Specializing Java Programs in a Distributed Environment

Jeff Magee and Jeff Kramer John Wiley and Sons, New York, NY, 1999, 374 pp. ISBN 0471987107, $64.99 The book is an introductory text to the ideas, concepts, and topics of concurrency. The text focuses on understanding concepts and techniques, and problems of concurrency, not on the implementation or language. The author's overall goal is that by a combination of learning and doing using Java should make the process of acquiring the skills relating to concurrency interesting, enjoyable, and challenging. The Java language is thus used only for illustration and programming experience of the reader. The book is intended for a computer science student or software developer. A background in programming is expected, as well as some familiarity with the essential concepts of object-oriented programming. Knowledge of the Java programming language and operating systems concepts is beneficial but not required. After reading the text, a reader can expect to have a broad understanding of the concepts of concurrency, the problems that arise, methods to emphasis desirable properties in a concurrent system, and ways to avoid the undesirable ones. The text provides a systematic treatment of concepts, as means to rigorously specify and model concurrent systems, with Java examples to animate and illustrate the concepts discussed. The book is organized into twelve chapters, with three appendices. The first eight chapters provide a concise and comprehensive foundation of concurrency, with the remaining four chapters focusing on more advanced concepts. The latter four chapters are somewhat supplemental and can be read at the discretion of the reader. The content of the text is self-contained, with no reliance upon external references. The authors provide a concluding set of notes and further topics which reference external works, but these are not used in the chapter contents. The introduction provides the foundation for the book, and an idea of what will follow in the rest of the text. The basics of modeling and Java are covered. Authors follow with the concepts of processes, threads and with the idea of concurrency. The emphasis is on using Java, and on the notation used to define a concurrent process or thread. The discussion continues covering interleaving and asynchronous concurrency. Various details about composition of parallel processes and finite state processing modeling are presented. The programming of concurrent execution using Java is then examined via the concept of multiple threads. Here, sharing objects among Java threads is also discussed. The concept of conditional synchronization is covered next, and is used to construct a monitor. The methods of the base object in Java is used, and a waiting queue associated with a Java object is discussed and implemented. This discussion is followed by introduction of deadlock. Authors show the conditions necessary for a deadlock to occur and present an analysis of a concurrent system establishing that such a system is deadlock-free. The classic Dining Philosopher's problem is used to illustrate the distinction between finding deadlocks in models and in programs. The presentation continues with the safety property (that asserts that nothing bad happens), and the liveliness property (that asserts that nothing good happens). Here, authors use the material on model-based design to consolidate many of the concepts previously discussed. No one modeling method or design methodology is emphasized. Then creation and elimination of threads in a running program is covered next. The dynamic starting and stopping of Java threads is presented. The discussion moves then to messaging passing. Asynchronous and synchronous messaging is presented with Java programming examples. The concept of a rendezvous, allowing for interaction in a messaging system, is also presented. Based on the concepts developed so far filter-pipeline, supervisor-worker, and announcer-listener concurrent architectures are examined. Java programs demonstrating how the elements of each model interact at runtime are developed. The presentation completes with modeling and implementing of timed systems. Time is signaled by the passage of successive time ticks. The authors then elaborate on a system that is event-based rather than thread-based. Java programs are used to illustrate in implementation the concepts discussed. The three appendices provide a reference, specification, and listing of semantics for the finite-state modeling algebra used by the authors throughout the book. The text is ideal for teaching in a classroom environment, or for a motivated reader to use for self-paced learning. Its organization follows a logical train of discussion and thought, with each chapter building successively on the other, with the more difficult concepts and topics withheld until later. This gradual approach makes the material flow smoothly and cohesively from the beginning to the end. The book is intended as a textbook, so does organize the material and discussion as one, but does not become too dry or bland to stifle the reader's interest in the material. The examples are inter-mixed with the discussion to highlight and emphasize essential points the authors make in each chapter. The text illustrates concepts well under discussion, and does not become a long-winded recital of theory. The topics examined are fundamental to concurrency, and are well illustrated and discussed, but no one topic is examined extensively. The code examples are well written concerning the programming style, indentation and comments. A CD is provided, containing the codes from the book. In addition supplementary material consisting of presentation slides and an errata is provided on the author's WWW site, as well as on the CD. The book is up to date both on the topics of concurrency, and with the Java applets, code, and programs used to illustrate them. Later, as the Java language evolves, the examples may need to be updated, but for the time being the text well represents that state of the Java language. William F. Gilreath, Micron Technology, Inc., Boise Idaho

Heterogeneous distributed computing has traditionally been a problematic undertaking which increases in complexity as heterogeneity increases. This paper presents results obtained using DOGMA--a Java based system which simplifies parallel computing on heterogeneous computers. The performance of Java just-in-time compilers currently approaches C++ for many applications, making Java a serious contender for parallel application development. DOGMA provides support for dedicated clusters as well as idle workstations through the use of a web based browse-in feature or the DOGMA screen saver. DOGMA supports parallel programming in both a traditional message passing form and a novel object-oriented approach. This research provides a unified environment for developing high performance parallel applications on heterogeneous systems.

