A Hybrid MPI+Threads Approach to Particle Group Finding Using Union-Find

Understand

The Friends-of-Friends (FoF) algorithm is a standard technique used in cosmological $N$-body simulations to identify structures.

• Its goal is to find clusters of particles (called groups) that are separated by at most a cut-off radius.
• $N$-body simulations typically use most of the memory present on a node, leaving very little free for a FoF algorithm to run on-the-fly.
• We propose a new method that utilises the common Union-Find data structure and a hybrid MPI+threads approach.