Fluid Dynamics Simulations on Multi-GPU Systems

The thesis describes the original design, implementation and testing of the multi-GPU version of two fluid flow simulation models, focusing on the cellular automaton MAGFLOW lava flow simulator and the GPU-SPH model for Navier-Stokes. In both cases, a spatial subdivision of the domain is performed, with a minimal overlap to ensure the correct evaluation of the bordering elements (cells in MAGFFLOW, particles in GPUSPH). The latencies introduces by the continuous transfer of the overlapping borders are completely hidden through the use of asynchronous transfers performed concurrently with computations. Different load balancing techniques are used (a priori for MAGFLOW, a posteriori for GPUSPH) and compared. The obtained speedup is linear with the number of the used devices and closely follows the ideal speedup. The performance results are formally analyzed and discussed. While the results are close to the ideal achievable speedups, some future improvements are hypothesized and open problems are mentioned.