  We present computational performance comparisons of gas-solid simulations
performed on current CPU and GPU architectures using MFiX Exa, a CFD-DEM solver
that leverages hybrid CPU+GPU parallelism. A representative fluidized bed
simulation with varying particle numbers from 2 to 67 million is used to
compare serial and parallel performance. A single GPU was observed to be about
10 times faster compared to a single CPU core. The use of 3 GPUs on a single
compute node was observed to be 4x faster than using all 64 CPU cores. We also
observed that using an error controlled adaptive time stepping scheme for
particle advance provided a consistent 4x speed-up on both CPUs and GPUs. Weak
scaling results indicate superior parallel efficiencies when using GPUs
compared to CPUs for the problem sizes studied in this work.
