Implementing Multipathing When Using Partitioned Communication in Open MPI
Jordan M. Abt, Ryan Eric Grant · 2024
MPI Partitioned communication is designed to allow parts of a message to be sent when ready while multipathing allows messages to travel simultaneously. This presents an opportunity to pair multipathing with partitioned communication to increase efficiency. This paper uses benchmarks to examine the impact of using hardware spraying with partitioned communication. The perceived bandwidth increases drastically from less than 1450 MB/s to over 5650 MB/s. With four or fewer partitions the overhead stays below 21, but with eight or more the overhead is in the hundreds for small messages. Finally, measuring the percentage of early communication shows that there are opportunities to send partitions early when messages stay below 4 MB.