bluuebunny/crossref_metadata_2025 huggingface dataset:
Performance evaluation of LAN sorting algorithms
Authors: Salehmohamed Mohamed , Luk W. S. , Peters Joseph G.
Published: January 2007

We adapt several parallel sorting algorithms (block sorting algorithms) and distributed sorting algorithms for implementation on an Ethernet network with diskless Sun workstations. We argue that the performance of sorting algorithms on local area networks (LANs) should be analyzed in a manner that is different from the ways that parallel and distributed sorting algorithms are usually analyzed. Consequently, we propose an empirical approach which will provide more insight into the performance of the algorithms. We obtain data on communication time, local processing time, and response time (i.e. total running time) of each algorithm for various file sizes and different numbers of processors. Comparing the performance data with our theoretical analysis, we attempt to provide rationale for the behaviour of the algorithms and project the future behaviour of the algorithms as file size, number of processors, or interprocessor communication facilities change.
“The Cobol dinosaur”
Authors: Krishnamurthi Malini
Published: January 2007

COBOL (common business oriented language) is a traditional third generation language that was introduced in 1959 and has been in use from then until now. Its longevity seems awesome to many.
Informativeness as an ordinal utility function for information retrieval
Authors: Tague J.
Published: January 2007

Information retrieval has all the elements of a classical decision problem: a set of possible actions, a set of potential states, and a reward or utility attached to each combination of action and state. How the actions, states, and utilities are described, however, is variable, and depends very much on the describer's point of view.
Book review: Artificial intelligence and mobile robots: case studies of successful robot systems by D. Kortenkamp, R. P. Bonasso, and R. Murphy (The MIT Press, Cambridge, MA 1998)
Authors: Clarke John
Published: January 2007

A
rtificial Intelligence and Mobile Robots
is a compilation of 13 chapters by well respected robotics researchers describing some of their most recent work. The book aims to provide a "how-to" guide to building the control system of a mobile robot. These case studies are definitely worth studying: seven of the 13 have placed highly in various robotics competitions. In the introduction, the editors give a good, yet brief, history of intelligent robots. The book is then divided into three sections.
Better operating system features for faster network servers
Authors: Bangs Gaurav , Druschel Peter , Mogul Jeffrey C.
Published: January 2007

Widely-used operating systems provide inadequate support for large-scale Internet server applications. Their algorithms and interfaces fail to efficiently support either event-driven or multi-threaded servers. They provide poor control over the scheduling and management of machine resources, making it difficult to provide robust and controlled service. We propose new UNIX interfaces to improve scalability, and to provide fine-grained scheduling and resource management.
httperf—a tool for measuring web server performance
Authors: Mosberger David , Jin Tai
Published: January 2007

This paper describes httperf, a tool for measuring web server performance. It provides a flexible facility for generating various HTTP workloads and for measuring server performance. The focus of httperf is not on implementing one particular benchmark but on providing a robust, high-performance tool that facilitates the construction of both micro- and macro-level benchmarks. The three distinguishing characteristics of httperf are its robustness, which includes the ability to generate and sustain server overload, support for the HTTP/1.1 protocol, and its extensibility to new workload generators and performance measurements. In addition to reporting on the design and implementation of httperf this paper also discusses some of the experiences and insights gained while realizing this tool.
Internet service performance failure detection
Authors: Ward Amy , Glynn Peter , Richardson Kathy
Published: January 2007

The increasing complexity of computer networks and our increasing dependence on them means enforcing reliability requirements is both more challenging and more critical. The expansion of network services to include both traditional interconnect services and user-oriented services such as the web and email has guaranteed both the increased complexity of networks and the increased importance of their performance. The first step toward increasing reliability is early detection of network performance failures. Here we consider the applicability of statistical model frameworks under the most general assumptions possible. Using measurements from corporate proxy servers, we test the framework against real world failures. The results of these experiments show we can detect failures, but with some tradeoff questions. The pull is in the warning time: either we miss early warning signs or we report some false warnings. Finally, we offer insight into the problem of failure diagnosis.
The question of finitely many steps in polynomial ideal theory
Authors: Hermann Grete
Published: January 2007

