Sequential Monte Carlo Methods & Particle Filters Resources

by Arnaud Doucet

Objectives

This webpage presents a list of references, codes and videolectures available for SMC / particle filters.

It is by no means exhaustive and obviously biased towards my work and the work of my close colleagues. A complementary site for SMC and Particle filters resources by Pierre Del Moral can be found here.

I keep on adding stuff from time to time, although not as often as I should.

References

Textbooks

Basic Introduction to SMC for state-space models

Early papers

Tutorials papers

Fighting degeneracy: Using MCMC steps & look-ahead strategies

A well-known problem with SMC approximations is that they suffer from the degeneracy problem, i.e. as time increases the approximations of the "earlier" marginal distributions collapse. You can try to mitigate (but not eliminate) this problem using either some MCMC moves as suggested by Gilks & Berzuini or by using lookahead strategies of which my favourite is block sampling.

Reducing the Variance using Rao-Blackwellization

Whenever you can compute an integral analytically, then do it and avoid Monte Carlo. An obvious principle one can put in practice for a wide range of state-space models of interest.

Reducing the Variance using Quasi Monte Carlo

Parallel implementation

SMC Methods on Trees, Partially Ordered Sets, Combinatorial Spaces

SMC Smoothing

In the context of state-space models, it is often of interest to perform smoothing. Standard SMC approximations do provide an estimate of the joint smoothing distributions but it is poor because of the degeneracy problem aforementioned. Specific smoothing procedures have been proposed to address this.

SMC for on-line Bayesian static parameter estimation in state-space models

It is tempting to do on-line Bayesian static parameter estimation in state-space models using SMC and MCMC moves. Unfortunately, all these methods suffer from the path degeneracy problems so should be used cautiously: definitely unreliable for big datasets and/or vague priors.

A pragmatic approach consists of adding an artificial dynamic noise on the static parameter:

SMC for on-line and batch maximum likelihood inference of static parameter estimation in state-space models

As all the SMC procedures for on-line Bayesian inference suffer from the degeneracy problem, me and my colleagues have tried for many years to develop alternative methods which bypass this problem. If you accept to be non-Bayesian about the parameter, this is possible. An earlier approach we considered consists of using a pseudo-likelihood, this yields an estimate which is not statistically efficient but you do not even need particle filters in this case. Eventually, we have come up with a forward-only implementation of the forward filtering-backward smoothing procedure: it is the key to obtain stable algorithms to perform on-line Maximum Likelihood (ML) static parameter estimation in state-space models. For off-line approaches, all the smoothing approaches described previously can be and have been used.

SMC for batch Bayesian static parameter estimation in state-space models

Obviously for batch joint Bayesian state and parameter estimation, you can use MCMC methods. However it can be difficult to design efficient algorithms. In the context where one can only simulate the latent process but does not have access to the transition prior, standard MCMC just fail. SMC can come to the rescue in these scenarios.

SMC as an alternative/complement to MCMC

The idea of mixing SMC and MCMC to sample from a sequence of distributions all defined on the same space has appeared independently in various papers.

SMC meets Machine Learning

Using the fact that the SMC estimator of the marginal likelihood is unbiased, we can obtain tighter lower variational bounds which can be used to train complex auto-encoders.

How to make Particle Filters differentiable so as to include them in Machine Learning pipelines.

How to combine Sequential Monte Carlo samplers with Normalizing Flows for improved performance.

Recent Convergence Results of Interest

Besides Del Moral's books (2004, 2013), here are a few papers of interest essentially weakening the assumptions in the aforementioned books.

What about SMC in high dimensional spaces?

Slides and Videolectures

Code