Particle Denoising Diffusion Sampler
Angus PhillipsHai-Dang DauMichael John HutchinsonValentin De BortoliGeorge DeligiannidisArnaud Doucet
Introduces the Particle Denoising Diffusion Sampler, an iterative particle method combining guided diffusions with a novel score matching loss to achieve asymptotically consistent sampling and normalizing constant estimation for complex, unnormalized target distributions.
Generating samples from complex, unnormalized probability distributions and computing their normalizing constants are fundamental challenges across scientific computing, statistics, and machine learning. Traditional methods like annealing often degrade when exploring multimodal landscapes, while standard diffusion-based generative models rely heavily on available data samples and introduce persistent approximation errors when adapted to general sampling. The article addresses these bottlenecks by developing the Particle Denoising Diffusion Sampler (PDDS), a methodology designed to reliably sample from unnormalized target densities and deliver consistent, unbiased normalizing constant estimates.
The approach integrates guided denoising diffusions with Sequential Monte Carlo (SMC), a particle-based filtering framework. Rather than relying on static or heuristic approximations to reverse the noising diffusion process, PDDS formulates the time-reversed process as an iterative particle scheme. To correct for intermediate drift errors, the methodology introduces a Novel Score Matching (NSM) loss function to train neural network potential approximations. This novel loss eliminates the variance blow-up that standard score matching encounters as time steps approach zero, allowing particles to be systematically reweighted, resampled, and optionally perturbed using standard Markov Chain Monte Carlo moves.
The evaluation demonstrates several critical findings across synthetic benchmarks, Bayesian logistic regression, and high-dimensional models scaling up to 1,600 dimensions. First, PDDS, especially when combined with optional Markov Chain Monte Carlo steps, consistently matches or exceeds the performance of state-of-the-art baselines like CRAFT, DDS, and Path Integral Samplers in estimating normalizing constants. Second, on multimodal problems—such as a 20-dimensional mixture of 40 separated Gaussian components—PDDS substantially outperforms flow-based methods by preventing mode collapse and significantly reducing transport error. Third, theoretical analysis confirms that PDDS provides asymptotically consistent estimates and establishes that sorted stratified resampling prevents particle degeneration as discretization steps become infinitely fine.
These results provide practitioners with a scalable, mathematically rigorous framework that reduces computational risk and improves fidelity in high-dimensional probabilistic inference. Unlike flow-based methods that require extensive, problem-specific re-training to adjust time-step resolutions, PDDS uses standard, task-agnostic network architectures that seamlessly refine when time steps are subdivided. Decision-makers should consider adopting PDDS for complex posterior inference and explore pilot implementations where capturing separated modes is critical. Users must note that practical deployment uses a finite particle budget and relies on well-behaved initial variational approximations to maintain numerical stability, warranting caution and validation in unconstrained density settings.
- Paper: Score-Based Generative Modeling through Stochastic Differential Equations, Yang Song et al. (2021). Its continuous-time SDE framework establishes the forward and reverse diffusion processes that PDDS turns into a particle-based sampling scheme.
- Paper: Denoising Diffusion Probabilistic Models, Jonathan Ho et al. (2020). Its foundational denoising diffusion formulation clarifies the noise-corruption and learned-reversal setup that PDDS adapts for sampling unnormalized targets.
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