| The GTC code scales new heights |
| Dr Stephane Ethier, PPPL |
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Owing to the introduction of a new multi-level Message Passing Interface (MPI)-based parallel
algorithm in which both the simulation volume and the particles are split between processors, the
gyrokinetic toroidal code (GTC; see feature "Simulating star power on Earth," p40) scales easily to
several thousand processors on the most powerful parallel supercomputers available, including
the IBM Blue Gene/L and modern parallel-vector systems such as the CRAY X1E and the Earth Simulator
in Japan.
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Compute power for simulations versus number of processors;
data Nov. 2005.
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Unlike most of the other gyrokinetic codes used to study plasma turbulence in toroidal
fusion devices, the GTC solves all of its equations in real space, rather than in Fourier (spectral)
space. While this introduces some algorithmic challenges, it has the major advantage of avoiding the
heavy global communication between processors that is necessary for full nonlinear turbulence
calculations when carried out in Fourier space.
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This has enabled the GTC to demonstrate impressive scaling capabilities - running on more
than 16,000 processors on the IBM Blue Gene/L computer - and perform very high-resolution simulations,
pushing 13 billion particles at 7.2 Tflop on 4,096 processors on the Earth Simulator.
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Dr Stephane Ethier is a Computational Physicist in CPPG at the Princeton Plasma Physics Laboratory.
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