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Feedback Guidance of Diffusion Models
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Proposes FeedBack Guidance (FBG), a state- and time-dependent guidance scale derived from an additive error model and a posterior estimated by tracking the diffusion Markov chain, evaluated on EDM2-XS ImageNet512 and SD2 text-to-image.
Problem
Classifier-free guidance applies a constant scale at all noise levels and states, which can reduce diversity, induce memorization, and over-saturate samples even when the conditional model is already adequate.
Approach
Replace CFG's implicit multiplicative error assumption with an additive mixture of conditional and unconditional distributions, yielding a guidance scale lambda(x_t,t) computed from a posterior p(c|x_t) that is estimated online by tracking the likelihood ratio of conditional vs unconditional denoising steps along the sampling chain.
Key results
- On ImageNet512 with EDM2-XS (stochastic sampler), FBG_LIG reaches FD_DINOv2 87.9 vs CFG 100.2, and FBG_pure reaches FID 3.76 vs CFG 5.00.
- On MS-COCO with SDv2, FBG_CFG reaches FID 18.63 and FD_DINOv2 52.14 versus CFG 19.64 and 54.56.
- FBG applies the strongest average guidance to the hardest prompt difficulty levels in a 60-prompt set of four difficulty classes.
Measured effects reported in the paper
| What was changed | Where | Measured | Effect |
|---|---|---|---|
| replace CFG with FBG_pure | EDM2-XS · ImageNet512×512 (Stoch.) | FID: 5.00 -> 3.76 | Helped |
| replace CFG with FBG_pure | EDM2-XS · ImageNet512×512 (PFODE) | FID: 2.97 -> 2.50 | Helped |
| replace CFG with FBG_pure | EDM2-XS · ImageNet512×512 (Stoch.) | FD_DinoV2: 100.2 -> 89.0 | Helped |
| replace CFG with FBG_pure | EDM2-XS · ImageNet512×512 (PFODE) | FD_DinoV2: 88.4 -> 75.6 | Helped |
| combine FBG with the LIG interval (ablation) | EDM2-XS · ImageNet512×512 (PFODE) | FD_DinoV2: 77.1 -> 74.6 | Helped |
| combine FBG with CFG (λ_CFG=1.5) (ablation) | Stable Diffusion 2 · MS-COCO (3k prompts) | FD_DinoV2: 53.11 -> 52.14 | Helped |
| replace CFG with FBG_pure | Stable Diffusion 2 · MS-COCO (3k prompts) | FID: 19.64 -> 18.63 | Helped |
| replace CFG with FBG_CFG | Stable Diffusion 2 · MS-COCO (3k prompts) | FD_DinoV2: 54.56 -> 52.14 | Helped |
| replace CFG with FBG_pure | Stable Diffusion 2 · MS-COCO (3k prompts) | Aesthetic Score: 5.65 -> 5.75 | Helped |
| use FBG guidance rather than CFG | EDM2-XS · ImageNet512×512 (Stoch.) | Recall: 0.73 -> 0.76 | Helped |
Surprising findings
- Late-stage guidance is found to be not only unnecessary but harmful, particularly for FD_DINOv2, contrary to prior work.
Limitations
- The additive mixture error model and prior are chosen for simplicity and may not approximate true model biases.
- Evaluation focuses on EDM2-XS; larger architectures and broader T2I prompt datasets are untested.
- Text-to-image evaluation is limited to MS-COCO, which has simple captions, and is shown qualitatively with a small 60-prompt set.
Experimental setup
Datasets: ImageNet512x512 MS-COCO
Benchmarks: ImageNet512x512 MS-COCO
Metrics: FID FD_DINOv2 Precision Recall Aesthetic Score
Baselines: CFG CFG++ Linear guidance weight scheduler LIG LinCFG
Builds on: Classifier-Free Guidance Limited Interval Guidance Dynamic Negative Guidance EDM2
Closest papers by meaning
- Adaptive Guidance: Training-free Acceleration of Conditional Diffusion Models (AAAI 2025 · similarity 0.92)
- Eliminating Oversaturation and Artifacts of High Guidance Scales in Diffusion Models (ICLR 2025 · similarity 0.92)
- Diffusion Models without Classifier-free Guidance (NeurIPS 2026 · similarity 0.92)
- No Training, No Problem: Rethinking Classifier-Free Guidance for Diffusion Models (ICLR 2025 · similarity 0.91)
- REG: Rectified Gradient Guidance for Conditional Diffusion Models (ICML 2025 · similarity 0.91)
- Rectified Diffusion Guidance for Conditional Generation (CVPR 2025 · similarity 0.91)
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