Deep Equilibrium Approaches to Diffusion Models
Ashwini PokleZhengyang GengJ. Zico Kolter
Formulates the diffusion sampling chain as a joint fixed-point system using deep equilibrium models, enabling parallel multi-GPU image generation and memory-efficient backpropagation for faster model inversion.
Diffusion-based generative models produce exceptionally high-quality images, often surpassing alternative methods in visual fidelity. However, their practical deployment in real-world workflows like image editing, restoration, and real-time generation is heavily restricted by slow, sequential generation steps. Standard diffusion models iteratively apply hundreds or thousands of serial denoising steps to convert random noise into an image. This serial structure fails to fully utilize modern multi-processor hardware and makes model inversion—the optimization process of discovering the specific starting noise that reproduces an existing image—computationally prohibitive and memory-intensive.
The article demonstrates that the sampling process of diffusion models can be reformulated as a joint, multi-variate fixed-point system using deep equilibrium frameworks. This approach evaluates whether modeling the entire generation chain simultaneously enables parallelized image generation and constant-memory optimization for model inversion, spanning deterministic and stochastic diffusion variants.
To achieve this, the authors restructured the generation chain so that all intermediate states are estimated together within a unified equilibrium state, solved using numerical fixed-point algorithms such as Anderson acceleration. This design replaces serial dependencies with parallel computations across graphics processing units. For model inversion, the formulation uses single-step damped implicit differentiation, enabling gradient updates without storing the complete generation trajectory in memory. The method was evaluated using standard benchmark image datasets across varying resolutions, including CIFAR-10, CelebA, and LSUN Bedroom and Church scenes.
The findings show substantial improvements in efficiency and inversion accuracy. For single-image generation on lower-resolution datasets, the equilibrium approach achieved up to a two-fold wall-clock speedup over sequential baselines—generating CIFAR-10 images in approximately 2.91 seconds compared to 20.16 seconds—while maintaining comparable or slightly improved image quality scores. In model inversion tasks, the equilibrium framework consistently converged in fewer iterations and attained dramatically lower reconstruction error across all datasets. For example, on 100-step CIFAR-10 inversion, the average error dropped from 15.74 in the baseline to 0.76, while reducing total inversion time from roughly 49 minutes to 13 minutes and capturing finer visual textures such as foliage and facial details.
These results provide a practical path to reducing computational bottlenecks and memory overheads in production-grade generative modeling. By decoupling generation and optimization from strictly serial chains, organizations can perform image manipulation and latent inversion tasks at a lower computational cost without requiring specialized differential equation solvers or excessive hardware memory. The method is orthogonal to other acceleration techniques, meaning it can readily integrate with existing model distillation or step-reduction strategies.
Engineering and research teams utilizing diffusion pipelines should consider adopting equilibrium solvers for workflows that require single-instance generation or frequent latent space inversions. Before broad deployment, teams should conduct pilot benchmarks on their target hardware and image resolutions. The authors note that the speed advantage diminishes on high-resolution images with very short diffusion chains and during large-batch processing, where memory scaling requirements across all time states can offset parallelization gains. However, within single-instance generation and model inversion workflows, the findings demonstrate a high level of empirical reliability and consistent performance gains.
- Paper: Denoising Diffusion Probabilistic Models, Jonathan Ho et al. (2020). This seminal paper introduces the fundamental denoising diffusion probabilistic framework that the source reformulates as an equilibrium system.
- Paper: Denoising Diffusion Implicit Models, Jiaming Song et al. (2021). It provides the non-Markovian deterministic sampling formulation (DDIM) and inversion mechanics that the source parallelizes via joint fixed-point solvers.
- Paper: Score-Based Generative Modeling through Stochastic Differential Equations, Yang Song et al. (2021). This foundational work establishes the continuous-time SDE and probability flow ODE perspective for diffusion models, which the source seeks to solve and invert efficiently.
- Paper: Improved Denoising Diffusion Probabilistic Models, Alex Nichol et al. (2021). It establishes key sampling efficiency improvements and noise scheduling techniques used to optimize reverse-step diffusion trajectories.
- Paper: Elucidating the Design Space of Diffusion-Based Generative Models, Tero Karras et al. (2022). It systematically formalizes the design space, ODE integrators, and preconditioning dynamics of diffusion models that the source benchmarks against.
- Paper: Fast Sampling of Diffusion Models via Operator Learning, Hongkai Zheng et al. (2023). This work extends parallel non-sequential sampling strategies for diffusion differential equations using neural operator learning.
- Paper: DPM-Solver: A Fast ODE Solver for Diffusion Probabilistic Model Sampling in Around 10 Steps, Cheng Lu et al. (2022). It develops dedicated high-order ODE solvers tailored to the semi-linear diffusion trajectory to dramatically compress sampling steps.
- Paper: Consistency Models, Yang Song et al. (2023). This paper advances fast generation by enforcing self-consistency along probability flow trajectories to enable single- and few-step sampling.
- Paper: FireFlow: Fast Inversion of Rectified Flow for Image Semantic Editing, Yingying Deng et al. (2025). It provides an accelerated numerical inversion framework for flow-based generative trajectories to facilitate fast latent editing.
- Paper: A Variational Perspective on Solving Inverse Problems with Diffusion Models, Morteza Mardani et al. (2024). It advances diffusion-based inverse problem solving through a variational optimization framework that circumvents costly multi-step backpropagation.
