Relativistic GAN

Code to replicate all analyses from the paper The relativistic discriminator: a key element missing from standard GAN

Now accepted at ICLR 2019: https://openreview.net/forum?id=S1erHoR5t7&noteId=S1erHoR5t7 😸

Note: Newer version of pretty much the same code, with extra features is on here: https://github.com/AlexiaJM/relativistic-f-divergences

Discussion at https://ajolicoeur.wordpress.com/RelativisticGAN.

To add Relativism to your own GANs in PyTorch, you can use pieces of code from this:

### Assuming this gets you real and fake data

# Real data
x.data.resize_as_(images).copy_(images)
y_pred = D(x)
y.data.resize_(current_batch_size).fill_(1)

# Fake data
z.data.resize_(current_batch_size, param.z_size, 1, 1).normal_(0, 1)
fake = G(z)
x_fake.data.resize_(fake.data.size()).copy_(fake.data)
y_pred_fake = D(x_fake.detach()) # For generator step do not detach
y2.data.resize_(current_batch_size).fill_(0)


### Standard GAN (non-saturating)

# Use torch.nn.Sigmoid() as last layer in discriminator

criterion = torch.nn.BCELoss()

# Real data Discriminator loss
errD_real = criterion(y_pred, y)
errD_real.backward()

# Fake data Discriminator loss
errD_fake = criterion(y_pred_fake, y2)
errD_fake.backward()

# Generator loss
errG = criterion(y_pred_fake, y)
errG.backward()


### Relativistic Standard GAN

# No sigmoid activation in last layer of discriminator because BCEWithLogitsLoss() already adds it

BCE_stable = torch.nn.BCEWithLogitsLoss()

# Discriminator loss
errD = BCE_stable(y_pred - y_pred_fake, y)
errD.backward()

# Generator loss (You may want to resample again from real and fake data)
errG = BCE_stable(y_pred_fake - y_pred, y)
errG.backward()


### Relativistic average Standard GAN

# No sigmoid activation in last layer of discriminator because BCEWithLogitsLoss() already adds it

BCE_stable = torch.nn.BCEWithLogitsLoss()

# Discriminator loss
errD = ((BCE_stable(y_pred - torch.mean(y_pred_fake), y) + BCE_stable(y_pred_fake - torch.mean(y_pred), y2))/2
errD.backward()

# Generator loss (You may want to resample again from real and fake data)
errG = ((BCE_stable(y_pred - torch.mean(y_pred_fake), y2) + BCE_stable(y_pred_fake - torch.mean(y_pred), y))/2
errG.backward()


### Relativistic average LSGAN

# No activation in discriminator

# Discriminator loss
errD = (torch.mean((y_pred - torch.mean(y_pred_fake) - y) ** 2) + torch.mean((y_pred_fake - torch.mean(y_pred) + y) ** 2))/2
errD.backward()

# Generator loss (You may want to resample again from real and fake data)
errG = (torch.mean((y_pred - torch.mean(y_pred_fake) + y) ** 2) + torch.mean((y_pred_fake - torch.mean(y_pred) - y) ** 2))/2
errG.backward()


### Relativistic average HingeGAN

# No activation in discriminator

# Discriminator loss
errD = (torch.mean(torch.nn.ReLU()(1.0 - (y_pred - torch.mean(y_pred_fake)))) + torch.mean(torch.nn.ReLU()(1.0 + (y_pred_fake - torch.mean(y_pred)))))/2
errD.backward()
 
# Generator loss  (You may want to resample again from real and fake data)
errG = (torch.mean(torch.nn.ReLU()(1.0 + (y_pred - torch.mean(y_pred_fake)))) + torch.mean(torch.nn.ReLU()(1.0 - (y_pred_fake - torch.mean(y_pred)))))/2
errG.backward()

To replicate analyses from the paper

Needed

Python 3.6
Pytorch (Latest from source)
Tensorflow (Latest from source, needed to get FID)
Cat Dataset (http://academictorrents.com/details/c501571c29d16d7f41d159d699d0e7fb37092cbd)

To do beforehand

Change all folders locations in fid_script.sh, stable.sh, unstable.sh, GAN_losses_iter.py, GAN_losses_iter_PAC.py
Make sure that there are existing folders at the locations you used
If you want to use the CAT dataset
- Run setting_up_script.sh in same folder as preprocess_cat_dataset.py and your CAT dataset (open and run manually)
- Move cats folder to your favorite place
- mv cats_bigger_than_64x64 "your_input_folder_64x64"
- mv cats_bigger_than_128x128 "your_input_folder_128x128"
- mv cats_bigger_than_256x256 "your_input_folder_256x256"

To run

To run models
- Use GAN_losses_iter.py (Version you probably will want to use)
- Use GAN_losses_iter_PAC.py (Version with PacGAN-2, to use when there is severe mode collapse only)
To Replicate
- Open stable.sh and run the lines you want
- Open unstable.sh and run the lines you want

Notes

If you just want to generate pictures and you do not care about the Fréchet Inception Distance (FID), you do not need to download Tensorflow.

If you don't want to generate cat, nor get the FID, you can skip ahead and focus entirely on "GAN_losses_iter.py".

Although I always used the same seed (seed = 1), keep in mind that your results may be sightly different. Neural networks are notoriously difficult to perfectly replicate. CUDNN introduce some randomness and slight changes in the code have been made over time. Tensorflow FIDs values may vary a little, but they should still be very stable since the sample size used for the calculations is large. Also, the original code to construct RaSGAN and RaLSGAN used "torch.mean(y_pred_fake) - y_pred" instead of "y_pred_fake - torch.mean(y_pred)" in the second terms of the equation with the expectation over fake data; results are comparable.

Citation

If you find this code useful please cite us in your work.

Paper introducing Relativistic GANs (https://github.com/AlexiaJM/RelativisticGAN):

@article{jolicoeur2018relativistic,
  title={The relativistic discriminator: a key element missing from standard GAN},
  author={Jolicoeur-Martineau, Alexia},
  journal={arXiv preprint arXiv:1807.00734},
  year={2018}
}

Paper providing the mathematical fundation for Relativistic GANs (https://github.com/AlexiaJM/relativistic-f-divergences)

@article{jolicoeur2018rfdiv,
  title={On Relativistic f-Divergences},
  author={Jolicoeur-Martineau, Alexia},
  journal={arXiv preprint arXiv:1901.02474},
  year={2019}
}