Ensembling Off-the-shelf Models for GAN Training

Nupur Kumari1    Richard Zhang2    Eli Shechtman2    Jun-Yan Zhu1

1CMU    2Adobe   

Paper | GitHub | YouTube | Slides

Abstract

The advent of large-scale training has produced a cornucopia of powerful visual recognition models. However, generative models, such as GANs, have traditionally been trained from scratch in an unsupervised manner. Can the collective "knowledge" from a large bank of pretrained vision models be leveraged to improve GAN training? If so, with so many models to choose from, which one(s) should be selected, and in what manner are they most effective? We find that pretrained computer vision models can significantly improve performance when used in an ensemble of discriminators. Notably, the particular subset of selected models greatly affects performance. We propose an effective selection mechanism, by probing the linear separability between real and fake samples in pretrained model embeddings, choosing the most accurate model, and progressively adding it to the discriminator ensemble. Interestingly, our method can improve GAN training in both limited data and large-scale settings. Given only 10k training samples, our FID on LSUN Cat matches the StyleGAN2 trained on 1.6M images. On the full dataset, our method improves FID by 1.5x to 2x on cat, church, and horse categories of LSUN.


paper thumbnail

Paper

arxiv:2112.09130 , 2021.

Citation

Nupur Kumari, Richard Zhang, Eli Shechtman, Jun-Yan Zhu. "Ensembling Off-the-shelf Models for GAN Training", in arXiv, 2021.
Bibtex




Quantitative Results

Our method outperforms recent GAN training methods by a large margin, especially in limited sample setting. For LSUN Cat, we achieve similar FID as StyleGAN2 trained on the full dataset using only 0.7% of the dataset. On the full dataset, our method improves FID by 1.5x to 2x on LSUN Cat and LSUN Church.

Interpolation video

We show generated images by interpolation between latent codes for model trained by our method on AnimalFace Cat (160 images), Dog (389 images), and Bridge-of-Sighs (100 photos).

Visual Comparison

We finetune StyleGAN2-ADA with our method and show randomly generated images for the same latent code by StyleGAN2-ADA and Ours.

FFHQ

1k training samples

StyleGAN2-ADA Ours

2k training samples:

StyleGAN2-ADA Ours

LSUN Cat

StyleGAN2-ADA Ours
StyleGAN2-ADA Ours

LSUN Church

StyleGAN2-ADA Ours
StyleGAN2-ADA Ours


Best and Worst sample comparison

We randomly sample 5k images and sort them according to Mahalanobis distance using mean and variance of real samples calculated in inception feature space. Below visualization shows the top and bottom 30 images according to the distance.

StyleGAN2-ADA

Baseline

Ours

Ours




Acknowledgment

We thank Muyang Li, Sheng-Yu Wang, Chonghyuk (Andrew) Song for proofreading the draft. We are also grateful to Alexei A. Efros, Sheng-Yu Wang, Taesung Park, and William Peebles for helpful comments and discussion. The work is partly supported by Adobe Inc., Kwai Inc, Sony Corporation, and Naver Corporation. Also, thanks to Kangle Deng for the website template.