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Bruno Castro da Silva

12 accepted papers

2026

PROMPTMINER: Black-Box Prompt Stealing against Text-to-Image Generative Models via Reinforcement Learning and VLM-Guided Optimization

CVPR 2026

Text-to-image (T2I) generative models such as Stable Diffusion and FLUX can synthesize realistic, high-quality images directly from textual prompts. The resulting image quality depends critically on well-crafted prompts that specify both subjects and stylistic modifiers, which have become valuable d

Cited by 0SourcecodeScholar
2025

Beyond Prediction: Managing the Repercussions of Machine Learning Applications

NeurIPS 2025poster

Machine learning models are often designed to maximize a primary goal, such as accuracy. However, as these models are increasingly used to inform decisions that affect people's lives or well-being, it is often unclear what the real-world repercussions of their deployment might be—making it crucial t…

Cited by 0SourceScholar
2025

Constructing an Optimal Behavior Basis for the Option Keyboard

NeurIPS 2025poster

Multi-task reinforcement learning aims to quickly identify solutions for new tasks with minimal or no additional interaction with the environment. Generalized Policy Improvement (GPI) addresses this by combining a set of base policies to produce a new one that is at least as good—though not necessar…

Cited by 0SourceScholar
2024

Abstract Reward Processes: Leveraging State Abstraction for Consistent Off-Policy Evaluation

NeurIPS 2024poster

Evaluating policies using off-policy data is crucial for applying reinforcement learning to real-world problems such as healthcare and autonomous driving. Previous methods for *off-policy evaluation* (OPE) generally suffer from high variance or irreducible bias, leading to unacceptably high predicti…

2024

From Past to Future: Rethinking Eligibility Traces

AAAI 2024technical

In this paper, we introduce a fresh perspective on the challenges of credit assignment and policy evaluation. First, we delve into the nuances of eligibility traces and explore instances where their updates may result in unexpected credit assignment to preceding states. From this investigation emerg…

Cited by 1SourcePDFScholar
2024

Position: Benchmarking is Limited in Reinforcement Learning Research

ICML 2024poster

Novel reinforcement learning algorithms, or improvements on existing ones, are commonly justified by evaluating their performance on benchmark environments and are compared to an ever-changing set of standard algorithms. However, despite numerous calls for improvements, experimental practices contin…

Cited by 7SourcePDFScholar
2023

A Toolkit for Reliable Benchmarking and Research in Multi-Objective Reinforcement Learning

NeurIPS 2023poster

Multi-objective reinforcement learning algorithms (MORL) extend standard reinforcement learning (RL) to scenarios where agents must optimize multiple---potentially conflicting---objectives, each represented by a distinct reward function. To facilitate and accelerate research and benchmarking in mult…

2023

Behavior Alignment via Reward Function Optimization

NeurIPS 2023spotlight

Designing reward functions for efficiently guiding reinforcement learning (RL) agents toward specific behaviors is a complex task. This is challenging since it requires the identification of reward structures that are not sparse and that avoid inadvertently inducing undesirable behaviors. Naively mo…

Cited by 15SourcePDFScholar
2023

Multi-Step Generalized Policy Improvement by Leveraging Approximate Models

NeurIPS 2023poster

We introduce a principled method for performing zero-shot transfer in reinforcement learning (RL) by exploiting approximate models of the environment. Zero-shot transfer in RL has been investigated by leveraging methods rooted in generalized policy improvement (GPI) and successor features (SFs). Alt…

Cited by 6SourcePDFScholar
2022

Fairness Guarantees under Demographic Shift

ICLR 2022poster

Recent studies have demonstrated that using machine learning for social applications can lead to injustice in the form of racist, sexist, and otherwise unfair and discriminatory outcomes. To address this challenge, recent machine learning algorithms have been designed to limit the likelihood such un…

Cited by 64SourcePDFScholar
2022

Off-Policy Evaluation for Action-Dependent Non-stationary Environments

NeurIPS 2022accept

Methods for sequential decision-making are often built upon a foundational assumption that the underlying decision process is stationary. This limits the application of such methods because real-world problems are often subject to changes due to external factors (\textit{passive} non-stationarity),…

2021

Universal Off-Policy Evaluation

NeurIPS 2021poster

When faced with sequential decision-making problems, it is often useful to be able to predict what would happen if decisions were made using a new policy. Those predictions must often be based on data collected under some previously used decision-making rule. Many previous methods enable such off-p…