  We present results of a performance study of an astrophysical radiation
hydrodynamics code, V2D, on the Arm-based A64FX processor developed by Fujitsu.
The code solves sparse linear systems, a task for which the A64FX architecture
should be well suited. We performed the performance analysis study on Ookami,
an Apollo 80 platform utilizing the A64FX processor. We explored several
compilers and performance analysis packages and found the code did not perform
as expected under scalable vector extension optimization, suggesting that a
"deeper dive" into analyzing the code is worthwhile. However, a simple driver
program that exercised basic sparse linear algebra routines used by V2D did
show significant speedup with the use of the scalable vector extension
optimization. We present the initial results from the study which used V2D on a
relatively simple test problem that emphasized the repeated solution of sparse
linear systems.
