Acceleration of Element-by-Element Kernel in Unstructured Implicit Low-Order Finite-Element Earthquake Simulation Using OpenACC on Pascal GPUs

The element-by-element computation used in matrix-vector multiplications is the key kernel for attaining high-performance in unstructured implicit low-order finite-element earthquake simulations. We accelerate this CPU-based element-by-element kernel by developing suitable algorithms for GPUs and porting to a GPU-CPU heterogeneous compute environment by OpenACC. Other parts of the earthquake simulation code are ported by directly inserting OpenACC directives into the CPU code. This porting approach enables high performance with relatively low development costs. When comparing eight K computer nodes and eight NVIDIA Pascal P100 GPUs, we achieve 23.1 times speedup for the element-by-element kernel, which leads to 16.7 times speedup for the 3 × 3 block Jacobi preconditioned conjugate gradient finite-element solver. We show the effectiveness of the proposed method through many-case crust-deformation simulations on a GPU cluster.