PFLOTRAN (http://www.pflotran.org) is an open-source, massively parallel surface-suburface multiphase flow and reactive transport simulator, designed from the ground up to run efficiently on computing platforms ranging from laptops to leadership-class supercomputers (O(100,000) cores), all from a single code base.  It is built on top of the widely-used, open-source framework of the Portable, Extensible Toolkit for Scientific Computation (PETSc), which has been critical to its success.  Development of PFLOTRAN began in 2000 with the first of two U.S. Department of Energy Computational Science Graduate Fellowship practicum experiences, followed by rapid development under the U.S. Department of Energy SciDAC-II program starting in 2006, when the code was open-sourced.  It has been used in applications as diverse as radionuclide fate and transport, geologic carbon sequestration, geothermal energy, permafrost dynamics, and terrestrial biogeochemistry. In this talk, I will chart how PFLOTRAN has evolved as both science goals and high-performance computing platforms have changed; how close interaction with the PETSc development team has led to advances in both code bases; and how a growing user and developer community has pushed PFLOTRAN in some surprising new directions through the synergy of open-source development.   I will also look ahead towards the exascale computing horizon: I will discuss strategies for how PFLOTRAN and PETSc can adapt to take advantage of anticipated disruptive hardware architectural changes, and I will discuss at least one (highly speculative) new science possibility -- hyperresolution global land-surface modeling -- that could emerge with this massive increase of available computing power.

Speaker Biography: Dr. Richard Tran Mills (http://climatemodeling.org/~rmills) is an HPC Earth System Models Architect at Intel Corporation, where he leads engineering efforts related to weather, climate, and Earth System models on current and next-generation Intel high-performance computing architectures.  Prior to joining Intel in 2014, he spent a decade as a research scientist at Oak Ridge National Laboratory, where he was a staff member in the Climate Change Science Institute, and also held a joint faculty appointment in the Department of Earth and Planetary Sciences at the University of Tennessee, Knoxville.  His work has spanned high-performance scientific computing, geospatiotemporal data mining, computational hydrology, and climate change science.  He is one of the original developers of PFLOTRAN, an open-source code for massively parallel simulation of hydrologic flow and reactive transport problems, and has also contributed to the development of PETSc, the Portable, Extensible Toolkit for Scientific Computation, a suite of data structures and associated routines for the solution of scientific problems modeled by partial differential equations.  He earned his Ph.D. in Computer Science in 2004 at the College of William and Mary, where he was a Department of Energy Computational Science Graduate Fellow.   Prior to that, he studied geology and physics at the University of Tennessee, Knoxville as a Chancellor's Scholar