iiinova — where your digital self keeps evolving

Robin Ryder @robinryder.bsky.social · 12/09/2026

A strong call to remember what Mathematics research is actually about. Thanks you for writing this. (I signed.)

In recent months, the success of AI in solving major mathematical problems has made headlines even outside mathematical circles. But solving problems is only a tool and proxy for achieving the primary goal of conceptual understanding and insight. Forgetting this in the world of AI may turn the tool against the primary goal. Indeed, the mass production at faster and faster pace of "true/false" statements could destroy fertile ground instead of breathing life into new ideas.

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Robin Ryder @robinryder.bsky.social · 08/07/2026

You can also read the letter directly here.

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Robin Ryder @robinryder.bsky.social · 27/01/2026

Antoine will be spending the next few months in Berkeley. You should definitely try to hire him as a postdoc!

Photo of Christian Robert, Antoine Luciano, and Robin Ryder

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Robin Ryder @robinryder.bsky.social · 27/01/2026

Congratulations to Dr Antoine Luciano, who defended his PhD on "Contributions to Bayesian Simulation-Based Inference"! I had a wonderful time supervising Antoine's PhD (jointly with Christian Robert), it's always emotional to reach the end.

Photo of 2026 PhD thesis by Antoine Luciano, with title "Contributions à l'inférence bayésienne par simulation"

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Robin Ryder @robinryder.bsky.social · 21/01/2026

Jinyuan's methodology, based on HMMs, is a significant improvement on the state of the art, and also allows for better uncertainty quantification. Here is what the output can look like, for Good Omens - notice the very large number of switches between the two authors.

Output of an HMM, showing the Posterior probability of each word in Good Omens being written by Neil Gaiman.

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Robin Ryder @robinryder.bsky.social · 21/01/2026

Congratulations to Dr Jinyuan Zhang, who defended his PhD in Edinburgh today! I was happy to be the external examiner. Jinyuan worked on Hidden Markov Models for Stylometry, to attribute authorship in texts with several authors. The thesis was supervised by Gordon Ross.

Photo of a PhD thesis with title "Sequential Stylometry: A Bayesian Stylometry Framework for Mixed Authorship Texts", by Jinyuan Zhang (University of Edinburgh, 2025)

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Robin Ryder @robinryder.bsky.social · 12/12/2025

Congratulations to Dr Roan Talbut, who successfully defended their PhD on "Tropical Geometry for Phylogenetic Statistics"! It was a pleasure to read the thesis and examine the viva. I learned a lot!

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Robin Ryder @robinryder.bsky.social · 09/07/2025

The methods scale well (by ABC standards). Here is the output on real data with about 300 parameters to infer. Notice that the local parameters do vary quite a lot, and allowing for that variation allows for better inference of the global parameters.

Posterior distribution for two parameters.
Left: parameter R0. The posterior using a model at the departmental level is much more peaked that the posteriror using a model at the national level.
Right: paramer ν. There is only one curve at the national curve, but many individual posteriors at the departmental level, showing a lot of heterogeneity.

Map of France showing the paramer ν_k at each department. values are lower in the North-East (ν_k of the order of 0.5 and larger in the West (values varying between 1 and 3.5).

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Robin Ryder @robinryder.bsky.social · 09/07/2025

We have found that both Over Sampling and Under Matching give significant improvements with mis-specified models or outliers, as these schemes make it easier to catch the tails of the posterior predictive.

Performance of 7 algorithms. For most of the figure, the ordering is: worst ABC-SMC, the ABC-Vanilla or ABC-SMC, then permABC-Vanilla or permABC-SMC, then Under-Matching, then Over-Sampling

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Robin Ryder @robinryder.bsky.social · 09/07/2025

Taken alone, this natural idea already gives us a gain of an order of magnitude. (In this figure, lower is better.)

Performance curve of various algorithms. For most of the figure, the ordering is: worst ABC-PMC, then ABC-Vanilla and ABC-SMC, best either permABC-Vanilla or permABC-SMC

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Robin Ryder @robinryder.bsky.social · 09/07/2025

We exploit the model structure to accelerate the inference. We use a linear assignment algorithm to find the permutation of the synthetic data that best matches the observed data.

$Vanilla ABC: d(x,z)<ε permABC: min_{σ∈S_K) d(y, z_σ)<ε$

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Robin Ryder @robinryder.bsky.social · 09/07/2025

We consider ABC for hierarchical models, with both local and global parameters. Our motivating example is an SIR model of early Covid data across 94 French departements: some parameters are shared across all departements (global), others are specific to each departement (local).

A hierarchical model with observations y_1, y_2,... y_K. Each y_i depends on a local parameter μ_i and on a global, shared parameter β.

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Robin Ryder @robinryder.bsky.social · 02/07/2025

We consider whether the communication systems of various species of tits, chickadees, and related birds, exhibit FD calls, a non-trivial composition of two base calls. These are plotted on the known phylogeny: red nodes exhibit FD calls, grey nodes (or don't pass our rather stringent condition).

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Robin Ryder @robinryder.bsky.social · 17/06/2025

Enjoying discovering Singapore, and ready for BayesComp 2025! I'll be giving a talk tomorrow (Wed) on Saddlepoint Monte Carlo and its application to exact Ecological Inference. Come say hi at 16:10 in room LT51 - it's a cool paper, I swear! arxiv.org/abs/2410.18243

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Robin Ryder @robinryder.bsky.social · 11/06/2025

Sloppier-than-usual academic spam. 😬 I'd never thought of publishing a paper whose title would be my name. Sounds like a highly efficient plan, it would eliminate the whole headache of trying to pick a good title! 🙄

Screenshot of an e-mail which reads
"Dear Dr.Ryder, Robin J.

Hello!

We understand that you have made outstanding achievements in the academic field and published many high-level papers. For example, your recent publication "Ryder, Robin J." has left a deep impression on us. We sincerely invite you to submit to our open access journals.

Our journals have been included in the Scopus database and cover multiple disciplines such as environmental and earth sciences, ecological research, linguistics, building materials, sustainable oceans, medicine, etc., and are committed to publishing high-"

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Robin Ryder @robinryder.bsky.social · 02/04/2025

We also look at a neuroscience application, to analyse brain connectivity networks.

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Robin Ryder @robinryder.bsky.social · 02/04/2025

We applied this to find the underlying structure of the Infinito criminal network. It is surprisingly well resolved, and it recovers both known structure and interesting positions of certain members of the network.

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Robin Ryder @robinryder.bsky.social · 02/04/2025

The underlying tree might be a fully resolved phylogeny, or it might be a simple hierarchical structure, such as a small number of clusters.

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Robin Ryder @robinryder.bsky.social · 02/04/2025

We observe several adjacency matrices - say, multiple measurements, or networks defined by different features - with the same underlying tree.

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Robin Ryder @robinryder.bsky.social · 22/11/2024

Congratulations to Dr Charly Andral who succesfully defended his PhD at Paris-Dauphine yesterday! His doctoral work was supervised by Christian Robert and Randal Douc; I was delighted to be part of the jury.

Charly Andral's PhD manuscript on "Some contributions to Monte Carlo methods in Statistics"

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