关键词: 集合通信, 通信性能, Alltoall

Abstract: Alltoall is an important collective operation of MPI (message passing interface), which impacts the parallel efficiency of many parallel numerical computing applications. Since theoretic analysis and evaluation of Alltoall collective communications on the massive parallel computer is still insufficient, improper communication module design and poor communication usage are widespread in many applications. The test of basic MPI communication performance shows that the communication latency is instable due to network contention and the variety increases with the number of MPI processes. In order to reduce the gap between the predicted run-time and the measured run-time, this paper proposes a new performance model to evaluate Alltoall operation. The model considers not only the standard parameters such as bandwidth and latency, but also takes into account network communication contention. Results on the BXJ supercomputer show that the performance prediction model accurately captures the Alltoall communication behavior even for the operations on a large number of processors and manifests network competition cost on the Alltoall communication.

Key words:  collective communication, communication performance, Alltoall