A GPU-Accelerated Linear Solver for Massively Parallel Underground Simulations

2021 ◽  
Author(s):  
Giovanni Isotton ◽  
Carlo Janna ◽  
Nicoló Spiezia ◽  
Omar Tosatto ◽  
Massimo Bernaschi ◽  
...  
Keyword(s):  
Large Scale ◽  
Iterative Solvers ◽  
Sparse Approximate Inverse ◽  
Modern Engineering ◽  
Numerical Experimentation ◽  
Approximate Inverses ◽  
Preconditioned Iterative ◽  
Set Up ◽  
High Level ◽  
Large Scale Simulations

Abstract Modern engineering applications require the solution of linear systems of millions or even billions of equations. The solution of the linear system takes most of the simulation for large scale simulations, and represent the bottleneck in developing scientific and technical software. Usually, preconditioned iterative solvers are preferred because of their low memory requirements and they can have a high level of parallelism. Approximate inverses have been proven to be robust and effective preconditioners in several contexts. In this communication, we present an adaptive Factorized Sparse Approximate Inverse (FSAI) preconditioner with a very high level of parallelism in both set-up and application. Its inherent parallelism makes FSAI an ideal candidate for a GPU-accelerated implementation, even if taking advantage of this hardware is not a trivial task, especially in the set-up stage. An extensive numerical experimentation has been performed on industrial underground applications. It is shown that the proposed approach outperforms more traditional preconditioners in challenging underground simulation, greatly reducing time-to-solution.

scholarly journals A GPU-accelerated adaptive FSAI preconditioner for massively parallel simulations

2021 ◽  
pp. 109434202110171
Author(s):  
Giovanni Isotton ◽  
Carlo Janna ◽  
Massimo Bernaschi
Keyword(s):  
Linear Systems ◽  
Large Scale ◽  
Iterative Solvers ◽  
Ideal Behavior ◽  
Parallel Simulations ◽  
Numerical Experimentation ◽  
Approximate Inverses ◽  
Preconditioned Iterative ◽  
Set Up ◽  
High Degree

The solution of linear systems of equations is a central task in a number of scientific and engineering applications. In many cases the solution of linear systems may take most of the simulation time thus representing a major bottleneck in the further development of scientific and technical software. For large scale simulations, nowadays accounting for several millions or even billions of unknowns, it is quite common to resort to preconditioned iterative solvers for exploiting their low memory requirements and, at least potential, parallelism. Approximate inverses have been shown to be robust and effective preconditioners in various contexts. In this work, we show how adaptive Factored Sparse Approximate Inverse (aFSAI), characterized by a very high degree of parallelism, can be successfully implemented on a distributed memory computer equipped with GPU accelerators. Taking advantage of GPUs in adaptive FSAI set-up is not a trivial task, nevertheless we show through an extensive numerical experimentation how the proposed approach outperforms more traditional preconditioners and results in a close-to-ideal behavior in challenging linear algebra problems.

Trilinos Solvers Scalability on a MFiX-Trilinos Framework Applied to Fluidized Bed Simulations

2020 ◽  
Author(s):  
Arturo Rodriguez ◽  
V. M. Krushnarao Kotteda ◽  
Luis F. Rodriguez ◽  
Vinod Kumar ◽  
Jorge A. Munoz
Keyword(s):  
Linear System ◽  
Fluidized Bed ◽  
Large Scale ◽  
Fossil Fuel ◽  
State Of The Art ◽  
Iterative Solvers ◽  
Flow Solver ◽  
Nonlinear Solvers ◽  
Fuel Reactor ◽  
Preconditioned Iterative

