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A Library of Reusable Model Components for Visual Simulation of the NCSTRL System
No full textThis paper presents a library of reusable model components for visual simulation of the Networked Computer Science Technical Report Library (NCSTRL) and illustrates how a visual simulation model can be developed for a new NCSTRL configuration by way of component reuse with no programming. Such a repository of reusable model components can be created for visual simulation of any digital library for the purpose of performance evaluation and tuning and conducting what-if analyses for different system design configurations
New Algorithms for Generating Conway Polynomials over Finite Fields
No full textArithmetic in a finite field of prime characteristic p normally employs an irreducible polynomial in Z_p[X]. A particular class of irreducible polynomials, generally known as Conway polynomials, provides a means for representing several finite fields of characteristic p in a compatible manner. Conway polynomials are used in computational algebra systems such as GAP and Magma to represent finite fields. The generation of the Conway polynomials for a particular finite field has previously been done by an often expensive brute force search. As a consequence, only a few Conway polynomials have been generated. We present two algorithms for generating Conway polynomials that avoid the brute force search. We have implemented one of these algorithms in Magma and present numerous new Conway polynomials that implementation generated
A Distributed Genetic Algorithm with Migration for the Design of Composite Laminate Structures
No full textThis paper describes the development of a general Fortran 90 framework for the solution of composite laminate design problems using a genetic algorithm (GA). The initial Fortran 90 module and package of operators result in a standard genetic algorithm (sGA). The sGA is extended to operate on a parallel processor, and a migration algorithm is introduced. These extensions result in the distributed genetic algorithm with migration (dGA). The performance of the dGA in terms of cost and reliability is studied and compared to a sGA baseline, using two types of composite laminate design problems. The nondeterminism of GAs and the migration and dynamic load balancing algorithm used in this work result in a changed (diminished) workload, so conventional measures of parallelizability are not meaningful. Thus, a set of experiments is devised to characterize the run time performance of the dGA
PSE Research at Virginia Tech: An Overview
No full textThe purpose of this report is to give an overview of the activities of the research group in problem solving environments (PSEs) at Virginia Tech. Most of the report is devoted to an introduction to the area itself, with particular emphasis on our perspective and goals. After a brief attempt at defining the term PSE, we consider individually the three key words: problem: what problem domains are we addressing? solving: what characterizes the solution process? environment: what should the computational environment include? The final section summarize our current specific interests. For more information about PSE research at Virginia Tech, please visit our home page at www.cs.vt.edu/~pse
POLSYS_PLP: A Partitioned Linear Product Homotopy Code for Solving Polynomial Systems of Equations
No full textGlobally convergent, probability-one homotopy methods have proven to be very effective for finding all the isolated solutions to polynomial systems of equations. After many years of development, homotopy path trackers based on probability-one homotopy methods are reliable and fast. Now, theoretical advances reducing the number of homotopy paths that must be tracked, and in the handling of singular solutions, have made probablitiy-one homotopy methods even more practical. POLSYS_PLP consists of Fortran 90 modules for finding all isolated solutions of a complex coefficient polynomial system of equations. The package is intended to be used in conjunction with HOMPACK90 (algorithm 777), and makes extensive use of Fortran 90 derived data types to support a partitioned linear product (PLP) polynomial system structure. PLP structure is a generalization of m-homogeneous structure, whereby each component of the system can have a different m-homogeneous structure. POLSYS_PLP employs a sophisticated power series end game for handling singular solutions, and provide support for problem definition both at a high level and via hand-crafted code. Different PLP structures and their corresponding Bezout numbers can be systematically explored before committing to root finding
Sorting by Short Block-Moves
No full textSorting permutations by operations such as reversals and block-moves has received much interest because of its applications in computational biology, particularly in the study of genome rearrangements. A short block-move is an operation on a permutation that moves an element at most two positions away from its original position. This paper investigates the problem of finding a minimum-length sorting sequence of short block-moves for a given permutation. A 4/3-approximation algorithm for this problem is presented. Exact polynomial-time algorithms are presented for woven bitonic permutations and woven double-strip permutations. A linear-time maximum matching algorithm for a special class of grid graphs is also discovered that improves the time complexity of one of these exact algorithms
Improving Polymorphism in Common Object Models
No full textMost common object models of distributed object systems lack support for 'polymorphism' (an abstraction mechanism that represents a quality or state of being able to assume different forms). This lack of support restricts the development of new components and limits reuse of existing components that use these advanced features. In this paper, the Interoperable Common Object Model (ICOM), which focuses on a subset of object-oriented languages, specifically statically typed languages, is presented. The ICOM model is an attempt to elevate common object models closer to the object models of statically typed object-oriented languages by including support for polymorphism. Specific features of the ICOM object model include: remote inheritance, method overloading, and parameterized types
Effect of a Sawtooth Boundary on Couette Flow
No full textThe relative tagential motion of a smooth plate and a corrugated plate separated by a viscous fluid is studied. The full Navier-Stokes equations are solved using Hermite collocation and Newton's method. Detailed streamlines and vorticity distributions are determined. The increased drag due to corrugation is found to be substantial
A Genetic Algorithm Approach to Cluster Analysis
No full textA common problem in the social and agricultural sciences is to find clusters in experimental data; the standard attack is a deterministic search terminating in a locally optimal clustering. We propose here a genetic algorithm (GA) for performing cluster analysis. GAs have been used profitably in a variety of contexts in which it is either impractical or impossible to directly solve for a globally optimal solution to complex numerical problems. In the present case, our GA clustering technique attempted to maximize a variance-ratio (VR) based goodness-of-fit criterion defined in terms of external cluster isolation and internal cluster homogeneity. Although our GA-based clustering algorithm cannot guarantee to recover the cluster solution that exhibits the global maximum of this fitness function, it does explicitly work toward this goal (in marked contrast to existing clustering algorithms, especially hierarchial agglomerative ones such as Ward's method). Using both constrained and unconstrained simulated datasets, Monte Carlo results showed that in some conditions the genetic clustering algorithm did indeed surpass the performance of conventional clustering techniques (Ward's and K-means) in terms of an internal (VR) criterion. Suggestions for future refinement and study are offered
Distributed Control Parallelism in Multidisciplinary Aircraft Design
No full textMultidisciplinary design optimization (MDO) for large-scale engineering problems poses many challenges (e.g., the design of an efficient concurrent paradigm for global optimization based on disciplinary analyses, expensive computations over vast data sets, etc.) This work focuses on the application of distributed schemes for massively parallel architectures to MDO problems, as a tool for reducing computation time and solving larger problems. The specific problem considered here is configuraton optimization of a high speed civil transport (HSCT), and the efficient parallelization of the embedded paradigm for reasonable design space identification. Two distributed dynamic load balancing techniques (random polling and global round robin with message combining) and two necessary termination detection schemes (global task count and token passing) were implemented and evaluated in terms of effectiveness and scalability to large problem sizes and a thousand processors. The effect of certain parameters on execution time was also inspected. Empirical results demonstrated stable performance and effectiveness for all schemes, and the parametric study showed that the selected algorithmic parameters have a negligible effect on performance