dogsVScats

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Kaggle: Dogs vs Cats Kernel Redux Edition

This repository consists a solution for the Cats vs Dogs classification challenge on Kaggle.
This solution scored a logloss of 0.04973 (#60 / 1314 teams). Top score was 0.03303 (#1).

This repository also contains links to my best and second best CNN models below.

Features

• Best model (download Keras model here) achieves accuracy of 99.6% on unseen data.
• Ensemble of the best model with the second best (download Keras model here) achieves 99.8% accuracy on unseen data. Predictions of the two models are simply averaged.
• The performance is a result of finetuning pretrained models (Resnet-50 & Inception v3 respectively).
• Used several data augmentation techniques -- channel jittering, blurs, brightness-contrast shifts, rotation, zooms, horizontal-vertical shifts and flips.

What worked

• Using ELU activations or BatchNorm + PReLu
• Using Dropout on Dense Layers with Data Augmentation
• Using Pretrained models works like magic! :pray:
• Training small models (10 layers max) from scratch for 25000 images plateaus at double the logloss than when using pretrained models, in my case.
• Using larger image sizes improves accuracy till 350 x 350
• Ensembling different models gives a very good accuracy boost. Higher the difference (different image sizes, different architectures etc.), better is the advantage of the ensemble.
• Using the trained model to detect mistakes in the training and validation data!

What didn't turn out as expected

• Going beyond the plateau logloss when training from scratch was almost impossible; probably because the lower layers did not learn good enough representations with limited data.
• Trying to finetune last conv block of the pretrained models leads to overfitting in my case.
• Using Dropout in conv layers leads to poor accuracy
• Training even small models without BatchNorm and only using plain ReLU activations takes a huge amount of time.
• Mean subtraction + Dividing by Standard Deviation speeds up training

Using the trained models

Download the trained models:
ResNet50 finetuned (best model) (Input shape: 350 x 350 x 3)
InceptionV3 finetuned (second best) (Input shape: 299 x 299 x 3)

from keras.models import load_model
model = load_model('bestvalyet.h5')  # weights path.

Both the models use Tensorflow dimension ordering.