1,937 research outputs found
Vectorization and Parallelization of the Adaptive Mesh Refinement N-body Code
In this paper, we describe our vectorized and parallelized adaptive mesh
refinement (AMR) N-body code with shared time steps, and report its performance
on a Fujitsu VPP5000 vector-parallel supercomputer. Our AMR N-body code puts
hierarchical meshes recursively where higher resolution is required and the
time step of all particles are the same. The parts which are the most difficult
to vectorize are loops that access the mesh data and particle data. We
vectorized such parts by changing the loop structure, so that the innermost
loop steps through the cells instead of the particles in each cell, in other
words, by changing the loop order from the depth-first order to the
breadth-first order. Mass assignment is also vectorizable using this loop order
exchange and splitting the loop into loops, if the cloud-in-cell
scheme is adopted. Here, is the number of dimension. These
vectorization schemes which eliminate the unvectorized loops are applicable to
parallelization of loops for shared-memory multiprocessors. We also
parallelized our code for distributed memory machines. The important part of
parallelization is data decomposition. We sorted the hierarchical mesh data by
the Morton order, or the recursive N-shaped order, level by level and split and
allocated the mesh data to the processors. Particles are allocated to the
processor to which the finest refined cells including the particles are also
assigned. Our timing analysis using the -dominated cold dark matter
simulations shows that our parallel code speeds up almost ideally up to 32
processors, the largest number of processors in our test.Comment: 21pages, 16 figures, to be published in PASJ (Vol. 57, No. 5, Oct.
2005
Application of Kawaguchi Lagrangian formulation to string theory
String-scalar duality proposed by Y. Hosotani and membrane-scalar duality by
A. Sugamoto are reexamined in the context of Kawaguchi Lagrangian formulation.
The characteristic feature of this formulation is the indifferent nature of
fields and parameters. Therefore even the exchange of roles between fields and
parameters is possible. In this manner, dualities above can be proved easily.
Between Kawaguchi metrics of the dually related theories, a simple relation is
found. As an example of the exchange between fermionic fields and parameters, a
replacement of the role of Grassmann parameters of the 2-dimensional superspace
by the 9th component of Neveu-Schwarz-Ramond (NSR) fermions is studied in
superstring model. Compactification is also discussed in this model.Comment: 12 pages, minor modification, published in Phys. Lett.
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Characteristics of cosmic ray pole-equator anisotropy derived from spherical harmonic analysis of neutron monitor data
The spherical harmonic analysis of cosmic ray neutron data from the worldwide network neutron monitor stations during the years, 1966 to 1969 was carried out. The second zonal harmonic component obtained from the analysis corresponds to the Pole-Equator anisotropy of the cosmic ray neutron intensity. Such an anisotropy makes a semiannual variation. In addition to this, it is shown that the Pole-Equator anisotropy makes a variation depending on the interplanetary magnetic field (IMF) sector polarities around the passages of the IMF sector boundary. A mechanism to interpret these results is also discussed
Application of matrix product states to the Hubbard model in one spatial dimension
We investigate the application of matrix product states to the Hubbard model
in one spatial dimension with both of open and periodic boundary conditions. We
develop the variatinal method that the optimization of the variational
parameters is carried out locally and sequentially in the framework of matrix
product operators (MPO) by including the sign, due to the anti-commutation
relation of fermion operators, in the matrix element of MPO. The numerical
accuracy of the ground state energy is examined.Comment: 5 pages, 2 figure
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