Using Blue Gene/P and GPUs to Accelerate Computations in the EULAG Model

EULAG (Eulerian/semi-Lagrangian fluid solver) is an established computational model developed by the group headed by Piotr K. Smolarkiewicz for simulating thermo-fluid flows across a wide range of scales and physical scenarios. This paper presents perspectives of the EULAG parallelization based on the MPI, OpenMP, and OpenCL standards. We focus on development of computational kernels of the EULAG model. They consist of the most time-consuming calculations of the model, which are: laplacian algorithm (laplc) and multidimensional positive definite advection transport algorithm (MPDATA).

The first challenge of our work was parallelization of the laplc subroutine using MPI across nodes and OpenMP within nodes, on the BlueGene/P supercomputer located in the Bulgarian Supercomputing Center. The second challenge was to accelerate computations of the Eulag model using modern GPUs. We discuss the scalability issue for the OpenCL implementation of the linear part of MPDATA on ATI Radeon HD 5870 GPU with AMD Phenom II X4 CPU, and NVIDIA Tesla C1060 GPU with AMD Phenom II X4 CPU.