6,115 research outputs found
Model Coupling between the Weather Research and Forecasting Model and the DPRI Large Eddy Simulator for Urban Flows on GPU-accelerated Multicore Systems
In this report we present a novel approach to model coupling for
shared-memory multicore systems hosting OpenCL-compliant accelerators, which we
call The Glasgow Model Coupling Framework (GMCF). We discuss the implementation
of a prototype of GMCF and its application to coupling the Weather Research and
Forecasting Model and an OpenCL-accelerated version of the Large Eddy Simulator
for Urban Flows (LES) developed at DPRI.
The first stage of this work concerned the OpenCL port of the LES. The
methodology used for the OpenCL port is a combination of automated analysis and
code generation and rule-based manual parallelization. For the evaluation, the
non-OpenCL LES code was compiled using gfortran, fort and pgfortran}, in each
case with auto-parallelization and auto-vectorization. The OpenCL-accelerated
version of the LES achieves a 7 times speed-up on a NVIDIA GeForce GTX 480
GPGPU, compared to the fastest possible compilation of the original code
running on a 12-core Intel Xeon E5-2640.
In the second stage of this work, we built the Glasgow Model Coupling
Framework and successfully used it to couple an OpenMP-parallelized WRF
instance with an OpenCL LES instance which runs the LES code on the GPGPI. The
system requires only very minimal changes to the original code. The report
discusses the rationale, aims, approach and implementation details of this
work.Comment: This work was conducted during a research visit at the Disaster
Prevention Research Institute of Kyoto University, supported by an EPSRC
Overseas Travel Grant, EP/L026201/
Modular System for Shelves and Coasts (MOSSCO v1.0) - a flexible and multi-component framework for coupled coastal ocean ecosystem modelling
Shelf and coastal sea processes extend from the atmosphere through the water
column and into the sea bed. These processes are driven by physical, chemical,
and biological interactions at local scales, and they are influenced by
transport and cross strong spatial gradients. The linkages between domains and
many different processes are not adequately described in current model systems.
Their limited integration level in part reflects lacking modularity and
flexibility; this shortcoming hinders the exchange of data and model components
and has historically imposed supremacy of specific physical driver models. We
here present the Modular System for Shelves and Coasts (MOSSCO,
http://www.mossco.de), a novel domain and process coupling system
tailored---but not limited--- to the coupling challenges of and applications in
the coastal ocean. MOSSCO builds on the existing coupling technology Earth
System Modeling Framework and on the Framework for Aquatic Biogeochemical
Models, thereby creating a unique level of modularity in both domain and
process coupling; the new framework adds rich metadata, flexible scheduling,
configurations that allow several tens of models to be coupled, and tested
setups for coastal coupled applications. That way, MOSSCO addresses the
technology needs of a growing marine coastal Earth System community that
encompasses very different disciplines, numerical tools, and research
questions.Comment: 30 pages, 6 figures, submitted to Geoscientific Model Development
Discussion
Data Registration, Match, and Model Component Coupling
A coupling toolkit has been developed to reduce the complexity of model component coupling, in particular among hierarchical model components. The toolkit provides the services of data registration, data matching, data filtering, and model component coupling. In addition, it can generate diagrams to reveal the "producer"-to-"consumer" relations among the components. We have tested this toolkit with the operational NASA Goddard Earth Observing System (GEOS-5), which is built on the Earth System Modeling Framework (ESMF) and consists of several-level Earth system components
Couplers for linking environmental models: scoping study and potential next steps
This report scopes out what couplers there are available in the hydrology and atmospheric modelling fields. The work reported here examines both dynamic runtime and one way file based coupling. Based on a review of the peer-reviewed literature and other open sources, there are a plethora of coupling technologies and standards relating to file formats. The available approaches have been evaluated against criteria developed as part of the DREAM project. Based on these investigations, the following recommendations are made:
• The most promising dynamic coupling technologies for use within BGS are OpenMI 2.0 and CSDMS (either 1.0 or 2.0)
• Investigate the use of workflow engines: Trident and Pyxis, the latter as part of the TSB/AHRC project “Confluence”
• There is a need to include database standards CSW and GDAL and use data formats from the climate community NetCDF and CF standards.