Abstract MFiX is a multiphase open-source suite that is developed at the National Energy Technology Laboratories. It is widely used by fossil fuel reactor communities to simulate flow in a fluidized bed reactor. It does not have advanced linear iterative solvers even though it spends 70% of the run time in solving the linear system. Trilinos contains algorithms and enabling technologies for the solution of large-scale, sophisticated multi-physics engineering and scientific problems. The library developed at Sandia National Laboratories has more than 60 packages. It consists of state-of-the-art preconditioners, nonlinear solvers, direct solvers, and iterative solvers. The packages are performant and portable on various hybrid computing architectures. To improve the capabilities of MFiX, we developed a framework, MFiX-Trilinos, to integrate the advanced linear solvers in Trilinos with the FORTRAN based multiphase flow solver, MFiX. The framework changes the semantics of the array in FORTRAN and C++ and solve the linear system with packages in Trilinos and returns the solution to MFiX. The preconditioned iterative solvers considered for the analysis are BiCGStab and GMRES. The framework is verified on various fluidized bed problems. The performance of the framework is tested on the Stampede supercomputer. The wall time for multiple sizes of fluidized beds is compared.

Estimates of surface fluxes from global operational numerical weather predictions

1989 ◽  
Vol 329 (1604) ◽  
pp. 303-315 ◽  
Keyword(s):  
Large Scale ◽  
Prediction Models ◽  
Research Programme ◽  
Surface Flux ◽  
Surface Fluxes ◽  
Coupled Models ◽  
Numerical Experimentation ◽  
Relevant Variables ◽  
Forecast Models ◽  
High Level

The success of coupled models of the ocean-atmosphere system depends in part on their ability to estimate the momentum, heat and water vapour fluxes at the interface accurately. Their accuracy as now calculated by atmospheric numerical forecast models with relevant variables at the sea surface given is uncertain. The achievement of an acceptable accuracy in this simpler situation is an essential preliminary to a solution of the more difficult interactive problem. The ISCU/WMO Joint Scientific Committee (JSC) for the World Climate Research Programme (WCRP) considered how best to obtain surface flux values primarily for running large-scale ocean models. They concluded that the most promising approach was to extract them from numerical prediction models whose capabilities in terms of assimilating observations of many diverse kinds and of quality controlling meteorological information, have reached a high level of development and are being improved continuously. The committee requested its Working Group on Numerical Experimentation (WGNE) to investigate and report on the accuracies now achieved. In the absence of measurements of surface fluxes suitable for validation, the WGNE decided that the first step was to compare surface fluxes as estimated by state-of-theart global prediction models. The ECMWF (European Centre for Medium-Range Weather Forecasts) and Meteorological Office models were considered suitable, and have the advantage of employing different approaches to data assimilation, model configuration and the parametrization of physical processes. This report will outline the results obtained by the two models for a first comparison period, May-June 1987.

scholarly journals Decision-Making at National Level for the Support of Research Infrastructures

2019 ◽  
Vol 3 ◽  
Author(s):  
Jeannette Ridder-Numan
Keyword(s):  
Decision Making ◽  
Large Scale ◽  
National Level ◽  
Scientific Research ◽  
Research Infrastructures ◽  
Special Request ◽  
Support Of Research ◽  
Set Up ◽  
High Level ◽  
Scientific Collections

The presentation will elaborate on the Dutch decision-making process concerning large-scale research infrastructures at national and European levels. The process involves several stakeholders, from scientists, to funders to Ministries. The Permanent Committee for Scientific Infrastructures (http://www.onderzoeksfaciliteiten.nl/permanente-commissie) plays a high-level decision-making and vision role in this effort. The committee is independent and part of NWO, the Netherland's Research Organisation for Scientific Research, on special request of the Minister of Education, Culture and Science. This level of decision making is necessary to participate at the next level within the vision of the European Roadmap for Research Infrastructures. This Roadmap is set up by the European Strategy Forum for Research Infrastrcutures (ESFRI, https://www.esfri.eu) and is a portfolio of Research Infrastructures regarded as crucial to shape the European Landscape of scientific Research Infrastrcutures. DiSCCo (Distributed System of Scientific Collections), led by Naturalis (Leiden) is a recent and good example of such an infrastructure that gained a place in the European research infrastructure environment connecting 115 Museums, Botanical Gardens and collection-holding Universities in 21 European countries.

