SC17 Denver, CO

P26: Optimizing Gravity and Nuclear Physics in FLASH for Exascale

Authors: Hannah Klion (University of California, Berkeley; Oak Ridge National Laboratory), Bronson Messer (Oak Ridge National Laboratory, University of Tennessee), J. Austin Harris (Oak Ridge National Laboratory), Thomas Papatheodore (Oak Ridge National Laboratory)

Abstract: In a Type Ia supernova, runaway fusion ignites in a white dwarf, causing it to explode. The heavy element yields of these events remain uncertain, and high-performance multiphysics simulations with tools like FLASH are critical for our understanding. Current simulations track approximately a dozen nuclear isotopes, as opposed to the thousands required to completely capture the event's nuclear physics.

Simulating nuclear physics and self-gravity accurately and efficiently is critical for modeling a Type Ia supernova, since supernovae are competitions between energy-releasing nuclear reactions and gravity. Currently, the FLASH nuclear reaction network and self-gravity solver requires substantial inter-node communication. We use non-blocking MPI collectives to overlap communication in the self-gravity calculation with the computation-heavy nuclear burning calculation. We find that speedups from this technique are possible, but are MPI implementation-dependent. We highlight some of the challenges associated with this type of optimization.

Award: Best Poster Finalist (BP): no

Poster: pdf
Two-page extended abstract: pdf

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