Alfredo Goldman

InteGrade: object‐oriented Grid middleware leveraging the idle computing power of desktop machines

Grid computing technology improves the computing experiences at organizations by effectively integrating distributed computing resources. However, just a small fraction of currently available Grid infrastructures focuses on reutilization of existing commodity computing resources. This paper introduces InteGrade, a novel object‐oriented middleware Grid infrastructure that focuses on leveraging the idle computing power of shared desktop machines. Its features include support for a wide range of parallel applications and mechanisms to assure that the owners of shared resources do not perceive any loss in the quality of service. A prototype implementation is under construction and the current version is available for download. Copyright

A comprehensive view of Hadoop research—A systematic literature review

Context: In recent years, the valuable knowledge that can be retrieved from petabyte scale datasets – known as Big Data – led to the development of solutions to process information based on parallel and distributed computing. Lately, Apache Hadoop has attracted strong attention due to its applicability to Big Data processing. Problem: The support of Hadoop by the research community has provided the development of new features to the framework. Recently, the number of publications in journals and conferences about Hadoop has increased consistently, which makes it difficult for researchers to comprehend the full body of research and areas that require further investigation. Solution: We conducted a systematic literature review to assess research contributions to Apache Hadoop. Our objective was to identify gaps, providing motivation for new research, and outline collaborations to Apache Hadoop and its ecosystem, classifying and quantifying the main topics addressed in the literature. Results: Our analysis led to some relevant conclusions: many interesting solutions developed in the studies were never incorporated into the framework; most publications lack sufficient formal documentation of the experiments conducted by authors, hindering their reproducibility; finally, the systematic review presented in this paper demonstrates that Hadoop has evolved into a solid platform to process large datasets, but we were able to spot promising areas and suggest topics for future research within the framework.

Performance Evaluation of Dynamic Networks using an Evolving Graph Combinatorial Model

The highly dynamic behavior of wireless networks make them very difficult to evaluate, e.g. as far as the performance of routing algorithms is concerned. However, some of these networks, such as intermittent wireless sensors networks, periodic or cyclic networks, and low Earth orbit (LEO) satellites systems have more predictable dynamics, as the temporal variations in the network topology are somehow deterministic. Recently, a graph theoretic model-the evolving graphs-was proposed to help capture the dynamic behavior of these networks, in view of the construction of least cost routing and other algorithms. The algorithms and insights obtained through this model are theoretically very efficient and intriguing. However, there is no study on the uses of these theoretical results into practical situations. Therefore, the objective of this work is to analyze the applicability of the evolving graph theory in the construction of efficient routing protocols in realistic scenarios. In this paper, we used the NS2 network simulator to first implement an evolving graph based routing protocol, and then to evaluate such protocol compared to three major ad-hoc protocols (DSDV, DSR, AODV). Interestingly, our experiments showed that evolving graphs have all the potentials to be an effective and powerful tool in the development of algorithms for dynamic networks, with predictable dynamics at least. In order to make this model widely applicable, however, some practical issues still have to be addressed and incorporated into the model, like stochastically predictable behavior. We also discuss such issues in this paper, as a result of our experience

The evolution of agile software development in Brazil

Agile software development methods have been increasingly adopted worldwide and became one of the mainstream software development approaches. Agile methods have also had an impact on software engineering education with universities adapting their courses to accommodate this new form of software development. Software engineering research has tried to evaluate the impact of agile methods in industrial projects and discover in which situations it is beneficial to apply such methods. However, there are almost no studies focusing on the progress of the agile movement in Brazil. In this paper, we present an overview of the evolution of the agile movement in Brazil, outlining the history of its first advocates in academia and industry. We describe existing educational initiatives, discuss the impact of the agile development on the national research, and present a report on the agile state-of-the-practice in the Brazilian IT industry.

