Stabilizing Generative Adversarial Networks: A Look at WGAN, GPGAN, and SNGAN

Yaniv Noema
imagescv
7 min readJan 13, 2023

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Generative Adversarial Networks (GANs) have revolutionized the field of generative models, allowing for the generation of new, synthetic data that is similar to a given dataset. However, GANs can be difficult to train and often suffer from instability during the training process. To address these problems, several variants of GANs have been proposed, including Wasserstein Generative Adversarial Networks (WGANs), Gradient Penalty Generative Adversarial Networks (GPGANs), and Spectral Normalization Generative Adversarial Networks (SNGANs).

WGANs, introduced in 2017 by Martin Arjovsky, Soumith Chintala and Léon Bottou, use the Wasserstein distance as the objective function, rather than the Jenson-Shannon divergence used in traditional GANs. This objective function is more stable and produces less noisy gradients during training, which can lead to better performance. Additionally, WGANs use a weight clipping technique to enforce the Lipschitz constraint of the discriminator network, which helps to prevent the generator network from collapsing to a single mode.

GPGANs, introduced in 2017 by Tero Karras, Timo Aila, Samuli Laine, and Jaakko Lehtinen, propose an approach to enforce the Lipschitz constraint of the discriminator network, by adding a gradient penalty term to the objective function. This method can be used with any objective function, and has been shown to be more stable and effective than traditional GANs and WGANs.

SNGANs, introduced in 2018 by Takeru Miyato, Toshiki Kataoka, Masanori Koyama, and Yuichi Yoshida, stabilize the training process of GANs by normalizing the weights of the discriminator network by their spectral norm. By doing this, SNGANs can help to prevent the collapse of the generator network and improve the quality of the generated images.

Each of these variants of GANs has its own advantages and can be used in different scenarios. WGANs are known for their stability during the training process and good performance in semi-supervised learning. GPGANs can be used with any objective function and it’s considered as a powerful and stable alternative to traditional GANs and WGANs. SNGANs are known for their ability to improve the stability and quality of GANs, and they have been used to generate high-quality images in various domains.

GAN — Generative Adversarial Networks

GANs (Generative Adversarial Networks) consists of two neural networks: a generator network and a discriminator network. The generator network is trained to generate new data that is similar to the given dataset, while the discriminator network is trained to distinguish between real data and synthetic data. GANs are trained using a two-player minimax game, where the generator network tries to generate samples that will fool the discriminator network, and the discriminator network tries to correctly identify real and fake samples.

WGAN — Wasserstein Generative Adversarial Networks

The main difference between GANs and WGANs is the use of the Wasserstein distance as the objective function. In GANs, the objective function is the Jenson-Shannon divergence, which measures the difference between the real data distribution and the generated data distribution. However, this objective function can be difficult to optimize and can lead to instability during training.

The Wasserstein distance, on the other hand, is a more stable and effective objective function. It measures the Earth-Mover (EM) distance between the real data distribution and the generated data distribution, which is a more meaningful measure of the similarity between the two distributions. Additionally, the Wasserstein distance is more smooth and has less local optima which makes the training process more stable.

Another important difference between GANs and WGANs is the use of weight clipping to enforce the Lipschitz constraint of the discriminator network. In GANs, the discriminator network can become too powerful, which can lead to the generator network collapsing to a single mode. To prevent this, WGANs use a weight clipping technique to enforce the Lipschitz constraint of the discriminator network, which helps to keep the generator network diverse and prevent it from collapsing to a single mode.

One of the most important advantages of WGANs is that it’s more stable during the training process and it’s less sensitive to the choice of hyperparameters. This makes it more robust to different datasets and architectures and allows for more efficient training. Additionally, WGANs can also be used in semi-supervised learning settings, where a limited amount of labeled data is available.

Wasserstein Generative Adversarial Networks (WGANs) was first introduced in a paper by Martin Arjovsky, Soumith Chintala, and Léon Bottou in 2017, titled “Wasserstein GAN”.

In this paper, the authors proposed a modification to the traditional GAN objective function, which uses the Wasserstein distance instead of the Jenson-Shannon divergence. They also introduced a weight clipping technique to enforce the Lipschitz constraint of the discriminator network, which helps to prevent the generator network from collapsing to a single mode.

This work has been very influential in the field of generative models, and WGANs have been widely used and improved since their initial introduction. WGANs have been shown to be more stable and effective than traditional GANs, and have been used to generate high-quality images and solve problems in semi-supervised learning.

