Performance evaluation of SDN-enhanced MPI allreduce on a cluster system with fat-tree interconnect

Nowadays, supercomputers play an essential role in high-performance computing. In general, modern supercomuputers are built as a cluster system, which is a system of multiple computers interconnected on a network. In coding a parallel program on such a cluster system, MPI (Message Passing Interface) is utilized. In this paper, we aim to reduce the execution time of MPI Allreduce, a frequently used MPI collective communication in many simulation codes. To this end, we have integrated network programmability by Software Defined Networking into MPI Allreduce so that it effectively uses the bandwidth of the interconnect of the cluster system. An experiment conducted on a cluster system with fat-tree interconnect indicates that our proposed MPI Allreduce is superior to MPI Allreduce in OpenMPI implementations.