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👁️ MultimodalID: diffusion-vs-gan

Diffusion vs GAN vs Autoregressive

扩散 vs GAN vs 自回归
🎯Core Definition
The three major generation families trade off quality/diversity/speed. GANs play a zero-sum game between generator and discriminator — one forward pass is fastest, but adversarial training is unstable and prone to mode collapse. Diffusion/flow models generate by progressive denoising: training is stable regression and diversity is strong, and current SOTA FID is lower (higher quality ceiling). Autoregressive models predict token by token — great for text and discrete modalities with natural conditioning, but sampling is serial. Comparison:
📌Overview
| Dimension | GAN | Diffusion (DDPM/distilled) | Autoregressive | |---|---|---|---| | Training stability | poor (adversarial) | good (MSE regression) | good (cross-entropy) | | Diversity | poor (mode collapse) | good (full coverage) | good | | Quality (FID) | realistic in-mode | SOTA lowest FID | weaker on images | | Sampling speed | 1 step (fastest) | 4–1000 steps (DDIM/distillable) | serial tokens | | High-res scaling | unstable | latent + DiT scalable | hard |
📌Overview
FID (Fréchet Inception Distance): pass real and generated images through an Inception network, assume the features are Gaussian, and measure the Fréchet distance between their means and covariances:
📌Overview
FID=μrμg2+Tr(Σr+Σg2(ΣrΣg)1/2)FID = \Vert \mu_r - \mu_g \Vert^2 + \mathrm{Tr}\left(\Sigma_r + \Sigma_g - 2(\Sigma_r\Sigma_g)^{1/2}\right)
📌Overview
Lower is better; it captures both fidelity and diversity, though note they are not the same — a GAN can have decent FID yet poor diversity.
💡Use Cases
interview comparison questions (“why is text-to-image SOTA diffusion, not GAN?”); architecture selection — low-latency interactive tasks (real-time filters, SR) favor GANs or distilled diffusion, quality/diversity-first tasks (text-to-image, video) favor diffusion.
Key Problems Solved
GANs' unstable adversarial training, mode collapse and hard high-resolution scaling; diffusion trades more sampling steps for stable training, full distribution coverage and lower FID; autoregressive models have been largely displaced for image generation by diffusion/flow models.
🎯5 High-Frequency Exam Points
1
Compare diffusion vs GAN on quality, diversity and speed; why is diffusion the T2I SOTA?
2
Write and explain the FID formula; why does it not fully capture diversity?
3
Causes and detection of GAN mode collapse; how does diffusion naturally avoid it?
4
Pros and cons of autoregressive vs diffusion generation; why is AR being displaced on images?
5
For real-time use (mobile SR/filters), GAN or distilled diffusion — how to trade off latency and quality?
📖 In-depth Guide:📄 diffusion-models
Updated 2026-08-12
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