Publications

Efficient Design-and-Control Automation with Reinforcement Learning and Adaptive Exploration
Hongyao Tang
Mariano Phielipp
Santiago Miret
Seeking good designs is a central goal of many important domains, such as robotics, integrated circuits (IC), medicine, and materials scienc… (see more)e. These design problems are expensive, time-consuming, and traditionally performed by human experts. Moreover, the barriers to domain knowledge make it challenging to propose a universal solution that generalizes to different design problems. In this paper, we propose a new method called Efficient Design and Stable Control (EDiSon) for automatic design and control in different design problems. The key ideas of our method are (1) interactive sequential modeling of the design and control process and (2) adaptive exploration and design replay. To decompose the difficulty of learning design and control as a whole, we leverage sequential modeling for both the design process and control process, with a design policy to generate step-by-step design proposals and a control policy to optimize the objective by operating the design. With deep reinforcement learning (RL), the policies learn to find good designs by maximizing a reward signal that evaluates the quality of designs. Furthermore, we propose an adaptive exploration and replay mechanism based on a design memory that maintains high-quality designs generated so far. By regulating between constructing a design from scratch or replaying a design from memory to refine it, EDiSon balances the trade-off between exploration and exploitation in the design space and stabilizes the learning of the control policy. In the experiments, we evaluate our method in robotic morphology design and Tetris-based design tasks. Our framework has the potential to significantly accelerate the discovery of optimized designs across diverse domains, including automated materials discovery, by improving the exploration in design space while ensuring efficiency.
fPLSA: Learning Semantic Structures in Document Collections Using Foundation Models
Weijia Xu
Nebojsa Jojic
Nicolas Roux
HoneyComb: A Flexible LLM-Based Agent System for Materials Science
Yu Song
Ziyu Hou
Santiago Miret
The emergence of specialized large language models (LLMs) has shown promise in addressing complex tasks in materials science. Many LLMs, how… (see more)ever, often struggle with the distinct complexities of materials science tasks, such as computational challenges, and rely heavily on outdated implicit knowledge, leading to inaccuracies and hallucinations. To address these challenges, we introduce HoneyComb, the first LLM-based agent system specifically designed for materials science. HoneyComb leverages a reliable, high-quality materials science knowledge base (MatSciKB) and a sophisticated tool hub (ToolHub) tailored specifically for materials science to enhance its reasoning and computational capabilities. MatSciKB is a curated, structured knowledge collection based on reliable literature, while ToolHub employs an Inductive Tool Construction method to generate, decompose, and refine API tools for materials science. Additionally, HoneyComb leverages a retriever module that adaptively selects the appropriate knowledge source or tools for specific tasks, thereby ensuring accuracy and relevance. Our results demonstrate that HoneyComb significantly outperforms baseline models across various tasks in materials science, effectively bridging the gap between current LLM capabilities and the specialized needs of this domain. Furthermore, our adaptable framework can be easily extended to other scientific domains, highlighting its potential for broad applicability in advancing scientific research and applications.
Toward Debugging Deep Reinforcement Learning Programs with RLExplorer
Deep reinforcement learning (DRL) has shown success in diverse domains such as robotics, computer games, and recommendation systems. However… (see more), like any other software system, DRL-based software systems are susceptible to faults that pose unique challenges for debugging and diagnosing. These faults often result in unexpected behavior without explicit failures and error messages, making debugging difficult and time-consuming. Therefore, automating the monitoring and diagnosis of DRL systems is crucial to alleviate the burden on developers. In this paper, we propose RLExplorer, the first fault diagnosis approach for DRL-based software systems. RLExplorer automatically monitors training traces and runs diagnosis routines based on properties of the DRL learning dynamics to detect the occurrence of DRL-specific faults. It then logs the results of these diagnoses as warnings that cover theoretical concepts, recommended practices, and potential solutions to the identified faults. We conducted two sets of evaluations to assess RLExplorer. Our first evaluation of faulty DRL samples from Stack Overflow revealed that our approach can effectively diagnose real faults in 83% of the cases. Our second evaluation of RLExplorer with 15 DRL experts/developers showed that (1) RLExplorer could identify 3.6 times more defects than manual debugging and (2) RLExplorer is easily integrated into DRL applications.
Understanding Web Application Workloads and Their Applications: Systematic Literature Review and Characterization
Roozbeh Aghili
Qiaolin Qin
Heng Li
Web applications, accessible via web browsers over the Internet, facilitate complex functionalities without local software installation. In … (see more)the context of web applications, a workload refers to the number of user requests sent by users or applications to the underlying system. Existing studies have leveraged web application workloads to achieve various objectives, such as workload prediction and auto-scaling. However, these studies are conducted in an ad hoc manner, lacking a systematic understanding of the characteristics of web application workloads. In this study, we first conduct a systematic literature review to identify and analyze existing studies leveraging web application workloads. Our analysis sheds light on their workload utilization, analysis techniques, and high-level objectives. We further systematically analyze the characteristics of the web application workloads identified in the literature review. Our analysis centers on characterizing these workloads at two distinct temporal granularities: daily and weekly. We successfully identify and categorize three daily and three weekly patterns within the workloads. By providing a statistical characterization of these workload patterns, our study highlights the uniqueness of each pattern, paving the way for the development of realistic workload generation and resource provisioning techniques that can benefit a range of applications and research areas.
