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Michael Gastpar

15 accepted papers

2026

From Markov to Laplace: How Mamba In-Context Learns Markov Chains

ICLR 2026oral

While transformer-based language models have driven the AI revolution thus far, their computational complexity has spurred growing interest in viable alternatives, such as structured state space sequence models (SSMs) and Selective SSMs. Among these, Mamba (S6) and its variant Mamba-2 have shown rem…

Cited by 0SourcecodeScholar
2025

Attention with Markov: A Curious Case of Single-layer Transformers

ICLR 2025spotlight

Attention-based transformers have achieved tremendous success across a variety of disciplines including natural languages. To deepen our understanding of their sequential modeling capabilities, there is a growing interest in using Markov input processes to study them. A key finding is that when trai…

Cited by 3SourcePDFScholar
2025

Leveraging Sparsity for Sample-Efficient Preference Learning: A Theoretical Perspective

ICML 2025poster

This paper considers the sample-efficiency of preference learning, which models and predicts human choices based on comparative judgments. The minimax optimal estimation error rate $\Theta(d/n)$ in classical estimation theory requires that the number of samples $n$ scales linearly with the dimension…

Cited by 0SourcePDFScholar
2025

What One Cannot, Two Can: Two-Layer Transformers Provably Represent Induction Heads on Any-Order Markov Chains

NeurIPS 2025spotlight

In-context learning (ICL) is a hallmark capability of transformers, through which trained models learn to adapt to new tasks by leveraging information from the input context. Prior work has shown that ICL emerges in transformers due to the presence of special circuits called induction heads. Given…

Cited by 0SourceScholar
2025

Which Algorithms Have Tight Generalization Bounds?

NeurIPS 2025spotlight

We study which machine learning algorithms have tight generalization bounds with respect to a given collection of population distributions. Our results build on and extend the recent work of Gastpar et al. (2023). First, we present conditions that preclude the existence of tight generalization bound…

Cited by 0SourceScholar
2025

zip2zip: Inference-Time Adaptive Tokenization via Online Compression

NeurIPS 2025poster

Tokenization efficiency plays a critical role in the performance and cost of large language models (LLMs), yet most models rely on static tokenizers optimized on general-purpose corpora. These tokenizers’ fixed vocabularies often fail to adapt to domain- or language-specific inputs, leading to longe…

Cited by 0SourcecodeScholar
2024

Fantastic Generalization Measures are Nowhere to be Found

ICLR 2024poster

We study the notion of a generalization bound being _uniformly tight_, meaning that the difference between the bound and the population loss is small for all learning algorithms and all population distributions. Numerous generalization bounds have been proposed in the literature as potential explana…

Cited by 12SourcePDFScholar
2024

Fundamental Limits of Prompt Compression: A Rate-Distortion Framework for Black-Box Language Models

NeurIPS 2024poster

We formalize the problem of prompt compression for large language models (LLMs) and present a framework to unify token-level prompt compression methods which create hard prompts for black-box models. We derive the distortion-rate function for this setup as a linear program, and provide an efficient…

Cited by 4SourcePDFScholar
2024

LASER: Linear Compression in Wireless Distributed Optimization

ICML 2024poster

Data-parallel SGD is the de facto algorithm for distributed optimization, especially for large scale machine learning. Despite its merits, communication bottleneck is one of its persistent issues. Most compression schemes to alleviate this either assume noiseless communication links, or fail to achi…

Cited by 7SourcePDFScholar
2024

Local to Global: Learning Dynamics and Effect of Initialization for Transformers

NeurIPS 2024poster

In recent years, transformer-based models have revolutionized deep learning, particularly in sequence modeling. To better understand this phenomenon, there is a growing interest in using Markov input processes to study transformers. However, our current understanding in this regard remains limited w…

2024

The Fundamental Limits of Least-Privilege Learning

ICML 2024poster

The promise of least-privilege learning – to find feature representations that are useful for a learning task but prevent inference of any sensitive information unrelated to this task – is highly appealing. However, so far this concept has only been stated informally. It thus remains an open questio…

Cited by 1SourcePDFScholar
2024

Transformers on Markov data: Constant depth suffices

NeurIPS 2024poster

Attention-based transformers have been remarkably successful at modeling generative processes across various domains and modalities. In this paper, we study the behavior of transformers on data drawn from $k^{\text{th}}$-order Markov processes, where the conditional distribution of the next symbol i…

Cited by 8SourcePDFScholar
2022

A Johnson-Lindenstrauss Framework for Randomly Initialized CNNs

ICLR 2022poster

How does the geometric representation of a dataset change after the application of each randomly initialized layer of a neural network? The celebrated Johnson-Lindenstrauss lemma answers this question for linear fully-connected neural networks (FNNs), stating that the geometry is essentially preserv…

Cited by 11SourcePDFScholar