Grete Hermann's 1926 paper Die Frage der endlich vielen Schritte in der Theorie der Polynomideale, which appears below in English translation, is an intriguing example of ideas before their time. While computational aspects of mathematics were more fashionable before the abstractions of the twentieth century took hold, mathematicians of that time certainly knew nothing of computers nor of today's idea of what an algorithm is. The significance of the paper can be found on the first page, where we find (in translation):The claim that a computation can be found in finitely many steps will mean here that an upper bound for the number of necessary operations for the computation can be specified. Thus it is not enough, for example, to suggest a procedure, for which it can be proved theoretically that it can be executed in finitely many operations, if no upper bound for the number of operations is known.The fact that the author requires an upper bound suggests that there must exist an actual procedure or algorithm for doing computations. We see in this paper the first examples of procedures (with upper bounds given) for a variety of computations in multivariate polynomial ideals. Thus we have here a paper anticipating by 39 years the birth of computer algebra (generally marked by Buchberger's invention of Gröbner bases in his 1965 Ph.D. thesis). The computational procedures which are presented in this paper include multivariate polynomial factorization, polynomial system solving, least common multiples, greatest common divisors, ideal quotients, divisibility of one ideal by another, fundamental ideals, norms, elementary divisor forms, associated prime ideals, primary decomposition, and isolated components. The statements of the theorems frequently end with "can be computed in finitely many steps". The proofs then outline the methods and compute the bounds. One would not at all expect a 1926 paper to contain optimal algorithms, but the fact that procedures for these computations even existed in 1926 make this paper worthy to be remembered.
Unmixed and prime decomposition of radicals of polynomial ideals
Authors: Wang Dongming
Published: January 2007

A method is presented for decomposing the radical of any finitely generated polynomial ideal into unmixed radical ideals or prime ideals. It proceeds by first computing simple systems of irreducible triangular systems using algorithms based on subresultant regular subchains and then computing the generating sets for the unmixed or prime ideals from the corresponding triangular sets using ideal saturation. The method method has been implemented in Maple V.
Cancellation errors in multivariate resultant computation with floating-point numbers
Authors: Sasaki Tateaki , Sato Tomoyuki
Published: January 2007

We test five methods of computing resultant of multivariate polynomials with floating-point number coefficients, mostly from the viewpoint of numerical errors. The methods tested are a) Brown-Traub's subresultant PRS algorithm, b) Collins' algorithm based on polynomial interpolation, c) minor expansion method of Bezout's determinant, d) Gaussian elimination method (Bareiss' algorithm) of Bezout's determinant, and e) efficient Gaussian elimination method (Sasaki-Murao's algorithm) of Bezout's determinant. We find that method a) causes so large cancellation errors that it is almost useless practically. The errors caused by methods b) and d) are not so large as those by a) but still large. The methods c) and e) are quite safe against the cancellation error and they are efficient, too. Mechanisms of occurrence of large cancellation errors in methods a), b) and d) are clarified. By these, we show that approximate algebraic computation often causes large cancellation errors hence the error analysis and development of error-safe algorithms are very important.
A hand gesture interface device
Authors: Zimmerman Thomas G. , Lanier Jaron , Blanchard Chuck , Bryson Steve , Harvill Young
Published: January 2007

This paper reports on the development of a hand to machine interface device that provides real-time gesture, position and orientation information. The key element is a glove and the device as a whole incorporates a collection of technologies. Analog flex sensors on the glove measure finger bending. Hand position and orientation are measured either by ultrasonics, providing five degrees of freedom, or magnetic flux sensors, which provide six degrees of freedom. Piezoceramic benders provide the wearer of the glove with tactile feedback. These sensors are mounted on the light-weight glove and connected to the driving hardware via a small cable.

Applications of the glove and its component technologies include its use in conjunction with a host computer which drives a real-time 3-dimensional model of the hand allowing the glove wearer to manipulate computer-generated objects as if they were real, interpretation of finger-spelling, evaluation of hand impairment in addition to providing an interface to a visual programming language.
Creating dynamic interaction techniques by demonstration
Authors: Myers Brad A.
Published: January 2007

When creating highly-interactive, Direct Manipulation interfaces, one of the most difficult design and implementation tasks is handling the mouse and other input devices. Peridot, a new User Interface Management System, addresses this problem by allowing the user interface designer to
demonstrate
how the input devices should be handled by giving an example of the interface in action. The designer uses sample values for parameters, and the system automatically infers the general operation and creates the code. After an interaction is specified, it can immediately be executed and edited. This promotes extremely rapid prototyping since it is very easy to design, implement and modify mouse-based interfaces. Peridot also supports additional input devices such as touch tablets, as well as multiple input devices operating in parallel (such as one in each hand) in a natural, easy to specify manner. This is implemented using
active values
, which are like variables except that the objects that depend on active values are updated immediately whenever they change. Active values are a straightforward and efficient mechanism for implementing dynamic interactions.
From contours to surfaces: testbed and initial results
Authors: Sloan Kenneth R. , Painter James
Published: January 2007

This paper is concerned with the problem of reconstructing the surface of three-dimensional objects, given a collection of planar contours representing cross-sections through the objects. This is an important problem, with applications in clinical medicine, bio-medical research and instruction, and industrial inspection. Current solutions to this problem have raised interesting theoretical questions about search techniques and the exploitation of domain-specific aspects of such search problems. In this paper, we survey known reconstruction techniques, describe a testbed for evaluating these techniques and present an improvement on the simple divide-and-conquer method analyzed by Fuchs, Kedem and Uselton [5].
Automated lip-synch and speech synthesis for character animation
Authors: Lewis J. P. , Parke F. I.
Published: January 2007

An automated method of synchronizing facial animation to recorded speech is described. In this method, a common speech synthesis method (linear prediction) is adapted to provide simple and accurate phoneme recognition. The recognized phonemes are then associated with mouth positions to provide keyframes for computer animation of speech using a parametric model of the human face.

