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Exploring the use of novel programming models in land surface models

by Ethan T Coon, Wael R Elwasif, Himanshu K Pillai, Peter E Thornton, Scott L Painter
Publication Type
Conference Paper
Book Title
Proceedings of PAW-ATM 2019: Parallel Applications Workshop, Alternatives To MPI+X
Publication Date
Page Numbers
1 to 10
Publisher Location
Los Alamitos, California, United States of America
Conference Name
International Conference for High Performance Computing, Networking, Storage, and Analysis (SC19): Parallel Applications Workshop, Alternatives To MPI+X
Conference Location
Denver, Colorado, United States of America
Conference Sponsor
Conference Date

A wide range of programming models are currently under rapid development to meet the needs of application developers looking to work on more complex machines. These models fill a variety of roles. Some look to abstract supercomputer architecture, including both processors and memory, to present a strategy for portable performance across a wide range of machines. Others look to expose concurrency by explicitly constructing task-driven dependency graphs that allow a scheduler to find parallelism. Here we explore the implications for application codes of adopting two such programming models, Kokkos and Legion, one from each class of models. We specifically focus on the software design implications on refactoring existing applications, rather than the performance and performance tuning of these models. We identify a strategy for refactoring the Energy Exascale Earth System Model's Land Surface Model, an extremely complex code for climate applications, and prototype a series of mini-apps that explore the adoption of Kokkos and Legion. In doing this, we identify commonalities across the models, leading to a series of conclusions about application software design and refactoring for the adoption of novel programming models.