2026-09-20T17:45:11Z https://www.ideals.illinois.edu/oai-pmh

oai:www.ideals.illinois.edu:2142/125706 2026-02-03 col_2142_5131 col_2142_10761 com_2142_5130 com_2142_10755 com_2142_234

application/pdf en text Submission published under a 24 month embargo labeled 'U of I Access', the embargo will last until 2026-08-01 The student, Thilina Ratnayaka Mudiyanselage, accepted the attached license on 2024-07-09 at 12:16. The student, Thilina Ratnayaka Mudiyanselage, submitted this Dissertation for approval on 2024-07-09 at 12:17. This Dissertation was approved for publication on 2024-07-09 at 14:48. DSpace SAF Submission Ingestion Package generated from Vireo submission #21005 on 2025-02-04 at 21:16:31 Exascale finite/spectral element simulations Ratnayaka Mudiyanselage, Thilina Bandara 2024-07-09 Fischer, Paul Olson, Luke Kloeckner, Andreas Rowe, Kris Fischer, Paul Hpc Gpu Mpi Graph Partitioning Schwarz Methods Coarse-grid P-multigrid Loopy Programming Models Clang Exascale Computing eng In this thesis, we present contributions by author and his collaborators to improve the efficiency of high-order spectral/finite element simulations (SEM/FEM) on state-of-the-art exascale and pre-exascale supercomputers with general purpose graphics processing units (GPUs). We briefly discuss the exascale computing landscape and the challenges involved in running high-order SEM/FEM simulations on these machines. Then we present contributions which span four important aspects of high-order SEM/FEM simulations. Firstly, we present representative benchmarks for SEM/FEM applications and use those to benchmark new GPU based exascale systems in order to understand their scalability characteristics. Secondly, we present a parallel partitioner suitable for the exascale era that is characterized by large local problem sizes. Our partitioner is based on recursive spectral bisection and is able to partition a mesh in parallel while preserving load balance and reducing mes- sage volume between partitions. Thirdly, we address one of the main bottlenecks in the SEM/FEM simulations: the coarse-grid solve of the p−Multigrid preconditioner used for solving the pressure Poisson equation. We introduce a novel two-level Schwarz based coarse solver which has the potential to scale well on the exascale machines due to its low communication and increased parallelism. Finally, we present a domain specific compiler framework to improve the productivity of the application engineers who use GPU-based supercomputers by reusing domain specific optimization patterns. 2024-08 Thesis https://hdl.handle.net/2142/125706 Copyright 2024 Thilina Ratnayaka Siebel Computing &DataScience Computer Science University of Illinois at Urbana-Champaign Ph.D. Dissertation