The paper can be found here: https://arxiv.org/abs/1701.07875

This is a widely cited paper in the field of generative models, and it is considered a fundamental reference for understanding WGANs and their development.

GPGAN — Gradient Penalty Generative Adversarial Networks

GPGANs propose an approach to enforce the Lipschitz constraint of the discriminator network, instead of weight clipping used in WGANs. This is done by adding a gradient penalty term to the objective function, which penalizes the discriminator network for producing large gradients. This helps to prevent the generator network from collapsing to a single mode, and can lead to better performance.

The main advantage of GPGANs is that they can be used with any objective function, not only Wasserstein distance. Additionally, the gradient penalty term can be interpreted as a form of implicit regularization, which can help to improve the generalization of the model.

GPGANs have been used to generate high-quality images, and have been shown to be more stable and effective than traditional GANs and WGANs.

Gradient Penalty Generative Adversarial Networks (GPGANs) was first introduced in a paper by Tero Karras, Timo Aila, Samuli Laine, and Jaakko Lehtinen in 2017, titled “Progressive Growing of GANs for Improved Quality, Stability, and Variation”.

In this paper, the authors proposed a new approach to enforce the Lipschitz constraint of the discriminator network, by adding a gradient penalty term to the objective function. This method can be used with any objective function, and has been shown to be more stable and effective than traditional GANs and WGANs.

This work has been very influential in the field of generative models, and GPGANs have been widely used and improved since their initial introduction. GPGANs have been used to generate high-quality images and solve problems in semi-supervised learning.

The paper can be found here: https://research.nvidia.com/publication/2017-10_Progressive-Growing-of

This is a widely cited paper in the field of generative models, and it is considered as a fundamental reference for understanding the GPGANs and it’s development.

SNGAN-Spectral normalization GAN

Spectral normalization GAN (SNGAN) is a variant of Generative Adversarial Networks (GANs) that aims to stabilize the training process and improve the quality of generated images. The main idea behind SNGAN is to normalize the weights of the discriminator network by their spectral norm, which is the largest singular value of the weight matrix.

The motivation for this is that the discriminator network of a GAN can become too powerful, which can lead to the generator network collapsing to a single mode. By normalizing the weights of the discriminator network by their spectral norm, SNGANs can help to prevent this collapse and improve the quality of the generated images.

The normalization of the weight matrix is done by dividing the weight matrix by its spectral norm, which is computed using the singular value decomposition (SVD) of the weight matrix. This is done after each update of the weights, and it helps to ensure that the weights of the discriminator network are within a certain range, which in turn helps to stabilize the training process.

SNGANs have been shown to improve the stability and quality of GANs, and they have been used to generate high-quality images in various domains. They also have been used in conditional GANs to improve the quality of the generated images. Additionally, SNGANs can be combined with other techniques, such as regularization and early stopping, to further improve performance.

Spectral normalization GAN (SNGAN) was first introduced in a paper by Takeru Miyato, Toshiki Kataoka, Masanori Koyama and Yuichi Yoshida in 2018, titled “Spectral Normalization for Generative Adversarial Networks”.

In this paper, the authors proposed a new technique to stabilize the training process of GANs by normalizing the weights of the discriminator network by their spectral norm. They showed that this technique can help to prevent the collapse of the generator network and improve the quality of the generated images.

This work has been very influential in the field of generative models, and SNGANs have been widely used and improved since their initial introduction. They have been used to generate high-quality images in various domains, and have been combined with other techniques to further improve the performance.

The paper can be found here: https://arxiv.org/abs/1802.05957

WGAN, GPGAN, and SNGAN are all variants of Generative Adversarial Networks (GANs), a popular deep learning architecture for generative tasks such as image synthesis. WGAN, or Wasserstein GAN, addresses the issue of stability in GANs training by using a different loss function called the Wasserstein distance. GPGAN, or Gradient Penalty GAN, is a modification of WGAN that enforces the Lipschitz constraint to improve the stability and quality of the generated images. SNGAN, or Spectral Normalization GAN, is another variant of GANs that utilizes a technique called spectral normalization to stabilize the training process and improve the quality of the generated images. All three of these variants have been shown to improve the performance of GANs in various generative task

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Yaniv Noema
imagescv

I’m a computer vision 💻👁️engineer who likes to write about artificial intelligence, machine learning, image processing, and Python🐍