The linear prediction software, once implemented, can also be used for speech resynthesis. The synthesis retains intelligibility and natural speech rhythm while achieving a “synthetic realism” consistent with computer animation. Speech synthesis also enables certain useful manipulations for the purpose of computer character animation.
Graphpak
Authors: Niehoff Walt
Published: January 2007

There have been several APL Quote Quad papers published in the past few years that discuss requirements for APL graphics capabilities. The Graphpak workspace now distributed with IBM's APL2 products evolved from its 1970 roots in an environment that projected similar requirements. This paper discusses the characteristics of Graphpak that have contributed to its evolving application and its longevity. Following an introduction that describes its evolution, the paper will focus on its "tool box" approach---using APL functions that can be used to build other functions to meet custom graphics requirements. Also, some opportunities for future exploitation of APL2 are sketched.
The impact of job memory requirements on gang-scheduling performance
Authors: Setia Sanjeev , Squillante Mark S. , Naik Vijay K.
Published: January 2007

Almost all previous research on gang-scheduling has ignored the impact of real job memory requirements on the performance of the policy. This is despite the fact that on parallel supercomputers, because of the problems associated with demand paging, executing jobs are typically allocated enough memory so that their
entire address space
is memory-resident. In this paper, we examine the impact of job memory requirements on the performance of gang-scheduling policies. We first present an analysis of the memory-usage characteristics of jobs in the production workload on the Cray T3E at the San Diego Supercomputer Center. We also characterize the memory usage of some of the applications that form part of the workload on the LLNL ASCI supercomputer. Next, we examine the issue of long-term scheduling on MPPs, i.e., we study policies for deciding which jobs among a set of competing jobs should be allocated memory and thus should be allowed to execute on the processors of the system. Using trace-driven simulation, we evaluate the impact of using different long-term scheduling policies on the overall performance of Distributed Hierarchical Control (DHC), a gang-scheduling policy that has been studied extensively in the research literature.
Scheduling issues in high-performance computing
Authors: Dowdy L. W. , Rosti E. , Serazzi G. , Smirni E.
Published: January 2007

In this paper we consider the problem of scheduling computational resources across a range of high-performance systems, from tightly coupled parallel systems to loosely coupled ones like networks of workstations and geographically dispersed meta-computing environments. We review the role of architecture issues in the choice of scheduling discipline and we present a selected set of policies that address different aspects of the scheduling problem. This discussion serves as the motivation for addressing the success of academic research in scheduling as well as its common criticisms.
The Fortran 90 bindings for OpenGL
Authors: Mitchell William F.
Published: January 2007

It is important to provide a good Fortran interface to OpenGL and related libraries for scientific visualization in mathematical software. OpenGL has had FORTRAN 77 bindings for some time, however these bindings rely upon several extensions to the FORTRAN 77 standard. By using the new features of Fortran 90 it is possible to define bindings for OpenGL that do not depend on any extensions to the standard and provide access to the full functionality of OpenGL.
From silicon valley to silicon prairie
Authors: Hendrickson Anthony R. , Strader Troy J.
Published: January 2007

The issues faced by firms in today's telecommunications environment are outlined and are discussed in juxtaposition with an actual telecommuting case study of Trade Reporting and Data Exchange, Inc. (T.R.A.D.E.), a software engineering company located in San Mateo, CA. Telecommuting was successful for T.R.A.D.E in the short term because a) required technology was widely available, b)the candidate initiated the idea and had the necessary industry and company experience, c)the organization could provide the flexible work arrangement while retaining a valuable employee, d)the employee was able to live in a geographic area of their choice, e)overall costs could be shared by the company and the employee, f)the job category was an ideal fit, and g)existing procedures were in place for communicating and managing the geographically detached worker. In the long run the employee left the company to take a job with a local software company because he missed the everyday interaction with co-workers.
Queueing analysis of nonpreemptive reservation priority discipline
Authors: Takagi Hideaki , Murata Masayuki
Published: January 2007

