geocomputation in the grid computing age · grid computing age qingfeng (gene) guan, tong zhang,...
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GeoComputation in the Grid Computing Age
Qingfeng (Gene) Guan,Tong Zhang,
Keith C. ClarkeDepartment of Geography
University of California, Santa BarbaraSan Diego State University
Dec. 5th, 2006
2006 W2GIS, Hong Kong, China
Content
1. Introduction
2. GeoComputation: Challenges and Opportunities– The Capital G and C in GeoComputation– Challenges and Opportunites
3. Emerging Technologies to Promote GeoComputation– Grid Computing– Web Portals for the Grid– Grid-enabled Parallel Computing
4. Strategies and Approaches– A Grid-based Geospatial Problem-Solving Architecture– Case Study: Grid-enabled Geographic Cellular Automata
5. Conclusions
Introduction
GeoComputation: the “art and science of solving complex spatial problems with computers” (www.geocomputation.org)
Introduction (cont.)
GeoComputation: a “grab-bag” of computational techniques for geospatial problem-solving (Couclelis, H., 1998) lacking in interoperability, and extremely hard to organize to form an integrated geospatial problem-solving environment
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Introduction (cont.)
Question: How do we make GeoComputation less like a “grab-bag”, and more like a “art and science”?
More specifically: How do we integrate those computational techniques effectively and efficiently into a collaborative geospatial problem-solving environment?
GeoComputation- The Capital G and C
Couclelis (1998) identified the “core GeoComputation” as the innovative (or derived from other disciplines) computer-based geospatial modeling and analysis
– Contrasted against the traditional computer-supported spatial data analysis and geospatial modeling
– Based on the theory of computation – effective procedure
Openshaw (2000) also emphasized the computational science as the origin of GeoComputation (the Computation part) and the essential concerns about geographical and earth systems (the Geopart)
The capital G and C, as the core of GeoComputation, fundamentally explain the philosophical origins of GeoComputation
– The revolutionary application of computational science in geography or an even broader domain
GeoComputation- Challenges, in a computing perspective
The high diversity of GeoComputation and the complexities of geospatial models
GeoComputation- Challenges, in a computing perspective
The high diversity of GeoComputation and the complexities of geospatial models
GeoComputation- Challenges, in a computing perspective
The high diversity of GeoComputation and the complexities of geospatial models
GeoComputation- Challenges, in a computing perspective
The high diversity of GeoComputation and the complexities of geospatial models
GeoComputation- Challenges, in a computing perspective
The high diversity of GeoComputation and the complexities of geospatial models
GeoComputation- Challenges, in a computing perspective
The high diversity of GeoComputation and the complexities of geospatial models
GeoComputation- Challenges, in a computing perspective
The high diversity of GeoComputation and the complexities of geospatial models
GeoComputation- Challenges, in a computing perspective
The high diversity of GeoComputation and the complexities of geospatial models
GeoComputation- Challenges, in a computing perspective (cont.)
Computational intensity– Artificial Intelligence (AI), or Computational
Intelligence (CI)– Massive amount of high-resolution
geospatial data– More sophisticated and complicated
geospatal models
High costs of high-performance supercomputers
GeoComputation- Opportunities provided by emerging computing technologies
GeoComputation- Opportunities provided by emerging computing technologies
Grid Computing (Cyberinfrastructure)
– High performance– Widely accessible– Low cost
GeoComputation- Opportunities provided by emerging computing technologies
Grid Computing (Cyberinfrastructure)
– High performance– Widely accessible– Low cost
Web services and Web portals– Interoperability– User friendly
GeoComputation- Opportunities provided by emerging computing technologies
Grid Computing (Cyberinfrastructure)
– High performance– Widely accessible– Low cost
Web services and Web portals– Interoperability– User friendly
Problem: Grid-enabled GeoComputation is largely lacking
New Computing Technologies- Grid Computing (Cyberinfrastructure)
Virtual Supercomputer– An “ integrated suite of computational
engines, mass storage, networks, digital libraries and databases, sensors, software and services” (NSF, 2003)
Virtual Organization– Cross the administrative and institutional
boundaries for resource and services sharing
– Network-based dynamic communities
Decentralized control, common and universal protocols plus “quality services”
New Computing Technologies- Web Portals for the Grid
The web portal offers a centralized and uniform interface to access the distributed and heterogeneous resources and services.
