HP-MPI User's Guide (11th Edition)

Tuning
Multilevel parallelism
Chapter 5192
Multilevel parallelism
There are several ways to improve the performance of applications that
use multilevel parallelism:
• Use the MPI library to provide coarse-grained parallelism and a
parallelizing compiler to provide fine-grained (that is, thread-based)
parallelism. An appropriate mix of coarse- and fine-grained
parallelism provides better overall performance.
• Assign only one multithreaded process per host when placing
application processes. This ensures that enough processors are
available as different process threads become active.