International audience

Classical simulation methods become not flexible and performant enough in complex models, necessitating the use of a distributed simulation technique to split the load and heterogeneity into separate sub-components and manage the simulation time between them. In this type of simulation, interoperability and reusability issues arise and should be addressed. The IEEE High-Level Architecture (HLA) standard for distributed simulation emphasizes federates interoperability and reusability, as well as time management and advanced data distribution techniques. This paper presents the methodologies and techniques used to develop the HLA federates, as part of the Simulation Exploration Experience (SEE) project, to virtually recreate a mission on the moon. This project is organized by the National Aeronautics and Space Administration (NASA) and the Simulation Interoperability Standards Organization (SISO). For each SEE component, an HLA interface was developed to make it compliant with other SEE federates and reusable during the simulation run. Based on HLA mechanisms, heterogeneous components with an HLA interface were able to interexchange objects/attributes and interactions/parameters.

In this work, we propose a distributed Memetic Algorithm for the traveling salesman problem focusing on small and medium-sized instances. The algorithm employs a new crossover operator that favors the fitter of the two parents and develops varying progeny from the same parents to evade premature convergence. In the implementation, we use the High-Level Architecture (HLA) to distribute laborious tasks and lower the lead time of the heuristic. Results show that our proposed approach significantly outperforms other algorithms when tested on instances from the TSPLIB benchmark.

In order to monitor and assess the spread of the Omicron variant of COVID-19, we propose a Distributed Digital Twin that virtually mirrors a hemodialysis unit in a hospital in Toronto, Canada. Since the solution involves heterogeneous components, we rely on the IEEE HLA distributed simulation standard. Based on the standard, we use an agent-based/discrete event simulator together with a virtual reality environment in order to provide to the medical staff an immersive experience that incorporates a platform showing predictive analytics during a simulation run. This can help professionals monitor the number of exposed, symptomatic, asymptomatic, recovered, and deceased agents. Agents are modeled using a redesigned version of the susceptible-exposed-infected-recovered (SEIR) model. A contact matrix is generated to help identify those agents that increase the risk of the virus transmission within the unit.

Different heterogeneous simulation components can be integrated to produce a more effective complex global system. The IEEE High-Level Architecture (HLA) is an international standard that promotes interoperability and reusability for distributed simulation (DS). This paper proposes a DS system that integrates an agent-based and discrete-event simulator with a 3D game engine to build virtual reality (VR) applications that replicate real environments. In this case study, AnyLogic is used as an agent-based and discrete event simulator to simulate the process flow and COVID-19 transmission inside the University Health Network dialysis unit, Toronto, Canada. Unity game engine delivers the 3D modelling replicating the real architecture and environment of the dialysis unit. The HLA standard plays a major role in the integration of AnyLogic and Unity to produce a more effective and powerful DS system for VR applications.

In many domains, Discrete-Event Simulations (DES) are usually used to reproduce the behavior of a certain system or process, where events are processed one after another in chronological and sequential order. Classical DES will no longer be a possible solution for Complex and Large-scale systems, System of Systems (SoS), and Performance Evaluation Systems that compare multiple different simulations running simultaneously in parallel. Advances in network and communications made the Distributed Simulation (DS) approach one of the best solutions for the aforementioned Systems Simulations. One of the challenges faced when developing a DS from DES components is the federation behavior including time management and synchronization between these components. In most of the traditional DES platforms, simulations cannot exchange messages, nor change the configuration at run time. This makes the DES connection and integration very hard and at times, impossible to implement. This article presents the method used to integrate different DES components, using High-Level Architecture (HLA) Evolved Standard, Business Process Model and Notation (BPMN), and Jaamsim, a Java open source DES.