SC13 Home > SC13 Schedule > SC13 Presentation - Optimizations of a Spectral/Finite Difference Gyrokinetic Code for Improved Strong Scaling Toward Million Cores

SCHEDULE: NOV 16-22, 2013

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Optimizations of a Spectral/Finite Difference Gyrokinetic Code for Improved Strong Scaling Toward Million Cores

SESSION: Research Poster Reception

EVENT TYPE: Posters, Electronic Posters, and Education Posters, Awards, Best Poster Finalist

TIME: 5:15PM - 7:00PM

AUTHOR(S):Shinya Maeyama, Tomohiko Watanabe, Yasuhiro Idomura, Motoki Nakata, Masanori Nunami, Akihiro Ishizawa

ROOM:Mile High Pre-Function

ABSTRACT:
Plasma turbulence is inherently multi-scale physics including electron and ion scales, which requires huge computations. In this work, we present optimizations of the gyrokinetic Vlasov simulation code GKV, which performs five-dimensional CFD calculation by using spectral and finite difference methods, on massively parallel platforms. First, segmented rank mapping on the three-dimensional torus network is advantageous to utilize the bi-section bandwidth and to reduce collisions of the messages, and therefore, to reduce communication costs. Second, uses of the collective communication optimized for the K computer and of the simultaneous communications on the Tofu interconnect further reduce the costs. Finally, computation-communication overlaps with pipelining methods effectively mask the communication cost. Thanks to the optimizations, GKV achieves excellent strong scaling up to ~600k cores with high parallel efficiency ~99.99994% on the K computer, and enables us to address first multi-scale plasma turbulence simulations employing the real ion-to-electron mass ratio.

Chair/Author Details:

Shinya Maeyama - Japan Atomic Energy Agency

Tomohiko Watanabe - National Institute for Fusion Science

Yasuhiro Idomura - Japan Atomic Energy Agency

Motoki Nakata - Japan Atomic Energy Agency

Masanori Nunami - National Institute for Fusion Science

Akihiro Ishizawa - National Institute for Fusion Science

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