• Development of a “standard” composition which will consist of two process models and a 3D geological model all linked to data stored in the BGS corporate database and flat file format. Web Feature Services should be included in these compositions.
There is also a need to investigate other approaches in different disciplines: The Loss Modelling Framework, OASIS-LMF is the best candidate
Models of everywhere revisited: a technological perspective
The concept ‘models of everywhere’ was first introduced in the mid 2000s as a means of reasoning about the
environmental science of a place, changing the nature of the underlying modelling process, from one in which
general model structures are used to one in which modelling becomes a learning process about specific places, in
particular capturing the idiosyncrasies of that place. At one level, this is a straightforward concept, but at another
it is a rich multi-dimensional conceptual framework involving the following key dimensions: models of everywhere,
models of everything and models at all times, being constantly re-evaluated against the most current
evidence. This is a compelling approach with the potential to deal with epistemic uncertainties and nonlinearities.
However, the approach has, as yet, not been fully utilised or explored. This paper examines the
concept of models of everywhere in the light of recent advances in technology. The paper argues that, when first
proposed, technology was a limiting factor but now, with advances in areas such as Internet of Things, cloud
computing and data analytics, many of the barriers have been alleviated. Consequently, it is timely to look again
at the concept of models of everywhere in practical conditions as part of a trans-disciplinary effort to tackle the
remaining research questions. The paper concludes by identifying the key elements of a research agenda that
should underpin such experimentation and deployment
Was Einstein Right? Testing Relativity at the Centenary
We review the experimental evidence for Einstein's special and general
relativity. A variety of high precision null experiments verify the weak
equivalence principle and local Lorentz invariance, while gravitational
redshift and other clock experiments support local position invariance.
Together these results confirm the Einstein Equivalence Principle which
underlies the concept that gravitation is synonymous with spacetime geometry,
and must be described by a metric theory. Solar system experiments that test
the weak-field, post-Newtonian limit of metric theories strongly favor general
relativity. The Binary Pulsar provides tests of gravitational-wave damping and
of strong-field general relativity. Recently discovered binary pulsar systems
may provide additional tests. Future and ongoing experiments, such as the
Gravity Probe B Gyroscope Experiment, satellite tests of the Equivalence
principle, and tests of gravity at short distance to look for extra spatial
dimensions could constrain extensions of general relativity. Laser
interferometric gravitational-wave observatories on Earth and in space may
provide new tests of gravitational theory via detailed measurements of the
properties of gravitational waves.Comment: 21 pages, 3 figures, to be published in "100 Years of Relativity:
Spacetime Structure - Einstein and Beyond", ed. Abhay Ashtekar (World
Scientific, Singapore
Method for predicting whispering gallery mode spectra of spherical microresonators
A full three-dimensional Finite-Difference Time-Domain (FDTD)-based toolkit
is developed to simulate the whispering gallery modes of a microsphere in the
vicinity of a dipole source. This provides a guide for experiments that rely on
efficient coupling to the modes of microspheres. The resultant spectra are
compared to those of analytic models used in the field. In contrast to the
analytic models, the FDTD method is able to collect flux from a variety of
possible collection regions, such as a disk-shaped region. The customizability
of the technique allows one to consider a variety of mode excitation scenarios,
which are particularly useful for investigating novel properties of optical
resonators, and are valuable in assessing the viability of a resonator for
biosensing.Comment: Published 10 Apr 2015 in Opt. Express Vol. 23, Issue 8, pp.
9924-9937; The FDTD toolkit supercomputer scripts are hosted at:
http://sourceforge.net/projects/npps/files/FDTD_WGM_Simulator
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