2,879 research outputs found
4.45 Pflops Astrophysical N-Body Simulation on K computer -- The Gravitational Trillion-Body Problem
As an entry for the 2012 Gordon-Bell performance prize, we report performance
results of astrophysical N-body simulations of one trillion particles performed
on the full system of K computer. This is the first gravitational trillion-body
simulation in the world. We describe the scientific motivation, the numerical
algorithm, the parallelization strategy, and the performance analysis. Unlike
many previous Gordon-Bell prize winners that used the tree algorithm for
astrophysical N-body simulations, we used the hybrid TreePM method, for similar
level of accuracy in which the short-range force is calculated by the tree
algorithm, and the long-range force is solved by the particle-mesh algorithm.
We developed a highly-tuned gravity kernel for short-range forces, and a novel
communication algorithm for long-range forces. The average performance on 24576
and 82944 nodes of K computer are 1.53 and 4.45 Pflops, which correspond to 49%
and 42% of the peak speed.Comment: 10 pages, 6 figures, Proceedings of Supercomputing 2012
(http://sc12.supercomputing.org/), Gordon Bell Prize Winner. Additional
information is http://www.ccs.tsukuba.ac.jp/CCS/eng/gbp201
2HOT: An Improved Parallel Hashed Oct-Tree N-Body Algorithm for Cosmological Simulation
We report on improvements made over the past two decades to our adaptive
treecode N-body method (HOT). A mathematical and computational approach to the
cosmological N-body problem is described, with performance and scalability
measured up to 256k () processors. We present error analysis and
scientific application results from a series of more than ten 69 billion
() particle cosmological simulations, accounting for
floating point operations. These results include the first simulations using
the new constraints on the standard model of cosmology from the Planck
satellite. Our simulations set a new standard for accuracy and scientific
throughput, while meeting or exceeding the computational efficiency of the
latest generation of hybrid TreePM N-body methods.Comment: 12 pages, 8 figures, 77 references; To appear in Proceedings of SC
'1
Numerical Simulations of the Dark Universe: State of the Art and the Next Decade
We present a review of the current state of the art of cosmological dark
matter simulations, with particular emphasis on the implications for dark
matter detection efforts and studies of dark energy. This review is intended
both for particle physicists, who may find the cosmological simulation
literature opaque or confusing, and for astro-physicists, who may not be
familiar with the role of simulations for observational and experimental probes
of dark matter and dark energy. Our work is complementary to the contribution
by M. Baldi in this issue, which focuses on the treatment of dark energy and
cosmic acceleration in dedicated N-body simulations. Truly massive dark
matter-only simulations are being conducted on national supercomputing centers,
employing from several billion to over half a trillion particles to simulate
the formation and evolution of cosmologically representative volumes (cosmic
scale) or to zoom in on individual halos (cluster and galactic scale). These
simulations cost millions of core-hours, require tens to hundreds of terabytes
of memory, and use up to petabytes of disk storage. The field is quite
internationally diverse, with top simulations having been run in China, France,
Germany, Korea, Spain, and the USA. Predictions from such simulations touch on
almost every aspect of dark matter and dark energy studies, and we give a
comprehensive overview of this connection. We also discuss the limitations of
the cold and collisionless DM-only approach, and describe in some detail
efforts to include different particle physics as well as baryonic physics in
cosmological galaxy formation simulations, including a discussion of recent
results highlighting how the distribution of dark matter in halos may be
altered. We end with an outlook for the next decade, presenting our view of how
the field can be expected to progress. (abridged)Comment: 54 pages, 4 figures, 3 tables; invited contribution to the special
issue "The next decade in Dark Matter and Dark Energy" of the new Open Access
journal "Physics of the Dark Universe". Replaced with accepted versio
The Theoretical Astrophysical Observatory: Cloud-Based Mock Galaxy Catalogues
We introduce the Theoretical Astrophysical Observatory (TAO), an online
virtual laboratory that houses mock observations of galaxy survey data. Such
mocks have become an integral part of the modern analysis pipeline. However,
building them requires an expert knowledge of galaxy modelling and simulation
techniques, significant investment in software development, and access to high
performance computing. These requirements make it difficult for a small
research team or individual to quickly build a mock catalogue suited to their
needs. To address this TAO offers access to multiple cosmological simulations
and semi-analytic galaxy formation models from an intuitive and clean web
interface. Results can be funnelled through science modules and sent to a
dedicated supercomputer for further processing and manipulation. These modules
include the ability to (1) construct custom observer light-cones from the
simulation data cubes; (2) generate the stellar emission from star formation
histories, apply dust extinction, and compute absolute and/or apparent
magnitudes; and (3) produce mock images of the sky. All of TAO's features can
be accessed without any programming requirements. The modular nature of TAO
opens it up for further expansion in the future.Comment: 17 pages, 11 figures, 2 tables; accepted for publication in ApJS. The
Theoretical Astrophysical Observatory (TAO) is now open to the public at
https://tao.asvo.org.au/. New simulations, models and tools will be added as
they become available. Contact [email protected] if you have data you
would like to make public through TAO. Feedback and suggestions are very
welcom
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