Sampling from an unnormalized probability distribution is a fundamental problem in machine learning with applications including Bayesian learning, latent factor inference, and energy-based model training. After decades of research, variations of MCMC remain the default approach to sampling despite slow convergence.
We propose a fundamentally different approach to this problem via a new Hamiltonian dynamics with a non-Newtonian momentum. In contrast to MCMC approaches like Hamiltonian Monte Carlo, no stochastic step is required. Instead, the proposed deterministic dynamics in an extended state space exactly sample the target distribution, specified by an energy function, under an assumption of ergodicity.
Energy Sampling Hamiltonian (ESH) dynamics converge faster than their MCMC competitors enabling faster, more stable training of neural network energy models.
For the non-Newtonian momentum used in Energy Sampling Hamiltonian (ESH) dynamics, when momentum is large, the changes in position appear in slow motion, and when momentum is small it goes into fast-forward. The outcome is that the amount of time spent in each region is exactly proportional to the density exp(-E(x))/Z.
The typical approach for sampling in high-dimensional spaces like images is to use Langevin dynamics. ESH dynamics sample faster because it eliminates the random walk behavior of Langevin dynamics
https://arxiv.org/abs/2212.08549
One potential issue with our method is that the dynamics may not be ergodic. This paper studies the problem and suggests a simple fix, momentum flips, to solve it.
https://arxiv.org/abs/2303.18221
This paper shows the stationary distribution for both deterministic and stochastic variations converges to the correct distribution. The "Micro-canonical Langevin Monte Carlo" method looks elegant and gives very promising results in experiments.
For physicists, using purely energy-preserving Hamiltonian dynamics corresponds to the "micro-canonical" ensemble. So calling this class of methods as Robnik et al "micro-canonical Monte Carlo" makes sense.
BibTex entry:
@inproceedings{esh,
title={Hamiltonian Dynamics with Non-Newtonian Momentum for Rapid Sampling},
author={Greg {Ver Steeg} and Aram Galstyan},
Booktitle={Advances in Neural Information Processing Systems},
year={2021}
}