3.4. Branson
The Branson benchmark defines both Priority 1 and Priority 2 problems. See the Branson benchmark documentation for the benchmark description, build instructions, run instructions, and problem definitions.
3.4.1. Problem
Priority 2 problem is multi-node. The inputs folder contains the 3D,
load-balanced hohlraum input file for multi-node: 3D_lb_holhraum.xml
This input should also be run with a 30 group build of Branson,
which is the default in the ats-6 branch.
The 3D_lb_holhraum.xml problem is meant to run on multiple nodes.
It is run with:
mpirun -n <devices_on_node> <install-location/BRANSON> <path/to/branson/inputs/3D_lb_hohlraum.xml>
For the multi-node problem, the particle_message_size value in the input is the main parameter
that will affect performance, especially on the GPU. Using a larger particle message size means that
more memory will be used in MPI buffers, which are statically sized to the particle message size and
allocated for each neighbor of a a domain. The memory used by MPI buffers on a rank is thus the
number of neighbors multiplied by the particle message size (which is in number of particles)
multiplied by the size of a particle.