Implicit Low-Order Unstructured Finite-Element Multiple Simulation Enhanced by Dense Computation Using OpenACC

In this paper, we develop a low-order three-dimensional finite-element solver for fast multiple-case crust deformation computation on GPU-based systems. Based on a highperformance solver designed for massively parallel CPU-based systems, we modify the algorithm to reduce random data access, and then insert OpenACC directives. By developing algorithm appropriate for each computer architecture, we enable to exhibit higher performance. The developed solver on ten Reedbush-H nodes (20 P100 GPUs) attained speedup of 14.2 times from the original solver on 20 K computer nodes. On the newest Volta generation V100 GPUs, the solver attained a further 2.52 times speedup with respect to P100 GPUs. As a demonstrative example, we computed 368 cases of crustal deformation analyses of northeast Japan with 400 million degrees of freedom. The total procedure of algorithm modification and porting implementation took only two weeks; we can see that high performance improvement was achieved with low development cost. With the developed solver, we can expect improvement in reliability of crust-deformation analyses by many-case analyses on a wide range of GPU-based systems.