“…At the same time, it serves as an advanced research tool, capable to run in different architectures with multiple processors and with suitable scalability properties, thus allowing to tackle complex problems that are beyond the capabilities of existing codes [38,40]. Indeed, whereas the implicit-in-time matrix-free approach shares some common features with some available DG codes [41][42][43], it contrasts with most of the available open-source DG approaches, such as [44][45][46][47][48][49][50][51], which are CPU-based, and also with other codes running on GPUs which rely on explicit time-marching schemes, like [52,53].…”