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Articles 211 - 240 of 532

Full-Text Articles in Computer Sciences

Verification And Validation Of Simulation Models, Robert G. Sargent Jan 1998

Verification And Validation Of Simulation Models, Robert G. Sargent

Electrical Engineering and Computer Science - All Scholarship

This paper discusses verification and validation of simulation models. The different approaches to deciding model validity are presented; how model verification and validation relate to the model development process are discussed; various validation techniques are defined; conceptual model validity, model verification, operational validity, and data validity are described; ways to document results are given; and a recommended procedure is presented.

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Skew-Insensitive Parallel Algorithms For Relational Join, Khaled Alsabti, Sanjay Ranka Jan 1998

Skew-Insensitive Parallel Algorithms For Relational Join, Khaled Alsabti, Sanjay Ranka

College of Engineering and Computer Science - Former Departments, Centers, Institutes and Projects

Join is the most important and expensive operation in relational databases. The parallel join operation is very sensitive to the presence of the data skew. In this paper, we present two new parallel join algorithms for coarse grained machines which work optimally in presence of arbitrary amount of data skew. The first algorithm is sort-based and the second is hash-based. Both of these algorithms employ a preprocessing phase (prior to the redistribution phase) to equally partition the work among the processors. The proposed algorithms have been designed for memory resident-data. However, they can be extended to disk resident-data. These algorithms …

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The Design And Evaluation Of A Virtual Distributed Computing Environment, Haluk Topcuoglu, Salim Hariri, Dongmin Kim, Yoonhee Kim, Xue Bing Jan 1998

The Design And Evaluation Of A Virtual Distributed Computing Environment, Haluk Topcuoglu, Salim Hariri, Dongmin Kim, Yoonhee Kim, Xue Bing

Electrical Engineering and Computer Science - All Scholarship

In this paper we present the Virtual Distributed Computing Environment (VDCE), a metacomputing environment currently being developed at Syracuse University. VDCE provides an efficient web-based approach for developing, evaluating and visualizing large-scale distributed applications that are based on predefined task libraries on diverse platforms. The VDCE task libraries relieve end-users of tedious task implementations and also support reusability. The VDCE software architecture is described in terms of three modules: a) the Application Editor, a user-friendly application development environment that generates the Application Flow Graph (AFG) of an application; b) the Application Scheduler, which provides an efficient task-to-resource mapping of AFG; …

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Adaptive Linkage Crossover, Ayed A. Salman, Kishan Mehrotra, Chilukuri K. Mohan Jan 1998

Adaptive Linkage Crossover, Ayed A. Salman, Kishan Mehrotra, Chilukuri K. Mohan

Electrical Engineering and Computer Science - All Scholarship

Problem-specific knowledge is often implemented in search algorithms using heuristics to determine which search paths are to be explored at any given instant. As in other search methods, utilizing this knowledge will more quickly lead a genetic algorithm (GA) towards better results. In many problems, crucial knowledge is not found in individual components, but in the interrelations between those components. For such problems, we develop an interrelation (linkage) based crossover operator that has the advantage of liberating GAs from the constraints imposed by the fixed representations generally chosen for problems. The strength of linkages between components of a chromosomal structure …

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Jworb - Java Web Object Request Broker For Commodity Software Based Visual Data Ow Metacomputing Programming Environment, Geoffrey C. Fox, Wojtek Furmanski, Hasan T. Ozdemir Jan 1998

Jworb - Java Web Object Request Broker For Commodity Software Based Visual Data Ow Metacomputing Programming Environment, Geoffrey C. Fox, Wojtek Furmanski, Hasan T. Ozdemir

Northeast Parallel Architecture Center

Programming environments and tools that are simultaneously sustainable, highly functional, robust and easy to use have been hard to come by in the HPDC area. This is partially due to the difficulty in developing sophisticated customized systems for what is relatively small part of the worldwide computing enterprise. As the commodity software becomes naturally distributed with the onset of Web and Intranets, we observe now a new trend in HPDC community [1, 8, 12] to base high performance computing on the modern enterprise computing technologies. .. JWORB is a multi-protocol Java server under development at NPAC, currently capable of handling …

