82,101 research outputs found
The Scalability-Efficiency/Maintainability-Portability Trade-off in Simulation Software Engineering: Examples and a Preliminary Systematic Literature Review
Large-scale simulations play a central role in science and the industry.
Several challenges occur when building simulation software, because simulations
require complex software developed in a dynamic construction process. That is
why simulation software engineering (SSE) is emerging lately as a research
focus. The dichotomous trade-off between scalability and efficiency (SE) on the
one hand and maintainability and portability (MP) on the other hand is one of
the core challenges. We report on the SE/MP trade-off in the context of an
ongoing systematic literature review (SLR). After characterizing the issue of
the SE/MP trade-off using two examples from our own research, we (1) review the
33 identified articles that assess the trade-off, (2) summarize the proposed
solutions for the trade-off, and (3) discuss the findings for SSE and future
work. Overall, we see evidence for the SE/MP trade-off and first solution
approaches. However, a strong empirical foundation has yet to be established;
general quantitative metrics and methods supporting software developers in
addressing the trade-off have to be developed. We foresee considerable future
work in SSE across scientific communities.Comment: 9 pages, 2 figures. Accepted for presentation at the Fourth
International Workshop on Software Engineering for High Performance Computing
in Computational Science and Engineering (SEHPCCSE 2016
Constraining the neutron star equation of state using Pulse Profile Modeling
One very promising technique for measuring the dense matter Equation of State
exploits hotspots that form on the neutron star surface due to the pulsar
mechanism, accretion streams, or during thermonuclear explosions in the neutron
star ocean. This article explains how Pulse Profile Modeling of hotspots is
being used by the Neutron Star Interior Composition Explorer (NICER), an X-ray
telescope installed on the International Space Station in 2017 - and why the
technique is a mission driver for the next, larger-area generation of
telescopes including the enhanced X-ray Timing and Polarimetry (eXTP) mission
and the Spectroscopic Time-Resolving Observatory for Broadband Energy X-rays
(STROBE-X).Comment: To appear in the AIP Conference Proceedings of the Xiamen-CUSTIPEN
Workshop on the EOS of Dense Neutron-Rich Matter in the Era of Gravitational
Wave Astronomy (January 3 - 7, 2019, Xiamen, China
Terrace reconstruction and long profile projection: a case study from the Solent river system near Southampton, England
River terrace sequences are important frameworks for archaeological evidence and as
such it is important to produce robust correlations between what are often fragmentary
remnants of ancient terraces. This paper examines both conceptual and practical issues
related to such correlations, using a case study from the eastern part of the former Solent
River system near Southampton, England. In this region two recent terrace schemes
have been constructed using different data to describe the terrace deposits: one based
mainly on terrace surfaces; the other on gravel thicknesses, often not recording the
terrace surface itself. The utility of each of these types of data in terrace correlation is
discussed in relation to the complexity of the record, the probability of post-depositional
alteration of surface sediments and comparison of straight-line projections with modern
river long profiles. Correlation using age estimates is also discussed, in relation to
optically-stimulated luminescence dating of sand lenses within terrace gravels in this
region during the PASHCC project. It is concluded that the need for replication at single
sites means that this approach has limited use for correlative purposes, although dating
of sediments is important for understanding wider landscape evolution and patterns of
human occupation
Data assurance in opaque computations
The chess endgame is increasingly being seen through the lens of, and therefore effectively defined by, a data ‘model’ of itself. It is vital that such models are clearly faithful to the reality they purport to represent. This paper examines that issue and systems engineering responses to it, using the chess endgame as the exemplar scenario. A structured survey has been carried out of the intrinsic challenges and complexity of creating endgame data by reviewing the past pattern of errors during work in progress, surfacing in publications and occurring after the data was generated. Specific measures are proposed to counter observed classes of error-risk, including a preliminary survey of techniques for using state-of-the-art verification tools to generate EGTs that are correct by construction. The approach may be applied generically beyond the game domain
Large Scale Earth's Bow Shock with Northern IMF as simulated by PIC code in parallel with MHD model
In this paper, we propose a 3D kinetic model (Particle-in-Cell PIC ) for the
description of the large scale Earth's bow shock. The proposed version is
stable and does not require huge or extensive computer resources. Because PIC
simulations work with scaled plasma and field parameters, we also propose to
validate our code by comparing its results with the available MHD simulations
under same scaled Solar wind ( SW ) and ( IMF ) conditions. We report new
results from the two models. In both codes the Earth's bow shock position is
found to be ~14.8 RE along the Sun-Earth line, and ~ 29 RE on the dusk side.
Those findings are consistent with past in situ observations. Both simulations
reproduce the theoretical jump conditions at the shock. However, the PIC code
density and temperature distributions are inflated and slightly shifted sunward
when compared to the MHD results. Kinetic electron motions and reflected ions
upstream may cause this sunward shift. Species distributions in the foreshock
region are depicted within the transition of the shock (measured ~2
c/{\omega}pi for {\Theta}Bn =90o and MMS =4.7 ) and in the downstream. The size
of the foot jump in the magnetic field at the shock is measured to be (1.7
c/{\omega}pi ). In the foreshocked region, the thermal velocity is found equal
to 213 km.sec-1 at 15 RE and is equal to 63 km.sec-1at 12 RE (Magnetosheath
region). Despite the large cell size of the current version of the PIC code, it
is powerful to retain macrostructure of planets magnetospheres in very short
time, thus it can be used for a pedagogical test purposes. It is also likely
complementary with MHD to deepen our understanding of the large scale
magnetosphereComment: 26 pages, 8 figures, 1 table , 66 references, JOAA-D-16-00005/201
A k-deformed Model of Growing Complex Networks with Fitness
The Barab\'asi-Bianconi (BB) fitness model can be solved by a mapping between
the original network growth model to an idealized bosonic gas. The well-known
transition to Bose-Einstein condensation in the latter then corresponds to the
emergence of "super-hubs" in the network model. Motivated by the preservation
of the scale-free property, thermodynamic stability and self-duality, we
generalize the original extensive mapping of the BB fitness model by using the
nonextensive Kaniadakis k-distribution. Through numerical simulation and
mean-field calculations we show that deviations from extensivity do not
compromise qualitative features of the phase transition. Analysis of the
critical temperature yields a monotonically decreasing dependence on the
nonextensive parameter k
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