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Scaled ILU Smoothers for Navier-Stokes Pressure Projection

Journal Article · · International Journal for Numerical Methods in Fluids
DOI:https://doi.org/10.1002/fld.5254· OSTI ID:2377647

Incomplete LU (ILU) smoothers are effective in the algebraic multigrid (AMG) V-cycle for reducing high-frequency components of the error. However, the requisite direct triangular solves are comparatively slow on GPUs. Previous work has demonstrated the advantages of Jacobi iteration as an alternative to direct solution of these systems. Depending on the threshold and fill-level parameters chosen, the factors can be highly nonnormal and Jacobi is unlikely to converge in a low number of iterations. We demonstrate that row scaling can reduce the departure from normality, allowing us to replace the inherently sequential solve with a rapidly converging Richardson iteration. There are several advantages beyond the lower compute time. Scaling is performed locally for a diagonal block of the global matrix because it is applied directly to the factor. Further, an ILUT Schur complement smoother maintains a constant GMRES iteration count as the number of MPI ranks increases, and thus parallel strong-scaling is improved. Our algorithms have been incorporated into hypre, and we demonstrate improved time to solution for linear systems arising in the Nalu-Wind and PeleLM pressure solvers. For large problem sizes, GMRES+AMG executes at least five times faster when using iterative triangular solves compared with direct solves on massively parallel GPUs.

Research Organization:
National Renewable Energy Laboratory (NREL), Golden, CO (United States)
Sponsoring Organization:
USDOE Office of Science (SC); USDOE National Nuclear Security Administration (NNSA); Exascale Computing Project (ECP)
DOE Contract Number:
AC36-08GO28308
OSTI ID:
2377647
Report Number(s):
NREL/JA-2C00-90371; MainId:92149; UUID:18eff499-f215-4475-8c69-0932fdeb3f4c; MainAdminId:72948
Journal Information:
International Journal for Numerical Methods in Fluids, Journal Name: International Journal for Numerical Methods in Fluids Journal Issue: 4 Vol. 96
Country of Publication:
United States
Language:
English

References (30)

Iterative Sparse Triangular Solves for Preconditioning book January 2015
Iterative Methods for Sparse Linear Systems book January 2003
Multigrid solvers for immersed finite element methods and immersed isogeometric analysis journal November 2019
Fields of values and iterative methods journal February 1993
NekRS, a GPU-accelerated spectral element Navier–Stokes solver journal December 2022
A conservative, thermodynamically consistent numerical approach for low Mach number combustion. Part I: Single-level integration journal August 2017
The Design and Implementation of hypre, a Library of Parallel High Performance Preconditioners book January 2006
Fast and Accurate Multicomponent Transport Property Evaluation journal August 1995
Experimental study of ILU preconditioners for indefinite matrices journal December 1997
On measures of nonnormality of matrices journal July 1987
CHEMKIN-III: A FORTRAN chemical kinetics package for the analysis of gas-phase chemical and plasma kinetics report May 1996
Preconditioning Parametrized Linear Systems journal January 2021
Multilevel block factorizations in generalized hierarchical bases journal January 2002
ExaDG: High-Order Discontinuous Galerkin for the Exa-Scale book July 2020
Fine-Grained Parallel Incomplete LU Factorization journal January 2015
hypre: A Library of High Performance Preconditioners
  • Falgout, Robert D.; Yang, Ulrike Meier; Goos, Gerhard
  • Computational Science — ICCS 2002: International Conference Amsterdam, The Netherlands, April 21–24, 2002 Proceedings, Part III https://doi.org/10.1007/3-540-47789-6_66
book April 2002
Hierarchical multigrid approaches for the finite cell method on uniform and multi-level hp-refined grids journal December 2021
MFIX-Exa: A path toward exascale CFD-DEM simulations journal April 2021
On long-range interpolation operators for aggressive coarsening: INTERPOLATION FOR AGGRESSIVE COARSENING journal December 2009
Condition numbers and equilibration of matrices journal December 1969
GMRES: A Generalized Minimal Residual Algorithm for Solving Nonsymmetric Linear Systems journal July 1986
Algorithm 915, SuiteSparseQR journal November 2011
Using Jacobi iterations and blocking for solving sparse triangular systems in incomplete factorization preconditioning journal September 2018
Porting hypre to heterogeneous computer architectures: Strategies and experiences journal December 2021
Bounds for iterates, inverses, spectral variation and fields of values of non-normal matrices journal December 1962
A Comparison of Classical and Aggregation-Based Algebraic Multigrid Preconditioners for High-Fidelity Simulation of Wind Turbine Incompressible Flows journal January 2019
Multigrid Smoothers for Ultraparallel Computing journal January 2011
AMReX: a framework for block-structured adaptive mesh refinement journal May 2019
Optimally scaled matrices journal December 1963
A New Class of AMG Interpolation Methods Based on Matrix-Matrix Multiplications journal July 2021