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Changa Maira
ChaNGa (Charm N-body GrAvity solver) is a computer program to perform collisionless ''N''-body simulations. It can perform cosmological simulations with periodic boundary conditions in comoving coordinates or simulations of isolated stellar systems. It is based on the Barnes–Hut algorithm and uses Ewald summation for periodic forces. ChaNGa makes use of the Charm++ parallel programming system, including its dynamic load balancing schemes, in order to scale to large processor configurations. Simulation results have been reported on up to 20,000 IBM Bluegene/L processor More information For more information on obtaining, building and running ChaNGa, please see the Wiki documentation a See also * PKDGRA* GADGET * GRAPE A grape is a fruit, botanically a berry, of the deciduous woody vines of the flowering plant genus ''Vitis''. Grapes are a non- climacteric type of fruit, generally occurring in clusters. The cultivation of grapes began perhaps 8,000 years ago, ... Exter ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
N-body Cosmological Simulation
In physics and astronomy, an ''N''-body simulation is a simulation of a dynamical system of particles, usually under the influence of physical forces, such as gravity (see n-body problem, ''n''-body problem for other applications). ''N''-body simulations are widely used tools in astrophysics, from investigating the dynamics of few-body systems like the Earth-Moon-Sun system to understanding the evolution of the large-scale structure of the universe. In physical cosmology, ''N''-body simulations are used to study processes of non-linear structure formation such as galaxy filaments and galaxy halos from the influence of dark matter. Direct ''N''-body simulations are used to study the dynamical evolution of star clusters. Nature of the particles The 'particles' treated by the simulation may or may not correspond to physical objects which are particulate in nature. For example, an N-body simulation of a star cluster might have a particle per star, so each particle has some physic ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Barnes–Hut Simulation
The Barnes–Hut simulation (named after Josh Barnes and Piet Hut) is an approximation algorithm for performing an ''n''-body simulation. It is notable for having order O(''n'' log ''n'') compared to a direct-sum algorithm which would be O(''n''2). The simulation volume is usually divided up into cubic cells via an octree (in a three-dimensional space), so that only particles from nearby cells need to be treated individually, and particles in distant cells can be treated as a single large particle centered at the cell's center of mass (or as a low-order multipole expansion). This can dramatically reduce the number of particle pair interactions that must be computed. Some of the most demanding high-performance computing projects do computational astrophysics using the Barnes–Hut treecode algorithm, such as DEGIMA. Algorithm The Barnes–Hut tree In a three-dimensional ''n''-body simulation, the Barnes–Hut algorithm recursively divides the ''n'' bodies into ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ewald Summation
Ewald summation, named after Paul Peter Ewald, is a method for computing long-range interactions (e.g. electrostatic interactions) in periodic systems. It was first developed as the method for calculating electrostatic energies of ionic crystals, and is now commonly used for calculating long-range interactions in computational chemistry. Ewald summation is a special case of the Poisson summation formula, replacing the summation of interaction energies in real space with an equivalent summation in Fourier space. In this method, the long-range interaction is divided into two parts: a short-range contribution, and a long-range contribution which does not have a singularity. The short-range contribution is calculated in real space, whereas the long-range contribution is calculated using a Fourier transform. The advantage of this method is the rapid convergence of the energy compared with that of a direct summation. This means that the method has high accuracy and reasonable speed when co ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Charm++
Charm++ is a parallel object-oriented programming paradigm based on C++ and developed in the Parallel Programming Laboratory at the University of Illinois at Urbana–Champaign. Charm++ is designed with the goal of enhancing programmer productivity by providing a high-level abstraction of a parallel program while at the same time delivering good performance on a wide variety of underlying hardware platforms. Programs written in Charm++ are decomposed into a number of cooperating message-driven objects called ''chares''. When a programmer invokes a method on an object, the Charm++ runtime system sends a message to the invoked object, which may reside on the local processor or on a remote processor in a parallel computation. This message triggers the execution of code within the chare to handle the message asynchronously. Chares may be organized into indexed collections called ''chare arrays'' and messages may be sent to individual chares within a chare array or to the entire chare a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Blue Gene
Blue Gene is an IBM project aimed at designing supercomputers that can reach operating speeds in the petaFLOPS (PFLOPS) range, with low power consumption. The project created three generations of supercomputers, Blue Gene/L, Blue Gene/P, and Blue Gene/Q. During their deployment, Blue Gene systems often led the TOP500 and Green500 rankings of the most powerful and most power-efficient supercomputers, respectively. Blue Gene systems have also consistently scored top positions in the Graph500 list. The project was awarded the 2009 National Medal of Technology and Innovation. As of 2015, IBM seems to have ended the development of the Blue Gene family though no public announcement has been made. IBM's continuing efforts of the supercomputer scene seems to be concentrated around OpenPower, using accelerators such as FPGAs and GPUs to battle the end of Moore's law. History In December 1999, IBM announced a US$100 million research initiative for a five-year effort to build a mass ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
GADGET
A gadget is a mechanical device or any ingenious article. Gadgets are sometimes referred to as '' gizmos''. History The etymology of the word is disputed. The word first appears as reference to an 18th-century tool in glassmaking that was developed as a spring pontil.Charles R. Hadjamach: ''British Glass, 1800-1914''. London. 1991. p. 35 As stated in the glass dictionary published by the Corning Museum of Glass, a gadget is a ''metal rod with a spring clip that grips the foot of a vessel and so avoids the use of a pontil''. Gadgets were first used in the late 18th century.Corning Museum of Glass: Glass Dictionary: Gadget}'' (accessed November 4, 2018) According to the Oxford English Dictionary, there is anecdotal evidence for the use of "gadget" as a placeholder name for a technical item whose precise name one can't remember since the 1850s; with Robert Brown's 1886 book ''Spunyarn and Spindrift, A sailor boy’s log of a voyage out and home in a China tea-clipper'' containing th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
GRAvity PipE
Gravity Pipe (abbreviated GRAPE) is a project which uses hardware acceleration to perform gravitational computations. Integrated with Beowulf-style commodity computers, the GRAPE system calculates the force of gravity that a given mass, such as a star, exerts on others. The project resides at Tokyo University. The GRAPE hardware acceleration component "pipes" the force computation to the general-purpose computer serving as a node in a parallelized cluster as the innermost loop of the gravitational model. Its shortened name, GRAPE, was chosen as an intentional reference to the Apple Inc. line of computers. Method The primary calculation in GRAPE hardware is a summation of the forces between a particular star and every other star in the simulation. Several versions (GRAPE-1, GRAPE-3 and GRAPE-5) use the logarithmic number system (LNS) in the pipeline to calculate the approximate force between two stars and take the antilogarithms of the ''x'', ''y'' and ''z'' components before ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Physical Cosmology
Physical cosmology is a branch of cosmology concerned with the study of cosmological models. A cosmological model, or simply cosmology, provides a description of the largest-scale structures and dynamics of the universe and allows study of fundamental questions about its Cosmogony, origin, structure, Chronology of the universe, evolution, and ultimate fate.For an overview, see Cosmology as a science originated with the Copernican principle, which implies that astronomical object, celestial bodies obey identical physical laws to those on Earth, and Newtonian mechanics, which first allowed those physical laws to be understood. Physical cosmology, as it is now understood, began with the development in 1915 of Albert Einstein's general relativity, general theory of relativity, followed by major observational discoveries in the 1920s: first, Edwin Hubble discovered that the universe contains a huge number of external Galaxy, galaxies beyond the Milky Way; then, work by Vesto Sli ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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