Two- and Three-Dimensional Multi-Physics Simulations of Core Collapse Supernovae: A Brief Status Report and Summary of Results from the Oak Ridge Group
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Mezzacappa, Anthony↗
Engineering topics
Harris, James A
Publications and source records attributed to Harris, James A.
Explicit Integration of Extremely Stiff Reaction Networks: Quasi-Steady-State Methods
A preceding paper [1] demonstrated that explicit asymptotic methods generally work much better for extremely stiff reaction networks than has previously been shown in the literature. There we showed that for systems well removed from equilibrium explicit asymptotic methods can rival standard implicit codes in speed and accuracy for solving extremely stiff differential equations. In this paper we continue the investigation of systems well removed from equilibrium by examining quasi-steady-state (QSS) methods as an alternative to asymptotic methods. We show that for systems well removed from equilibrium, QSS methods also can compete with, or even exceed, standard implicit methods, even for extremely stiff networks, and in many cases give somewhat better integration speed than for asymptotic methods. As for asymptotic methods, we will find that QSS methods give correct results, but with non-competitive integration speed as equilibrium is approached. Thus, we shall find that both asymptotic and QSS methods must be supplemented with partial equilibrium methods as equilibrium is approached to remain competitive with implicit methods.
Guidry, Mike W↗
Multicore and Accelerator Development for a Leadership-Class Stellar Astrophysics Code
We describe recent development work on the core-collapse supernova code CHIMERA. CHIMERA has consumed more than 100 million cpu-hours on Oak Ridge Leadership Computing Facility (OLCF) platforms in the past 3 years, ranking it among the most important applications at the OLCF. Most of the work described has been focused on exploiting the multicore nature of the current platform (Jaguar) via, e.g., multithreading using OpenMP. In addition, we have begun a major effort to marshal the computational power of GPUs with CHIMERA. The impending upgrade of Jaguar to Titan a 20+ PF machine with an NVIDIA GPU on many nodes makes this work essential.
Messer, Bronson↗