[Paper Review] SS-GAN: Self-Supervised GANs via Auxiliary Rotation Loss 간단한 논문 리뷰

• Paper : SS-GAN: Self-Supervised GANs via Auxiliary Rotation Loss (CVPR 2019)

• GAN-Zoos! (GAN 포스팅 모음집)

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• Conditional GAN은 안정적이고 학습이 쉽지만, label이 꼭 필요

⭐ Unsupervised Generative Model that combines adversarial training with self-supervised learning

• SS-GAN : GAN에 self-supervised learning을 거의 처음으로 적용한 논문
• SS-GAN은 labeled data가 없어도 conditional GAN의 이점을 가짐
• D에 auxiliary, self-supervised loss를 추가하여 학습이 stable + useful 하도록 함.
• natural image synthesis에서 self-supervised GAN은 label이 없어도 label이 있는 것과 비슷하게 학습이 됨

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The Self-Supervised GAN

• The main idea behind self-supervision is to train a model on a pretext task like predicting rotation angle or relativelocation of an image patch, and then extracting representations from the resulting networks
• 본 논문은 SOTA self-supervision method 중 하나인 Image Rotation를 GAN에 적용
• rotation-based loss로 D를 augment !

Loss Function

• Original GAN Loss

\[\begin{equation} \begin{aligned} V(G, D)=& \mathbb{E}_{\boldsymbol{x} \sim P_{\text {data }}(\boldsymbol{x})}\left[\log P_{D}(S=1 \mid \boldsymbol{x})\right] \\ &+\mathbb{E}_{\boldsymbol{x} \sim P_{G}(\boldsymbol{x})}\left[\log \left(1-P_{D}(S=0 \mid \boldsymbol{x})\right)\right] \end{aligned} \end{equation}\]

• Original GAN Loss + Rotation-based Loss

\[L_{G}=-V(G, D)-\alpha \mathbb{E}_{\boldsymbol{x} \sim P_{G}} \mathbb{E}_{r \sim \mathcal{R}}\left[\log Q_{D}\left(R=r \mid \boldsymbol{x}^{r}\right)\right] \\ L_{D}=V(G, D)-\beta \mathbb{E}_{\boldsymbol{x} \sim P_{\text {data }}} \mathbb{E}_{r \sim \mathcal{R}}\left[\log Q_{D}\left(R=r \mid \boldsymbol{x}^{r}\right)\right]\]

Experimental Results

• 학습은 생각보다 잘됨
• Unconditional-GAN보다는 훨씬 결과가 좋고, Conditional-GAN과는 비슷한 결과를 가짐