27,683 research outputs found
NBODY6++GPU: Ready for the gravitational million-body problem
Accurate direct -body simulations help to obtain detailed information
about the dynamical evolution of star clusters. They also enable comparisons
with analytical models and Fokker-Planck or Monte-Carlo methods. NBODY6 is a
well-known direct -body code for star clusters, and NBODY6++ is the extended
version designed for large particle number simulations by supercomputers. We
present NBODY6++GPU, an optimized version of NBODY6++ with hybrid
parallelization methods (MPI, GPU, OpenMP, and AVX/SSE) to accelerate large
direct -body simulations, and in particular to solve the million-body
problem. We discuss the new features of the NBODY6++GPU code, benchmarks, as
well as the first results from a simulation of a realistic globular cluster
initially containing a million particles. For million-body simulations,
NBODY6++GPU is times faster than NBODY6 with 320 CPU cores and 32
NVIDIA K20X GPUs. With this computing cluster specification, the simulations of
million-body globular clusters including primordial binaries require
about an hour per half-mass crossing time.Comment: 13 pages, 9 figures, 3 table
Performance analysis of parallel gravitational -body codes on large GPU cluster
We compare the performance of two very different parallel gravitational
-body codes for astrophysical simulations on large GPU clusters, both
pioneer in their own fields as well as in certain mutual scales - NBODY6++ and
Bonsai. We carry out the benchmark of the two codes by analyzing their
performance, accuracy and efficiency through the modeling of structure
decomposition and timing measurements. We find that both codes are heavily
optimized to leverage the computational potential of GPUs as their performance
has approached half of the maximum single precision performance of the
underlying GPU cards. With such performance we predict that a speed-up of
can be achieved when up to 1k processors and GPUs are employed
simultaneously. We discuss the quantitative information about comparisons of
two codes, finding that in the same cases Bonsai adopts larger time steps as
well as relative energy errors than NBODY6++, typically ranging from
times larger, depending on the chosen parameters of the codes. While the two
codes are built for different astrophysical applications, in specified
conditions they may overlap in performance at certain physical scale, and thus
allowing the user to choose from either one with finetuned parameters
accordingly.Comment: 15 pages, 7 figures, 3 tables, accepted for publication in Research
in Astronomy and Astrophysics (RAA
GLB: Lifeline-based Global Load Balancing library in X10
We present GLB, a programming model and an associated implementation that can
handle a wide range of irregular paral- lel programming problems running over
large-scale distributed systems. GLB is applicable both to problems that are
easily load-balanced via static scheduling and to problems that are hard to
statically load balance. GLB hides the intricate syn- chronizations (e.g.,
inter-node communication, initialization and startup, load balancing,
termination and result collection) from the users. GLB internally uses a
version of the lifeline graph based work-stealing algorithm proposed by
Saraswat et al. Users of GLB are simply required to write several pieces of
sequential code that comply with the GLB interface. GLB then schedules and
orchestrates the parallel execution of the code correctly and efficiently at
scale. We have applied GLB to two representative benchmarks: Betweenness
Centrality (BC) and Unbalanced Tree Search (UTS). Among them, BC can be
statically load-balanced whereas UTS cannot. In either case, GLB scales well--
achieving nearly linear speedup on different computer architectures (Power,
Blue Gene/Q, and K) -- up to 16K cores
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