Exploiting temporal parallelism in particle-based incompressive fluid simulation on FPGA

—While the semiconductor manufacturing process is shrinking, the Bytes per Flop (B/F) ratio on recent machines is becoming lower. Particle-based computational fluid dynamics (CFD) methods such as Moving Particle Simulation (MPS) require a higher B/F ratio than that of stencil-based CFD methods. Techniques to reduce the B/F ratio by exploiting temporal parallelism is becoming popular in stencil-based CFD methods on CPU and GPU. It is also reported that a technique to combine temporal blocking with stencil buffer is suitable for FPGA and can outperform CPU and GPU. On the other hand, it has been considered that temporal parallelism cannot be exploited in the particle-based CFD methods. This is because the number of particles in each bucket, a three-dimensional grid covering a computational domain, changes every time-step. In this paper, we propose a technique to exploit temporal parallelism in MPS method, a particle-based CFD method for incompressive fluid. The key idea is that the buckets in MPS can be considered as stencils in stencil-based CFD. This is because the maximum number of particles in a bucket can be assumed empirically in the case of an incompressible fluid. To the best of our knowledge, this is the first research which exploits temporal parallelism in the particle-based incompressible fluid method. We implemented the proposed technique with a degree of temporal parallelism of three. We also optimized it on Intel Arria10 FPGA in Intel HLS, and measured the performance and resource consumption. The result shows that the optimized implementation with a degree of temporal parallelism of three achieved 2.1 times speedup compared with implementation without exploiting temporal parallelism on CPU.