Analysis is given to a nonpreemptive priority queueing system with
P
classes of messages where the class of message to be served next is the highest priority class waiting at the time of service start. (If this were the highest priority class waiting at the service completion epoch, we would have a classical nonpreemptive head-of-line priority queueing system.) We assume that the message service time distribution is identical for all classes. The mean message waiting time is obtained explicitly for each class, and numerically compared to the values in the corresponding head-of-line system. We have also proposed and evaluated a fairness measure to demonstrate the degree of discrimination. This model can be applied to the performance analysis of the prioritized token-ring scheme in local area computer networks when the propagation delay and bit latency are negligible compared to the frame transmission time.
Performance modeling in integrated curcuit design (tutorial)
Authors: Hedlund Kye
Published: January 2007

This tutorial is an introduction to performance modeling in the design of integrated circuits (ICs). It assumes no background in either electrical engineering or VLSI design; all relevant concepts and terminology will be introduced. The goal is to give an overview of the role of performance modeling in IC design, the current state of the art, central problems and research challenges.

First, the process of IC design will be reviewed. Every design progresses through a series of stages: concept, architecture, implementation and realization. Each level of design manipulates different abstractions and hence is concerned with different measures of design quality. Some principle measures are: speed, silicon area, power consumption and the number of input/output connections. There are several different major design paradigms such as gate array, standard cell and custom design. Each results in different tradeoffs between flexibility, ease of implementation and design quality. This has a fundamental impact on both the design process and the resulting design.

Performance considerations enter into IC design at a variety of levels: device, circuit, logic design and architecture. Each requires different performance models, and the designer must make tradeoffs that are qualitatively different at different levels. Circuit level design requires fast and accurate models of logic gate behavior. A circuit's speed, silicon area and power consumption must be accurately estimated. Each of these circuit characteristics can be traded off against the others, and the designer may adjust the tradeoff in order to tune the circuit to the needs of a particular application. Accurate and computationally fast models form the basis for the tools that assist the designer in circuit optimization. Tools exist that accurately predict circuit performance and that automatically optimize circuits.

Integrated circuit design is a field still in its infancy. This, coupled with the fact that the underlying technological base has undergone rapid change in recent years, means that performance modeling of IC design is still in its formative stages. Some areas (e.g. device modeling) are more mature and better understood than others (e.g. architectural modeling). Research opportunities are plentiful.
Degradable computer systems with dependent subsystems
Authors: Khelalfa Halin M. , von Mayrhauser Anneliese K.
Published: January 2007

When building a model for degradable computer systems, it is not sufficient to merely quantify reliability and performance measures. These indices must be mathematically sound if they are to be used to design such systems in an optimal way. The paper presents an analysis of design optimisation for degradable computer systems and shows how this particular application leads to a system model with interdepedent subsystems. A procedure is presented on how to solve the resulting Markov model. Its computational complexity is compared to another solution method and shown to be largely more efficient.
Performance characteristics of two Ethernets
Authors: Gonsalves Timothy A.
Published: January 2007

Local computer networks are increasing in popularity for the interconnection of computers for a variety of applications. One such network that has been implemented on a large scale is the Ethernet. This paper describes an experimental performance evaluation of a 3 and a 10 Mb/s Ethernet. The effects of varying packet length and transmission speed on throughput, mean delay and delay distribution are quantified. The protocols are seen to be fair and stable. These measurements span the range from the region of high performance of the CSMA/CD protocol to the upper limits of its utility where performance is degraded. The measurements are compared to the predictions of existing analytical models. The correlation is found to range from good to poor, with more sophisticated models yielding better results than a simple one.
A note on service interruptions
Authors: Branwajn Alexandre , Jow Yung-Li Lily
Published: January 2007

This note is devoted to a few remarks on the performance evaluation of systems with service interruptions such as priority queues for lower priority customers, systems subject to breakdowns, etc. Recent work on priority queues has shown that a popular approximation method, the “reduced occupancy approximation”, can be exceedingly inaccurate for a range of parameter values. We identify a cause of inaccuracy and, hence, propose a simple correction that provides a substantial improvement in the results. Using the example of a simple model with service interruptions, we show also that conditional probabilities can be of value in deriving recurrent solutions to some problems.
EGREGION
Authors: Bernecky Robert
Published: January 2007

This article describes our experience with test suites and automated branch coverage tools for APL software maintenance, based on our use of them to verify Y2K compliance of an APL-based database system. We introduce
egregion,
a simple, easy-to-use tool that assesses branch coverage in APL functions. The tool comprises a pair of APL functions that report detailed and summary function-level information about code coverage of test suites. The
egregion
tool provides a line-by-line analysis of statement coverage, labels not branched to, branches never taken, branches always taken, transfer of control via non-branches, and branches to non-labeled lines. Although we do not consider this groundbreaking work, we do believe that the coverage tool will be valuable to APL programmers who are engaged in the creation of large, reliable applications.
The comparison of C++ and Mathematica in the generation of pseudo random numbers for financial and actuarial applications
Authors: Micocci Marco , Manna Angelo , Tomassetti Alvaro
Published: January 2007

