Optimized Reduce Communication Performance with the Tree Topology

Communication plays an important role in MPI applications, and reduce operations are heavily used part of MPI. In this paper, we propose a k-nomial tree topology and a hierarchy tree topology to optimize the Reduce operation in MPI. The k-nomial tree can effectively decrease the communication steps and is suitable for lots of processes. Compared with the binomial tree algorithm in small and medium size messages, the Reduce operation performed by the k-nomial tree can improve communication performance by 46%. Hierarchy trees can dynamically group processes at run time to take advantage of high bandwidth to communicate as much as possible within nodes. The test results show that compared with the binomial tree algorithm, the performance of the hierarchy tree algorithm is stable. For Reduce operation, we can get a 30% performance improvement.