NWChemEx: Tackling Chemical, Materials, and Biochemical Challenges in the Exascale Era*

Historically, the NWChem computational chemistry package has been adapted and optimized for supercomputer architectures as they emerged. While this strategy has been successful over the past two decades, adapting NWChem to the major changes in hardware and programming models anticipated at the exascale is infeasible without a revolutionary redesign of the code. The NWChemEx project is redesigning and re-implementing NWChem for exascale computers using C++ with the goal of dramatically improving upon the scalability, performance, extensibility, and portability of the original application. In the first portion of this talk, the limitations of NWChem will be described. Next, we will illustrate how the scalability limitations are addressed in the NWChemEx design via the implementation of novel reduced-scaling methods with a new high-performance tensor library. Finally, we will show how lossy compression and differenced checkpointing techniques are utilized in NWChemEx to address more general exascale challenges related to data volume and system resilience.