The paper considers the role of pseudo random number generators in the financial and actuarial numerical applications. Some generators are compared and some considerations are made about the distortion coming from their use. A general approach for the calculation of risk in financial and actuarial problems is presented.
Japanese language handling in APL environments
Authors: Saigusa Kyosuke
Published: January 2007

While Japan is amongst the first countries to use APL back in the early 1970's and enjoyed at one time as high as 40% of IBM main-frame customers using APL, the lack of Japanese language support of APL in popular computing environments today such as UNIX/AIX, OS/2 and Windows seems to be driving APL out of the scene.This paper tries to bring up this subject more officially than I have done in the past for more public discussion not only for Japan, but also for those countries, where the characters required by national languages cannot be contained in the ASCII table of 256 codes.
Compiling a simulation language in APL
Authors: Alfonseca Manuel , Alfonseca Enrique , de Lara Juan
Published: January 2007

This paper describes the procedure used to build several compilers, written in APL and APL2, to translate two continuous simulation languages into APL and C+ +. The advantages and disadvantages of using APL to write a compiler are discussed. A compromise had to be found between performance (the model execution speed) and flexibility (the ease to modify parameters and test "what if" situations). The resulting compiler (an APL2 packaged workspace) has been used successfully to generate educational applications and in medical research.
The mobile people architecture
Authors: Maniatis Petros , Roussopoulos Mema , Swierk Ed , Lai Kevin , Appenzeller Guido , Zhao Xinhua , Baker Mary
Published: January 2007

People are the outsiders in the current communications revolution. Computer hosts, pagers, and telephones are the addressable entities throughout the Internet and telephony systems. Human beings, however, still need application-specific tricks to be identified, like email addresses, telephone numbers, and ICQ IDs. The key challenge today is to find people and communicate with them personally, as opposed to communicating merely with their possibly inaccessible machines---cell phones that are turned off or PCs on faraway desktops.
We introduce the
Mobile People Architecture
which aims to put the
person,
rather than the devices that the person uses, at the endpoints of a communication session. We describe a prototype that performs
person-level routing;
the prototype allows people to receive communication regardless of the network, device, or application they use, while maintaining their privacy.
On the significance of the theory of convex polyhedra for formal algebra
Authors: Ostrowski A.
Published: January 2007

This paper was originally published as Über die Bedeutung der Theorie der konvexen Polyeder für die formale Algebra in Jahresbericht d. Deutschen Math. Ver.

30

(1922): 98-99. It is based on a talk given in Jena to the German Mathematical Society on 23 September 1921. Quoted in Ostrowski's later paper On Multiplication and Factorization of Polynomials. I Lexicographic Orderings and Extreme Aggregates of Terms. Aequationes Math.

13

(1975): 201-228.
Analysis of ISP IP/ATM network traffic measurements
Authors: Epsilon Raja , Ke Jun , Williamson Carey
Published: January 2007

This paper presents network traffic measurements collected from a commercial Internet Service Provider (ISP) whose traffic is being carried over an ATM backbone network. Much of the aggregate traffic is Web-related, and thus represents a Web/TCP/IP/AAL-5/ATM protocol stack. Four traces have been collected at the AAL-5 frame level, using a NavTel IW95000 ATM test set. These traces provide a detailed look at protocol-level behaviours, but only for rather short time durations (e.g., 30-40 seconds per trace). Analyses focus on aggregate-level traffic characteristics, as well as host-level and TCP connection-level traffic characteristics.The main workload characteristics observed from the measurements are the burstiness of the aggregate and individual traffic flows, a non-uniform distribution of traffic amongst hosts, a trimodal packet size distribution, and the strong presence of network-level effects (e.g., client modem speed, network Maximum Transmission Unit (MTU), network round trip time, TCP slow start) in the traffic structures seen. The workload characteristics are quite consistent across the four traces studied.
CHI meets PLoP
Authors: Borchers Jan O.
Published: January 2007

This report summarizes the results of a workshop on pattern languages for human-computer interaction which took place at the ChiliPLoP'99 Conference on Pattern Languages of Programming.It suggests a definition and taxonomy for interaction patterns, explains how Writers' Workshops are used to improve patterns, and points out some surprising issues about pattern languages as they are understood by key players in that field. It shows the importance of user interface and software engineering researchers to exchange their thoughts on this hot topic.
Language translators
Authors: Benedicenti Luigi , Vernazza Tullio
Published: January 2007

