A Scalable Semi-Implicit Barotropic Mode Solver for the MPAS-Ocean

Hyun Gyu Kang, Katherine J. Evans, Mark R. Petersen, Philip W. Jones, Siddhartha Bishnu

Research output: Contribution to journalArticlepeer-review

6 Scopus citations

Abstract

A scalable semi-implicit barotropic mode solver for the ocean component of the model for prediction across scales has been implemented as a competitor to an existing explicit-subcycling scheme to allow faster and more stable simulations while not sacrificing accuracy. The semi-implicit solver adopts the pipelined preconditioned bi-conjugate gradient stabilization algorithm as an iterative solver in conjunction with the restricted additive Schwarz preconditioner that accelerates the convergence rate of the iterative solver. The preconditioner is constructed from a linearized barotropic system that also reorders the system for optimal performance, while the semi-implicit solver deals with the fully nonlinear barotropic system that requires reassembly of the coefficient matrix for every time step. Several numerical experiments, from simple one-dimensional tests to three-dimensional real-world tests, demonstrate that the semi-implicit solver has almost the same accuracy and better parallel scalability compared with the existing scheme while allowing faster and more stable simulations. The semi-implicit solver accelerates the barotropic mode up to 2.9 times faster than the existing scheme on 16,320 processors, leading to an overall runtime speedup of 1.9.

Original languageEnglish
Article numbere2020MS002238
JournalJournal of Advances in Modeling Earth Systems
Volume13
Issue number4
DOIs
StatePublished - Apr 2021

Funding

This research was supported as a part of the E3SM project, funded by the U.S. Department of Energy (DOE), Office of Science, Office of Biological and Environmental Research. The authors are grateful to Dr. Florian Lemarié for helpful comments and suggestions to improve the manuscript. The comments of two anonymous reviewers are gratefully acknowledged. The authors also wish to thank Andrew G. Salinger in Sandia National Laboratories for constructive suggestions and useful comments. The real‐world simulations were performed at the National Energy Research Scientific Computing Center (NERSC, DE‐AC05‐00OR22725) which is one of the primary scientific computing facilities for the Office of Science, U.S. Department of Energy. This research also used resources of the Oak Ridge Leadership Computing Facility at the Oak Ridge National Laboratory, which is supported by the Office of Science of the U.S. Department of Energy under Contract No. DE‐AC05‐00OR22725, and by the LANL Institutional Computing Program, supported by the DOE National Nuclear Security Admin. under contract 89233218CNA000001. MPAS‐Ocean, an open‐source global ocean model, was obtained from the E3SM project. This research was supported as a part of the E3SM project, funded by the U.S. Department of Energy (DOE), Office of Science, Office of Biological and Environmental Research. The authors are grateful to Dr. Florian Lemari? for helpful comments and suggestions to improve the manuscript. The comments of two anonymous reviewers are gratefully acknowledged. The authors also wish to thank Andrew G. Salinger in Sandia National Laboratories for constructive suggestions and useful comments. The real-world simulations were performed at the National Energy Research Scientific Computing Center (NERSC, DE-AC05-00OR22725) which is one of the primary scientific computing facilities for the Office of Science, U.S. Department of Energy. This research also used resources of the Oak Ridge Leadership Computing Facility at the Oak Ridge National Laboratory, which is supported by the Office of Science of the U.S. Department of Energy under Contract No. DE-AC05-00OR22725, and by the LANL Institutional Computing Program, supported by the DOE National Nuclear Security Admin. under contract 89233218CNA000001. MPAS-Ocean, an open-source global ocean model, was obtained from the E3SM project.

Keywords

  • barotropic mode
  • implicit solver
  • ocean modeling
  • performance

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