Alex Kipnis

I'm a PhD researcher with Eric Schulz at the Institute for Human-Centered AI.

I develop amortized models for Bayesian inference on structured data and statistical methods for foundation-model evaluation. I build open-source research software.

2026 Under review

MetaBeta

In-context Bayesian inference for hierarchical data.

Grouped tabular data is everywhere; GLMMs allow statistical inference on it. Bayesian models incorporate prior knowledge and properly quantify uncertainty. But fitting them (repeatedly) with Hamiltonian Monte Carlo is expensive.

Our bespoke neural model combines Laplace approximation, Set Transformers, Neural Spline Flows, and Independence Metropolis-Hastings. It takes data, models and priors as in-context inputs, and samples from the full posterior.

10²–10³× faster than NUTS median wall-clock time for data with up to 3,000 observations

Across controlled benchmarks and real datasets, metabeta closely matches NUTS in parameter recovery, calibration, posterior geometry, and out-of-sample prediction. This still holds in stress tests including misspecification, distribution shift, collinearity, and data-poor regimes.

2025 ICLR 2025

MetaBench

Sparse LLM evaluation: asking the right set of questions.

Evaluating a language model on large benchmarks like MMLU takes thousands of responses. Many of those carry redundant information. We found a method for picking the most informative subset of questions for 6 widely used benchmarks.

We fit item-level responses from thousands of LLMs using Item Response Theory, separating item properties and model abilities. We then used Fisher-information filtering to select the most informative items along the ability spectrum. The latent-ability estimators from the resulting subsets turn out to be excellent for reconstructing the original benchmark scores.

<3% of the original size 28,632 test items of the Open LLM Leaderboard

Our method recovers the held-out scores with a mean RMSE of 1.24% across 6 benchmarks (ARC, GSM8K, HellaSwag, MMLU, TruthfulQA, and WinoGrande). The joint score is reconstructed with an RMSE of 0.58%.

Further work

All publications →

Open-source benchmark

MixedBench

Bayesian methods for GLMMs are hard to compare: each paper tests them on its own few datasets. mixedbench collects the documented mixed-effects models of 641 public tabular datasets. Each is turned into a ready-to-fit Bayesian inference problem, delivering a broad suite for benchmarking GLMM methods.

Open-source research software

TabDGP

A data-generating process for grouped tabular datasets. It simulates data from a random hierarchical structural causal model and aims to reproduce the quirks of real data. Each table comes with the graph and the settings that generated it.

A little background

My path into machine learning began in cognitive neuroscience: psychology at Heidelberg University (with a thesis on EEG decomposition and drift-diffusion modeling). Neuro-cognitive psychology at LMU Munich (with a thesis on validating representational similarity analysis). Then I did a proper course on probability theory at the LMU and enjoyed it much more. I subsequently studied statistics, computer science, and machine learning. At the same time I started my doctoral research with Eric Schulz at the Max Planck Institute for Biological Cybernetics before the lab moved to Helmholtz Munich.

My doctoral work has been additionally supported by the German Academic Scholarship Foundation.

Beyond research →