  This article presents new algorithms for massively parallel granular dynamics
simulations on distributed memory architectures using a domain partitioning
approach. Collisions are modelled with hard contacts in order to hide their
micro-dynamics and thus to extend the time and length scales that can be
simulated. The multi-contact problem is solved using a non-linear block
Gauss-Seidel method that is conforming to the subdomain structure. The parallel
algorithms employ a sophisticated protocol between processors that delegate
algorithmic tasks such as contact treatment and position integration uniquely
and robustly to the processors. Communication overhead is minimized through
aggressive message aggregation, leading to excellent strong and weak scaling.
The robustness and scalability is assessed on three clusters including two
peta-scale supercomputers with up to 458752 processor cores. The simulations
can reach unprecedented resolution of up to ten billion non-spherical particles
and contacts.