Generic programming is likely to become a new challenge for a critical mass of developers. Therefore, it is crucial to refine the support for generic programming in mainstream Object-Oriented languages — both at the design and at the implementation level — as well as to suggest novel ways to exploit the additional degree of expressiveness made available by genericity. This study is meant to provide a contribution towards bringing Java genericity to a more mature stage with respect to mainstream programming practice, by increasing the effectiveness of its implementation, and by revealing its full expressive power in real world scenario. With respect to the current research setting, the main contribution of the thesis is twofold. First, we propose a revised implementation for Java generics that greatly increases the expressiveness of the Java platform by adding reification support for generic types. Secondly, we show how Java genericity can be leveraged in a real world case-study in the context of the multi-paradigm language integration. Several approaches have been proposed in order to overcome the lack of reification of generic types in the Java programming language. Existing approaches tackle the problem of reification of generic types by defining new translation techniques which would allow for a runtime representation of generics and wildcards. Unfortunately most approaches suffer from several problems: heterogeneous translations are known to be problematic when considering reification of generic methods and wildcards. On the other hand, more sophisticated techniques requiring changes in the Java runtime, supports reified generics through a true language extension (where clauses) so that backward compatibility is compromised. In this thesis we develop a sophisticated type-passing technique for addressing the problem of reification of generic types in the Java programming language; this approach — first pioneered by the so called EGO translator — is here turned into a full-blown solution which reifies generic types inside the Java Virtual Machine (JVM) itself, thus overcoming both performance penalties and compatibility issues of the original EGO translator. Java-Prolog integration Integrating Object-Oriented and declarative programming has been the subject of several researches and corresponding technologies. Such proposals come in two flavours, either attempting at joining the two paradigms, or simply providing an interface library for accessing Prolog declarative features from a mainstream Object-Oriented languages such as Java. Both solutions have however drawbacks: in the case of hybrid languages featuring both Object-Oriented and logic traits, such resulting language is typically too complex, thus making mainstream application development an harder task; in the case of library-based integration approaches there is no true language integration, and some “boilerplate code” has to be implemented to fix the paradigm mismatch. In this thesis we develop a framework called PatJ which promotes seamless exploitation of Prolog programming in Java. A sophisticated usage of generics/wildcards allows to define a precise mapping between Object-Oriented and declarative features. PatJ defines a hierarchy of classes where the bidirectional semantics of Prolog terms is modelled directly at the level of the Java generic type-system.

Mark Watson Morgan Kaufmann Publishers, San Francisco, 1997, 377 pp. ISBN 1-55860-420-0, $44.95 This book is well written and organized to cover how to apply AI (Artificial Intelligence) techniques for practical Internet and Intranet tools by using the Java programming language. In the book, the author uses neural network and genetic algorithms to develop distributed systems that are applied for the Internet and Intranets, such as client/server model and information retrieval tool and so on. Part 1 begins with a good general introduction to AI. The history and survey of Artificial Intelligence research are given briefly. In addition, symbolic processing versus neural networks approaches are discussed. This author opts to use neural network to develop example Internet/Intranet systems in the book. Part 2 consists of Java programs developed for AI, neural networks, genetic algorithms, natural language processing, and expert systems. Chapter 2 illustrates Graphical User Interface (GUI) class that is derived from Applet and Canvas classes in Java, which is used in most example programs in the book. Chapter 3 introduces a frame data structure that is used as a message in distributed systems in the later chapters. Chapter 4 shows neural network classes developed in Java and its theory and implementation. Chapter 5 explains the genetic algorithms and the Java genetic algorithm classes. Chapter 6 describes how to develop and implement natural language processing classes using Java. Chapter 7 shows how to share data objects in distributed systems. For example, distributed AI agent classes are developed to share data objects, WWW data collection agent classes are shown to retrieve documents in the Internet, and small POP (Post Office Protocol) mail classes are developed to send and receive mails. Chapter 8 illustrates how to develop expert systems by using Java Jess, which is based on OPS5/CLIPS expert systems. Part 3 explains how to generate and implement the projects using the Java classes that are developed in Part 2. Chapter 9 shows the project that demonstrates the use of genetic algorithms in chapter 5 to control enemy ships in a scrolling arcade game. Chapter 10 describes the real-time handwriting recognition system developed by using the neural network classes in chapter 4. Chapter 11 illustrates a greedy algorithm to optimize neural networks that is based on the author’s hand-tuning neural training data. Chapter 12 improves neural network training data by applying genetic algorithms, to discard bad training data and to avoid discarding good training data. Chapter 13 describes the distributed natural language processing system that uses natural language processing classes in chapter 6. The data structures in chapter 2 are used to store historical data in a separate server application on any other computer in the Internet or Intranets. The final chapter provides the design and implementation of a complete agent-based information retrieval tool for the Internet. The retrieved documents are stored in ASCII or HTML format. This book is a very good reference book for anyone interested in developing systems using Java in distributed environments, especially applying AI techniques. Also, the author provides the CD-ROM that includes the source code for Java classes developed in the book. Haklin Kimm, University of Tennessee

