Master Thesis Defense Nga Ying Lo

Title: The Need for Speed: An investigation of bottlenecks towards optimization of EC-Earth3-HR (on CRAY XC50)

Abstract: Earth system models are state-of-the-art tools that climate physicists use to understand climate feedbacks, attribute changes to specific drivers, and make projections for the future. With more fine resolution, models would be able to account for fine scale transient processes that are crucial for improving results' fidelity. The drawback is decrease in the model's performance efficiency due to requirement of long computation to extract signals of climate change. Thus, optimization of these models is most necessary to study climate evolution. Currently, the global high-resolution coupled climate model EC-Earth3-HR can simulate about 1.31 years of climate evolution per day on the high performance computing platform (CRAY XC50) at the Danish Meteorological Institute. Meanwhile the standard-resolution of this model's efficiency is 10.07 simulated years per day. In order to improve efficiency of EC-Earth3-HR, scalability and performance analysis are performed to diagnose the bottlenecks of the model. And, various optimization methods are considered in order to address these bottlenecks. With the tools available on CRAY XC50, the optimal load balance was not obtained, due to incompatibility between performance analysis tool with the ocean component of EC-Earth3-HR. From scalability analysis, the ocean component shows to be performing worse compared to the atmosphere component. The least optimal subroutine within the ocean component is identified to be one handling the computation of sea-ice dynamics. Specifically, the computation for sea-ice rheology and velocities using the EVP framework. Potential optimization via vectorization is then identified by the Intel compiler v18.0.0 on the HPC platform. Following these results, a vectorization method is designed specifically to optimize the computation for shear strain rates. Implementation of the vectorization method is reserved for future work.

Internal Supervisors: Jens Hesselbjerg Christiansen, Cosmin Eugene Oancea

External Supervisors: Shuting Yang, Marianne Sloth Madsen 

External Censor: Peter Aakjaer

Place: Tagensvej 16, Room 0-08

Zoom link: https://ucph-ku.zoom.us/j/64927051643?pwd=NWRnVVpQTWJpL2pxTWRoZUdYRUR1dz09

Meeting ID: 649 2705 1643
Passcode: 442577

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Meeting ID: 649 2705 1643
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