The authors present a reasoned synopsis of the state of the art of compiler techniques. A classification scheme is employed that divides compilers according to two layers. The first layer is the input layer, dealing with the kind of language that the compiler will find. The second layer is the architectural layer, that will define the compiler's internals and the method employed to produce the output.
The application of JavaCC to develop a C/C++ preprocessor
Authors: Succi Giancarlo , Wong Raymond W.
Published: January 2007

The commonly available software metrics-extraction tools for C/C++ depend on commercial preprocessors to preprocess the source file before being input into the analyzers. The following paper introduces a Java compiler generator called JavaCC and the application of the generator to develop a Java-based preprocessor for C/C++. Some technical features to the development of preprocessor are also mentioned, such as (1) handling of rescanning in preprocessing with LL(k) parsers, (2) managing conditional compiling with the state-based features of the lexical analyzer in JavaCC, and (3) resolving macro replacement and expansion with parsers.
Be careful...
Authors: Wolff Terris
Published: January 2007

I am sure that at one time or another you have heard some version of this statement: "Be careful what you ask for, you just might get it!" It's a warning not to be ignored. While asking for something, we tend to be aware of only the positive aspects of that item, only the potential immediate gratification. But what of the down side of attaining this sometimes long sought after goal?
Cost-based query optimization for metadata repositories
Authors: Staudt Martin , Soiron René , Quix Christoph , Jarke Matthias
Published: January 2007

Query optimization strategies for repository systems must take into account the rich and often unpredictable structure of metadata, as well as supporting complex analysis of relationships between those structures. This paper describes rationale, design, and system integration of a cost-based query optimizer offered in ConceptBase, a metadata manager that supports these capabilities by a deductive object-oriented data model. In contrast to most implemented DBMS, the optimizer is not based on the concept of join selectivity, but on detailed distribution information about object and literal fan-out, with heavy exploitation of materialized views and end-biased histograms. Experiences from two real-world applications in software configuration management and cooperative design demonstrate the practical advantages but also point to some lessons for further improvement.
Statistical inference of internal network loss and topology
Authors: Cáceres R. , Duffield N. G. , Horowitz J. , Presti F. Lo , Towsley D.
Published: January 2007

The use of inference from end-to-end multicast measurements has recently been proposed to find the internal characteristics in a network. Here we describe statistically rigorous methods for inferring link loss rates, and their application to identifying the underlying multicast topology.
Process algebras are getting mature for performance evaluation?!
Authors: Herzog Ulrich
Published: January 2007

Designing hardware/software systems in the traditional way we clearly separate methods for the functional design and performance evaluation. Beside many merits the well known insularity-problem is one of the consequences. Therefore, in system engineering we see a clear trend towards an integral treatment of both aspects.We briefly summarize research results obtained during the last decade by embedding stochastic processes into process algebras, an advanced concept for the design of parallel and distributed systems. The central objective of these Stochastic Process Algebras is the modular and hierarchical modelling and analysis of complex systems. A general introduction and related references from different research groups may be found in [1, 2].
PLM
Authors: Legout A. , Biersack E. W.
Published: January 2007

A major challenge in the Internet is to deliver live audio/video content with a good quality and to transfer files to large number of heterogeneous receivers. Multicast and cumulative layered transmission are two mechanisms of interest to accomplish this task efficiently. However, protocols using these mechanisms suffer from slow convergence time, lack of inter-protocol fairness or TCP-fairness, and loss induced by the join experiments.

In this paper we define and investigate the properties of a new multicast congestion control protocol (called PLM) for audio/video and file transfer applications based on a cumulative layered multicast transmission. A fundamental contribution of this paper is the introduction and evaluation of a
new
and
efficient
technique based on packet pair to infer which layers to join. We evaluated PLM for a large variety of scenarios and show that it converges fast to the optimal link utilization, induces no loss to track the available bandwidth, has inter-protocol fairness and TCP-fairness, and scales with the number of receivers and the number of sessions. Moreover, all these properties hold in self similar and multifractal environment.
Feasibility of a serverless distributed file system deployed on an existing set of desktop PCs
Authors: Bolosky William J. , Douceur John R. , Ely David , Theimer Marvin
Published: January 2007

We consider an architecture for a serverless distributed file system that does not assume mutual trust among the client computers. The system provides security, availability, and reliability by distributing multiple encrypted replicas of each file among the client machines. To assess the feasibility of deploying this system on an existing desktop infrastructure, we measure and analyze a large set of client machines in a commercial environment. In particular, we measure and report results on disk usage and content; file activity; and machine uptimes, lifetimes, and loads. We conclude that the measured desktop infrastructure would passably support our proposed system, providing availability on the order of one unfilled file request per user per thousand days.
Automated disk drive characterization (poster session)
Authors: Schindler Jiri , Ganger Gregory R.
Published: January 2007

