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Optimizing BIT1, a Particle-in-Cell Monte Carlo Code, with OpenMP/OpenACC and GPU Acceleration
KTH, School of Electrical Engineering and Computer Science (EECS), Computer Science, Computational Science and Technology (CST).ORCID iD: 0000-0003-2095-3063
KTH, School of Electrical Engineering and Computer Science (EECS), Computer Science, Computational Science and Technology (CST).ORCID iD: 0000-0001-6865-9379
Institute of Plasma Physics of the CAS, Prague, Czech Republic.ORCID iD: 0000-0002-4229-0961
LeCAD, University of Ljubljana, Ljubljana, Slovenia.ORCID iD: 0000-0003-0594-0555
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2024 (English)In: 24th International Conference on Computational Science, Málaga, Spain, July 2-4, Part I, LNCS 14832, Springer Nature, 2024Conference paper, Published paper (Refereed)
Abstract [en]

On the path toward developing the first fusion energy devices, plasma simulations have become indispensable tools for supporting the design and development of fusion machines. Among these critical simulation tools, BIT1 is an advanced Particle-in-Cell code with Monte Carlo collisions, specifically designed for modeling plasma-material interaction and, in particular, analyzing the power load distribution on tokamak divertors. The current implementation of BIT1 relies exclusively on MPI for parallel communication and lacks support for GPUs. In this work, we address these limitations by designing and implementing a hybrid, shared-memory version of BIT1 capable of utilizing GPUs. For shared-memory parallelization, we rely on OpenMP and OpenACC, using a task-based approach to mitigate load-imbalance issues in the particle mover. On an HPE Cray EX computing node, we observe an initial performance improvement of approximately 42%, with scalable performance showing an enhancement of about 38% when using 8 MPI ranks. Still relying on OpenMP and OpenACC, we introduce the first version of BIT1 capable of using GPUs. We investigate two different data movement strategies: unified memory and explicit data movement. Overall, we report BIT1 data transfer findings during each PIC cycle. Among BIT1 GPU implementations, we demonstrate performance improvement through concurrent GPU utilization, especially when MPI ranks are assigned to dedicated GPUs. Finally, we analyze the performance of the first BIT1 GPU porting with the NVIDIA Nsight tools to further our understanding of BIT1’s computational efficiency for large-scale plasma simulations, capable of exploiting current supercomputer infrastructures.

Place, publisher, year, edition, pages
Springer Nature, 2024.
Keywords [en]
OpenMP, Task-Based Parallelism, OpenACC, Hybrid Programming, GPU Offloading, Large-Scale PIC Simulations
National Category
Computer Sciences Computer Systems Fusion, Plasma and Space Physics
Research subject
Computer Science
Identifiers
URN: urn:nbn:se:kth:diva-346931DOI: 10.1007/978-3-031-63749-0_22ISI: 001279316700022Scopus ID: 2-s2.0-85199628891OAI: oai:DiVA.org:kth-346931DiVA, id: diva2:1860744
Conference
24th International Conference on Computational Science, Málaga, Spain, July 2-4
Note

 Part of ISBN 9783031637483

QC 20240529

Available from: 2024-05-24 Created: 2024-05-24 Last updated: 2024-09-10Bibliographically approved

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Williams, Jeremy J.Liu, FelixMarkidis, Stefano

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