NWChemEx: Designing a computational chemistry app store for the exascale era (and beyond)

With the advent of the exascale era, the NWChem team decided to rewrite the open-source NWChem package from the ground up. From conception, the resulting electronic structure package, NWChemEx, was envisoned as being a radical departure from the original NWChem. NWChemEx is written using object-oriented C++17 for performance, with all user-facing APIs mirrored in Python for user convenience. Internally, NWChemEx is entirely plugin-based, a design with a number of benefits including ease of refactoring, encapsulation, and interoperability. This presentation will primarily focus on the computer science behind NWChemEx's design, and how the design facilitates Open Science. In particular we describe how the design lays the foundations for a computational chemistry app store, and why such a design is imperative for performance at the exascale.