9 research outputs found
Effective File-I/O Bandwidth Benchmark
The effective I/O bandwidth benchmark (b{_}eff{_}io) covers two goals: (1) to achieve a characteristic average number for the I/O bandwidth achievable with parallel MPI-I/O applications, and (2) to get detailed information about several access patterns and buffer lengths. The benchmark examines ''first write'', ''rewrite'' and ''read'' access, strided (individual and shared pointers) and segmented collective patterns on one file per application and non-collective access to one file per process. The number of parallel accessing processes is also varied and well-formed I/O is compared with non-well formed. On systems, meeting the rule that the total memory can be written to disk in 10 minutes, the benchmark should not need more than 15 minutes for a first pass of all patterns. The benchmark is designed analogously to the effective bandwidth benchmark for message passing (b{_}eff) that characterizes the message passing capabilities of a system in a few minutes. First results of the b{_}eff{_}io benchmark are given for IBM SP and Cray T3E systems and compared with existing benchmarks based on parallel Posix-I/O
Network Bandwidth Measurements and Ratio Analysis with the HPC Challenge Benchmark Suite (HPCC
Abstract. The HPC Challenge benchmark suite (HPCC) was released to analyze the performance of high-performance computing architectures using several kernels to measure different memory and hardware access patterns comprising latency based measurements, memory streaming, inter-process communication and floating point computation. HPCC defines a set of benchmarks augmenting the High Performance Linpack used in the Top500 list. This paper describes the inter-process communication benchmarks of this suite. Based on the effective bandwidth benchmark, a special parallel random and natural ring communication benchmark has been developed for HPCC. Ping-Pong benchmarks on a set of process pairs can be used for further characterization of a system. This paper analyzes first results achieved with HPCC. The focus of this paper is on the balance between computational speed, memory bandwidth, and inter-node communication. Keywords. HPCC, network bandwidth, effective bandwidth, Linpack
Modeling NIF experimental designs with adaptive mesh refinement and Lagrangian hydrodynamics
Incorporation of adaptive mesh refinement (AMR)
into Lagrangian hydrodynamics algorithms allows for the creation of a highly
powerful simulation tool effective for complex target designs with
three-dimensional structure. We are developing an advanced modeling tool
that includes AMR and traditional arbitrary Lagrangian-Eulerian (ALE)
techniques. Our goal is the accurate prediction of vaporization,
disintegration and fragmentation in National Ignition Facility (NIF)
experimental target elements. Although our focus is on minimizing the
generation of shrapnel in target designs and protecting the optics, the
general techniques are applicable to modern advanced targets that include
three-dimensional effects such as those associated with capsule fill tubes.
Several essential computations in ordinary radiation hydrodynamics need to
be redesigned in order to allow for AMR to work well with ALE, including
algorithms associated with radiation transport. Additionally, for our goal
of predicting fragmentation, we include elastic/plastic flow into our
computations. We discuss the integration of these effects into a new ALE-AMR
simulation code. Applications of this newly developed modeling tool as well
as traditional ALE simulations in two and three dimensions are applied to
NIF early-light target designs
Optimization of experimental designs by incorporating NIF facility impacts
For experimental campaigns on the National Ignition Facility (NIF)
to be successful, they must obtain useful data without causing
unacceptable impact on the facility. Of particular concern is
excessive damage to optics and diagnostic components. There are 192
fused silica main debris shields (MDS) exposed to the potentially
hostile target chamber environment on each shot. Damage in these
optics results either from the interaction of laser light with
contamination and pre-existing imperfections on the optic surface or
from the impact of shrapnel fragments. Mitigation of this second
damage source is possible by identifying shrapnel sources and
shielding optics from them. It was recently demonstrated that the
addition of 1.1-mm thick borosilicate disposable debris shields
(DDS) blocks the majority of debris and shrapnel fragments from
reaching the relatively expensive MDS's. However, DDS's cannot stop
large, fast moving fragments. We have experimentally demonstrated
one shrapnel mitigation technique showing that it is possible to
direct fast moving fragments by changing the source orientation, in
this case a Ta pinhole array. Another mitigation method is to change
the source material to one that produces smaller fragments.
Simulations and validating experiments are necessary to determine
which fragments can penetrate or break 1-3 mm thick DDS's.
Three-dimensional modeling of complex target-diagnostic
configurations is necessary to predict the size, velocity, and
spatial distribution of shrapnel fragments. The tools we are
developing will be used to assure that all NIF experimental
campaigns meet the requirements on allowed level of debris and
shrapnel generation
Hard X-ray and hot electron environment in vacuum hohlraums at NIF
Time resolved hard x-ray images (hv 9 keV) and time
integrated hard x-ray spectra (hv 18-150 keV) from vacuum hohlraums
irradiated with four 351 nm wavelength NIF laser beams are presented as a
function of hohlraum size and laser power and duration. The hard x-ray
images and spectra provide insight into the time evolution of the hohlraum
plasma filling and the production of hot electrons. The fraction of laser
energy detected as hot electrons (f shows correlation with both
laser intensity and with an analytic plasma filling model
Laser coupling to reduced-scale targets at NIF Early Light
Deposition of maximum laser energy into a small, high-Z enclosure in a short laser pulse creates a hot environment. Such targets
were recently included in an experimental campaign using the first four of
the 192 beams of the National Ignition Facility [J. A. Paisner, E. M.
Campbell, and W. J. Hogan, Fusion Technology 26, 755 (1994)], under
construction at the University of California Lawrence Livermore National
Laboratory. These targets demonstrate good laser coupling, reaching a
radiation temperature of 340 eV. In addition, the Raman backscatter spectrum
contains features consistent with Brillouin backscatter of Raman forward
scatter [A. B. Langdon and D. E. Hinkel, Physical Review Letters 89, 015003 (2002)]. Also,
NIF Early Light diagnostics indicate that 20% of the direct backscatter
from these reduced-scale targets is in the polarization orthogonal to that
of the incident light
X-ray flux and X-ray burnthrough experiments on reduced-scale targets at the NIF and OMEGA lasers
An experimental campaign to maximize radiation drive in small-scale
hohlraums has been carried out at the National Ignition Facility
(NIF) at the Lawerence Livermore National Laboratory (Livermore, CA,
USA) and at the OMEGA laser at the Laboratory for Laser Energetics
(Rochester, NY, USA). The small-scale hohlraums, laser energy, laser
pulse, and diagnostics were similar at both facilities but the
geometries were very different. The NIF experiments used on-axis
laser beams whereas the OMEGA experiments used 19 beams in three
beam cones. In the cases when the lasers coupled well and produced
similar radiation drive, images of x-ray burnthrough and laser
deposition indicate the pattern of plasma filling is very different
The first experiments on the national ignition facility
A first set of shock propagation, laser-plasma
interaction, hohlraum energetics and hydrodynamic experiments have been
performed using the first 4 beams of the National Ignition Facility (NIF),
in support of indirect drive Inertial Confinement Fusion (ICF) and High
Energy Density Physics