1,718 research outputs found
Parallel Spherical Harmonic Transforms on heterogeneous architectures (GPUs/multi-core CPUs)
Spherical Harmonic Transforms (SHT) are at the heart of many scientific and
practical applications ranging from climate modelling to cosmological
observations. In many of these areas new, cutting-edge science goals have been
recently proposed requiring simulations and analyses of experimental or
observational data at very high resolutions and of unprecedented volumes. Both
these aspects pose formidable challenge for the currently existing
implementations of the transforms.
This paper describes parallel algorithms for computing SHT with two variants
of intra-node parallelism appropriate for novel supercomputer architectures,
multi-core processors and Graphic Processing Units (GPU). It also discusses
their performance, alone and embedded within a top-level, MPI-based
parallelisation layer ported from the S2HAT library, in terms of their
accuracy, overall efficiency and scalability. We show that our inverse SHT run
on GeForce 400 Series GPUs equipped with latest CUDA architecture ("Fermi")
outperforms the state of the art implementation for a multi-core processor
executed on a current Intel Core i7-2600K. Furthermore, we show that an
MPI/CUDA version of the inverse transform run on a cluster of 128 Nvidia Tesla
S1070 is as much as 3 times faster than the hybrid MPI/OpenMP version executed
on the same number of quad-core processors Intel Nahalem for problem sizes
motivated by our target applications. Performance of the direct transforms is
however found to be at the best comparable in these cases. We discuss in detail
the algorithmic solutions devised for major steps involved in the transforms
calculation, emphasising those with a major impact on their overall
performance, and elucidates the sources of the dichotomy between the direct and
the inverse operations
Using hybrid GPU/CPU kernel splitting to accelerate spherical convolutions
We present a general method for accelerating by more than an order of
magnitude the convolution of pixelated functions on the sphere with a
radially-symmetric kernel. Our method splits the kernel into a compact
real-space component and a compact spherical harmonic space component. These
components can then be convolved in parallel using an inexpensive commodity GPU
and a CPU. We provide models for the computational cost of both real-space and
Fourier space convolutions and an estimate for the approximation error. Using
these models we can determine the optimum split that minimizes the wall clock
time for the convolution while satisfying the desired error bounds. We apply
this technique to the problem of simulating a cosmic microwave background (CMB)
anisotropy sky map at the resolution typical of the high resolution maps
produced by the Planck mission. For the main Planck CMB science channels we
achieve a speedup of over a factor of ten, assuming an acceptable fractional
rms error of order 1.e-5 in the power spectrum of the output map.Comment: 9 pages, 11 figures, 1 table, accepted by Astronomy & Computing w/
minor revisions. arXiv admin note: substantial text overlap with
arXiv:1211.355
Multi-Architecture Monte-Carlo (MC) Simulation of Soft Coarse-Grained Polymeric Materials: SOft coarse grained Monte-carlo Acceleration (SOMA)
Multi-component polymer systems are important for the development of new
materials because of their ability to phase-separate or self-assemble into
nano-structures. The Single-Chain-in-Mean-Field (SCMF) algorithm in conjunction
with a soft, coarse-grained polymer model is an established technique to
investigate these soft-matter systems. Here we present an im- plementation of
this method: SOft coarse grained Monte-carlo Accelera- tion (SOMA). It is
suitable to simulate large system sizes with up to billions of particles, yet
versatile enough to study properties of different kinds of molecular
architectures and interactions. We achieve efficiency of the simulations
commissioning accelerators like GPUs on both workstations as well as
supercomputers. The implementa- tion remains flexible and maintainable because
of the implementation of the scientific programming language enhanced by
OpenACC pragmas for the accelerators. We present implementation details and
features of the program package, investigate the scalability of our
implementation SOMA, and discuss two applications, which cover system sizes
that are difficult to reach with other, common particle-based simulation
methods
PGAS-FMM: Implementing a distributed fast multipole method using the X10 programming language
The fast multipole method (FMM) is a complex, multi-stage algorithm over a distributed tree data structure, with multiple levels of parallelism and inherent data locality. X10 is a modern partitioned global address space language with support for asynchr
GPU-Based Data Processing for 2-D Microwave Imaging on MAST
The Synthetic Aperture Microwave Imaging (SAMI) diagnostic is a Mega Amp Spherical Tokamak (MAST) diagnostic based at Culham Centre for Fusion Energy. The acceleration of the SAMI diagnostic data-processing code by a graphics processing unit is presented, demonstrating acceleration of up to 60 times compared to the original IDL (Interactive Data Language) data-processing code. SAMI will now be capable of intershot processing allowing pseudo-real-time control so that adjustments and optimizations can be made between shots. Additionally, for the first time the analysis of many shots will be possible
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