activity
20242026
collaborators

9 papers

cs.LG2026

Reinforcement Learning for Hierarchical Reasoning Rewards: Minimax-Optimal Rates with Transformers

Naoki Nishikawa, Taiji Suzuki

Reinforcement learning (RL) has become a standard tool for post-training language models on reasoning tasks, where the policy is updated by reward feedback while exploring the spac…

cs.LG2026

Escaping Iterative Parameter-Space Noise: Differentially Private Learning with a Hypernetwork

Naoki Nishikawa, Shokichi Takakura, Satoshi Hasegawa

Differentially private (DP) training of neural networks is often hindered by the large amount of noise required by gradient-based methods such as DP-SGD, which repeatedly inject hi…

cs.CG2026

Persistence-based topological optimization: a survey

Mathieu Carriere, Yuichi Ike, Théo Lacombe +1

Computational topology provides a tool, persistent homology, to extract quantitative descriptors from structured objects (images, graphs, point clouds, etc). These descriptors can…

cs.LG2026

Dataset Distillation Efficiently Encodes Low-Dimensional Representations from Gradient-Based Learning of Non-Linear Tasks

Yuri Kinoshita, Naoki Nishikawa, Taro Toyoizumi

Dataset distillation, a training-aware data compression technique, has recently attracted increasing attention as an effective tool for mitigating costs of optimization and data st…

cs.LG2025

From Shortcut to Induction Head: How Data Diversity Shapes Algorithm Selection in Transformers

Ryotaro Kawata, Yujin Song, Alberto Bietti +4

Transformers can implement both generalizable algorithms (e.g., induction heads) and simple positional shortcuts (e.g., memorizing fixed output positions). In this work, we study h…

cs.LG2025

Degrees of Freedom for Linear Attention: Distilling Softmax Attention with Optimal Feature Efficiency

Naoki Nishikawa, Rei Higuchi, Taiji Suzuki

Linear attention has attracted interest as a computationally efficient approximation to softmax attention, especially for long sequences. Recent studies have explored distilling so…

cs.LG2025

Mixture of Experts Provably Detect and Learn the Latent Cluster Structure in Gradient-Based Learning

Ryotaro Kawata, Kohsei Matsutani, Yuri Kinoshita +2

Mixture of Experts (MoE), an ensemble of specialized models equipped with a router that dynamically distributes each input to appropriate experts, has achieved successful results i…

cs.CL2025

When Does Metadata Conditioning (NOT) Work for Language Model Pre-Training? A Study with Context-Free Grammars

Rei Higuchi, Ryotaro Kawata, Naoki Nishikawa +7

The ability to acquire latent semantics is one of the key properties that determines the performance of language models. One convenient approach to invoke this ability is to prepen…

stat.ML2024

State Space Models are Provably Comparable to Transformers in Dynamic Token Selection

Naoki Nishikawa, Taiji Suzuki

Deep neural networks based on state space models (SSMs) are attracting significant attention in sequence modeling since their computational cost is much smaller than that of Transf…