Platelet Anti-Aggregating Activity and Tolerance of Clopidogrel in Atherosclerotic Patients

1996 ◽  
Vol 76 (06) ◽  
pp. 0939-0943 ◽  
Author(s):  
B Boneu ◽  
G Destelle ◽  
Keyword(s):  
Platelet Aggregation ◽  
Large Scale ◽  
Bleeding Time ◽  
Antithrombotic Activity ◽  
Ambulatory Patients ◽  
Patients At Risk ◽  
Set Up ◽  
Ischemic Events ◽  
Large Scale Clinical Trial ◽  
Selection Of

SummaryThe anti-aggregating activity of five rising doses of clopidogrel has been compared to that of ticlopidine in atherosclerotic patients. The aim of this study was to determine the dose of clopidogrel which should be tested in a large scale clinical trial of secondary prevention of ischemic events in patients suffering from vascular manifestations of atherosclerosis [CAPRIE (Clopidogrel vs Aspirin in Patients at Risk of Ischemic Events) trial]. A multicenter study involving 9 haematological laboratories and 29 clinical centers was set up. One hundred and fifty ambulatory patients were randomized into one of the seven following groups: clopidogrel at doses of 10, 25, 50,75 or 100 mg OD, ticlopidine 250 mg BID or placebo. ADP and collagen-induced platelet aggregation tests were performed before starting treatment and after 7 and 28 days. Bleeding time was performed on days 0 and 28. Patients were seen on days 0, 7 and 28 to check the clinical and biological tolerability of the treatment. Clopidogrel exerted a dose-related inhibition of ADP-induced platelet aggregation and bleeding time prolongation. In the presence of ADP (5 \lM) this inhibition ranged between 29% and 44% in comparison to pretreatment values. The bleeding times were prolonged by 1.5 to 1.7 times. These effects were non significantly different from those produced by ticlopidine. The clinical tolerability was good or fair in 97.5% of the patients. No haematological adverse events were recorded. These results allowed the selection of 75 mg once a day to evaluate and compare the antithrombotic activity of clopidogrel to that of aspirin in the CAPRIE trial.

An HPC Framework for Large Scale Simulations and Visualizations of Oil Spill Trajectories

2013 ◽  
Author(s):  
Jian Tao ◽  
Werner Benger ◽  
Kelin Hu ◽  
Edwin Mathews ◽  
Marcel Ritter ◽  
...  
Keyword(s):  
Oil Spill ◽  
Large Scale ◽  
Large Scale Simulations

Social inequality in the evolution of human societies

2019 ◽  
pp. 98-120
Author(s):  
Georgi Derluguian
Keyword(s):  
Social Inequality ◽  
Large Scale ◽  
Human Beings ◽  
Mass Violence ◽  
Public And Private ◽  
Tangible Assets ◽  
Transition To Agriculture ◽  
New Institutions ◽  
High Level ◽  
Political Economic

The author develops ideas about the origin of social inequality during the evolution of human societies and reflects on the possibilities of its overcoming. What makes human beings different from other primates is a high level of egalitarianism and altruism, which contributed to more successful adaptability of human collectives at early stages of the development of society. The transition to agriculture, coupled with substantially increasing population density, was marked by the emergence and institutionalisation of social inequality based on the inequality of tangible assets and symbolic wealth. Then, new institutions of warfare came into existence, and they were aimed at conquering and enslaving the neighbours engaged in productive labour. While exercising control over nature, people also established and strengthened their power over other people. Chiefdom as a new type of polity came into being. Elementary forms of power (political, economic and ideological) served as a basis for the formation of early states. The societies in those states were characterised by social inequality and cruelties, including slavery, mass violence and numerous victims. Nowadays, the old elementary forms of power that are inherent in personalistic chiefdom are still functioning along with modern institutions of public and private bureaucracy. This constitutes the key contradiction of our time, which is the juxtaposition of individual despotic power and public infrastructural one. However, society is evolving towards an ever more efficient combination of social initiatives with the sustainability and viability of large-scale organisations.

