CapsNet-Keras

A Keras implementation of CapsNet in the paper:
Sara Sabour, Nicholas Frosst, Geoffrey E Hinton. Dynamic Routing Between Capsules. NIPS 2017
The current average test error = 0.34% and best test error = 0.30%.

Differences with the paper:
- We use the learning rate decay with decay factor = 0.9 and step = 1 epoch,
while the paper did not give the detailed parameters (or they didn't use it?). - We only report the test errors after 50 epochs training.
In the paper, I suppose they trained for 1250 epochs according to Figure A.1? Sounds crazy, maybe I misunderstood. - We use MSE (mean squared error) as the reconstruction loss and the coefficient for the loss is lam_recon=0.0005*784=0.392.
This should be equivalent with using SSE (sum squared error) and lam_recon=0.0005 as in the paper.

TODO - Conduct experiments on other datasets. - Explore interesting characteristics of CapsuleNet.

Contacts - Your contributions to the repo are always welcome. Open an issue or contact me with E-mail guoxifeng1990@163.com or WeChat wenlong-guo.

Usage

Step 1. Install Keras>=2.0.7 with TensorFlow>=1.2 backend.

pip install tensorflow-gpu
pip install keras

Step 2. Clone this repository to local.

git clone https://github.com/XifengGuo/CapsNet-Keras.git capsnet-keras
cd capsnet-keras

Step 3. Train a CapsNet on MNIST

Training with default settings:

python capsulenet.py

More detailed usage run for help:

python capsulenet.py -h

Step 4. Test a pre-trained CapsNet model

Suppose you have trained a model using the above command, then the trained model will be saved to result/trained_model.h5. Now just launch the following command to get test results.

$ python capsulenet.py -t -w result/trained_model.h5

It will output the testing accuracy and show the reconstructed images. The testing data is same as the validation data. It will be easy to test on new data, just change the code as you want.

You can also just download a model I trained from https://pan.baidu.com/s/1sldqQo1 or https://drive.google.com/open?id=1A7pRxH7iWzYZekzr-O0nrwqdUUpUpkik

Step 5. Train on multi gpus

This requires Keras>=2.0.9. After updating Keras:

python capsulenet-multi-gpu.py --gpus 2

It will automatically train on multi gpus for 50 epochs and then output the performance on test dataset. But during training, no validation accuracy is reported.

Results

Test Errors

CapsNet classification test error on MNIST. Average and standard deviation results are reported by 3 trials. The results can be reproduced by launching the following commands.
``` python capsulenet.py --routings 1 --lam_recon 0.0 #CapsNet-v1
python capsulenet.py --routings 1 --lam_recon 0.392 #CapsNet-v2 python capsulenet.py --routings 3 --lam_recon 0.0 #CapsNet-v3 python capsulenet.py --routings 3 --lam_recon 0.392 #CapsNet-v4

   Method     |   Routing   |   Reconstruction  |  MNIST (%)  |  *Paper*    
   :---------|:------:|:---:|:----:|:----:
   Baseline |  -- | -- | --             | *0.39* 
   CapsNet-v1 |  1 | no | 0.39 (0.024)  | *0.34 (0.032)* 
   CapsNet-v2  |  1 | yes | 0.36 (0.009)| *0.29 (0.011)*
   CapsNet-v3 |  3 | no | 0.40 (0.016)  | *0.35 (0.036)*
   CapsNet-v4  |  3 | yes| 0.34 (0.016) | *0.25 (0.005)*

Losses and accuracies:   
![](result/log.png)


#### Training Speed 

About `100s / epoch` on a single GTX 1070 GPU.   
About `80s / epoch` on a single GTX 1080Ti GPU.   
About `55s / epoch` on two GTX 1080Ti GPU by using `capsulenet-multi-gpu.py`.      

#### Reconstruction result  

The result of CapsNet-v4 by launching

python capsulenet.py -t -w result/trained_model.h5

Digits at top 5 rows are real images from MNIST and 
digits at bottom are corresponding reconstructed images.

![](result/real_and_recon.png)

#### Manipulate latent code

python capsulenet.py -t --digit 5 -w result/trained_model.h5 `` For each digit, the *i*th row corresponds to the *i*th dimension of the capsule, and columns from left to right correspond to adding[-0.25, -0.2, -0.15, -0.1, -0.05, 0, 0.05, 0.1, 0.15, 0.2, 0.25]` to the value of one dimension of the capsule.

As we can see, each dimension has caught some characteristics of a digit. The same dimension of different digit capsules may represent different characteristics. This is because that different digits are reconstructed from different feature vectors (digit capsules). These vectors are mutually independent during reconstruction.