Workshops Archive

Performance Optimizations within GPU Memory Constraints in Nyx Cosmology Code

Workshop: Women in HPC: Diversifying the HPC Community and Engaging Male Allies

Authors: Jean Sexton (Lawrence Berkeley National Laboratory (LBNL))

Abstract: The Nyx cosmology code is used to simulate the formation of large scale structure in Lyα simulations of the universe. As the dark matter particles begin clustering, the cost of a single time step grows due to the load imbalance. These highly clustered regions can also prohibit fitting the entire problem in GPU HBM. If the entire problem does not fit on the HBM, Nyx should use managed memory, and the cost of each time step becomes dependent on the host-device memory bandwidth. This also imposes dynamic restrictions on the best domain decomposition for other physic components such as the heating-cooling and the hydrodynamics solve.

In this talk, we will focus on different performance characteristics of Nyx when constrained by load imbalance and the GPU memory capacity, as well as the current approach in Nyx to optimizing this.

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