Onchocerciasis in Osse, Ondo State, Nigeria: Effectiveness of Motivational Strategies in Sustaining Compliance with Community Ivermectin Therapy

2002 ◽  
Vol 21 (2) ◽  
pp. 177-189
Author(s):  
O. U. Manafa ◽  
T. S. Awolola ◽  
A. N. Isamah
Keyword(s):  
Community Intervention ◽  
Intervention Group ◽  
Control Group ◽  
Group Discussions ◽  
Participant Satisfaction ◽  
Attitudes And Practices ◽  
Ondo State ◽  
Set Up ◽  
High Level ◽  
Knowledge Attitudes And Practices

A study in human Onchocerciasis was undertaken in four endemic communities in Ondo State, Nigeria. In-depth interviews were conducted on peoples' knowledge, attitudes, and practices regarding Onchocerciasis aetiology, treatment, prevention, and symptoms. These were complemented by key informant interviews and focus group discussions. Based on this information, an educational program was set up which included the training of selected villagers (motivators) and community intervention organized by these motivators. Evaluation used a control group where intervention was focused on other health problems in the area. Onchocerciasis education took place only with the intervention group. At the start of the project, peoples' knowledge about Onchocerciasis, its cause, treatment, prevention, and symptoms were varied and only a small proportion could link the bite of the blackfly to Onchocerciasis. The educational intervention achieved a high level of participant satisfaction which was expressed in continuous attendance at workshops and keeping appointments with motivators. The intervention helped to bring a significant improvement in the knowledge, attitudes, and practices (KAP) of the respondents. The knowledge of Onchocerciasis aetiology increased to 79.8 percent, 71.5 percent, and 74 percent from 48.5 percent, 48.7 percent, 34 percent, and 45 percent pre-intervention in the four study areas used. The project demonstrated that a community-based health education can be effective in Onchocerciasis control.

MODELING THE SOUTH ATLANTIC OCEAN FROM MEDIUM TO HIGH RESOLUTION

2014 ◽  
Vol 31 (2) ◽  
Author(s):  
Mariela Gabioux ◽  
Vladimir Santos da Costa ◽  
Joao Marcos Azevedo Correia de Souza ◽  
Bruna Faria de Oliveira ◽  
Afonso De Moraes Paiva
Keyword(s):  
High Resolution ◽  
Atlantic Ocean ◽  
Large Scale ◽  
South Atlantic ◽  
Surface Relaxation ◽  
The South ◽  
Small Surface ◽  
Basic Model ◽  
Basic Set ◽  
Set Up

Results of the basic model configuration of the REMO project, a Brazilian approach towards operational oceanography, are discussed. This configuration consists basically of a high-resolution eddy-resolving, 1/12 degree model for the Metarea V, nested in a medium-resolution eddy-permitting, 1/4 degree model of the Atlantic Ocean. These simulations performed with HYCOM model, aim for: a) creating a basic set-up for implementation of assimilation techniques leading to ocean prediction; b) the development of hydrodynamics bases for environmental studies; c) providing boundary conditions for regional domains with increased resolution. The 1/4 degree simulation was able to simulate realistic equatorial and south Atlantic large scale circulation, both the wind-driven and the thermohaline components. The high resolution simulation was able to generate mesoscale and represent well the variability pattern within the Metarea V domain. The BC mean transport values were well represented in the southwestern region (between Vitória-Trinidade sea mount and 29S), in contrast to higher latitudes (higher than 30S) where it was slightly underestimated. Important issues for the simulation of the South Atlantic with high resolution are discussed, like the ideal place for boundaries, improvements in the bathymetric representation and the control of bias SST, by the introducing of a small surface relaxation. In order to make a preliminary assessment of the model behavior when submitted to data assimilation, the Cooper & Haines (1996) method was used to extrapolate SSH anomalies fields to deeper layers every 7 days, with encouraging results.

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