Consistent application performance at the exascale

We examine the future of application performance consistency on exascale parallel computing systems. By performance consistency we mean the regularity of wall clock times to complete a fixed amount of application progress. Exascale systems will have dramatically increased complexity along with their capability. Contributors to inconsistency include architectural choices, software functions and subtle interactions, and inconsistency will lead to lost potential. The challenge is how to maintain consistency at the exascale. In order for exascale systems to exhibit the consistency that is required to make the applications and systems productive, a new understanding of the causes and solutions to inconsistency is required, along with new ways of measuring the impact that design, implementation and operational choices have on consistency.