Abstract
The ability to sustain magnetically confined
plasma in a state of stable equilibrium is crucial for optimal
and cost-effective operations of fusion devices like tokamaks
and stellarators. The Variational Moments Equilibrium Code
(VMEC) is the de-facto serial application used by fusion
scientists to compute magnetohydrodynamics (MHD) equilibria
and study the physics of three dimensional plasmas in confined
configurations. Modern fusion energy experiments have larger
system scales with more interactive experimental workflows,
both demanding faster analysis turnaround times on computational
workloads that are stressing the capabilities of sequential
VMEC. In this paper, we present PARVMEC, an efficient,
parallel version of its sequential counterpart, capable of scaling
to thousands of processors on distributed memory machines.
PARVMEC is a non-linear code, with multiple numerical
physics modules, each with its own computational complexity. A
detailed speedup analysis supported by scaling results on 1,024
cores of a Cray XC30 supercomputer is presented. Depending
on the mode of PARVMEC execution, speedup improvements
of one to two orders of magnitude are reported. PARVMEC
equips fusion scientists for the first time with a state-of-theart
capability for rapid, high fidelity analyses of magnetically
confined plasmas at unprecedented scales.
