Multi-GPGPU Cellular Automata Simulations using OpenCL

The aim of this research it to examine the possibility of parallelizing the Frish-Hasslacher-Pomeau (FHP) model, a cellular automata algorithm for modeling fluid flow, on clusters of modern graphics processing units (GPUs). To this end an Open Computing Language (OpenCL) implementation for GPUs was written and compared with a previous, semi-automatic one based on the OpenACC compiler pragmas (S. Szkoda, Z. Koza, and M. Tykierko, Multi-GPGPU Cellular Automata Simulations using OpenACC, http://www.prace-project.eu/IMG/pdf/wp154.pdf). Both implementations were tested on up to 16 Fermi-class GPUs using the MPICH3 library for the inter-process communication. We found that for both of the multiGPU implementations the weak scaling is practically linear for up to 16 devices, which suggests that the FHP model can be successfully run even on much larger clusters. Secondly, while the pragma-based OpenACC implementation is much easier to develop and maintain, it gives as good performance as the manually written OpenCL code.