Spatial Parallelism of a 3D Finite Difference Velocity-Stress Elastic Wave Propagation Code

In a three-dimensional isotropic elastic earth, the wave equation solution consists of three velocity components and six stresses. We discretize the partial derivatives using second order in time and fourth order in space staggered finite difference operators. The parallel implementation uses the message passing interface library for platform portability and a spatial decomposition for efficiency. Most of the communication in the code consists of passing subdomain face information to neighboring processors. When the parallel communication is balanced against computation by allocating subdomains of reasonable size, we observe excellent scaled speedup. Allocating subdomains of size 25 × 25 × 25 on each node, we achieve efficiencies of 94% on 128 processors of an Intel Paragon.