Experiences with Sweep3D implementations in Co-Array Fortran

As part of the recent focus on increasing the productivity of parallel application developers, Co-array Fortran (CAF) has emerged as an appealing alternative to the Message Passing Interface (MPI). CAF belongs to the family of global address space parallel programming languages; such languages provide the abstraction of globally addressable memory accessed using one-sided communication. At Rice University we are developing cafc, an open source, multiplatform CAF compiler. Our earlier studies show that cafc-compiled CAF programs achieve similar perfor-mance to that of corresponding MPI codes for the NAS Parallel Benchmarks. In this paper, we present a study of several CAF implementations of Sweep3D on four modern architectures. We analyze the impact of using one-sided communication in Sweep3D, identify potential sources of inefficiencies and suggest ways to address them. Our re-sults show that we achieve comparable performance to that of the MPI version on three cluster-based architectures and outperform it by up to 10 % on the SGI Altix 3000.