Biological and Environmental Research - Earth and Environmental System Sciences
Earth and Environmental System Modeling

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

TitleA Scalable Semi‐Implicit Barotropic Mode Solver for the MPAS‐Ocean
Publication TypeJournal Article
Year of Publication2021
AuthorsKang, Hyun-Gyu, Evans Katherine J., Petersen Mark R., Jones Philip W., and Bishnu Siddhartha
JournalJournal of Advances in Modeling Earth Systems
Volume13
Number4
Abstract / Summary

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. Furthermore, 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.

URLhttp://dx.doi.org/10.1029/2020ms002238
DOI10.1029/2020ms002238
Journal: Journal of Advances in Modeling Earth Systems
Year of Publication: 2021
Volume: 13
Number: 4
Publication Date: 04/2021

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. Furthermore, 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.

DOI: 10.1029/2020ms002238
Citation:
Kang, H, KJ Evans, MR Petersen, PW Jones, and S Bishnu.  2021.  "A Scalable Semi‐Implicit Barotropic Mode Solver for the MPAS‐Ocean."  Journal of Advances in Modeling Earth Systems 13(4).  https://doi.org/10.1029/2020ms002238.