Intelligent Internet Computing (IIC) is emerging rapidly including grid, cluster computing, and peer-topeer computing to provide computing and communication services any time and anywhere. IIC foresees the integration of communicating and computational devices and applications in our heterogeneous computing environments. In this paper, we focus on the task allocation, which is a typical problem in the area of high performance computing and has been extensively studied in the past. Efficient task allocation is critical for achieving secure and high performance in a heterogeneous computing (HC) environment. In addition, the problem of allocating these tasks to the machines of a HC environment has been shown, in general, to be NP-complete, requiring the development of heuristic techniques. Therefore, a task allocation algorithm based on discrete particle swarm optimization (PSO) algorithm in the HC environment is proposed in this paper. Firstly, a new structure of cluster system is designed, and a mathematical model is built for dynamic server alliance according to practical tasks and situations of servers. Then an efficient discrete PSO with a well-designed particle position code and fitness function is proposed. A mutation operator which can effectively improve the algorithm's ability of global search and population diversity is also introduced in this algorithm. Finally, the simulation results compared with other algorithms show that this proposed algorithm produces better results in terms of both quality of solution and convergence speed.

In this paper, the problem of parallel loop scheduling for heterogeneous networks of workstations is discussed. A practical network of workstations is heterogeneous where computing power varies in different composing workstations. A simple loop scheduling technique is insufficient in exploiting maximum computing power of such a system. We propose a fundamental idea for a performance prediction tool to gauge the relative computing power among composing workstations so that parallel performance of a program run on a given network can be predicted. In view of the performance prediction results, a loop scheduling approach is then incorporated into the system to achieve close-to-optimal parallel performance. Examples running benchmark programs demonstrate a significant gain from the proposed approach over traditional scheduling approaches.

Publication in the conference proceedings of EUSIPCO, Rhodes, Greece, 1998

We propose a unifying framework based on configuration linear programs and randomized rounding, for different energy optimization problems in the dynamic speed-scaling setting. We apply our framework to various scheduling and routing problems in heterogeneous computing and networking environments. We first consider the energy minimization problem of scheduling a set of jobs on a set of parallel speed-scalable processors in a fully heterogeneous setting. For both the preemptive-non-migratory and the preemptive-migratory variants, our approach allows us to obtain solutions of almost the same quality as for the homogeneous environment. By exploiting the result for the preemptive-non-migratory variant, we are able to improve the best known approximation ratio for the single processor non-preemptive problem. Furthermore, we show that our approach allows to obtain a constant-factor approximation algorithm for the power-aware preemptive job shop scheduling problem. Finally, we consider the min-power routing problem where we are given a network modeled by an undirected graph and a set of uniform demands that have to be routed on integral routes from their sources to their destinations so that the energy consumption is minimized. We improve the best known approximation ratio for this problem.

The aim of this work was to analyze the cooperation efficiency of the distributed objects based on the CORBA standard. The obtained results show the possibilities of application to the object-relational databases or object oriented computation of data received via the network from the object managed data base. The distributed objects for the client-server model were implemented in Java and C++ languages. All possible configurations of the implementation for the client and the server were analyzed. Best results were received for the client and the server implementation in C++ language. The worst results were received for the client and the server implementation in Java.

Small changes can have major and nonlocal effects in object oriented languages, due to the extensive use of subtyping and dynamic dispatch. This makes it difficult to understand value flow through a program and complicates life for maintenance programmers. Change impact analysis provides feedback on the semantic impact of a set of program changes.The change impact analysis method presented in this thesis presumes the existence of a suite of regression tests associated with a Java program and access to the original and edited versions of the code. The primary goal of our research is to provide programmers with tool support that can help them understand why a test is suddenly failing after a long editing session by isolating the changes responsible for the failure. The tool analyzes two versions of an application and decomposes their difference into a set of atomic changes. Change impact is then reported in terms of affected tests whose execution behavior may have been modified by the applied changes. For each affected test, it also determines a set of affecting changes that were responsible for the test's modified behavior.The first contribution of this thesis is the demonstration of the utility of the basic change impact analysis framework of [51], by implementing a proof-of-concept prototype, Chianti, and applying it to Daikon, for an experimental validation.The second contribution is the definition and implementation of the dependences between atomic changes. Extensive experiments show that our dependences can help build the intermediate programs automatically in most cases.Another contribution is the heuristics for ranking the atomic changes for fault localization. This thesis proposes a heuristic that ranks method changes that might have affected a failed test, indicating the likelihood that they may have contributed to a test failure. Our results indicate that when a failure is caused by a single method change, our heuristic ranked the failure-inducing change as number 1 or number 2 of all the method changes in 67% of the delegate tests (i.e., representatives of all failing tests).

