Advances on the multiblock extension of a DNS solver in the Legion framework

A multiblock extension of the Hypersonic Task-based Research (HTR) solver [Di Renzo et al., Comp. Phys. Comm. 255, 2020] is described in this work. The solver under investigation is a structured, scalable, single block solver which solves the Navier--Stokes (NS) equations for a multispecies, chemically reacting, high enthalpy flow. It uses the task-based programming model provided by the Legion runtime, which is also the building framework for this work, to schedule the work across all the available computational resources. In contrast to a conventional MPI based approach, our multiblock solver uses Legion's data structures and their supported logical operations to handle task scheduling and parallelism. The advantage of this approach lies in the fact that the whole computational domain is considered as a single logical instance, which is cognizant of all the partitions, thus automatically performing the appropriate communications when needed. The specific patterns of these communications are automatically determined at runtime by Legion using the boundary conditions and block connectivity information specified as user inputs. Verification tests for inviscid vortex rotation in a ring and an application example of a compressible flow through a pipe, which is simulated in a butterfly grid topology, will be discussed in this talk along with the computational performance of the proposed framework.