardsigmoid(scale, inplace=True)
+        return scale * input
+
+
+class InvertedResidualConfig:
+
+    def __init__(self, input_channels: int, kernel: int, expanded_channels: int, out_channels: int, use_se: bool,
+                 activation: str, stride: int, width_mult: float):
+        self.input_channels = self.adjust_channels(input_channels, width_mult)
+        self.kernel = kernel
+        self.expanded_channels = self.adjust_channels(expanded_channels, width_mult)
+        self.out_channels = self.adjust_channels(out_channels, width_mult)
+        self.use_se = use_se
+        self.use_hs = activation == "HS"
+        self.stride = stride
+
+    @staticmethod
+    def adjust_channels(channels: int, width_mult: float):
+        return _make_divisible(channels * width_mult, 8)
+
+
+class InvertedResidual(nn.Module):
+
+    def __init__(self, cnf: InvertedResidualConfig, norm_layer: Callable[..., nn.Module]):
+        super().__init__()
+        if not (1 <= cnf.stride <= 2):
+            raise ValueError('illegal stride value')
+
+        self.use_res_connect = cnf.stride == 1 and cnf.input_channels == cnf.out_channels
+
+        layers: List[nn.Module] = []
+        activation_layer = nn.Hardswish if cnf.use_hs else nn.ReLU
+
+        # expand
+        if cnf.expanded_channels != cnf.input_channels:
+            layers.append(ConvBNActivation(cnf.input_channels, cnf.expanded_channels, kernel_size=1,
+                                           norm_layer=norm_layer, activation_layer=activation_layer))
+
+        # depthwise
+        layers.append(ConvBNActivation(cnf.expanded_channels, cnf.expanded_channels, kernel_size=cnf.kernel,
+                                       stride=cnf.stride, groups=cnf.expanded_channels, norm_layer=norm_layer,
+                                       activation_layer=activation_layer))
+        if cnf.use_se:
+            layers.append(SqueezeExcitation(cnf.expanded_channels))
+
+        # project
+        layers.append(ConvBNActivation(cnf.expanded_channels, cnf.out_channels, kernel_size=1, norm_layer=norm_layer,
+                                       activation_layer=Identity))
+
+        self.block = nn.Sequential(*layers)
+        self.out_channels = cnf.out_channels
+        self.is_strided = cnf.stride > 1
+
+    def forward(self, input: Tensor) -> Tensor:
+        result = self.block(input)
+        if self.use_res_connect:
+            result += input
+        return result
+
+
+class MobileNetV3(nn.Module):
+
+    def __init__(
+            self,
+            inverted_residual_setting: List[InvertedResidualConfig],
+            last_channel: int,
+            num_classes: int = 1000,
+            block: Optional[Callable[..., nn.Module]] = None,
+            norm_layer: Optional[Callable[..., nn.Module]] = None
+    ) -> None:
+        """
+        MobileNet V3 main class
+
+        Args:
+            inverted_residual_setting (List[InvertedResidualConfig]): Network structure
+            last_channel (int): The number of channels on the penultimate layer
+            num_classes (int): Number of classes
+            block (Optional[Callable[..., nn.Module]]): Module specifying inverted residual building block for mobilenet
+            norm_layer (Optional[Callable[..., nn.Module]]): Module specifying the normalization layer to use
+        """
+        super().__init__()
+
+        if not inverted_residual_setting:
+            raise ValueError("The inverted_residual_setting should not be empty")
+        elif not (isinstance(inverted_residual_setting, Sequence) and
+                  all([isinstance(s, InvertedResidualConfig) for s in inverted_residual_setting])):
+            raise TypeError("The inverted_residual_setting should be List[InvertedResidualConfig]")
+
+        if block is None:
+            block = InvertedResidual
+
+        if norm_layer is None:
+            norm_layer = partial(nn.BatchNorm2d, eps=0.001, momentum=0.01)
+
+        layers: List[nn.Module] = []
+
+        # building first layer
+        firstconv_output_channels = inverted_residual_setting[0].input_channels
+        layers.append(ConvBNActivation(3, firstconv_output_channels, kernel_size=3, stride=2, norm_layer=norm_layer,
+                                       activation_layer=nn.Hardswish))
+
+        # building inverted residual blocks
+        for cnf in inverted_residual_setting:
+            layers.append(block(cnf, norm_layer))
+
+        # building last several layers
+        lastconv_input_channels = inverted_residual_setting[-1].out_channels
+        lastconv_output_channels = 6 * lastconv_input_channels
+        layers.append(ConvBNActivation(lastconv_input_channels, lastconv_output_channels, kernel_size=1,
+                                       norm_layer=norm_layer, activation_layer=nn.Hardswish))
+
+        self.features = nn.Sequential(*layers)
+        self.avgpool = nn.AdaptiveAvgPool2d(1)
+        self.classifier = nn.Sequential(
+            nn.Linear(lastconv_output_channels, last_channel),
+            nn.Hardswish(inplace=True),
+            nn.Dropout(p=0.2, inplace=True),
+            nn.Linear(last_channel, num_classes),
+        )
+
+        for m in self.modules():
+            if isinstance(m, nn.Conv2d):
+                nn.init.kaiming_normal_(m.weight, mode='fan_out')
+                if m.bias is not None:
+                    nn.init.zeros_(m.bias)
+            elif isinstance(m, (nn.BatchNorm2d, nn.GroupNorm)):
+                nn.init.ones_(m.weight)
+                nn.init.zeros_(m.bias)
+            elif isinstance(m, nn.Linear):
+                nn.init.normal_(m.weight, 0, 0.01)
+                nn.init.zeros_(m.bias)
+
+    def _forward_impl(self, x: Tensor) -> Tensor:
+        x = self.features(x)
+
+        x = self.avgpool(x)
+        x = torch.flatten(x, 1)
+
+        x = self.classifier(x)
+
+        return x
+
+    def forward(self, x: Tensor) -> Tensor:
+        return self._forward_impl(x)
+
+
+def _mobilenet_v3(
+    arch: str,
+    inverted_residual_setting: List[InvertedResidualConfig],
+    last_channel: int,
+    pretrained: bool,
+    progress: bool,
+    **kwargs: Any
+):
+    model = MobileNetV3(inverted_residual_setting, last_channel, **kwargs)
+    if pretrained:
+        if model_urls.get(arch, None) is None:
+            raise ValueError("No checkpoint is available for model type {}".format(arch))
+        state_dict = load_state_dict_from_url(model_urls[arch], progress=progress)
+        model.load_state_dict(state_dict)
+    return model
+
+
+def mobilenet_v3_large(pretrained: bool = False, progress: bool = True, reduced_tail: bool = False,
+                       **kwargs: Any) -> MobileNetV3:
+    """
+    Constructs a large MobileNetV3 architecture from
+    `"Searching for MobileNetV3" <https://arxiv.org/abs/1905.02244>`_.
