# MobileNet v2

**MobileNetV2** is a convolutional neural network architecture that seeks to perform well on mobile devices. It is based on an [inverted residual structure](https://paperswithcode.com/method/inverted-residual-block) where the residual connections are between the bottleneck layers.  The intermediate expansion layer uses lightweight depthwise convolutions to filter features as a source of non-linearity. As a whole, the architecture of MobileNetV2 contains the initial fully convolution layer with 32 filters, followed by 19 residual bottleneck layers.

## How do I use this model on an image?

To load a pretrained model:

```py
>>> import timm
>>> model = timm.create_model('mobilenetv2_100', pretrained=True)
>>> model.eval()
```

To load and preprocess the image:

```py 
>>> import urllib
>>> from PIL import Image
>>> from timm.data import resolve_data_config
>>> from timm.data.transforms_factory import create_transform

>>> config = resolve_data_config({}, model=model)
>>> transform = create_transform(**config)

>>> url, filename = ("https://github.com/pytorch/hub/raw/master/images/dog.jpg", "dog.jpg")
>>> urllib.request.urlretrieve(url, filename)
>>> img = Image.open(filename).convert('RGB')
>>> tensor = transform(img).unsqueeze(0) # transform and add batch dimension
```

To get the model predictions:

```py
>>> import torch
>>> with torch.no_grad():
...     out = model(tensor)
>>> probabilities = torch.nn.functional.softmax(out[0], dim=0)
>>> print(probabilities.shape)
>>> # prints: torch.Size([1000])
```

To get the top-5 predictions class names:

```py
>>> # Get imagenet class mappings
>>> url, filename = ("https://raw.githubusercontent.com/pytorch/hub/master/imagenet_classes.txt", "imagenet_classes.txt")
>>> urllib.request.urlretrieve(url, filename) 
>>> with open("imagenet_classes.txt", "r") as f:
...     categories = [s.strip() for s in f.readlines()]

>>> # Print top categories per image
>>> top5_prob, top5_catid = torch.topk(probabilities, 5)
>>> for i in range(top5_prob.size(0)):
...     print(categories[top5_catid[i]], top5_prob[i].item())
>>> # prints class names and probabilities like:
>>> # [('Samoyed', 0.6425196528434753), ('Pomeranian', 0.04062102362513542), ('keeshond', 0.03186424449086189), ('white wolf', 0.01739676296710968), ('Eskimo dog', 0.011717947199940681)]
```

Replace the model name with the variant you want to use, e.g. `mobilenetv2_100`. You can find the IDs in the model summaries at the top of this page.

To extract image features with this model, follow the [timm feature extraction examples](../feature_extraction), just change the name of the model you want to use.

## How do I finetune this model?

You can finetune any of the pre-trained models just by changing the classifier (the last layer).

```py
>>> model = timm.create_model('mobilenetv2_100', pretrained=True, num_classes=NUM_FINETUNE_CLASSES)
```
To finetune on your own dataset, you have to write a training loop or adapt [timm's training
script](https://github.com/rwightman/pytorch-image-models/blob/master/train.py) to use your dataset.

## How do I train this model?

You can follow the [timm recipe scripts](../scripts) for training a new model afresh.

## Citation

```BibTeX
@article{DBLP:journals/corr/abs-1801-04381,
  author    = {Mark Sandler and
               Andrew G. Howard and
               Menglong Zhu and
               Andrey Zhmoginov and
               Liang{-}Chieh Chen},
  title     = {Inverted Residuals and Linear Bottlenecks: Mobile Networks for Classification,
               Detection and Segmentation},
  journal   = {CoRR},
  volume    = {abs/1801.04381},
  year      = {2018},
  url       = {http://arxiv.org/abs/1801.04381},
  archivePrefix = {arXiv},
  eprint    = {1801.04381},
  timestamp = {Tue, 12 Jan 2021 15:30:06 +0100},
  biburl    = {https://dblp.org/rec/journals/corr/abs-1801-04381.bib},
  bibsource = {dblp computer science bibliography, https://dblp.org}
}
```

