← Search

Youhei Akimoto

10 accepted papers

2026

Cost-Minimized Label-Flipping Poisoning Attack to LLM Alignment

AAAI 2026technical

Large language models (LLMs) are increasingly deployed in real-world systems, making it critical to understand their vulnerabilities. While data poisoning attacks during RLHF/DPO alignment have been studied empirically, their theoretical foundations remain unclear. We investigate the minimum-cost po

Cited by 0SourcePDFScholar
2025

A Provable Approach for End-to-End Safe Reinforcement Learning

NeurIPS 2025poster

A longstanding goal in safe reinforcement learning (RL) is a method to ensure the safety of a policy throughout the entire process, from learning to operation. However, existing safe RL paradigms inherently struggle to achieve this objective. We propose a method, called Provably Lifetime Safe RL (PL…

Cited by 0SourceScholar
2025

Harnessing the Power of Vicinity-Informed Analysis for Classification under Covariate Shift

AISTATS 2025poster

Transfer learning enhances prediction accuracy on a target distribution by leveraging data from a source distribution, demonstrating significant benefits in various applications. This paper introduces a novel dissimilarity measure that utilizes vicinity information, i.e., the local structure of data…

Cited by 0SourceScholar
2024

Stepwise Alignment for Constrained Language Model Policy Optimization

NeurIPS 2024poster

Safety and trustworthiness are indispensable requirements for real-world applications of AI systems using large language models (LLMs). This paper formulates human value alignment as an optimization problem of the language model policy to maximize reward under a safety constraint, and then proposes…

2023

Statistically Significant Concept-based Explanation of Image Classifiers via Model Knockoffs

IJCAI 2023poster

A concept-based classifier can explain the decision process of a deep learning model by human understandable concepts in image classification problems. However, sometimes concept-based explanations may cause false positives, which misregards unrelated concepts as important for the prediction task. O…

Cited by 2SourcePDFScholar
2022

Max-Min Off-Policy Actor-Critic Method Focusing on Worst-Case Robustness to Model Misspecification

NeurIPS 2022accept

In the field of reinforcement learning, because of the high cost and risk of policy training in the real world, policies are trained in a simulation environment and transferred to the corresponding real-world environment. However, the simulation environment does not perfectly mimic the real-world en…

2022

Unsupervised Causal Binary Concepts Discovery with VAE for Black-Box Model Explanation

AAAI 2022technical

We aim to explain a black-box classifier with the form: "data X is classified as class Y because X has A, B and does not have C" in which A, B, and C are high-level concepts. The challenge is that we have to discover in an unsupervised manner a set of concepts, i.e., A, B and C, that is useful for e…

Cited by 10SourcePDFScholar
2021

AdvantageNAS: Efficient Neural Architecture Search with Credit Assignment

AAAI 2021technical

Neural architecture search (NAS) is an approach for automatically designing a neural network architecture without human effort or expert knowledge. However, the high computational cost of NAS limits its use in commercial applications. Two recent NAS paradigms, namely one-shot and sparse propagation,…

2021

Warm Starting CMA-ES for Hyperparameter Optimization

AAAI 2021technical

Hyperparameter optimization (HPO), formulated as black-box optimization (BBO), is recognized as essential for automation and high performance of machine learning approaches. The CMA-ES is a promising BBO approach with a high degree of parallelism, and has been applied to HPO tasks, often under paral…

2019

Adaptive Stochastic Natural Gradient Method for One-Shot Neural Architecture Search

ICML 2019oral

High sensitivity of neural architecture search (NAS) methods against their input such as step-size (i.e., learning rate) and search space prevents practitioners from applying them out-of-the-box to their own problems, albeit its purpose is to automate a part of tuning process. Aiming at a fast, robu…