New Computing Technologies- Grid-enabled Parallel Computing
A Computational Grid is “a hardware and software infrastructure that provides dependable, consistent, pervasive, and inexpensive access to high-end computational capabilities” (Foster, I. and C. Kesselman, 1999)
Transparent to users
Strategies and Approaches- A Grid-based Geospatial Problem-Solving Architecture
Strategies and Approaches- A Grid-based Geospatial Problem-Solving Architecture
Strategies and Approaches- A Grid-based Geospatial Problem-Solving Architecture (cont.)
Presentation Tier: GIS/GeoComputation Web Portals as user-Grid interfaces; serves as a Visual Problem-Solving Environment (VPSE)
Service Tier: to locate and fetch requested GIServices;
Model Tier: Grid-enabled parallel GeoComputation algorithms and models
Grid Tier: Grid Infrastructure
Strategies and Approaches- Case Study: Grid-enabled Geographic Cellular Automata
Geographic Cellular Automata (Geo-CA) are typical GeoComputation models, and have been widely used for simulating and forecasting complex spatial-temporal phenomena
Model parameters represent multiple geospatial factors and non-geospatial factors
Calibration processes are needed produce more realistic simulation results
Extremely computationally intensive
Prediction of urban development to the Prediction of urban development to the year 2050 over southeastern Pennsylvania year 2050 over southeastern Pennsylvania and part of Delaware using the SLEUTH and part of Delaware using the SLEUTH modelmodel
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Case Study: Grid-enabled Geo-CA- Parallel Algorithm Design
Case Study: Grid-enabled Geo-CA- Parallel Algorithm Design
CA models were born to be parallelized
Distinguishing characteristics of geospatial data
– irregular in location and geometric characteristics (shape, size)
– heterogeneous in domain, e.g., dense and sparse
Regular data-decomposition methods might not be efficient to produce evenly distributed partitions in terms of workloads of sub cell spaces
Case Study: Grid-enabled Geo-CA- Parallel Algorithm Design: Data Decomposition
Spatial-adaptive data decomposition– Workload oriented– Spatial indexing methods: grid hierarchy, quad-trees, R-
treesReducing the granularity of decomposition, and assigning multiple sub cell spaces onto a computing unit
The region quad-tree (Worboys and Duckham, 2004)
Workload oriented decomposition
Case Study: Grid-enabled Geo-CA- Parallel Algorithm Design: Neighborhood issue
Case Study: Grid-enabled Geo-CA- Parallel Algorithm Design: Neighborhood issue
Ghost Cells: A sub cell space’s overlapping cells with its neighboring sub cell spaces.
The update processes of ghost cells’ states cause communication overheads
Solution: update on change
Case Study: Grid-enabled Geo-CA- Parallel Algorithm Design: Object Model
Object-Oriented Approach
– To support data decomposition and data transfer among computing units
– Globally indexed coordinates for data communication
Case Study: Grid-enabled Geo-CA- Implementation on the Grid
Implemented in C++
Resides in the Model Tier of the architecture
Conclusions
GeoComputation implies the revolutionary application of computational science in geography or an even broader domain
New computing technologies, especially Grid Computing, offer an opportunity to promote GeoComputation in terms of usability, feasibility, applicability and availability
A Grid-based geospatial problem-solving architecture is proposed to provides a solution for building an easy-to-use, widely accessible and high-performance geospatial problem-solving environment integrating multiple complicated GeoComputational processes at an acceptable cost
Spatial-adaptive data decomposition and “update on change”technique should deliver better efficient workload distribution onto computing units.
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