Pytorch-Image-Classification

A simple demo of image classification using pytorch. Here, we use a custom dataset containing 43956 images belonging to 11 classes for training(and validation). Also, we compare three different approaches for training viz. training from scratch, finetuning the convnet and convnet as a feature extractor, with the help of pretrained pytorch models. The models used include: VGG11, Resnet18 and MobilenetV2.

Dependencies

• Python3, Scikit-learn
• Pytorch, PIL
• Torchsummary, Tensorboard

pip install torchsummary # keras-summary
pip install tensorboard  # tensoflow-logging

NB: Update the libraries to their latest versions before training.

How to run

Download and extract training dataset: imds_small

Run the following scripts for training and/or testing

python train.py # For training the model [--mode=finetune/transfer/scratch]
python test.py test # For testing the model on sample images
python eval.py eval_ds # For evaluating the model on new dataset

Training results

	Accuracy	Size	Training Time	Training Mode
VGG11	96.73	515.3 MB	900 mins	scratch
Resnet18	99.85	44.8 MB	42 mins	finetune
MobilenetV2	97.72	9.2 MB	32 mins	transfer

Batch size: 64, GPU: Tesla K80

Both Resnet18 and MobilenetV2(transfer leraning) were trained for 10 epochs; whereas VGG11(training from scratch) was trained for 100 epochs.

Training graphs

Resnet18:-

Finetuning the pretrained resnet18 model.

Mobilenetv2:-

Mobilenetv2 as a fixed feature extractor.

Sample outputs

Sample classification results

Evaluation

Here we evaluate the performance of our best model - resnet18 on a new data-set containing 50 images per class.

Accuracy of the network on the 550 test images: 99.09%

Confusion Matrix

[[50  0  0  0  0  0  0  0  0  0  0]
 [ 0 50  0  0  0  0  0  0  0  0  0]
 [ 0  0 50  0  0  0  0  0  0  0  0]
 [ 0  0  0 50  0  0  0  0  0  0  0]
 [ 0  0  0  0 50  0  0  0  0  0  0]
 [ 0  4  0  0  0 46  0  0  0  0  0]
 [ 0  1  0  0  0  0 49  0  0  0  0]
 [ 0  0  0  0  0  0  0 50  0  0  0]
 [ 0  0  0  0  0  0  0  0 50  0  0]
 [ 0  0  0  0  0  0  0  0  0 50  0]
 [ 0  0  0  0  0  0  0  0  0  0 50]] 

Per class accuracy

Accuracy of class    apple : 100.00 %
Accuracy of class atm card : 100.00 %
Accuracy of class   camera : 100.00 %
Accuracy of class      cat : 100.00 %
Accuracy of class   banana : 100.00 %
Accuracy of class   bangle : 92.00 %
Accuracy of class  battery : 98.00 %
Accuracy of class   bottle : 100.00 %
Accuracy of class    broom : 100.00 %
Accuracy of class     bulb : 100.00 %
Accuracy of class calender : 100.00 %

Observations

1. In transfer learning, if your custom dataset is similar to the pretrained model's training dataset, then you can easily acheive very high accuracy(>90) with very few training epochs(<10).
2. The VGG11 network with 128M params has a very large size i.e 0.5 GB, compared to other models like Resnet18(40 MB) with 11M params and MobilnetV2(10 MB), with 2M parameters.
3. In comparison to other models the VGG network is computationally inefficient, since they use large convolutional layer widths. Also, multiple fully connected layers at the end of the network drastically increases the number of paramters and memory requirements.
4. The MobilenetV2 with depthwise convolution and inverted residuals has fewer operations(faster) and less parameters(smaller) compared to other models. Additionally, it has a tunable depth-multiplier parameter(speed-accuracy) for application specific requirements.
5. Adjusting parameters like batch size, number of workers, pin_memory, non_blocking etc. may help you reduce training time, especially if you have a big dataset and a high-end machine(hardware).

Todo

1. Experiments with different learning-rate and optimizers.
2. Converting and optimizing pytorch models for mobile deployment.

License

This project is licensed under the terms of the MIT license.

Versioning

Version 1.0

Authors

Anil Sathyan

Citations

If you find this code useful in your research, please consider citing:

Acknowledgments

• "https://pytorch.org/tutorials/beginner/transfer_learning_tutorial.html"
• "https://pytorch.org/tutorials/beginner/finetuning_torchvision_models_tutorial.html"
• "https://www.learnopencv.com/image-classification-using-transfer-learning-in-pytorch/"
• "https://towardsdatascience.com/https-medium-com-dinber19-take-a-deeper-look-at-your-pytorch-model-with-the-new-tensorboard-built-in-513969cf6a72"
• "https://www.aiworkbox.com/lessons/how-to-define-a-convolutional-layer-in-pytorch#lesson-transcript-section"
• "https://medium.com/udacity-pytorch-challengers/ideas-on-how-to-fine-tune-a-pre-trained-model-in-pytorch-184c47185a20"
• "https://github.com/FrancescoSaverioZuppichini/Pytorch-how-and-when-to-use-Module-Sequential-ModuleList-and-ModuleDict"
• "https://www.kaggle.com/c/understanding_cloud_organization/discussion/112582"
• "https://stackoverflow.com/questions/53290306/confusion-matrix-and-test-accuracy-for-pytorch-transfer-learning-tutorial"