189 research outputs found
Architectural choices for the Columbia 0.8 Teraflops machine
We discuss the hardware design choices made in our 16K-node 0.8 Teraflops
supercomputer project, a machine architecture optimized for full QCD
calculations. The efficiency of the conjugate gradient algorithm in terms of
balance of floating-point operations, memory handling and utilization, and
communication overhead is addressed. We also discuss the technological
innovations and software tools that facilitate hardware design and what
opportunities these give to the academic community.Comment: Contribution to Lattice 94. 3 pages. Latex source followed by
compressed, uuenocded postscript file of the complete pape
QCDSP: The first 64 nodes
We present a summary of the progress on QCDSP in the last year. QCDSP,
Quantum Chromodynamics on Digital Signal Processors, is an inexpensive computer
being built at Columbia that can achieve 0.8 teraflops for three million
dollars.Comment: 4 pages, 1 figur
The status of US Teraflops-scale projects
The current status of United States projects pursuing Teraflops-scale
computing resources for lattice field theory is discussed. Two projects are in
existence at this time: the Multidisciplinary Teraflops Project, incorporating
the physicists of the QCD Teraflops Collaboration, and a smaller project,
centered at Columbia, involving the design and construction of a 0.8 Teraflops
computer primarily for QCD.Comment: Contribution to Lattice 94. 7 pages. Latex source followed by
compressed, uuenocded postscript file of the complete paper. Individual
figures available from [email protected]
Status of the QCDSP project
We describe the completed 8,192-node, 0.4Tflops machine at Columbia as well
as the 12,288-node, 0.6Tflops machine assembled at the RIKEN Brookhaven
Research Center. Present performance as well as our experience in commissioning
these large machines is presented. We outline our on-going physics program and
explain how the configuration of the machine is varied to support a wide range
of lattice QCD problems, requiring a variety of machine sizes. Finally a brief
discussion is given of future prospects for large-scale lattice QCD machines.Comment: LATTICE98(machines), 3 pages, 1 picture, 1 figur
Energy of eigen-modes in magnetohydrodynamic flows of ideal fluids
Analytical expression for energy of eigen-modes in magnetohydrodynamic flows
of ideal fluids is obtained. It is shown that the energy of unstable modes is
zero, while the energy of stable oscillatory modes (waves) can assume both
positive and negative values. Negative energy waves always correspond to
non-symmetric eigen-modes -- modes that have a component of wave-vector along
the equilibrium velocity. These results suggest that all non-symmetric
instabilities in ideal MHD systems with flows are associated with coupling of
positive and negative energy waves. As an example the energy of eigen-modes is
calculated for incompressible conducting fluid rotating in axial magnetic
field.Comment: 10 pages, 3 figure
Better than $1/Mflops sustained: a scalable PC-based parallel computer for lattice QCD
We study the feasibility of a PC-based parallel computer for medium to large
scale lattice QCD simulations. The E\"otv\"os Univ., Inst. Theor. Phys. cluster
consists of 137 Intel P4-1.7GHz nodes with 512 MB RDRAM. The 32-bit, single
precision sustained performance for dynamical QCD without communication is 1510
Mflops/node with Wilson and 970 Mflops/node with staggered fermions. This gives
a total performance of 208 Gflops for Wilson and 133 Gflops for staggered QCD,
respectively (for 64-bit applications the performance is approximately halved).
The novel feature of our system is its communication architecture. In order to
have a scalable, cost-effective machine we use Gigabit Ethernet cards for
nearest-neighbor communications in a two-dimensional mesh. This type of
communication is cost effective (only 30% of the hardware costs is spent on the
communication). According to our benchmark measurements this type of
communication results in around 40% communication time fraction for lattices
upto 48^3\cdot96 in full QCD simulations. The price/sustained-performance ratio
for full QCD is better than 1.5/Mflops for
staggered) quarks for practically any lattice size, which can fit in our
parallel computer. The communication software is freely available upon request
for non-profit organizations.Comment: 14 pages, 3 figures, final version to appear in Comp.Phys.Com
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