DIXtrac is a program that automatically characterizes the performance of modern disk drives. This extended abstract overviews the contents of [3], which describes and validates DIXtrac's algorithms for extracting accurate values for over 100 performance-critical parameters in 2-6 minutes without human intervention or special hardware support. The extracted data includes detailed layout and geometry information, mechanical timings, cache management policies, and command processing overheads. DIXtrac is validated by configuring a detailed disk simulator with its extracted parameters; in most cases, the resulting accuracies match those of the most accurate disk simulators reported in the literature. To date, DIXtrac has been successfully used on ten different models from four different manufacturers. A growing database of validated disk characteristics is available in DiskSim [1] format at http://www.ece.cmu.edu/~ganger/disksim/diskspecs.html.
Using the exact state space of a Markov model to compute approximate stationary measures
Authors: Miner Andrew S. , Ciardo Gianfranco , Donatelli Susanna
Published: January 2007

We present a new approximation algorithm based on an exact representation of the state space
S
, using decision diagrams, and of the transition rate matrix R, using Kronecker algebra, for a Markov model with
K
submodels. Our algorithm builds and solves
K
Markov chains, each corresponding to a different aggregation of the exact process, guided by the structure of the decision diagram, and iterates on their solution until their entries are stable. We prove that exact results are obtained if the overall model has a product-form solution. Advantages of our method include good accuracy, low memory requirements, fast execution times, and a high degree of automation, since the only additional information required to apply it is a partition of the model into the
K
submodels. As far as we know, this is the first time an approximation algorithm has been proposed where knowledge of the exact state space is explicitly used.
Quantifying the energy consumption of a pocket computer and a Java virtual machine
Authors: Farkas Keith I. , Flinn Jason , Back Godmar , Grunwald Dirk , Anderson Jennifer M.
Published: January 2007

In this paper, we examine the energy consumption of a state-of-the-art pocket computer. Using a data acquisition system, we measure the energy consumption of the Itsy Pocket Computer, developed by Compaq Computer Corporation's Palo Alto Research Labs. We begin by showing that the energy usage characteristics of the Itsy differ markedly from that of a notebook computer. Then, since we expect that flexible software environments will become increasingly prevalent on pocket computers, we consider applications running in a Java environment. In particular, we explain some of the Java design tradeoffs applicable to pocket computers, and quantify their energy costs. For the design options we considered and the three workloads we studied, we find a maximum change in energy use of 25%.
Online multicast routing with bandwidth guarantees
Authors: Kodialam Murali S. , Lakshman T. V. , Sengupta Sudipta
Published: January 2007

This paper presents a new algorithm for on-line routing of bandwidth-guaranteed multicasts where routing requests arrive one-by-one without there being any a priori knowledge of future requests. A multicast routing request consists of a source
s
, a set of receivers
R
, and a bandwidth requirement
b
. This multicast routing problem arises in many contexts. Two applications of interest are routing of point-to-multipoint label-switched paths in Multi-Protocol Label Switched (MPLS) networks, and the provision of bandwidth guaranteed Virtual Private Network (VPN) services under the “hose” service model [17]. Offline multicast routing algorithms cannot be used since they require a priori knowledge of all multicast requests that are to be routed. Instead, on-line algorithms that handle requests arriving one-by-one and that satisfy as many potential future demands as possible are needed. The newly developed algorithm is an on-line algorithm and is based on the idea that a newly routed multicast must follow a route that does not “interfere too much” with network paths that may be critical to satisfy future demands. We develop a multicast tree selection heuristic that is based on the idea of deferred loading of certain “critical” links. These critical links are identified by the algorithm as links that, if heavily loaded, would make it impossible to satisfy future demands between certain ingress-egress pairs. The presented algorithm uses link-state information and some auxilliary capacity information for multicast tree selection and is amenable to distributed implementation. Unlike previous algorithms, the proposed algorithm exploits any available knowledge of the network ingress-egress points of potential future demands even though the demands themselves are unknown and performs very well.
Load distribution among replicated Web servers
Authors: Conti Marco , Gregori Enrico , Panzieri Fabio
Published: January 2007

A dominant factor for the success of an Internet based Web service is the Quality of Service (QoS) perceived by its users. The principal QoS attributes these users perceive include those related to the service "responsiveness", i.e. the service availability and timeliness. In this paper, we argue that QoS can be provided by distributing the processing load among replicated Web servers, and that these servers can be geographically distributed across the Internet. In this context, we discuss strategies for load distribution, and summarize a number of alternative architectures that can implement those strategies. The principal figure of merit we use in order to assess the effectiveness of the load distribution strategies we discuss is the response time experienced by the users.
File popularity characterisation
Authors: Roadknight Chris , Marshall Ian , Vearer Debbie
Published: January 2007

