Fast ODE-based Sampling for Diffusion Models in Around 5 Steps
Zhenyu ZhouDefang ChenCan WangChun Chen
Proposes AMED-Solver, a single-step ODE solver that exploits the two-dimensional subspace geometry of diffusion sampling trajectories to eliminate truncation errors and generate high-quality images in only around 5 evaluation steps.
Diffusion models have established themselves as a leading class of generative artificial intelligence, producing exceptionally high-quality and diverse images. However, their practical deployment is severely hindered by slow generation speeds, traditionally requiring hundreds to thousands of iterative computational steps. While recent mathematical techniques have reduced this requirement to under twenty steps, cutting the computational budget down to extremely few steps—such as five—causes standard numerical solvers to suffer severe approximation errors and sharp drops in image quality. Alternative distillation-based techniques can achieve rapid generation but demand massive re-training expenses and alter model behavior.
The article aims to develop and evaluate a new sampling approach that maintains high image generation quality under extreme computational constraints of around five function evaluations, without requiring costly model retraining.
To achieve this, the authors observed an underlying geometric property of diffusion sampling trajectories: despite existing in image spaces with thousands of dimensions, the generation paths consistently lie almost entirely within a simple two-dimensional plane. Leveraging this insight, the authors created the Approximate Mean-Direction Solver (AMED-Solver) and a generalized plugin extension (AMED-Plugin). The approach trains a tiny auxiliary neural network using knowledge distillation from pre-generated sample paths. This network learns to predict optimal intermediate time steps and scaling factors, allowing the solver to directly navigate along the true mean direction of the trajectory rather than relying on heuristic approximations. The authors evaluated the framework across benchmark datasets spanning image resolutions from 32x32 to 512x512 pixels, including CIFAR-10, ImageNet, FFHQ, LSUN Bedroom, and Stable Diffusion.
The findings show that the proposed approach delivers substantial performance gains in ultra-fast sampling regimes. First, when operating at only 5 function evaluations, the method achieved state-of-the-art image quality among numerical solver methods across multiple benchmarks, reaching Fréchet Inception Distance scores of 6.61 on CIFAR-10, 10.74 on ImageNet 64x64, and 13.20 on LSUN Bedroom. Second, applying the plugin to existing multi-step solvers significantly improved baseline outputs, reducing error scores by roughly 30% to 50% in low-step settings. Third, the lightweight predictor network introduces virtually no sampling overhead and requires negligible training resources—taking as little as a few minutes to a few hours on a single standard graphics processing unit.
These results demonstrate that organizations deploying diffusion models can achieve near-instantaneous image generation while reducing inference compute costs and hardware requirements. Unlike full-model distillation, this approach preserves the core mathematical formulation of the underlying model, ensuring stability and compatibility with existing workflows.
Organizations operating or deploying diffusion models in production should consider integrating this plug-and-play solver framework to lower generation latency and hosting expenses. The authors note, however, that solver performance remains sensitive to the underlying scheduling of time steps, indicating that time-schedule tuning is necessary to maximize image fidelity across different model architectures and data domains.
- Paper: DPM-Solver: A Fast ODE Solver for Diffusion Probabilistic Model Sampling in Around 10 Steps, Cheng Lu et al. (2022). It introduces DPM-Solver, the foundational fast ODE numerical solver whose semi-linear formulation and multi-step approximation errors in ultra-low step counts directly motivate AMED's mean-direction approach.
- Paper: Denoising Diffusion Implicit Models, Jiaming Song et al. (2021). It establishes deterministic, non-Markovian sampling for diffusion models, framing generative inference as an ODE trajectory that subsequent fast ODE solvers optimize.
- Paper: Elucidating the Design Space of Diffusion-Based Generative Models, Tero Karras et al. (2022). It systematizes diffusion ODE formulations, noise schedules, and high-order deterministic numerical integrators that serve as standard baselines for fast sampling.
- Paper: Score-Based Generative Modeling through Stochastic Differential Equations, Yang Song et al. (2021). It introduces the continuous probability flow ODE formulation that enables deterministic ODE-based trajectory sampling in diffusion models.
- Paper: Progressive Distillation for Fast Sampling of Diffusion Models, Tim Salimans et al. (2022). It establishes few-step generation through progressive distillation, providing the primary retraining-heavy baseline that the retraining-free AMED solver aims to improve upon.
- Paper: Consistency Models, Yang Song et al. (2023). It defines consistency distillation along diffusion ODE trajectories, representing the benchmark standard for few-step sampling against which numerical solvers are compared.
- Paper: High-Resolution Image Synthesis with Latent Diffusion Models, Robin Rombach et al. (2022). It provides the latent diffusion architecture and pre-trained Stable Diffusion models on which fast ODE sampling plug-ins and evaluations are executed.
- Paper: Denoising Diffusion Probabilistic Models, Jonathan Ho et al. (2020). It introduces the core denoising diffusion probabilistic modeling paradigm upon which all subsequent ODE trajectory formulations and acceleration solvers depend.
- Paper: Mean Flows for One-step Generative Modeling, Zhengyang Geng et al. (2025). It extends the concept of learning average velocities across trajectory intervals to achieve direct one-step generative flow modeling.
- Paper: Variational Flow Maps: Make Some Noise for One-Step Conditional Generation, Abbas Mammadov et al. (2026). It applies few-step and one-step generative flow principles to solve downstream conditional inverse problems.
- Paper: Generative Modeling via Drifting, Mingyang Deng et al. (2026). It develops an alternative paradigm to multi-step ODE integration by training models via drifting fields to accomplish one-step generation.
