PHEW: a parallel segmentation algorithm for three-dimensional AMR datasets - application to structure detection in self-gravitating flows

TL;DR

PHEW is a parallel watershed-based segmentation algorithm designed for 3D adaptive mesh refinement datasets, enabling efficient detection of structures and substructures in astrophysical fluid simulations.

Contribution

This paper introduces PHEW, a novel parallel segmentation algorithm for AMR datasets, with detailed implementation and scalability analysis.

Findings

Successfully detects connected regions above density thresholds

Capable of identifying hierarchical substructures

Operates efficiently on massively parallel systems

Abstract

We introduce PHEW (Parallel HiErarchical Watershed), a new segmentation algorithm to detect structures in astrophysical fluid simulations, and its implementation into the adaptive mesh refinement (AMR) code ramses. PHEW works on the density field defined on the adaptive mesh, and can thus be used on the gas density or the dark matter density after a projection of the particles onto the grid. The algorithm is based on a "watershed" segmentation of the computational volume into dense regions, followed by a merging of the segmented patches based on the saddle point topology of the density field. PHEW is capable of automatically detecting connected regions above the adopted density threshold, as well as the entire set of substructures within. Our algorithm is fully parallel and uses the MPI library. We describe in great detail the parallel algorithm and perform a scaling experiment which proves the capability of phew to run efficiently on massively parallel systems.