Mark S. Gordon, Monica H. Lamm, Masha Sosonkina, and Theresa L. Windus are supported by the Office of Cyberinfrastructure through the PetaApps solicitation to develop software that will scale efficiently to petascale computer architectures. Co-funding for this proposal is provided by the Division of Chemistry and the Office of Multidisciplinary Activities in the Mathematical and Physical Sciences Directorate, and by the Computer and Information Science and Engineering Directorate.
The focus of this research is on enabling high quality electronic structure theory and multi-scale computational methods to run efficiently on petascale-class computer systems. Many important problems in the chemical sciences are so computationally demanding that the only current option for addressing such problems is to employ low-level methods whose reliability is suspect. The electronic structure community has well established protocols for assessing the reliability of methods applied to small and medium systems by employing increasingly sophisticated methods that are generally accepted to be reliable, and studying convergence of results. Such protocols have not been available for the very large systems that are typified by the three examples in the present proposal, water, aerosols, and dendrimer-ligand binding. A primary motivation for the research is to ensure that reliable levels of electronic structure theory (e.g., many body perturbation theory and coupled cluster theory) can realistically be employed to solve challenging problems of national interest. Combined with novel multi-scale methods and new developments in computer and computational science, this research is extending the sizes of chemical systems that can be addressed with accurate theoretical methods. The code developments are providing the computational chemistry community with a way forward to make use of massively parallel computer architectures to solve important problems using highly accurate methods. Driving the need for petascale computing in this community are a vast array of problems, ranging from simulations of liquids with unquestionable accuracy to studies of reaction mechanisms in the condensed phase to ground and excited state studies of polymers, biomolecules, and other extended systems. The two primary electronic structure codes that are being modified to run on petascale architectures are GAMESS and NWChem. These two codes implement broadly scalable electronic structure algorithms, and are made available to all users at no cost.
This work is having a broader impact in making all developments enabled by this research freely available to the general community and accessible to other code developers. New courses are being designed and existing courses are being modified to educate students (undergraduate and graduate) and faculty regarding the crucial considerations that arise when scaling codes from a small number of processors to thousands of processors or more.