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Language Bindings For A Data-Parallel Runtime, Bryan Carpenter, Geoffrey C. Fox, Donald Leskiw, Xinying Li, Yuhong Wen Jan 1998

Language Bindings For A Data-Parallel Runtime, Bryan Carpenter, Geoffrey C. Fox, Donald Leskiw, Xinying Li, Yuhong Wen

Northeast Parallel Architecture Center

The NPAC kernel runtime, developed in the PCRC (Parallel Compiler Runtime Consortium) project, is a runtime library with special support for the High Performance Fortran data model. It provides array descriptors for a generalized class of HPF-like distributed arrays, support for parallel access to their elements, and a rich library of collective communication and arithmetic operations for manipulating these arrays. The library has been successfully used as a component in experimental HPF translation systems. With prospects for early appearance of fully-featured, efficient HPF compilers looking questionable, we discuss a class of more easily implementable data-parallel language extensions that preserve many …

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Java/Corba Based Real-Time Infrastructure To Integrate Event-Driven Simulations, Collaboration And Distributed Object/Componentware Computing, Geoffrey C. Fox, Wojtek Furmanski, Hasan T. Ozdemir Jan 1998

Java/Corba Based Real-Time Infrastructure To Integrate Event-Driven Simulations, Collaboration And Distributed Object/Componentware Computing, Geoffrey C. Fox, Wojtek Furmanski, Hasan T. Ozdemir

Northeast Parallel Architecture Center

We are discussing the four major standard candidates for distributed object/componentware computing: Java, CORBA, COM and WOM within our proposed coordination framework we call Pragmatic Object Web (POW). We describe our integration approach based on multi-protocol middleware server JWORB (Java Web Object Request Broker) that currently integrates HTTP and IIOP and which we now further develop to also support COM and WOM core functionalities. We are also experimenting with visual data ow authoring front-ends using NPAC WebFlow system on top of JWORB based software bus. Finally, we illustrate our technologies in one major application domain- DoD Modeling and Simulation- where …

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Towards A Java Environment For Spmd Programming, Bryan Carpenter, Guansong Zhang, Geoffrey C. Fox, Xiaoming Li Jan 1998

Towards A Java Environment For Spmd Programming, Bryan Carpenter, Guansong Zhang, Geoffrey C. Fox, Xiaoming Li

Northeast Parallel Architecture Center

As a relatively straightforward object-oriented language, Java is a plausible basis for a scientific parallel programming language. We outline a conservative set of language extensions to support this kind of programming. The programming style advocated is Single Program Multiple Data (SPMD), with parallel arrays added as language primitives. Communications involving distributed arrays are handled through a standard library of collective operations. Because the underlying programming model is SPMD programming, direct calls to other communication packages are also possible from this language.

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Considerations In Hpjava Language Design And Implementation, Guansong Zhang, Bryan Carpenter, Geoffrey C. Fox, Xinying Li, Yuhong Wen Jan 1998

Considerations In Hpjava Language Design And Implementation, Guansong Zhang, Bryan Carpenter, Geoffrey C. Fox, Xinying Li, Yuhong Wen

Northeast Parallel Architecture Center

This paper discusses some design and implementation issues in the HPJava language. The language is briefly reviewed, then the class library that forms the foundation of the translation scheme is described. Through example codes, we illustrate how HPJava source codes can be translated straightforwardly to ordinary SPMD Java programs calling this library. This is followed by a discussion of the rationale for introducing the language in the first place, and of how various language features have been designed to facilitate efficient implementation.

