Co-simulation of FMUs and Distributed Applications with SimGrid.

The Functional Mock-up Interface (FMI) standard is becoming an essential solution for co-simulation. In this paper, we address a specific issue which arises in the context of Distributed Cyber-Physical System (DCPS) co-simulation where Functional Mock-up Units (FMU) need to interact with distributed application models. The core of the problem is that, in general, complex distributed application behaviors cannot be easily and accurately captured by a modeling formalism but are instead directly specified using a standard programming language. As a consequence, the model of a distributed application is often a concurrent program. The challenge is then to bridge the gap between this programmatic description and the equation-based framework of FMI in order to make FMUs interact with concurrent programs. In this article, we show how we use the unique model of execution of the SimGrid simulation platform to tackle this issue. The platform manages the co-evolution and the interaction between IT models and the different concurrent processes which compose a distributed application code. Thus, SimGrid offers a framework to mix models and concurrent programs. We show then how we specify an FMU as a SimGrid model to solve the DCPS co-simulation issues. Compared to other works of the literature, our solution is not limited to a specific use case and benefits from the versatility and scalability of SimGrid.