A HPX Communication Benchmark: Distributed FFT using Collectives

Due to increasing core counts in modern processors, several task-based runtimes emerged, including the C++ Standard Library for Concurrency and Parallelism (HPX). Although the asynchronous many-task runtime HPX allows implicit communication via an Active Global Address Space, it also supports explicit collective operations. Collectives are an efficient way to realize complex communication patterns. In this work, we benchmark the TCP, MPI, and LCI communication backends of HPX, which are called parcelports in HPX terms. We use a distributed multi-dimensional FFT application relying on collectives. Furthermore, we compare the performance of the HPX all-to-all and scatter collectives against an FFTW3 reference based on MPI+X on a 16-node cluster. Of the three parcelports, LCI performed best for both scatter and all-to-all collectives. Furthermore, the LCI parcelport was up to factor 3 faster than the MPI+X reference. Our results highlight the potential of message abstractions and the parcelports of HPX.