All online map service providers are working hard to maintain high-quality maps to provide high-quality services. Example inaccuracies that can be encountered in the provided maps may include missing road segments, shifted road segments, missing road connections, missing or incorrect turn restrictions, and mislabeling road attributes like marking a directional road as one-way. Maps may also be rapidly changing in some areas due to new constructions. While the accuracy of various mapping systems, as given by service providers, is known to be high, even the minor discrepancies in the underlying maps may lead to unsatisfactory user experience in routing and location-based services.

As an open license project, Open Street Map (OSM) aims to make the collectively produced geographic data freely available to be used for various purposes. Routing engines frequently take advantage of this data set. Nonetheless, providing routing services on top of OSM requires the full connectivity of the OSM road network graph in the interest area. This connectivity needs to be achieved individually at every level of the road network graph: the motorway, trunk, primary, secondary, tertiary, and residential roads. However, due to its open-editing nature, the OSM data often contains faults attributed to issues like missing road network connections or mistakenly attributed road segments.

During the last decade of the 20th century, Turkey was shocked with numerous disasters. As a result, central government or Turkey has decided to settle a national Crises Management Center. One of the main responsibilities of this center is to predict, track and minimize the effects of disasters in any part of the country. GIS-based disaster simulators are currently being developed for this purpose. In this paper, a subset of those simulators will be reviewed. Some technical details of the simulations, basic underlying models of simulations, and extent of required RS data will be presented.

We exploited the recent advances in Internet connectivity and Web technologies for building Web-based parallel programming environments (WPPEs) that facilitate the development and execution of parallel programs on remote high-performance computers. A Web browser running on the user's machine provides a user-friendly interface to server-site user accounts and allows the use of parallel computing platforms and software in a convenient manner. The user may create, edit, and execute files through this Web browser interface. This new Web-based client-server architecture has the potential of being used as a future front-end to high-performance computer systems. We discuss the design and implementation of several prototype WPPEs that are currently in use at the Northeast Parallel Architectures Center and the Cornell Theory Center. These initial prototypes support high-level parallel programming with Fortran 90 and High Performance Fortran (HPF), as well as explicit low-level programming with Message Passing Interface (MPI). We detail the lessons learned during the development process and outline the tradeoffs of various design choices in the realization of the design. We especially concentrate on providing server-site user accounts, mechanisms to access those accounts through the Web, and the Web-related system security issues.

The Virtual Programming Laboratory (VPL) is a Web-based virtual programming environment built based on a client–server architecture. The system can be accessed on any platform (Unix, PC or Mac) using a standard Java-enabled browser. Software delivery over the Web imposes a novel set of constraints on design. We outline the tradeoffs in this design space, motivate the choices necessary to deliver an application, and detail the lessons learned in the process. We discuss the role of Java and other Web technologies in the realization of the design. VPL facilitates the development and execution of parallel programs. The initial prototype supports high-level parallel programming based on Fortran 90 and High Performance Fortran (HPF), as well as explicit low-level programming with the MPI message-passing interface. Supplementary Java-based platform-independent tools for data and performance visualization are an integral part of the VPL. Pablo SDDF trace files generated by the Pablo performance instrumentation system are used for post-mortem performance visualization. © 1997 John Wiley & Sons, Ltd.

Evaluates the High Performance Fortran (HPF) language for the compact expression and efficient implementation of conjugate-gradient iterative matrix-solvers on high-performance computing and communications (HPCC) platforms. We discuss the use of intrinsic functions, data distribution directives and explicitly parallel constructs to optimize performance by minimizing communications requirements in a portable manner. We focus on implementations using the existing HPF definitions but also discuss issues arising that may influence a revised definition for HPF-2. Some of the codes discussed are available on the World Wide Web at http://www.npac.syr.edu/hpfa/, along with other educational and discussion material related to applications in HPF.

Particle-in-Cell (PIC) plasma simulation codes model the interaction of charged particles with surrounding electrostatic and magnetic fields. Its computational requirements made it to be classified as one of the grand-challenge problems facing the high performance community. In this paper we present the implementation of 1-D and 2-D electrostatic PIC codes in High Performance Fortran(HPF) on a IBM SP-2. HPF expands Fortran 90 with data distribution and alignment directives and data parallel statements. It is a powerful language for writing portable and high performance programs across many platforms. We used one of the most successful commerical HPF compilers currently available in the market and augmented the compiler's missing HPF functions with extrinsic routines when necessary. We obtained near linear speed-up in all of our test cases. The performance of the HPF programs is comparable to the native message passing implementations of the same codes on the SP-2.

In today's high performance computing arena, there is a strong trend toward building virtual computers from heterogeneous resources on a network. In this paper we describe our experiences in building a world-wide virtual machine (WWVM) based on emerging Web and existing HPCC technologies. We have constructed a Web-based parallel/distributed programming environment on top of this machine demonstrating MPI and PVM message-passing programs and High Performance Fortran programs. Alternatively, the WWVM can be configured as a metacomputer for the solution of metaproblems.

Thinking Machines' CM-5 machine is a distributed-memory, message-passing computer. In the paper we devise a performance benchmark for the base and vector units and the data communication networks of the CM-5 machine. We model the communication characteristics such as communication latency and bandwidths of point-to-point and global communication primitives. We show, on a simple Gaussian elimination code, that an accurate static performance estimation of parallel algorithms is possible by using those basic machine properties connected with computation, vectorization, communication and synchronization. Futhermore, we describe the embedding of meshes or hypercubes on the CM-5 fat-tree topology and illustrate the performance results of their basic communication primitives.