+
+    Args:
+        pretrained (bool): If True, returns a model pre-trained on ImageNet
+        progress (bool): If True, displays a progress bar of the download to stderr
+        reduced_tail (bool): If True, reduces the channel counts of all feature layers
+            between C4 and C5 by 2. It is used to reduce the channel redundancy in the
+            backbone for Detection and Segmentation.
+    """
+    width_mult = 1.0
+    bneck_conf = partial(InvertedResidualConfig, width_mult=width_mult)
+    adjust_channels = partial(InvertedResidualConfig.adjust_channels, width_mult=width_mult)
+
+    reduce_divider = 2 if reduced_tail else 1
+
+    inverted_residual_setting = [
+        bneck_conf(16, 3, 16, 16, False, "RE", 1),
+        bneck_conf(16, 3, 64, 24, False, "RE", 2),  # C1
+        bneck_conf(24, 3, 72, 24, False, "RE", 1),
+        bneck_conf(24, 5, 72, 40, True, "RE", 2),  # C2
+        bneck_conf(40, 5, 120, 40, True, "RE", 1),
+        bneck_conf(40, 5, 120, 40, True, "RE", 1),
+        bneck_conf(40, 3, 240, 80, False, "HS", 2),  # C3
+        bneck_conf(80, 3, 200, 80, False, "HS", 1),
+        bneck_conf(80, 3, 184, 80, False, "HS", 1),
+        bneck_conf(80, 3, 184, 80, False, "HS", 1),
+        bneck_conf(80, 3, 480, 112, True, "HS", 1),
+        bneck_conf(112, 3, 672, 112, True, "HS", 1),
+        bneck_conf(112, 5, 672, 160 // reduce_divider, True, "HS", 2),  # C4
+        bneck_conf(160 // reduce_divider, 5, 960 // reduce_divider, 160 // reduce_divider, True, "HS", 1),
+        bneck_conf(160 // reduce_divider, 5, 960 // reduce_divider, 160 // reduce_divider, True, "HS", 1),
+    ]
+    last_channel = adjust_channels(1280 // reduce_divider)  # C5
+
+    return _mobilenet_v3("mobilenet_v3_large", inverted_residual_setting, last_channel, pretrained, progress, **kwargs)
+
+
+def mobilenet_v3_small(pretrained: bool = False, progress: bool = True, reduced_tail: bool = False,
+                       **kwargs: Any) -> MobileNetV3:
+    """
+    Constructs a small MobileNetV3 architecture from
+    `"Searching for MobileNetV3" <https://arxiv.org/abs/1905.02244>`_.
+
+    Args:
+        pretrained (bool): If True, returns a model pre-trained on ImageNet
+        progress (bool): If True, displays a progress bar of the download to stderr
+        reduced_tail (bool): If True, reduces the channel counts of all feature layers
+            between C4 and C5 by 2. It is used to reduce the channel redundancy in the
+            backbone for Detection and Segmentation.
+    """
+    width_mult = 1.0
+    bneck_conf = partial(InvertedResidualConfig, width_mult=width_mult)
+    adjust_channels = partial(InvertedResidualConfig.adjust_channels, width_mult=width_mult)
+
+    reduce_divider = 2 if reduced_tail else 1
+
+    inverted_residual_setting = [
+        bneck_conf(16, 3, 16, 16, True, "RE", 2),  # C1
+        bneck_conf(16, 3, 72, 24, False, "RE", 2),  # C2
+        bneck_conf(24, 3, 88, 24, False, "RE", 1),
+        bneck_conf(24, 5, 96, 40, True, "HS", 2),  # C3
+        bneck_conf(40, 5, 240, 40, True, "HS", 1),
+        bneck_conf(40, 5, 240, 40, True, "HS", 1),
+        bneck_conf(40, 5, 120, 48, True, "HS", 1),
+        bneck_conf(48, 5, 144, 48, True, "HS", 1),
+        bneck_conf(48, 5, 288, 96 // reduce_divider, True, "HS", 2),  # C4
+        bneck_conf(96 // reduce_divider, 5, 576 // reduce_divider, 96 // reduce_divider, True, "HS", 1),
+        bneck_conf(96 // reduce_divider, 5, 576 // reduce_divider, 96 // reduce_divider, True, "HS", 1),
+    ]
+    last_channel = adjust_channels(1024 // reduce_divider)  # C5
+
+    return _mobilenet_v3("mobilenet_v3_small", inverted_residual_setting, last_channel, pretrained, progress, **kwargs)