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Training Unbiased Diffusion Models From Biased Dataset
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Proposes time-dependent importance reweighting (TIW-DSM) that uses a time-dependent discriminator's density ratio both for reweighting and score correction to train unbiased diffusion models from a biased dataset plus a small unbiased reference set.
Problem
Diffusion models trained on biased datasets inherit and amplify dataset bias; existing time-independent importance reweighting relies on a density ratio estimated only at t=0, which is inaccurate in high dimensions with few reference samples.
Approach
Estimate the density ratio between perturbed biased and unbiased distributions at every diffusion time with a time-dependent discriminator, and use it both as a per-time importance weight and as a score correction term, yielding a tractable objective equivalent to unbiased score matching.
Key results
- On CIFAR-10 (LT, 5% reference) TIW-DSM achieves FID 11.51 versus 12.99 for DSM(obs) and 15.79 for IW-DSM; it is best in every tested CIFAR setting.
- On FFHQ (80% female, 1.25% reference) TIW-DSM reaches FID 7.10 versus 7.29 for DSM(obs) and 11.30 for IW-DSM.
- On CelebA benchmark with 5% reference, TIW-DSM reaches FID 2.40, the best among DSM(ref) 2.82, DSM(obs) 3.55, IW-DSM 2.43, and yields more balanced subgroup proportions.
Measured effects reported in the paper
| What was changed | Where | Measured | Effect |
|---|---|---|---|
| Use TIW-DSM instead of DSM(obs) | Diffusion models trained on biased CIFAR-10 (LT) · CIFAR-10 (LT), 5% reference | FID: 12.99 -> 11.51 | Helped |
| Use TIW-DSM instead of DSM(obs) | Diffusion models trained on biased CIFAR-100 (LT) · CIFAR-100 (LT), 5% reference | FID: 15.20 -> 14.46 | Helped |
| Use TIW-DSM instead of DSM(obs) | Diffusion models trained on biased FFHQ · FFHQ (80% bias), 1.25% reference | FID: 7.29 -> 7.10 | Helped |
| Use TIW-DSM instead of DSM(obs) | Diffusion models trained on biased FFHQ · FFHQ (90% bias), 1.25% reference | FID: 8.59 -> 8.06 | Helped |
| Use TIW-DSM instead of IW-DSM | Diffusion models trained on CelebA · CelebA benchmark, 5% reference | FID: 2.43 -> 2.40 | Helped |
| Add score correction to time-dependent reweighting (ablation) | TIW-DSM · CIFAR-10 (LT), 5% reference | FID: 13.27 -> 11.51 | Helped |
| Add score correction to time-dependent reweighting (ablation) | TIW-DSM · CIFAR-10 (LT), 10% reference | FID: 10.80 -> 8.08 | Helped |
| Add score correction to time-dependent reweighting (ablation) | TIW-DSM · CIFAR-10 (LT), 25% reference | FID: 8.26 -> 5.59 | Helped |
| Add score correction to time-dependent reweighting (ablation) | TIW-DSM · CIFAR-10 (LT), 50% reference | FID: 7.28 -> 4.06 | Helped |
| Add time-dependent reweighting to score correction (ablation) | TIW-DSM · CIFAR-10 (LT), 5% reference | FID: 11.62 -> 11.51 | Helped |
| Add time-dependent reweighting to score correction (ablation) | TIW-DSM · CIFAR-10 (LT), 10% reference | FID: 8.15 -> 8.08 | Helped |
| Add time-dependent reweighting to score correction (ablation) | TIW-DSM · CIFAR-10 (LT), 25% reference | FID: 5.43 -> 5.59 | Hurt |
Surprising findings
- IW-DSM with time-independent weights is often worse than naively training on the biased data (DSM(obs)) in CIFAR settings, because the t=0 weights for biased samples are very small (over 75% below 0.01).
- Score correction alone (without time-dependent reweighting) already achieves most of the gain, while reweighting alone performs close to DSM(obs).
Limitations
- The theoretical convergence guarantee assumes optimal density ratio estimation, which is not achieved in practice.
- Requires a small unbiased reference set D_ref and access to group-origin labels distinguishing D_ref from D_bias (weak supervision).
- Evaluation is limited to FID and bias proportions on relatively small image datasets at low resolution.
Experimental setup
Datasets: CIFAR-10 CIFAR-100 FFHQ CelebA
Benchmarks: CIFAR-10 (LT) CIFAR-100 (LT) FFHQ CelebA
Metrics: FID latent bias statistics recall
Baselines: DSM(ref) DSM(obs) IW-DSM
Builds on: denoising score matching importance reweighting for unbiased generative learning variance preserving SDE noise contrastive estimation
Closest papers by meaning
- Data Unlearning in Diffusion Models (ICLR 2025 · similarity 0.88)
- Dimension-free Score Matching and Time Bootstrapping for Diffusion Models (NeurIPS 2025 · similarity 0.87)
- Generalization through variance: how noise shapes inductive biases in diffusion models (ICLR 2025 · similarity 0.87)
- Training Data Attribution in Diffusion Models via Mirrored Unlearning and Noise-Consistent Skew (NeurIPS 2026 · similarity 0.87)
- Diffusion Attribution Score: Evaluating Training Data Influence in Diffusion Models (ICLR 2025 · similarity 0.86)
- The Emergence of Reproducibility and Consistency in Diffusion Models (ICML 2024 · similarity 0.86)
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