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A Global Communication Optimization Technique Based On Data-Flow Analysis And Linear Algebra, Mahmut Kandemir, P. Banerjee, Alok Choudhary, J. Ramanujam Jan 1998

A Global Communication Optimization Technique Based On Data-Flow Analysis And Linear Algebra, Mahmut Kandemir, P. Banerjee, Alok Choudhary, J. Ramanujam

Electrical Engineering and Computer Science - All Scholarship

Reducing communication overhead is extremely important in distributed-memory message-passing architectures. In this paper, we present a technique to improve communication that considers data access patterns of the entire program. Our approach is based on a combination of traditional data-flow analysis and a linear algebra framework, and works on structured programs with conditional statements and nested loops but without arbitrary goto statements. The distinctive features of the solution are the accuracy in keeping communication set information, support for general alignments and distributions including block-cyclic distributions and the ability to simulate some of the previous approaches with suitable modifications. We also show …

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Clouds: A Decision Tree Classifier For Large Datasets, Khaled Alsabti, Sanjay Ranka, Vineet Singh Jan 1998

Clouds: A Decision Tree Classifier For Large Datasets, Khaled Alsabti, Sanjay Ranka, Vineet Singh

Electrical Engineering and Computer Science - All Scholarship

Classification for very large datasets has many practical applications in data mining. Techniques such as discretization and dataset sampling can be used to scale up decision tree classifiers to large datasets. Unfortunately, both of these techniques can cause a significant loss in accuracy. We present a novel decision tree classifier called CLOUDS, which samples the splitting points for numeric attributes followed by an estimation step to narrow the search space of the best split. CLOUDS reduces computation and I/O complexity substantially compared to state of the art classifiers, while maintaining the quality of the generated trees in terms of accuracy …

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Steady State Memetic Algorithm For Partial Shape Matching, Ender Ozcan, Chilukuri K. Mohan Jan 1998

Steady State Memetic Algorithm For Partial Shape Matching, Ender Ozcan, Chilukuri K. Mohan

Electrical Engineering and Computer Science - All Scholarship

Shape matching techniques are important in machine intelligence, especially in applications such as robotics. Currently, there are three major approaches to shape recognition: statistical, syntactic and neural approaches. This paper presents a fourth approach: evolutionary algorithms. A steady state memetic algorithm is shown to be successful in matching shapes even when they are partially obscured, and even in the presence of noise in the input image.

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Integrating Security Into The Curriculum, Cynthia E. Irvine, Shiu-Kai Chin, Deborah Frincke Jan 1998

Integrating Security Into The Curriculum, Cynthia E. Irvine, Shiu-Kai Chin, Deborah Frincke

Electrical Engineering and Computer Science - All Scholarship

The number of skilled practitioners of computer security who are able to address the complexities of modern technology and are familiar with successful approaches to system security is very small. People want security but are faced with two difficulties. First, they do not know how to achieve it in the context of their enterprises. They may not even know of a way to translate organizational procedures into policies, much less implement a set of mechanisms to enforce those policies. Second, they have no way of knowing whether their chosen mechanisms are effective. The recent US Presidential Commission on Critical Infrastructure …

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Secure Delegation For Distributed Object Environments, Nataraj Nagaratnam, Doug Lea Jan 1998

Secure Delegation For Distributed Object Environments, Nataraj Nagaratnam, Doug Lea

Electrical Engineering and Computer Science - All Scholarship

SDM is a Secure Delegation Model for Java-based distributed object environments. SDM extends current Java security features to support secure remote method invocations that may involve chains of delegated calls across distributed objects. The framework supports a control API for application developers to specify mechanisms and security policies surrounding simple or cascaded delegation. Delegation may also be disabled and optionally revoked. These policies may be controlled explicitly in application code, or implicitly via administrative tools.

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Automatic Granularity Control For Load Balancing Of Concurrent Particle Simulations, Marc Rieffel, Stephen Taylor, Jerrell Watts Jan 1998

Automatic Granularity Control For Load Balancing Of Concurrent Particle Simulations, Marc Rieffel, Stephen Taylor, Jerrell Watts

Electrical Engineering and Computer Science - All Scholarship

This paper demonstrates the use of automatic granularity control as part of dynamic load balancing for irregular, particle-based simulations. Performance optimization techniques are considered in the context of a concurrent Direct Simulation Monte Carlo method used to study the rarefied gas flow inside three-dimensional plasma reactors. Several computational techniques are used to reduce the overall time to deliver realistic threedimensional results. The effectiveness of dynamic load balancing and granularity control are presented for large-scale simulations on distributed-memory multicomputers.

