4,792 research outputs found
Partition Around Medoids Clustering on the Intel Xeon Phi Many-Core Coprocessor
Abstract. The paper touches upon the problem of implementation Partition Around Medoids (PAM) clustering algorithm for the Intel Many Integrated Core architecture. PAM is a form of well-known k-Medoids clustering algorithm and is applied in various subject domains, e.g. bioinformatics, text analysis, intelligent transportation systems, etc. An optimized version of PAM for the Intel Xeon Phi coprocessor is introduced where OpenMP parallelizing technology, loop vectorization, tiling technique and efficient distance matrix computation for Euclidean metric are used. Experimental results for different data sets confirm the efficiency of the proposed algorithm
First results from the LUCID-Timepix spacecraft payload onboard the TechDemoSat-1 satellite in Low Earth Orbit
The Langton Ultimate Cosmic ray Intensity Detector (LUCID) is a payload
onboard the satellite TechDemoSat-1, used to study the radiation environment in
Low Earth Orbit (635km). LUCID operated from 2014 to 2017, collecting
over 2.1 million frames of radiation data from its five Timepix detectors on
board. LUCID is one of the first uses of the Timepix detector technology in
open space, with the data providing useful insight into the performance of this
technology in new environments. It provides high-sensitivity imaging
measurements of the mixed radiation field, with a wide dynamic range in terms
of spectral response, particle type and direction. The data has been analysed
using computing resources provided by GridPP, with a new machine learning
algorithm that uses the Tensorflow framework. This algorithm provides a new
approach to processing Medipix data, using a training set of human labelled
tracks, providing greater particle classification accuracy than other
algorithms. For managing the LUCID data, we have developed an online platform
called Timepix Analysis Platform at School (TAPAS). This provides a swift and
simple way for users to analyse data that they collect using Timepix detectors
from both LUCID and other experiments. We also present some possible future
uses of the LUCID data and Medipix detectors in space.Comment: Accepted for publication in Advances in Space Researc
Jet analysis by Deterministic Annealing
We perform a comparison of two jet clusterization algorithms. The first one
is the standard Durham algorithm and the second one is a global optimization
scheme, Deterministic Annealing, often used in clusterization problems, and
adapted to the problem of jet identification in particle production by high
energy collisions; in particular we study hadronic jets in WW production by
high energy electron positron scattering. Our results are as follows. First, we
find that the two procedures give basically the same output as far as the
particle clusterization is concerned. Second, we find that the increase of CPU
time with the particle multiplicity is much faster for the Durham jet
clustering algorithm in comparison with Deterministic Annealing. Since this
result follows from the higher computational complexity of the Durham scheme,
it should not depend on the particular process studied here and might be
significant for jet physics at LHC as well.Comment: 15 pages, 4 figure
Mixing multi-core CPUs and GPUs for scientific simulation software
Recent technological and economic developments have led to widespread availability of
multi-core CPUs and specialist accelerator processors such as graphical processing units
(GPUs). The accelerated computational performance possible from these devices can be very
high for some applications paradigms. Software languages and systems such as NVIDIA's
CUDA and Khronos consortium's open compute language (OpenCL) support a number of
individual parallel application programming paradigms. To scale up the performance of some
complex systems simulations, a hybrid of multi-core CPUs for coarse-grained parallelism and
very many core GPUs for data parallelism is necessary. We describe our use of hybrid applica-
tions using threading approaches and multi-core CPUs to control independent GPU devices.
We present speed-up data and discuss multi-threading software issues for the applications
level programmer and o er some suggested areas for language development and integration
between coarse-grained and ne-grained multi-thread systems. We discuss results from three
common simulation algorithmic areas including: partial di erential equations; graph cluster
metric calculations and random number generation. We report on programming experiences
and selected performance for these algorithms on: single and multiple GPUs; multi-core CPUs;
a CellBE; and using OpenCL. We discuss programmer usability issues and the outlook and
trends in multi-core programming for scienti c applications developers
UHECR besides CenA: hints of galactic sources
Ultra High Energy Cosmic Rays, UHECR, maybe protons, as most still believe
and claim, or nuclei; in particular lightest nuclei as we advocated recently.
