Heterogeneous CPU+GPU approaches for mesh refinement over Lattice-Boltzmann simulations.

The use of mesh refinement in CFD is an efficient and widely used methodology to minimize the computational cost by solving those regions of high geometrical complexity with a finer grid. In this work, the author focuses on studying two methods, one based on Multi-Domain and one based on Irregular meshing, to deal with mesh refinement over LBM simulations. The numerical formulation is presented in detail. It is proposed two approaches, homogeneous GPU and heterogeneous CPU+GPU, on each of the refinement methods. Obviously, the use of the two architectures, CPU and GPU, to compute the same problem involves more important challenges with respect to the homogeneous counterpart. These challenges and the strategies to deal with them are described in detail into the present work. We pay a particular attention to the differences among both methodologies/implementations in terms of programmability, memory management, and performance. The size of the refined sub-domain has important consequences over both methodologies; however, the influence on Multi-Domain approach is much higher. For instance, when dealing with a big refined sub-domain, the Multi-Domain approach achieves an important fall in performance with respect to other cases, where the size of the refined sub-domain is smaller. Otherwise, using the Irregular approach, there is no such a dramatic fall in performance when increasing the size of the refined sub-domain. Copyright (C) 2016 John Wiley & Sons, Ltd.