DescriptionThe HPX asynchronous many-task runtime system has been using TCP and MPI as its communication backends (parcelports). We developed a new HPX parcelport using a new communication library, the Lightweight Communication Interface (LCI) that was designed to better match the needs of systems such as HPX. We evaluate its performance with various microbenchmarks and a real-world astrophysics application, Octo-Tiger. Compared to the best configuration of the MPI parcelport, microbenchmarks show that the new LCI parcelport improves the message rate by up to 30x and decreases latencies by up to 5x. It also reduces the total execution time of Octo-Tiger by up to 1.175x compared to the best configuration of the MPI parcelport and up to 13.6x compared to the same configuration of the MPI parcelport. We discuss the performance impacts of different design choices.