The first (Auger Collaboration) nucleon proposal (2007)[2] foresaw to trace
clearly the UHECR GZK Universe reaching far (up to 100 Mpc)
Super-Galactic-Plane, with little angular dispersion. On the contrary Lightest
Nuclei model (2008)[3], inspired by observed composition and by nearest CenA
clustering (almost a quarter of the AUGER events) explains a modest and narrow
(few Mpc) Universe view, as well as the puzzling Virgo absence: lightest nuclei
offer a fragile (and therefore very nearby) blurred Astronomy. Here we address
to a part of the remaining scattered events in the new up-dated Auger map
(March 2009-ICRC09). We found within rarest clustering the surprising imprint
of a few galactic sources, a partial component of UHECR sources. In particular
we recognize a first trace of Vela, brightest gamma and radio galactic source,
and smeared sources along Galactic Plane and Center. The clustering may imply
additional tails of fragments (by nuclei photo-dissociation) at half energies.
The UHECR light-nuclei fragility and opacity may also reflect into a train of
secondaries as gamma and neutrinos UHE events at tens-hundred PeVs. These UHE
neutrinos might be detectable in a coming future within nearest AUGER and Array
Fluorescence Telescope views,(few km distances) by fast fluorescence flashing
of horizontal up-going tau Air-showers.Comment: 3 pages, 6 figures + 1 original Map figure (from public web service
SCINEGHE Oct. 2009: Daniele Martello for AUGER Collab:
http://agenda.infn.it/conferenceOtherViews.py?view=standard&confId=1369, Talk
n.21
Control Infrastructure for a Pulsed Ion Accelerator
We report on updates to the accelerator controls for the Neutralized Drift
Compression Experiment II, a pulsed induction-type accelerator for heavy ions.
The control infrastructure is built around a LabVIEW interface combined with an
Apache Cassandra backend for data archiving. Recent upgrades added the storing
and retrieving of device settings into the database, as well as ZeroMQ as a
message broker that replaces LabVIEW's shared variables. Converting to ZeroMQ
also allows easy access via other programming languages, such as Python
UHECR Acceleration in Dark Matter Filaments of Cosmological Structure Formation
A mechanism for proton acceleration to ~10^21eV is suggested. It may operate
in accretion flows onto thin dark matter filaments of cosmic structure
formation. The flow compresses the ambient magnetic field to strongly increase
and align it with the filament. Particles begin the acceleration by the ExB
drift with the accretion flow. The energy gain in the drift regime is limited
by the conservation of the adiabatic invariant p_perp^2/B. Upon approaching the
filament, the drift turns into the gyro-motion around the filament so that the
particle moves parallel to the azimuthal electric field. In this 'betatron'
regime the acceleration speeds up to rapidly reach the electrodynamic limit
for an accelerator with magnetic field and the orbit radius
(Larmor radius). The periodic orbit becomes unstable and the particle
slings out of the filament to the region of a weak (uncompressed) magnetic
field, which terminates the acceleration.
The mechanism requires pre-acceleration that is likely to occur in structure
formation shocks upstream or nearby the filament accretion flow. Previous
studies identify such shocks as efficient proton accelerators to a firm upper
limit ~10^19.5 eV placed by the catastrophic photo-pion losses. The present
mechanism combines explosive energy gain in its final (betatron) phase with
prompt particle release from the region of strong magnetic field. It is this
combination that allows protons to overcome both the photo-pion and the
synchrotron-Compton losses and therefore attain energy 10^21 eV. A requirement
on accelerator to reach a given E_max placed by the accelerator energy
dissipation \propto E_{max}^{2}/Z_0 due to the finite vacuum impedance Z_0 is
circumvented by the cyclic operation of the accelerator.Comment: 34 pages, 10 figures, to be published in JCA
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