Leveraging HPC Profiling & Tracing Tools to Understand the Performance of Particle-in-Cell Monte Carlo Simulations

TL;DR

This paper evaluates the performance of the BIT1 plasma simulation code on HPC systems, identifying bottlenecks and factors affecting scalability through profiling and scaling tests.

Contribution

It provides a detailed performance analysis of the BIT1 code using various HPC profiling tools, highlighting key bottlenecks and scalability factors.

Findings

Sorting function is the main on-node performance bottleneck.

Strong scaling achieves up to 96% efficiency on 2,560 MPI ranks.

Communication and load imbalance significantly impact large-scale performance.

Abstract

Large-scale plasma simulations are critical for designing and developing next-generation fusion energy devices and modeling industrial plasmas. BIT1 is a massively parallel Particle-in-Cell code designed for specifically studying plasma material interaction in fusion devices. Its most salient characteristic is the inclusion of collision Monte Carlo models for different plasma species. In this work, we characterize single node, multiple nodes, and I/O performances of the BIT1 code in two realistic cases by using several HPC profilers, such as perf, IPM, Extrae/Paraver, and Darshan tools. We find that the BIT1 sorting function on-node performance is the main performance bottleneck. Strong scaling tests show a parallel performance of 77% and 96% on 2,560 MPI ranks for the two test cases. We demonstrate that communication, load imbalance and self-synchronization are important factors impacting the performance of the BIT1 on large-scale runs.