Saddle-Free Guidance: Improved On-Manifold Sampling without Labels or Additional Training

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Main Authors: Yeats, Eric, Hannan, Darryl, Fearn, Wilson, Doster, Timothy, Kvinge, Henry, Mahan, Scott
Format: Preprint
Published: 2025
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author Yeats, Eric
Hannan, Darryl
Fearn, Wilson
Doster, Timothy
Kvinge, Henry
Mahan, Scott
author_facet Yeats, Eric
Hannan, Darryl
Fearn, Wilson
Doster, Timothy
Kvinge, Henry
Mahan, Scott
contents Score-based generative models require guidance in order to generate plausible, on-manifold samples. The most popular guidance method, Classifier-Free Guidance (CFG), is only applicable in settings with labeled data and requires training an additional unconditional score-based model. More recently, Auto-Guidance adopts a smaller, less capable version of the original model to guide generation. While each method effectively promotes the fidelity of generated data, each requires labeled data or the training of additional models, making it challenging to guide score-based models when (labeled) training data are not available or training new models is not feasible. We make the surprising discovery that the positive curvature of log density estimates in saddle regions provides strong guidance for score-based models. Motivated by this, we develop saddle-free guidance (SFG) which maintains estimates of maximal positive curvature of the log density to guide individual score-based models. SFG has the same computational cost of classifier-free guidance, does not require additional training, and works with off-the-shelf diffusion and flow matching models. Our experiments indicate that SFG achieves state-of-the-art FID and FD-DINOv2 metrics in single-model unconditional ImageNet-512 generation. When SFG is combined with Auto-Guidance, its unconditional samples achieve general state-of-the-art in FD-DINOv2 score. Our experiments with FLUX.1-dev and Stable Diffusion v3.5 indicate that SFG boosts the diversity of output images compared to CFG while maintaining excellent prompt adherence and image fidelity.
format Preprint
id arxiv_https___arxiv_org_abs_2511_21863
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Saddle-Free Guidance: Improved On-Manifold Sampling without Labels or Additional Training
Yeats, Eric
Hannan, Darryl
Fearn, Wilson
Doster, Timothy
Kvinge, Henry
Mahan, Scott
Computer Vision and Pattern Recognition
Machine Learning
Score-based generative models require guidance in order to generate plausible, on-manifold samples. The most popular guidance method, Classifier-Free Guidance (CFG), is only applicable in settings with labeled data and requires training an additional unconditional score-based model. More recently, Auto-Guidance adopts a smaller, less capable version of the original model to guide generation. While each method effectively promotes the fidelity of generated data, each requires labeled data or the training of additional models, making it challenging to guide score-based models when (labeled) training data are not available or training new models is not feasible. We make the surprising discovery that the positive curvature of log density estimates in saddle regions provides strong guidance for score-based models. Motivated by this, we develop saddle-free guidance (SFG) which maintains estimates of maximal positive curvature of the log density to guide individual score-based models. SFG has the same computational cost of classifier-free guidance, does not require additional training, and works with off-the-shelf diffusion and flow matching models. Our experiments indicate that SFG achieves state-of-the-art FID and FD-DINOv2 metrics in single-model unconditional ImageNet-512 generation. When SFG is combined with Auto-Guidance, its unconditional samples achieve general state-of-the-art in FD-DINOv2 score. Our experiments with FLUX.1-dev and Stable Diffusion v3.5 indicate that SFG boosts the diversity of output images compared to CFG while maintaining excellent prompt adherence and image fidelity.
title Saddle-Free Guidance: Improved On-Manifold Sampling without Labels or Additional Training
topic Computer Vision and Pattern Recognition
Machine Learning
url https://arxiv.org/abs/2511.21863