Beyond the lab: Feasibility of cognitive neuroscience data collection during a speleological expedition
Anita Paas
Hugo R. Jourde
Arnaud Brignol
Marie-Anick Savard
Zseyvfin Eyqvelle
Samuel Bassetto
Emily B.J. Coffey
Multi-Objective Risk Assessment Framework for Exploration Planning Using Terrain and Traversability Analysis
Riana Gagnon Souleiman
Vivek Shankar Vardharajan
DECOLLAGE: 3D Detailization by Controllable, Localized, and Learned Geometry Enhancement
Qimin Chen
Zhiqin Chen
Vladimir Kim
Hao (Richard) Zhang
Hao Zhang 0002
Siddhartha Chaudhuri
Probabilistic Temporal Prediction of Continuous Disease Trajectories and Treatment Effects Using Neural SDEs
Joshua D. Durso-Finley
Jean-Pierre R. Falet
Douglas Arnold
Nick Pawlowski
Personalized medicine based on medical images, including predicting future individualized clinical disease progression and treatment respons… (see more)e, would have an enormous impact on healthcare and drug development, particularly for diseases (e.g. multiple sclerosis (MS)) with long term, complex, heterogeneous evolutions and no cure. In this work, we present the first stochastic causal temporal framework to model the continuous temporal evolution of disease progression via Neural Stochastic Differential Equations (NSDE). The proposed causal inference model takes as input the patient's high dimensional images (MRI) and tabular data, and predicts both factual and counterfactual progression trajectories on different treatments in latent space. The NSDE permits the estimation of high-confidence personalized trajectories and treatment effects. Extensive experiments were performed on a large, multi-centre, proprietary dataset of patient 3D MRI and clinical data acquired during several randomized clinical trials for MS treatments. Our results present the first successful uncertainty-based causal Deep Learning (DL) model to: (a) accurately predict future patient MS disability evolution (e.g. EDSS) and treatment effects leveraging baseline MRI, and (b) permit the discovery of subgroups of patients for which the model has high confidence in their response to treatment even in clinical trials which did not reach their clinical endpoints.
Sparse Bayesian Networks: Efficient Uncertainty Quantification in Medical Image Analysis
Efficiently quantifying predictive uncertainty in medical images remains a challenge. While Bayesian neural networks (BNN) offer predictive … (see more)uncertainty, they require substantial computational resources to train. Although Bayesian approximations such as ensembles have shown promise, they still suffer from high training and inference costs. Existing approaches mainly address the costs of BNN inference post-training, with little focus on improving training efficiency and reducing parameter complexity. This study introduces a training procedure for a sparse (partial) Bayesian network. Our method selectively assigns a subset of parameters as Bayesian by assessing their deterministic saliency through gradient sensitivity analysis. The resulting network combines deterministic and Bayesian parameters, exploiting the advantages of both representations to achieve high task-specific performance and minimize predictive uncertainty. Demonstrated on multi-label ChestMNIST for classification and ISIC, LIDC-IDRI for segmentation, our approach achieves competitive performance and predictive uncertainty estimation by reducing Bayesian parameters by over 95\%, significantly reducing computational expenses compared to fully Bayesian and ensemble methods.
TrajGPT: Irregular Time-Series Representation Learning for Health Trajectory Analysis
Ziyang Song
Qincheng Lu
Mike He Zhu
David L Buckeridge
Yuemei Li
Were RNNs All We Needed?
Frederick Tung
Mohamed Osama Ahmed
Hossein Hajimirsadeghi
The introduction of Transformers in 2017 reshaped the landscape of deep learning. Originally proposed for sequence modelling, Transformers h… (see more)ave since achieved widespread success across various domains. However, the scalability limitations of Transformers - particularly with respect to sequence length - have sparked renewed interest in novel recurrent models that are parallelizable during training, offer comparable performance, and scale more effectively. In this work, we revisit sequence modelling from a historical perspective, focusing on Recurrent Neural Networks (RNNs), which dominated the field for two decades before the rise of Transformers. Specifically, we examine LSTMs (1997) and GRUs (2014). We demonstrate that by simplifying these models, we can derive minimal versions (minLSTMs and minGRUs) that (1) use fewer parameters than their traditional counterparts, (2) are fully parallelizable during training, and (3) achieve surprisingly competitive performance on a range of tasks, rivalling recent models including Transformers.