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A One-Pass Algorithm For Accurately Estimating Quantiles For Disk-Resident Data, Khaled Alsabti, Sanjay Ranka, Vineet Singh Jan 1997

A One-Pass Algorithm For Accurately Estimating Quantiles For Disk-Resident Data, Khaled Alsabti, Sanjay Ranka, Vineet Singh

College of Engineering and Computer Science - Former Departments, Centers, Institutes and Projects

The '-quantile of an ordered sequence of data values is the element with rank ' \Theta n, where n is the total number of values. Accurate estimates of quantiles are required for the solution of many practical applications. In this paper, we present a new algorithm for estimating the quantile values for disk-resident data. Our algorithm has the following characteristics: (1) It requires only one pass over the data; (2) It is deterministic; (3) It produces good lower and upper bounds of the true values of the quantiles; (4) It requires no a priori knowledge of the distribution of the …

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Semantics Vs. Syntax Vs. Computations: Machine Models For Type-2 Polynomial-Time Bounded Functionals, James S. Royer Jan 1997

Semantics Vs. Syntax Vs. Computations: Machine Models For Type-2 Polynomial-Time Bounded Functionals, James S. Royer

College of Engineering and Computer Science - Former Departments, Centers, Institutes and Projects

This paper investigates analogs of the Kreisel-Lacombe-Shoenfield Theorem in the context of the type-2 basic feasible functionals. We develop a direct, polynomial-time analog of effective operation in which the time bounding on computations is modeled after Kapron and Cook's scheme for their basic polynomial-time functionals. We show that if P = NP, these polynomial-time effective operations are strictly more powerful on R (the class of recursive functions) than the basic feasible functions. We also consider a weaker notion of polynomial-time effective operation where the machines computing these functionals have access to the computations of their procedural parameter, but not to …

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Concurrent Simulation Of Plasma Reactors, Marc Rieffel, Stephen Taylor, Jerrell Watts, Sadasivan Shankar Jan 1997

Concurrent Simulation Of Plasma Reactors, Marc Rieffel, Stephen Taylor, Jerrell Watts, Sadasivan Shankar

College of Engineering and Computer Science - Former Departments, Centers, Institutes and Projects

This paper summarizes the computational techniques behind a novel concurrent simulation method used for studying the neutral flow inside plasma reactors. The technique is intended to cope with low pressure flow (less than 1.5 Torr) in realistic three-dimensional geometries. It is based on the Direct Simulation Monte Carlo method to accurately model rarefied gas flow. The concurrent formulation operates on a broad variety of shared-memory multiprocessors, multicomputers, and networked workstations.

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Practical Algorithms For Selection On Coarse-Grained Parallel Computers, Ibraheem Al-Furaih, Srinivas Aluru, Sanjay Goil, Sanjay Ranka Jan 1997

Practical Algorithms For Selection On Coarse-Grained Parallel Computers, Ibraheem Al-Furaih, Srinivas Aluru, Sanjay Goil, Sanjay Ranka

College of Engineering and Computer Science - Former Departments, Centers, Institutes and Projects

In this paper, we consider the problem of selection on coarse-grained distributed memory parallel computers. We discuss several deterministic and randomized algorithms for parallel selection. We also consider several algorithms for load balancing needed to keep a balanced distribution of data across processors during the execution of the selection algorithms. We have carried out detailed implementations of all the algorithms discussed on the CM-5 and report on the experimental results. We demonstrate that the randomized algorithms are superior to their deterministic counterparts.

