This award supports the development of software tools for advanced algorithms on a cluster of high performance graphics processing units(GPUs). The initial goal of this library will focus on a single driver application, the fundamental numerical study of Nuclear Forces (Lattice Quantum Chromodynamics: LQCD), and a second target application, the numerical simulation of the exciting nano-technology of graphene. These are both multi-fermion problems well suited to solution via multi-scale algorithms on many-core architectures. This pilot project draws on experience gained by the small team at Boston University and Harvard in developing Dirac solvers for lattice field theory. Two building blocks from prior research are (1) the construction of an adaptive multigrid (MG) solver for the Wilson Dirac operator of LQCD, which demonstrates a 20x speedup compared to the best Krylov solvers in production code and (2) a highly optimized Krylov solver for the same operator on GPUs (but without multigrid), realizing a 10x improvement in price/performance over traditional clusters. The library will unite these feature and generalize their domain of applicability.
As an example of the broader impact, it is estimated that combining these two technologies (MG algorithms and GPU architectures) will yield a 100-fold improvement in price/performance for the most compute-intensive component of LQCD simulations. Such an advance would be truly transformative, making an immediate impact in nuclear and particle physics. At the same time, it will serve as a prototype of the more generic problem of mapping hierarchical algorithms onto heterogeneous architectures, a challenge of paramount importance on the path to the exascale. The software library will be designed to bring similar benefits to graphene technology and to evolve to accommodate additional target application and additional domain decomposition algorithm to mitigate the communication bottleneck of Exascale designs. The award will provide partial support for two postdoctoral scholars who play essential roles in this project.
