Archive for CRiSM

[more than] everything you always wanted to know about marginal likelihood

Posted in Books, Statistics, University life with tags , , , , , , , , , , , , , , , , , , , , , on February 10, 2022 by xi'an

Earlier this year, F. Llorente, L. Martino, D. Delgado, and J. Lopez-Santiago have arXived an updated version of their massive survey on marginal likelihood computation. Which I can only warmly recommend to anyone interested in the matter! Or looking for a base camp to initiate a graduate project. They break the methods into four families

  1. Deterministic approximations (e.g., Laplace approximations)
  2. Methods based on density estimation (e.g., Chib’s method, aka the candidate’s formula)
  3. Importance sampling, including sequential Monte Carlo, with a subsection connecting with MCMC
  4. Vertical representations (mostly, nested sampling)

Besides sheer computation, the survey also broaches upon issues like improper priors and alternatives to Bayes factors. The parts I would have done in more details are reversible jump MCMC and the long-lasting impact of Geyer’s reverse logistic regression (with the noise contrasting extension), even though the link with bridge sampling is briefly mentioned there. There is even a table reporting on the coverage of earlier surveys. Of course, the following postnote of the manuscript

The Christian Robert’s blog deserves a special mention , since Professor C. Robert has devoted several entries of his blog with very interesting comments regarding the marginal likelihood estimation and related topics.

does not in the least make me less objective! Some of the final recommendations

  • use of Naive Monte Carlo [simulate from the prior] should be always considered [assuming a proper prior!]
  • a multiple-try method is a good choice within the MCMC schemes
  • optimal umbrella sampling estimator is difficult and costly to implement , so its best performance may not be achieved in practice
  • adaptive importance sampling uses the posterior samples to build a suitable normalized proposal, so it benefits from localizing samples in regions of high posterior probability while preserving the properties of standard importance sampling
  • Chib’s method is a good alternative, that provide very good performances [but is not always available]
  • the success [of nested sampling] in the literature is surprising.

Gabriel’s talk at Warwick on optimal transport

Posted in Statistics with tags , , , , , , on March 4, 2020 by xi'an

Bayesian intelligence in Warwick

Posted in pictures, Statistics, Travel, University life, Wines with tags , , , , , , , , , , , , on February 18, 2019 by xi'an

This is an announcement for an exciting CRiSM Day in Warwick on 20 March 2019: with speakers

10:00-11:00 Xiao-Li Meng (Harvard): “Artificial Bayesian Monte Carlo Integration: A Practical Resolution to the Bayesian (Normalizing Constant) Paradox”

11:00-12:00 Julien Stoehr (Dauphine): “Gibbs sampling and ABC”

14:00-15:00 Arthur Ulysse Jacot-Guillarmod (École Polytechnique Fedérale de Lausanne): “Neural Tangent Kernel: Convergence and Generalization of Deep Neural Networks”

15:00-16:00 Antonietta Mira (Università della Svizzera italiana e Università degli studi dell’Insubria): “Bayesian identifications of the data intrinsic dimensions”

[whose abstracts are on the workshop webpage] and free attendance. The title for the workshop mentions Bayesian Intelligence: this obviously includes human intelligence and not just AI!

LMS Invited Lecture Series / CRISM Summer School 2018

Posted in pictures, Statistics, Travel, University life with tags , , , , , , , on July 12, 2018 by xi'an

chance meeting

Posted in Statistics with tags , , , , , , , , , on July 10, 2018 by xi'an

As I was travelling to Coventry yesterday, I spotted this fellow passenger on the train from Birmingham with a Valencia 9 bag, and a chat with him. It was a pure chance encounter as he was not attending our summer school, but continued down the line. (These bags are quite sturdy and I kept mine until a zipper broke.)

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