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Integer Sorting Algorithms For Coarse-Grained Parallel Machines, Khaled Alsabti, Sanjay Ranka Jan 1997

Integer Sorting Algorithms For Coarse-Grained Parallel Machines, Khaled Alsabti, Sanjay Ranka

College of Engineering and Computer Science - Former Departments, Centers, Institutes and Projects

Integer sorting is a subclass of the sorting problem where the elements have integer values and the largest element is polynomially bounded in the number of elements to be sorted. It is useful for applications in which the size of the maximum value of element to be sorted is bounded. In this paper, we present a new distributed radix-sort algorithm for integer sorting. The structure of our algorithm is similar to radix sort except that it typically requires less number of communication phases. We present experimental results for our algorithm on two distributed memory multiprocessors, the Intel Paragon and the …

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The Software Architecture Of A Virtual Distributed Computing Environment, Haluk Topcuoglu, Salim Hariri, Wojtek Furmanski, Jon Valente Jan 1997

The Software Architecture Of A Virtual Distributed Computing Environment, Haluk Topcuoglu, Salim Hariri, Wojtek Furmanski, Jon Valente

Electrical Engineering and Computer Science - All Scholarship

The requirements of grand challenge problems and the deployment of gigabit networks makes the network computing framework an attractive and cost effective computing environment with which to interconnect geographically distributed processing and storage resources. Our project, Virtual Distributed Computing Environment (VDCE), provides a problem-solving environment for high-performance distributed computing over wide area networks. VDCE delivers well-defined library functions that relieve end-users of tedious task implementations and also support reusability. In this paper we present the conceptual design of VDCE software architecture, which is defined in three modules: a) the Application Editor, a user-friendly application development environment that generates the Application …

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Parallel Domain Decomposition And Load Balancing Using Space-Filling Curves, Srinivas Aluru, Faith E. Sevilgen Jan 1997

Parallel Domain Decomposition And Load Balancing Using Space-Filling Curves, Srinivas Aluru, Faith E. Sevilgen

Electrical Engineering and Computer Science - All Scholarship

Partitioning techniques based on space-filling curves have received much recent attention due to their low running time and good load balance characteristics. The basic idea underlying these methods is to order the multidimensional data according to a space-filling curve and partition the resulting one-dimensional order. However, space-filling curves are defined for points that lie on a uniform grid of a particular resolution. It is typically assumed that the coordinates of the points are representable using a fixed number of bits, and the run-times of the algorithms depend upon the number of bits used. In this paper, we present a simple …

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Selective Crossover: Towards Fitter Offspring, Chilukuri K. Mohan Jan 1997

Selective Crossover: Towards Fitter Offspring, Chilukuri K. Mohan

Electrical Engineering and Computer Science - All Scholarship

A new general-purpose crossover operator is proposed. The representation of a candidate solution is slightly perturbed, and the ensuing changes in fitness are calculated. Such fitness changes (for parents) are used in constructing the offspring resulting from crossover. Experiments with several sets of problems demonstrate that this approach leads to rapid increases in average and best fitness, and performs much better than traditional general-purpose crossover operators.

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A Global Computing Environment For Networked Resources, Haluk Topcuoglu, Salim Hariri Jan 1997

A Global Computing Environment For Networked Resources, Haluk Topcuoglu, Salim Hariri

Electrical Engineering and Computer Science - All Scholarship

Current advances in high-speed networks and WWW technologies have made network computing a cost-effective, high-performance computing alternative. New software tools are being developed to utilize efficiently the network computing environment. Our project, called Virtual Distributed Computing Environment (VDCE), is a high-performance computing environment that allows users to write and evaluate networked applications for different hardware and software configurations using a web interface. In this paper we present the software architecture of VDCE by emphasizing application development and specification, scheduling, and execution/runtime aspects.

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Simulated Annealing And Genetic Algorithms For Partial Shape Matching, Ender Ozcan, Chilukuri K. Mohan Jan 1997

Simulated Annealing And Genetic Algorithms For Partial Shape Matching, Ender Ozcan, Chilukuri K. Mohan

Electrical Engineering and Computer Science - All Scholarship

Partial shape matching may be viewed as an optimization problem, to be solved using methods such as simulated annealing (SA) and genetic algorithms (GAs). We apply and compare both these methods for matching input shapes with model shapes described in terms of features such as line segments and angles. The quality of matching is gauged using a measure derived from attributed shape grammars [10, 11]. Current results show that both SA and GA succeed in the shape matching task; the GA is faster and yields the global optimum more often than the versions of SA implemented.

