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SNGAN

Unofficial implementation of SNGAN in PyTorch

Spectral Normalization for Generative Adversarial Networks
https://arxiv.org/abs/1802.05957

Reimplementation

Experiments mostly based on the paper.

CIFAR-10 (Standard CNN)

Fixed conditions

  • Generator: Standard CNN
  • Discriminator : Standard CNN
  • n_epochs : 321 (approx. 50k G updates)
  • n_dis = 5
  • Adam parameters : lr=0.0002, beta1=0.0, beta2 = 0.9
  • Using training data (10 classes, 50k images)

Changing conditions

Case 0 1 2 3
Loss Cross Entropy Hinge Cross Entropy Hinge
Conditional FALSE FALSE TRUE TRUE
Inception Score 5.844 6.077 6.094 5.821

Incpetion score log

Sampling and Interpolation

Case 0

IS = 5.844

Case 1

IS = 6.077

Case 2

IS = 6.094 (Best)

Case 3

IS = 5.821

CIFAR-10 (ResNet)

Fixed conditions

  • Generator: ResNet (32x32)
  • Discriminator : ResNet (32x32)
  • n_epochs : 321 (approx. 50k G updates)
  • n_dis = 5
  • Adam parameters : lr=0.0002, beta1=0.5, beta2 = 0.9
  • Using training data (10 classes, 50k images)

Note: beta1=0.0 failed to converge (seems to stuck into saddle points).

Changing conditions

Case 0 1 2 3
Loss Cross Entropy Hinge Cross Entropy Hinge
Conditional FALSE FALSE TRUE TRUE
Inception Score 3.916 5.962 3.908 5.900

Hinge loss performs well.

Incpetion score log

Sampling and Interpolation

Case 0

IS = 3.916

Case 1

IS = 5.962 (Best)

Case 2

IS = 3.908

Case 3

IS = 5.900

STL-10 (Standard)

Fixed conditions

  • Generator: Standard CNN (48x48)
  • Discriminator : Standard CNN (48x48)
  • n_epochs : 1301 (approx. 53k G updates)
  • n_dis = 5
  • Hinge loss
  • Adam parameters : lr=0.0002, beta2 = 0.9
  • Using training + test data (10 classes, 13k (5k + 8k) images)

Changing conditions

Case 0 1 2 3
Conditional FALSE FALSE TRUE TRUE
Beta1 0.5 0 0.5 0
IS 5.932 6.058 6.157 5.813

GANs in STL-10 is bit difficult than CIFAR-10 (Too sensitive to hyper parameters.).

Incpetion score log

Sampling and Interpolation

Case 0

IS = 5.932

Case 1

IS = 6.058

Case 2

IS = 6.157 (Best)

Case 3

IS = 5.813

STL-10 (Res Net)

Fixed conditions

  • Generator: Res Net (48x48)
  • Discriminator : Res Net (48x48)
  • n_epochs : 1301 if n_dis=5, 261 if n_dis=1 (approx. 53k G updates)
  • Hinge loss
  • Adam parameters : lr=0.0002, beta1=0.5, beta2 = 0.9
  • Using training + test data (10 classes, 13k (5k + 8k) images)

Changing conditions

Case 0 1 2 3 4 5 6 7
Conditional FALSE TRUE FALSE TRUE FALSE TRUE FALSE TRUE
N dis update 5 5 1 1 5 5 1 1
D last ch 512 512 512 512 1024 1024 1024 1024
IS 5.795 7.136 3.421 3.883 6.538 7.314 3.444 3.653

Trainings in n_dis = 1 are very difficult. Some additional experiments are written in appendix.

Incpetion score log

Sampling and Interpolation

Case 0

IS = 5.795

Case 1

IS = 7.136 (2nd)

Case 2

IS = 3.421

Case 3

IS = 3.883

Case 4

IS = 6.538

Case 5

IS = 7.314 (Best)

Case 6

IS = 3.444

Case 7

IS = 3.653

Additional Implementation

Experiments with datasets that were not written in the paper.

AnimeFace Character Dataset

http://www.nurs.or.jp/~nagadomi/animeface-character-dataset/

14490 images with 176 classes. Much less images per class than CIFAR-10 and STL-10.

Fixed conditions

  • Generator: Res Net (96x96)
  • Discriminator : Res Net (96x96)
  • n_epochs : 1301 (approx. 53k G updates)
  • Hinge loss, n_dis = 5
  • Adam parameters : lr=0.0002, beta1=0.5, beta2 = 0.9

The network architecture is based on a 128x128 paper and the resolution is changed to 96x96 (dense : 4x4x1024 -> 3x3x1024).

Changing conditions

  • Case 0 = unconditional
  • Case 1 = conditional

Inception score was not measured. Because the domain is different and pre-trained inception is useless.

Sampling and interpolation uses the final epoch model.

