AB

A.J. Bartlett

info

Please Note

6 records found

Multi-objective Testing of Deep Reinforcement Learning Agents

Conference paper (2026) - Antony Bartlett, Cynthia Liem, Annibale Panichella
Testing deep reinforcement learning (DRL) agents in safety-critical domains requires discovering diverse failure scenarios. Existing tools such as INDAGO rely on single-objective optimization focused solely on maximizing failure counts, but this does not ensure discovered scenarios are diverse or reveal distinct error types. We introduce INDAGO-Nexus, a multi-objective search approach that jointly optimizes for failure likelihood and test scenario diversity using multi-objective evolutionary algorithms with multiple diversity metrics and Pareto front selection strategies. We evaluated INDAGO-Nexus on three DRL agents: humanoid walker, self-driving car, and parking agent. On average, INDAGO-Nexus discovers up to 83% and 40% more unique failures (test effectiveness) than INDAGO in the SDC and Parking scenarios, respectively, while reducing time-to-failure by up to 67% across all agents. ...
Conference paper (2025) - A. Bartlett, C. Liem, A. Panichella
DRVN is a regression testing tool that aims to diversify the test scenarios (road maps) to execute for testing and validating self-driving cars. DRVN harnesses the power of convolutional neural networks to identify possible failing roads in a set of generated examples before applying a greedy algorithm that selects and prioritizes the most diverse roads during regression testing. Initial testing discovered that DRVN performed well against random-based test selection. ...
Conference paper (2025) - A.J. Bartlett, C.C.S. Liem, A. Panichella
Resolving Python dependency issues remains a tedious and error-prone process, forcing developers to manually trial compatible module versions and interpreter configurations. Existing automated solutions, such as knowledge-graph-based and database-driven methods, face limitations due to the variety of dependency error types, large sets of possible module versions, and conflicts among transitive dependencies. This paper investigates the use of Large Language Models (LLMs) to automatically repair dependency issues in Python programs. We propose pllm (pronounced 'plum'), a novel retrieval-augmented generation (RAG) approach that iteratively infers missing or incorrect dependencies. PLLM builds a test environment where the LLM proposes module combinations, observes execution feedback, and refines its predictions using natural language processing (NLP) to parse error messages. We evaluate PLLM on the Gistable HG2. 9K dataset, a curated collection of real-world Python programs. Using this benchmark, we explore multiple PLLM configurations, including six open-source LLMs evaluated both with and without RAG. Our findings show that RAG consistently improves fix rates, with the best performance achieved by Gemma-2 9B when combined with RAG. Compared to two state-of-the-art baselines, PyEGo and ReadPyE, PLLM achieves significantly higher fix rates; +15.97% more than ReadPyE and +21.58% more than PyEGo. Further analysis shows that PLLM is especially effective for projects with numerous dependencies and those using specialized numerical or machine-learning libraries. ...
Developments in the field of Artificial Intelligence (AI), and particularly large language models (LLMs), have created a 'perfect storm' for observing 'sparks' of Artificial General Intelligence (AGI) that are spurious. Like simpler models, LLMs distill meaningful representations in their latent embeddings that have been shown to correlate with external variables. Nonetheless, the correlation of such representations has often been linked to human-like intelligence in the latter but not the former. We probe models of varying complexity including random projections, matrix decompositions, deep autoencoders and transformers: all of them successfully distill information that can be used to predict latent or external variables and yet none of them have previously been linked to AGI. We argue and empirically demonstrate that the finding of meaningful patterns in latent spaces of models cannot be seen as evidence in favor of AGI. Additionally, we review literature from the social sciences that shows that humans are prone to seek such patterns and anthropomorphize. We conclude that both the methodological setup and common public image of AI are ideal for the misinterpretation that correlations between model representations and some variables of interest are 'caused' by the model's understanding of underlying 'ground truth' relationships. We, therefore, call for the academic community to exercise extra caution, and to be keenly aware of principles of academic integrity, in interpreting and communicating about AI research outcomes. ...
Adversarial examples remain a critical concern for the robustness of deep learning models, showcasing vulnerabilities to subtle input manipulations. While earlier research focused on generating such examples using white-box strategies, later research focused on gradient-based black-box strategies, as models' internals often are not accessible to external attackers. This paper extends our prior work by exploring a gradient-free search-based algorithm for adversarial example generation, with particular emphasis on differential evolution (DE). Building on top of the classic DE operators, we propose five variants of gradient-free algorithms: a single-objective approach (GADE), two multi-objective variations (NSGA-IIDE and MOEA/DDE), and two many-objective strategies (NSGA-IIIDE and AGE-MOEADE). Our study on five canonical image classification models shows that whilst GADE variant remains the fastest approach, NSGA-IIDE consistently produces more minimal adversarial attacks (i.e., with fewer image perturbations). Moreover, we found that applying a post-process minimization to our adversarial images, would further reduce the number of changes and overall delta variation (image noise). ...
Deep learning (DL) models are known to be highly accurate, yet vulnerable to adversarial examples. While earlier research focused on generating adversarial examples using whitebox strategies, later research focused on black-box strategies, as models often are not accessible to external attackers. Prior studies showed that black-box approaches based on approximate gradient descent algorithms combined with meta-heuristic search (i.e., the BMI-FGSM algorithm) outperform previously proposed white- and black-box strategies. In this paper, we propose a novel black-box approach purely based on differential evolution (DE), i.e., without using any gradient approximation method. In particular, we propose two variants of a customized DE with customized variation operators: (1) a single-objective (Pixel-SOO) variant generating attacks that fool DL models, and (2) a multi-objective variant (Pixel-MOO) that also minimizes the number of changes in generated attacks. Our preliminary study on five canonical image classification models shows that Pixel-SOO and Pixel-MOO are more effective than the state-of-the-art BMI-FGSM in generating adversarial attacks. Furthermore, Pixel-SOO is faster than Pixel-MOO, while the latter produces subtler attacks than its single-objective variant. ...