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Christophe Roux

6 accepted papers

2026

From Associations to Activations: Comparing Behavioral and Hidden-State Semantic Geometry in LLMs

ICML 2026poster

We investigate the extent to which an LLM’s hidden-state geometry can be recovered from its behavior in psycholinguistic experiments. Across eight instruction-tuned transformer models, we run two experimental paradigms---similarity-based forced choice and free association---over a shared 5,000-word …

Cited by 0SourceScholar
2026

Lower Bounds for Frank-Wolfe on Strongly Convex Sets

ICML 2026poster

We present a constructive lower bound of $\Omega(1/\sqrt{\varepsilon})$ for Frank-Wolfe (FW) when both the objective and the constraint set are smooth and strongly convex, showing that the known uniform $\mathcal{O}(1/\sqrt{\varepsilon})$ guarantees in this regime are tight. It is known that under a…

Cited by 0SourceScholar
2025

Accelerated Methods for Riemannian Min-Max Optimization Ensuring Bounded Geometric Penalties

AISTATS 2025poster

In this work, we study optimization problems of the form $\min_x \max_y f(x, y)$, where $f(x, y)$ is defined on a product Riemannian manifold $\mathcal{M} \times \mathcal{N}$ and is $\mu_x$-strongly geodesically convex (g-convex) in $x$ and $\mu_y$-strongly g-concave in $y$, for $\mu_x, \mu_y \geq 0…

Cited by 0SourceScholar
2025

Implicit Riemannian Optimism with Applications to Min-Max Problems

ICML 2025poster

We introduce a Riemannian optimistic online learning algorithm for Hadamard manifolds based on inexact implicit updates. Unlike prior work, our method can handle in-manifold constraints, and matches the best known regret bounds in the Euclidean setting with no dependence on geometric constants, like…

Cited by 0SourcePDFScholar
2025

On the Byzantine-Resilience of Distillation-Based Federated Learning

ICLR 2025poster

Federated Learning (FL) algorithms using Knowledge Distillation (KD) have received increasing attention due to their favorable properties with respect to privacy, non-i.i.d. data and communication cost. These methods depart from transmitting model parameters and instead communicate information about…

2024

Convergence and Trade-Offs in Riemannian Gradient Descent and Riemannian Proximal Point

ICML 2024poster

In this work, we analyze two of the most fundamental algorithms in geodesically convex optimization: Riemannian gradient descent and (possibly inexact) Riemannian proximal point. We quantify their rates of convergence and produce different variants with several trade-offs. Crucially, we show the ite…

Cited by 1SourcePDFScholar