Direct Diffusion Score Preference Optimization via Stepwise Contrastive Policy-Pair Supervision

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Hauptverfasser: Kim, Dohyun, Lyu, Seungwoo, Kim, Seung Wook, Seo, Paul Hongsuck
Format: Preprint
Veröffentlicht: 2025
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author Kim, Dohyun
Lyu, Seungwoo
Kim, Seung Wook
Seo, Paul Hongsuck
author_facet Kim, Dohyun
Lyu, Seungwoo
Kim, Seung Wook
Seo, Paul Hongsuck
contents Diffusion models have achieved impressive results in generative tasks such as text-to-image synthesis, yet they often struggle to fully align outputs with nuanced user intent and maintain consistent aesthetic quality. Existing preference-based training methods like Diffusion Direct Preference Optimization help address these issues but rely on costly and potentially noisy human-labeled datasets. In this work, we introduce Direct Diffusion Score Preference Optimization (DDSPO), which directly derives per-timestep supervision from winning and losing policies when such policies are available. Unlike prior methods that operate solely on final samples, DDSPO provides dense, transition-level signals across the denoising trajectory. In practice, we avoid reliance on labeled data by automatically generating preference signals using a pretrained reference model: we contrast its outputs when conditioned on original prompts versus semantically degraded variants. This practical strategy enables effective score-space preference supervision without explicit reward modeling or manual annotations. Empirical results demonstrate that DDSPO improves text-image alignment and visual quality, outperforming or matching existing preference-based methods while requiring significantly less supervision. Our implementation is available at: https://dohyun-as.github.io/DDSPO
format Preprint
id arxiv_https___arxiv_org_abs_2512_23426
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Direct Diffusion Score Preference Optimization via Stepwise Contrastive Policy-Pair Supervision
Kim, Dohyun
Lyu, Seungwoo
Kim, Seung Wook
Seo, Paul Hongsuck
Computer Vision and Pattern Recognition
Diffusion models have achieved impressive results in generative tasks such as text-to-image synthesis, yet they often struggle to fully align outputs with nuanced user intent and maintain consistent aesthetic quality. Existing preference-based training methods like Diffusion Direct Preference Optimization help address these issues but rely on costly and potentially noisy human-labeled datasets. In this work, we introduce Direct Diffusion Score Preference Optimization (DDSPO), which directly derives per-timestep supervision from winning and losing policies when such policies are available. Unlike prior methods that operate solely on final samples, DDSPO provides dense, transition-level signals across the denoising trajectory. In practice, we avoid reliance on labeled data by automatically generating preference signals using a pretrained reference model: we contrast its outputs when conditioned on original prompts versus semantically degraded variants. This practical strategy enables effective score-space preference supervision without explicit reward modeling or manual annotations. Empirical results demonstrate that DDSPO improves text-image alignment and visual quality, outperforming or matching existing preference-based methods while requiring significantly less supervision. Our implementation is available at: https://dohyun-as.github.io/DDSPO
title Direct Diffusion Score Preference Optimization via Stepwise Contrastive Policy-Pair Supervision
topic Computer Vision and Pattern Recognition
url https://arxiv.org/abs/2512.23426