Checkpointing-based rollback recovery for parallel applications on the InteGrade grid middleware

InteGrade is a grid middleware infrastructure that enables the use of idle computing power from user workstations. One of its goals is to support the execution of long-running parallel applications that present a considerable amount of communication among application nodes. However, in an environment composed of shared user workstations spread across many different LANs, machines may fail, become unaccessible, or may switch from idle to busy very rapidly, compromising the execution of the parallel application in some of its nodes. Thus, to provide some mechanism for fault-tolerance becomes a major requirement for such a system. In this paper, we describe the support for checkpoint-based rollback recovery of parallel BSP applications running over the InteGrade middleware. This mechanism consists of periodically saving application state to permit to restart its execution from an intermediate execution point in case of failure. A precompiler automatically instruments the source-code of a C/C++ application, adding code for saving and recovering application state. A failure detector monitors the application execution. In case of failure, the application is restarted from the last saved global check-point.

Being Extreme in the Classroom: experiences Teaching XP

Agile Methods propose a new way of looking at software development that questions many of the beliefs of conventional Software Engineering. Agile methods such as Extreme Programming (XP) have been very effective in producing high-quality software in real-world projects with strict time constraints.Nevertheless, most university courses and industrial training programs are still based on old-style heavyweight methods. This article, based on our experiences teaching XP in academic and industrial environments, presents effective ways of teaching students and professionals on how to develop high-quality software following the principles of agile software development. We also discuss related work in the area, describe real-world cases, and discuss open problems not yet resolved.

On Graph Reduction for QoS Prediction of Very Large Web Service Compositions

In this paper, we investigate the question of QoS prediction of Web Service Composition (WSC) implementing a business process. We focus on the graph reduction technique and the prediction of the Service Response Time. In the graph reduction technique, we assume that a Web Service Composition can be represented as a graph. The main thesis is that the QoS of such a graph graph can be obtained from a composition of the ones of its nodes. Multiple graph reduction algorithms have been proposed in the literature. Our contribution is twofold. We propose first a fast algorithm based on graph reduction for the prediction of the Service Response Time of a Web Service Composition. In comparison to those existing in the literature, this algorithm uses less memory space and has a better time complexity. The obtained improvements are in particular significant on very large Web Service Composition where the number of services is huge. Our second contribution is an analysis of the graph reduction technique for QoS prediction that takes into account the unfolding of services. In such cases, we show that the prediction of QoS can lead to a NP-complete problem. We also provide an integer programming model for predicting the Service Response Time in this case.

Application execution management on the InteGrade opportunistic grid middleware

The InteGrade project is a multi-university effort to build a novel grid computing middleware based on the opportunistic use of resources belonging to user workstations. The InteGrade middleware currently enables the execution of sequential, bag-of-tasks, and parallel applications that follow the BSP or the MPI programming models. This article presents the lessons learned over the last five years of the InteGrade development and describes the solutions achieved concerning the support for robust application execution. The contributions cover the related fields of application scheduling, execution management, and fault tolerance. We present our solutions, describing their implementation principles and evaluation through the analysis of several experimental results.

Exchanging messages of different sizes

This paper deals with the study of the exchange of messages among a set of processors linked through an interconnection network. We focus on general, non-uniform versions of message exchange problems in asynchronous systems with a linear cost model and messages of arbitrary sizes. We extend previous complexity results to show that the general asynchronous problems are NP-complete. We present several heuristics and determine which algorithms are best suited to several parallel systems. We propose new algorithms that combine the advantages of some of the heuristics. We conclude with experiments and simulations of the algorithms and analyses of their performances.

Fostering effective inter-team knowledge sharing in agile software development

Agile methods have different practices that ultimately foster intra-team knowledge sharing (KS). However, they do not provide recommendations about coping with inter-team KS. Supporting inter-team KS is fundamental in scaling agility across the entire organization, and is regarded as the new horizon for agile software development. This study seeks to understand inter-team knowledge sharing effectiveness in agile software development organizations. Using grounded theory, we analyzed data from four Brazilian organizations and also from an expert in agile methods implementation. We observed that the companies employ different work practices that allow knowledge sharing to occur across team boundaries. Our main contribution is a conceptual model that explains how effective knowledge sharing across agile teams depends on applying purposeful practices, along with organizational conditions and stimuli. This understanding represents an innovative focus within the context of agile methods and suggests what one needs to take into account when striving on this path. Yet, it yields opportunities for further studies in refining and extending the model to other organizational contexts. Inter-team knowledge sharing reflects the way agile software development organizations are coping with enterprise agility and the way they consider knowledge as a resource for competitiveness.