Case 0 (Un-conditional)

Case 1 (Conditional)

Oxford Flower Dataset

http://www.robots.ox.ac.uk/~vgg/data/flowers/

8189 images with 102 classes. Much less images per class than CIFAR-10 and STL-10.

Changing conditions

  • Case 0 = unconditional
  • Case 1 = conditional

Sampling and interpolation uses the final epoch model.

Case 0 (Un-conditional)

Case 1 (Conditional)

It seems that the generation of flowers is still difficult (outlines are too complicated).

Appendix (More expertiments on STL-10)

The goal is to train with n_dis = 1, but there are many negative results

STL-10 (Post-act Res Net / Standard CNN)

Fixed conditions

  • Generator: Post-act Res Net (48x48)
  • Discriminator : Standard CNN (48x48)
  • Generator leraning rate : 0.0002

For generator, ResNet implementation in the paper was pre-act ResNet (BN / SN-> ReLU-> Conv), but change this to post-act (Conv-> BN / SN-> ReLU).

For discriminator, simply used Standard CNN to reduce computation.

Changing conditions

Case 0 1 2 3 4 5 6 7 8 9
N dis 5 5 1 1 1 1 1 1 1 1
Beta2 in Adam 0.9 0.9 0.9 0.9 0.999 0.999 0.999 0.999 0.999 0.999
Leaky relu slope in D 0.1 0.1 0.1 0.1 0.1 0.1 0.2 0.2 0.2 0.2
D learning rate 0.0002 0.0002 0.0002 0.0002 0.0002 0.0002 0.0002 0.0002 0.001 0.001
Conditional FALSE TRUE FALSE TRUE FALSE TRUE FALSE TRUE FALSE TRUE
Inception Score 6.419 5.663 1.285 2.634 2.342 2.447 2.499 2.722 2.355 2.544
  • case 8, 9 = inbalanced learning rate, G:0.0002, D=0.001
Case Condition IS
0 uncoditional n_dis = 5 6.419
2 uncoditional n_dis = 1 1.285
4 + beta2 = 0.999 2.342
6 + lrelu slope = 0.2 2.499
8 + lr_d = 0.001 2.355
Case Condition IS
1 coditional n_dis = 5 5.663
3 coditional n_dis = 1 2.634
5 + beta2 = 0.999 2.447
7 + lrelu slope = 0.2 2.722
9 + lr_d = 0.001 2.544

It's not good at training with n_dis = 1. Other tunings are also subtle.

Incpetion score log

Sampling and Interpolation

Only a part is described. The rest, please refer to them in the repository folder.

Case 0

IS = 6.419

Case 1

IS = 5.663

Case 6

IS = 2.499

Case 7

IS = 2.722

Why n_dis=1 don't work ?

These are loss plot of case 0, 6 (both uncoditional). Case 0(n_dis=5) works well, but case 6(n_dis=1) does not.

As you can see, the loss of D in case 6 has hardly decreased.　If it doesn’t work, G is too strong to learn nothing. This is due to set Spectral Norm in D.

Therefore, n_dis=5 which increases D update is easier to work.

STL-10 (Post-act Res Net / Post-act Res Net)

Fixed conditions

  • Generator: Post-act Res Net (48x48)
  • Discriminator : Post-act Res Net (48x48, initial ch changeable)
  • Generator leraning rate : 0.0002
  • n_epochs : 1301 if n_dis=5, 261 if n_dis=1 (approx. 53k G updates)
  • Adam parameters : beta1=0.5, beta2 = 0.999

Changing conditions

Case 0 1 2 3 4 5
D initial ch 16 16 32 32 64 64
N dis 5 1 5 1 5 1
Inception Score 4.621 3.004 4.789 4.365 4.990 4.341

Incpetion score log

Case 0

IS = 4.621

Case 2

IS = 4.789

Case 4

IS = 4.990

STL-10 (ResNet in the paper / some changed Res Net)

Fixed conditions

  • Generator: Res Net in the paper (48x48)
  • Generator leraning rate : 0.0002
  • n_dis : 5
  • n_epochs : 1301
  • All conditional
  • Adam parameters : lr=0.0002, beta1=0.5

Changing conditions

Case 0 1 2 3
Beta2 in Adam 0.9 0.999 0.9 0.999
D architecture postact postact strided resnet strided resnet
Inception Score 5.955 5.708 6.906 7.222

Strided ResNet is the original ResNet D with stride conv at the beginning. This reduces the amount of computation.

Incpetion score log

Case 0

IS = 5.955

Case 1

IS = 5.708

Case 2

IS = 6.906

Case 3

IS = 7.222 (Best)

Discussion

Larger D model will improve IS slightly. But in any case, I could not find a way to generate clearly with n_dis = 1.

In image classification, the diffrence between pre-act and post-act is slightly. But in gan, the difference seems to be quite large.