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Experiments With "Hp Java", Bryan Carpenter, Yuh-Jye Chang, Geoffrey C. Fox, Donald Leskiw Jan 1997

Experiments With "Hp Java", Bryan Carpenter, Yuh-Jye Chang, Geoffrey C. Fox, Donald Leskiw

Northeast Parallel Architecture Center

We consider the possible role of Java as a language for High Performance Computing. After discussing reasons why Java may be a natural candidate for a portable parallel programming language, we describe several case studies. These cover Java socket programming, message-passing through a Java interface to MPI, and class libraries for data-parallel programming in Java.

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Hpjava: Data Parallel Extensions To Java, Bryan Carpenter, Guansong Zhang, Geoffrey C. Fox, Xinying Li Jan 1997

Hpjava: Data Parallel Extensions To Java, Bryan Carpenter, Guansong Zhang, Geoffrey C. Fox, Xinying Li

Northeast Parallel Architecture Center

We outline an extension of Java for programming with distributed arrays. The basic programming style is Single Program Multiple Data (SPMD), but parallel arrays are provided as new language primitives. Further extensions include three distributed control constructs, the most important being a data-parallel loop construct. Communications involving distributed arrays are handled through a standard library of collective operations. Because the underlying programming model is SPMD programming, direct calls to MPI or other communication packages are also allowed in an HPJava program.

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A Comparison Of Annealing Techniques For Academic Course Scheduling, M.A. Saleh Elmohamed, Geoffrey C. Fox, Paul Coddington Jan 1997

A Comparison Of Annealing Techniques For Academic Course Scheduling, M.A. Saleh Elmohamed, Geoffrey C. Fox, Paul Coddington

Northeast Parallel Architecture Center

In this study we have tackled the NP-hard problem of academic class scheduling (or timetabling) at the university level. We have investigated a variety of approaches based on simulated annealing, including mean-field annealing, simulated annealing with three different cooling schedules, and the use of a rule-based preprocessor to provide a good initial solution for annealing. The best results were obtained using simulated annealing with adaptive cooling and reheating as a function of cost, and a rule-based preprocessor. This approach enabled us to obtain valid schedules for the timetabling problem for a large university, using a complex cost function that includes …

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A Load Balancing Technique For Multiphase Computations, Jerrell Watts, Marc Rieffel, Stephen Taylor Jan 1997

A Load Balancing Technique For Multiphase Computations, Jerrell Watts, Marc Rieffel, Stephen Taylor

College of Engineering and Computer Science - Former Departments, Centers, Institutes and Projects

Parallel computations comprised of multiple, tightly interwoven phases of computation may require a different approach to dynamic load balancing than single-phase computations. This paper presents a load sharing method based on the view of load as a vector, rather than as a scalar. This approach allows multiphase computations to achieve higher efficiency on large-scale multicomputers than possible with traditional techniques. Results are presented for two large-scale particle simulations running on 128 nodes of an Intel Paragon and on 256 processors of a Cray T3D, respectively.

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Standardization Of A Communication Middleware For High-Performance Real-Time Systems, Arkady Kanevsky, Anthony Skjellum, Jerrell Watts Jan 1997

Standardization Of A Communication Middleware For High-Performance Real-Time Systems, Arkady Kanevsky, Anthony Skjellum, Jerrell Watts

Electrical Engineering and Computer Science - All Scholarship

The last several years saw an emergence of standardization activities for real-time systems including standardization of operating systems (series of POSIX standards [1]), of communication for distributed (POSIX.21 [10]) and parallel systems (MPI/RT [5]) and real-time object management (realtime CORBA [9]). This article describes the ongoing standardization work and implementation of communication middleware for high performance real-time computing. The real-time message passing interface (MPI/RT) advances the non-real-time high-performance communication standard Message Passing Interface Standard (MPI), emphasizing changes that enable and support real-time communication, and is targeted for embedded, fault-tolerant and other real-time systems. MPI/RT is the only communication middleware layer …

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