Scaling NWChem with Efficient and Portable Asynchronous Communication in MPI RMA

Abstract—NWChem is one of the most widely used compu-tational chemistry application suites for chemical and biological systems. Despite its vast success, the computational efficiency of NWChem is still low. This is especially true in higher accuracy methods such as the CCSD(T) coupled cluster method, where it currently achieves a mere 50 % computational efficiency when run at large scales. In this paper, we demonstrate the most computationally efficient scaling of NWChem CCSD(T) to date, and use it to solve large water clusters. We use our recently proposed process-based asynchronous progress framework for MPI RMA, called Casper, to scale the computation on water clusters at near-100 % computational efficiency on up to 12288 cores. Keywords-NWChem; Global Arrays; CCSD(T); MPI RMA; one-sided; asynchronous progres