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Multimedia Traffic Analysis Using CHITRA95
No full textWe describe how to investigate collections of trace data representing network delivery of multimedia information with CHITRA95, a tool that allows a user to visualize, query, statistically analyze and test, transform, and model collections of trace data. CHITRA95 is applied to characterize World Wide Web (WWW) traffic from three workloads: students in a classroom of network-connected workstations, graduate students browsing the Web, undergraduates browsing educational and other materials, as well as traffic on a courseware repository server. We explore the inter-access time of files on a server (i.e., recency), the hit rate from a proxy server cache, and the distributions of file sizes and media types requested. The traffic study also yields statistics on the effectiveness of caching to improve transfer rates. In contrast to past WWW traffic studies, we analyze client as well as server traffic; we compare three workloads rather than drawing conclusions from one workload; and we analyze tcpdump logs to calculate the performance improvement in throughput that an end user sees due to caching
Visualizing and Modeling Categorical Time Series Data
No full textCategorical time series data can not be effectively visualized and modeled using methods developed for ordinary data. The arbitrary mapping of categorical data to ordinal values can have a number of undesirable consequences. New techniques for visualizing and modeling categorical time series data are described, and examples are presented using computer and communications network traces
The Pagenumber of k-Trees is 0(k)
No full textA k-tree is a graph defined inductively in the following way: the complete graph K(sub-k) is a K-tree, and if G is a k-tree, then the graph resulting from adding a new vertex to k vertices inducing a K(sub-k) in G is also a k-tree. This paper examines the book embedding problem for k-trees. A book embedding of a graph maps the vertices onto a line along the spine of the book and assigns the edges to pages of the book such that no two edges on the same page cross. The pagenumber of a graph is the minimum number of pages in a valid book embedding. In this paper, it is proven that the pagenumber of a k-tree is at most k + 1. Furthermore, it is shown that there exist k-trees that require k pages. The upper bound leads to bounds on the pagenumber of a variety of classes of graphs for which no bounds were previously known
Software Reuse and Reusability Metrics and Models
No full textAs organizations implement systematic software reuse programs to improve productivity and quality, they must be able to measure their progress and identify the most effective reuse strategies. This is done with reuse metrics and models. In this paper, we survey metrics and models of software reuse and reusability, and provide a classification structure that will help users select them. Six types of metrics and models are reviewed: cost-benefit models, maturity assessment models, amount of reuse metrics, failure modes models, reusability assessment models, and reuse library metrics
Cost-Effective Parallel Processing for H-squared/H-to infinity Controller Synthesis
No full textA distributed version of a homotopy algorithm for solving the H-squared/H-to infinity mixed-norm controller synthesis problem is presented. The main purpose of the study is to explore the possibility of achieving high performance with low cost. Existing UNIX workstations running PVM (Parallel Virtual Machine) are utilized. Only the Jacobian matrix computation is distributed and therefore the modification to the original sequential code is minimal. The same algorithm has also been implemented on an Intel Paragon parallel machine. Our implementation shows that acceptable speedup is achieved and the larger the problem sizes, the higher the speedup. Comparing with the results from the Intel Paragon, the study concludes that utilizing the existing UNIX workstations can be a very cost-effective approach to shorten computation time. Furthermore, this economical way to achieve high performance computation can easily be realized and incorporated in a practical industrial design environment
Optimization in Aircraft Design
No full textA parallel variable-complexity modeling approach, permitting the efficient use of emerging parallel computing in multidisciplinary optimization (MDO) technology, is presented for the particular instance of High Speed Civil Transport (HSCT) design. In this method simple analyses are used to limit the approximation domain based on the D-optimality criterion through the use of a genetic alogorithm. At the D-optimal points, a refined analysis is performed. The optimization code is composed of a sequence of analysis cycles between aerodynamic and structural calculations. Results for coarse grained parallelization of the aerodynamic and structural codes on an Intel Paragon are presented for an example HSCT design problem involving only two variables. The full HSCT design problem employs twenty-eight design variables
Geometric Performance Analysis of Periodic Behavior in Detail
No full textA fundamental problem in designing parallel programs that achieve a desired performance goal is the ability to exactly analyze program performance, given a specification of the process synchronization structure and the execution timings of all code segments. This paper presents a novel performance analysis method based on geometry. Given a definition of program state, an execution of a program can be represented by a timed execution sequence (TES). A TES is a sequence of states that the program passes through in an execution, along with the duration of time spent in each state. In some parallel programs, all TESs that can arise in any execution contain a suffix that consists of the repetition of a finite sequence of states, excluding deadlocks and nondeterministic behavior. The repeated sequence is termed the limit cycle execution sequence. This paper derives, for all possible process starting times, a representation of the set of all possible limit cycle execution sequences in which a process blocks. The paper makes two contributions. First, it employs a novel analysis method to derive TESs from a geometric program execution model, using timed progress graphs (TPGs). TPGs represent the progress of each process by an axis in a Cartesian graph; process synchronization by line segments; and a TES by a direct, continuous path that does not cross a segment. Second, it solves for TESs in TPGs not by a computational geometric algorithm, as employed by most solutions in the literature to (untimed) progress graphs, but by an analytic solution
Using Reflection for Implementing ICOM, An Interoperable Common Object Model
No full textReuse of already developed object-oriented software components is reduced when software is written in different object-oriented languages, or when it is not easy to relocate the software components from one machine to another machine. Software development in a distributed and heterogeous environment is a solution to this problem. Several common object models have been defined for software development in a distributed and heterogeous environment. Most of the existing common object models do not agree upon a common set of object-oriented features. These models are weak (i.e., they have only a modest subset of object-oriented features) because they support both object-oriented and non object-oriented languages and mapping of the model into non object-oriented languages is a complex problem. In this paper an interoperable common object model (ICOM) that supports statically typed object-oriented languages is presented. The ICOM model has an extensive set of object-oriented features that uses reflection techniques to support the model. The architecture of ICOM framework is described and a detailed account on how reflection is used is given. A prototype involving dynamic method binding feature is explained in detail
Report on Quasi-Experiment for Evaluating SEES
No full textThe purpose of this document is to describe the design and execution of the quasi-experiment conducted in the Department of Computer Science, Virginia Tech, in accordance with the procedures described in the document, "An Experimental Design for Evaluating SEES" prepared for NASA under contract NASI-19610, Task 17. (Hereafter that report is called the general design document.) The quasi-experiment serves three important purposes. First, the quasi-experiment is the proof of concept of the general experiment design. It shows that the procedures defined in the general experiment design can be implemented. Second, provides details for setting up a true experiment: identifying the research hypothesis, designing the investigation, selecting various variables, procedures, and controls, measuring the variables, and evaluating the results. Third, any insights revealed during the course of the quasi-experiment can be incorporated in the costly true experiment, thus providing a cost-effective experimental methodology. This report contains sufficient information so that the quasi-experiment can be replicated at an appropriate level of abstraction. We also document and interpret all the results of the quasi-experiment
The Swan User's Manual, Version 1.1
No full textSwan is a data structure visualization program. Its main purpose is to allow the user to visualize the data structures used in a C/C++ program. Swan is specifically designed to support visualization of programs implementing various graph algorithms