SCHEDULE: NOV 15-20, 2015

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Improving the Scalability of the Ocean Barotropic Solver in the Community Earth System Model

SESSION: Applications: Climate and Weather

EVENT TYPE: Papers

TIME: 2:00PM - 2:30PM

SESSION CHAIR(S): Daniel S. Katz

AUTHOR(S):Yong Hu, Xiaomeng Huang, Allison H. Baker, Yu-heng Tseng, Frank O. Bryan, John M. Dennis, Guangwen Yang

ROOM:18CD

ABSTRACT:

High-resolution climate simulations require tremendous computing resources. In the Community Earth System Model (CESM), the ocean model is computationally expensive for high-resolution grids and is the least scalable component for most production simulations. In particular, the modified preconditioned Conjugate Gradient, used to solve the elliptic system of equations in the barotropic mode, scales poorly at the high core counts. In this work, we demonstrate that the communication costs in the barotropic solver occupy an increasing portion of the total execution time as core counts are increased. To mitigate this problem, we implement a Chebyshev-type iterative method (CSI) in the ocean model, which requires fewer global reductions, and develop an effective block preconditioner based on the Error Vector Propagation (EVP) method. We demonstrate that CSI with EVP preconditioning improves the scalability of the ocean component and produces an ocean climate statistically consistent with the original one.

Chair/Author Details:

Daniel S. Katz (Chair) - University of Chicago and Argonne National Laboratory|

Yong Hu - Tsinghua University

Xiaomeng Huang - Tsinghua University

Allison H. Baker - National Center for Atmospheric Research

Yu-heng Tseng - National Center for Atmospheric Research

Frank O. Bryan - National Center for Atmospheric Research

John M. Dennis - National Center for Atmospheric Research

Guangwen Yang - Tsinghua University

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Paper provided by the ACM Digital Library

Paper also available from IEEE Computer Society