A key determinant of the effectiveness of a web cache is the locality of the files requested. In the past this has been difficult to model, as locality appears to be cache specific. We show that locality can be characterised with a single parameter, which primarily varies with the topological position of the cache, and is largely independent of the culture of the cache users. Accurate cache models can therefore be built without any need to consider cultural effects that are hard to predict.
A decision support system for tuning Web servers in distributed object oriented network architectures
Authors: van der Mei R. D. , Ehrlich W. K. , Reeser P. K. , Francisco J. P.
Published: January 2007

Web technologies are currently being employed to provide end user interfaces in diverse computing environments. The core element of these Web solutions is a Web server that is based on the Hypertext Transfer Protocol (HTTP) running over TCP/IP. Web servers are required to respond to millions of transaction requests per day at an "acceptable" Quality of Service (QoS) level with respect to the end-to-end response time and the server throughput. In many applications, the server performs significant server-side processing in distributed, object-oriented (OO) computing environments. In these applications, a Web server retrieves a file, parses the file for scripting language content, interprets the scripting statements and then executes embedded code, possibly requiring a TCP connection to a remote application for data transfer. In this paper, we present an end-to-end model that addresses this new class of Web servers that engage in OO computing. We have implemented the model in a simulation tool. Performance predictions based on the simulations are shown to match well with performance observed in a test environment. Therefore, the model forms an excellent basis for a Decision Support System for system architects, allowing them to predict the behavior of systems prior to their creation, or the behavior of existing systems under new load scenarios.
HCI for Web-based development of interactive medical mulitmedia courseware - lessons learned
Authors: Janvier Bill
Published: January 2007

This is an industrial placement project, which aimed at implementing principles from Human Computer Interaction (HCI) to develop a usable interactive Web Site for the Central Manchester Healthcare NHS Trust. Some of the lessons learned from this experience are reported here in the article.This report starts with an appraisal of how learning develops to outline the components required in any learning package. The development life cycle has been outlined, starting with defining problem specification, into analysis, design, development and ending with evaluation Some relevant sources, technical and others, with a brief bibliography are included.
Welcome to the silent zone multimedia courseware on sign language
Authors: Jacks Michael , Marsh Darren , Massey Charles
Published: January 2007

This coursework aimed at developing a multimedia courseware on Sign Language. A CD has been developed. Some of the topics covered in the courseware are included in this article.
Robust methodology for the discrimination of brain tumors from
in vivo
magnetic resonance spectra (abstract only)
Authors: Lee Yuen Yuen Barbara
Published: January 2007

Magnetic resonance spectroscopy has become an important clinical tool, serving as a quantitative indicator of the chemical composition of tissue, whether sampled
in vitro
or
in vivo.
In particular,
1
H-MRS provides detailed biochemical information of tissues of interest and is increasingly used in tumors diagnosis and grading, where a number of automated decision support have shown promising results. Statistical pattern recognition (PR) techniques have an important role in the allocation of spectra to diagnostic classes because they utilise the multivariate nature of spectraHowever, the very large number of spectral components combined with significant noise effects, especially when acquired
in vivo
, pose substantial difficulties for their statistical analysis, and severely limit to generalise to future data the conclusion from studies using limited number of samples. Linear statistical models commonly be applied after the dimensionality of the spectrum has been reduced to a fraction of the number of samples available, and the reproducibility of the results obtained is strongly dependent on how this parsimony is achieved. Previous studies have passed on clinically identified variables of interest, typically area ratios or attempted to identify the most predictive frequency components. We propose a systematic variable selection methodology based on a well established statistical technique know as the bootstrap to select subset of variable for linear discriminant analysis (LDA) to classify different tissue types to class. This is complemented by the further use of the bootstrap to provide robust estimates of the accuracy of the discriminant models when they are applied to future data.The multivariate structure of MRS also makes it very difficult to visualise the separation between different tissues types. A 2-dimensional map of the class membership of the spectra also has considerable potential as a graphical aid for interactive decision support for differential diagnosis by clinicians. Therefore, we propose the application of a planar representation of the spectra, which preserves their relationship to the multivariate class means and variances. In this way, the discriminatory power for different selections of frequency components can be visually demonstrated. Finally, a reject option is introduced into the graphical display with the aim of minimising the risks of misclassification by the explicit visualisation of the overlap between spectra from tumor.
Programming cellular automata in APL2
Authors: Alfonseca Manuel
Published: January 2007

This paper reviews the concept of cellular automata and describes a simple way to implement them in APL2. Two cellular automata are programmed: the well-known Conway's game of life, and one that simulates an ecosystem and displays a behaviour similar to that represented by the Volterra differential equations. Cellular automata are shown to be a powerful simulation tool for this kind of systems.