This work investigates the application of deductive verification techniques to safety critical Java programs, in particular RTSJ programs. A focus is put on the formalization of the RTSJ memory model in dynamic logic, the utilization of a region-based memory model for ensuring non-interference and a design-by-contract based approach for the formal specification and verification of worst case memory consumption.

Java bytecodes can be executed with the following three methods: a Java interpreter running on a particular machine interprets bytecodes; a Just-in-Time (JIT) compiler translates bytecodes to the native primitives of the particular machine and the machine executes the translated codes; and a Java processor executes bytecodes directly. The first two methods require no special hardware support for the execution of Java bytecodes and are widely used currently. The last method requires an embedded Java processor, picoJavaI or picoJavaII for instance. The picoJavaI and picoJavaII are simple pipelined processors with no ILP (instruction level parallelism) and TLP (thread level parallelism) supports. A so-called MAJC (microprocessor architecture for Java computing) design can exploit ILP and TLP by using a modified VLIW (very long instruction word) architecture and vertical multithreading technique, but it has its own instruction set and cannot execute Java bytecodes directly. In this paper, we investigate a processor architecture which can directly execute Java bytecodes meanwhile can exploit Java ILP and TLP simultaneously. The proposed processor consists of multiple slots implementing horizontal multithreading and multiple functional units shared by all threads executed in parallel. Our architectural simulation results show that the Java processor could achieve an average 20 IPC (instructions per cycle), or 7.33 EIPC (effective IPC), with 8 slots and a 4-instruction scheduling window for each slot. We also check other configurations and give the utilization of functional units as well as the performance improvement with various kinds of working loads.

When implementing multi-user cooperation systems in a networked virtual environment, synchronizing local representations of a shared virtual world has to be considered. It involves distributing and storing the data that represent users' activity in the virtual world. The authors propose a concept of general variables, which formalizes the task of distributing, journaling and locking the data in the client-server model. To verify the employability of the concept, we have implemented a Java bundle comprising a server and a client-side library. Four multi-user applications are presented to demonstrate that with the help of the bundle, a single-user application can be turned into a multi-user one with minimum effort.

In this paper we seek to provide a foundation for the study of the level of use of object-oriented techniques in Java programs in general, and scientific applications in particular. Specifically, w...

Stephen J. Hartley Oxford University Press, New York, 1998, 260 pp. ISBN 0-19-511315-2, $45.00 Concurrent Programming is a thorough treatment of Java multi-threaded programming for both a stand-alone and distributed environment. Designed mostly for students in concurrent or parallel programming classes, the text is also an excellent reference for the practicing professional developing multi-threaded programs or applets. Hartley first provides a complete explanation of the features of Java necessary to write concurrent programs, including topics such as exception handling, interfaces, and packages. He then gives the reader a solid background to write multi-threaded programs and also presents the problems introduced when writing concurrent programs—namely race conditions, mutual exclusion, and deadlock. Hartley also provides several software solutions that do not require the use of common process and thread mechanisms. Once the groundwork is laid for writing concurrent programs, Hartley then takes a different approach than most Java references. Rather than presenting how Java handles mutual exclusion with the synchronized keyword (although it is covered later), he first looks at semaphore-based solutions to classic concurrent problems such as bounded-buffer, readers-writers, and the dining philosophers. Hartley also uses the same approach to develop Java classes for monitors and message passing. This unique approach to introducing concurrency allows the readers to both understand how Java threads are synchronized and how the basic synchronization mechanism can be used to construct more abstract tools such as semaphores. If there is a shortcoming with the text it is with the lack of sufficient coverage of remote method invocation (RMI), although there is a section covering RMI. This is quite understandable as RMI is a fairly recent phenomenon with the Java community. Also, the classes that Hartley provides could easily implement RMI rather than sockets to handle communication. The strengths of the book include its ease in reading, several examples at the end of chapters, a package similar to Xtango that provides algorithm animation, and a supportive web site by the author (see www.mcs.drexel.edu/~shartley/ConcProgJava/index.html ) including compressed source code. As Java becomes more dominant on the server side of multi-tier applications, writing thread-safe concurrent applications becomes even more important. Concurrent Programming is a strong step towards teaching students and professionals such skills. Greg Gagne, Westminster College of Salt Lake City Salt Lake City, Utah