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One-Step Diffusion Distillation through Score Implicit Matching
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Distills pre-trained diffusion models (EDM on CIFAR-10, PixArt-α 0.6B DiT for text-to-image) into one-step generators data-free via a score-gradient theorem that makes gradients of score-based divergences tractable.
Problem
Distilling multi-step diffusion models into one-step generators while preserving sample quality, without needing real training data, and with a tractable training objective.
Approach
Shows that gradients of a broad class of score-based divergences between a generator and a teacher diffusion model can be computed exactly via a score-gradient theorem (score-projection identity with stop-gradient), yielding a tractable Score Implicit Matching loss; uses a Pseudo-Huber distance whose gradient adaptively normalizes the loss, and recovers SiD for the squared L2 distance.
Key results
- On CIFAR-10, SIM achieves FID 2.06 unconditional (1 step) and 1.96 class-conditional (1 step).
- SIM-DiT-600M reaches aesthetic score 6.42 in one step, matching the 30-step PixArt-α teacher's 5.97 and beating SDXL-Turbo (5.33), SDXL-Lightning (5.34) and Hyper-SDXL (5.85).
- Distilling PixArt-α took about 2 days on 4 A100-40G GPUs, data-free for the generator training.
Measured effects reported in the paper
| What was changed | Where | Measured | Effect |
|---|---|---|---|
| Use Pseudo-Huber distance instead of squared L2 distance (ablation) | SIM on CIFAR-10 · CIFAR-10 unconditional | FID | Helped |
| Use the modified log-normal time distribution instead of Karr time distribution (ablation) | SIM generator training · CIFAR-10 | FID | Helped |
| Use constant generator loss weighting instead of SiD weighting (ablation) | SIM generator training · CIFAR-10 | FID | Helped |
| Train with a learning rate of 1e-4 rather than the smaller-rate setting (ablation) | SIM, SiD, and DI on EDM · CIFAR-10 unconditional | FID stability | Mixed |
| Use SIM instead of SiD at matched training iterations | One-step EDM distillation · CIFAR-10 unconditional | FID | Helped |
| Concentrate the noise distribution around smaller values (ablation) | SIM-DiT-600M · Text-to-image generation | image brightness | Hurt |
| Use a slightly larger noise distribution (ablation) | SIM-DiT-600M · Text-to-image generation | structural stability | Hurt |
| Increase generator initialization noise level t* (ablation) | SIM-DiT-600M · Text-to-image generation | convergence speed | Helped |
| Distill into one step instead of using the 30-step PixelArt-α teacher | SIM-DiT-600M · COCO-2017 validation | aesthetic score: 5.97 -> 6.42 | Helped |
| Distill into one step instead of using the 30-step PixelArt-α teacher | SIM-DiT-600M* · SAM-LLaVA-Caption10M | aesthetic score: 5.93 -> 5.91 | No clear effect |
| Distill into one step instead of using the 30-step PixelArt-α teacher | SIM-DiT-600M* · SAM-LLaVA-Caption10M | Image Reward: 0.53 -> 0.44 | Hurt |
Surprising findings
- Pseudo-Huber SIM stays stable at large learning rates where SiD and DI are unstable.
- The SiD-style Karras time schedule did not work well in practice; a modified log-normal time distribution performed better.
Limitations
- Fails to generate tiny human faces, correct arms and fingers, and sometimes the wrong number of objects.
- Image Reward of SIM-DiT-600M is slightly lower than the teacher's.
- Only evaluated on diffusion (EDM, PixArt-α) teachers; not extended to flow-matching models.
Experimental setup
Datasets: CIFAR-10 SAM-LLaVA-Caption10M
Benchmarks: CIFAR-10 COCO-2017 validation SAM-LLaVA-Caption10M
Metrics: FID Inception Score Aesthetic Score PickScore ImageReward User preference win rate
Baselines: DDPM Diff-Instruct SiD CTM DMD SDXL-Turbo SDXL-Lightning Hyper-SDXL LCM TCD PeRFlow Hyper-SD
Builds on: Diff-Instruct Score identity Distillation (SiD) EDM PixArt-α
Closest papers by meaning
- Score identity Distillation: Exponentially Fast Distillation of Pretrained Diffusion Models for One-Step Generation (ICML 2024 · similarity 0.92)
- One-step Diffusion with Distribution Matching Distillation (CVPR 2024 · similarity 0.92)
- Evaluating the design space of diffusion-based generative models (NeurIPS 2024 · similarity 0.91)
- Accelerating Convergence of Score-Based Diffusion Models, Provably (ICML 2024 · similarity 0.91)
- Distribution Backtracking Builds A Faster Convergence Trajectory for Diffusion Distillation (ICLR 2025 · similarity 0.91)
- Revisiting Diffusion Models: From Generative Pre-training to One-Step Generation (ICML 2025 · similarity 0.91)
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