<!--
Type: model-index
Collections:
- Name: MobileNet V2
  Paper:
    Title: 'MobileNetV2: Inverted Residuals and Linear Bottlenecks'
    URL: https://paperswithcode.com/paper/mobilenetv2-inverted-residuals-and-linear
Models:
- Name: mobilenetv2_100
  In Collection: MobileNet V2
  Metadata:
    FLOPs: 401920448
    Parameters: 3500000
    File Size: 14202571
    Architecture:
    - 1x1 Convolution
    - Batch Normalization
    - Convolution
    - Depthwise Separable Convolution
    - Dropout
    - Inverted Residual Block
    - Max Pooling
    - ReLU6
    - Residual Connection
    - Softmax
    Tasks:
    - Image Classification
    Training Techniques:
    - RMSProp
    - Weight Decay
    Training Data:
    - ImageNet
    Training Resources: 16x GPUs
    ID: mobilenetv2_100
    LR: 0.045
    Crop Pct: '0.875'
    Momentum: 0.9
    Batch Size: 1536
    Image Size: '224'
    Weight Decay: 4.0e-05
    Interpolation: bicubic
    RMSProp Decay: 0.9
  Code: https://github.com/rwightman/pytorch-image-models/blob/9a25fdf3ad0414b4d66da443fe60ae0aa14edc84/timm/models/efficientnet.py#L955
  Weights: https://github.com/rwightman/pytorch-image-models/releases/download/v0.1-weights/mobilenetv2_100_ra-b33bc2c4.pth
  Results:
  - Task: Image Classification
    Dataset: ImageNet
    Metrics:
      Top 1 Accuracy: 72.95%
      Top 5 Accuracy: 91.0%
- Name: mobilenetv2_110d
  In Collection: MobileNet V2
  Metadata:
    FLOPs: 573958832
    Parameters: 4520000
    File Size: 18316431
    Architecture:
    - 1x1 Convolution
    - Batch Normalization
    - Convolution
    - Depthwise Separable Convolution
    - Dropout
    - Inverted Residual Block
    - Max Pooling
    - ReLU6
    - Residual Connection
    - Softmax
    Tasks:
    - Image Classification
    Training Techniques:
    - RMSProp
    - Weight Decay
    Training Data:
    - ImageNet
    Training Resources: 16x GPUs
    ID: mobilenetv2_110d
    LR: 0.045
    Crop Pct: '0.875'
    Momentum: 0.9
    Batch Size: 1536
    Image Size: '224'
    Weight Decay: 4.0e-05
    Interpolation: bicubic
    RMSProp Decay: 0.9
  Code: https://github.com/rwightman/pytorch-image-models/blob/9a25fdf3ad0414b4d66da443fe60ae0aa14edc84/timm/models/efficientnet.py#L969
  Weights: https://github.com/rwightman/pytorch-image-models/releases/download/v0.1-weights/mobilenetv2_110d_ra-77090ade.pth
  Results:
  - Task: Image Classification
    Dataset: ImageNet
    Metrics:
      Top 1 Accuracy: 75.05%
      Top 5 Accuracy: 92.19%
- Name: mobilenetv2_120d
  In Collection: MobileNet V2
  Metadata:
    FLOPs: 888510048
    Parameters: 5830000
    File Size: 23651121
    Architecture:
    - 1x1 Convolution
    - Batch Normalization
    - Convolution
    - Depthwise Separable Convolution
    - Dropout
    - Inverted Residual Block
    - Max Pooling
    - ReLU6
    - Residual Connection
    - Softmax
    Tasks:
    - Image Classification
    Training Techniques:
    - RMSProp
    - Weight Decay
    Training Data:
    - ImageNet
    Training Resources: 16x GPUs
    ID: mobilenetv2_120d
    LR: 0.045
    Crop Pct: '0.875'
    Momentum: 0.9
    Batch Size: 1536
    Image Size: '224'
    Weight Decay: 4.0e-05
    Interpolation: bicubic
    RMSProp Decay: 0.9
  Code: https://github.com/rwightman/pytorch-image-models/blob/9a25fdf3ad0414b4d66da443fe60ae0aa14edc84/timm/models/efficientnet.py#L977
  Weights: https://github.com/rwightman/pytorch-image-models/releases/download/v0.1-weights/mobilenetv2_120d_ra-5987e2ed.pth
  Results:
  - Task: Image Classification
    Dataset: ImageNet
    Metrics:
      Top 1 Accuracy: 77.28%
      Top 5 Accuracy: 93.51%
- Name: mobilenetv2_140
  In Collection: MobileNet V2
  Metadata:
    FLOPs: 770196784
    Parameters: 6110000
    File Size: 24673555
    Architecture:
    - 1x1 Convolution
    - Batch Normalization
    - Convolution
    - Depthwise Separable Convolution
    - Dropout
    - Inverted Residual Block
    - Max Pooling
    - ReLU6
    - Residual Connection
    - Softmax
    Tasks:
    - Image Classification
    Training Techniques:
    - RMSProp
    - Weight Decay
    Training Data:
    - ImageNet
    Training Resources: 16x GPUs
    ID: mobilenetv2_140
    LR: 0.045
    Crop Pct: '0.875'
    Momentum: 0.9
    Batch Size: 1536
    Image Size: '224'
    Weight Decay: 4.0e-05
    Interpolation: bicubic
    RMSProp Decay: 0.9
  Code: https://github.com/rwightman/pytorch-image-models/blob/9a25fdf3ad0414b4d66da443fe60ae0aa14edc84/timm/models/efficientnet.py#L962
  Weights: https://github.com/rwightman/pytorch-image-models/releases/download/v0.1-weights/mobilenetv2_140_ra-21a4e913.pth
  Results:
  - Task: Image Classification
    Dataset: ImageNet
    Metrics:
      Top 1 Accuracy: 76.51%
      Top 5 Accuracy: 93.0%
-->