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2013
Soares, J., J. M. Lourenço, and N. Preguiça, "Software Component Replication for Improved Fault-Tolerance: Can Multicore Processors Make It Work?", Dependable Computing, vol. 7869: Springer Berlin Heidelberg, pp. 173-180, 2013. Abstractewdc2013.pdf

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2008
Cunha, G., J. Lourenço, and R. J. Dias, "Consistent State Software Transactional Memory", IV Jornadas de Engenharia de Electrónica e Telecomunicações e de Computadores (JETC'08), Lisboa, Portugal, ISEL - Instituto Superior de Engenharia de Lisboa, pp. 251–256, 2008. Abstractjetc_2008.pdf

Software transactional memory (STM) is a promising programming model that adapts many concepts borrowed from the databases world to control concurrent accesses to memory (RAM) locations. In this paper we propose a new classification for the active states of a transaction; a new memory quiescing algorithm, to allow the safe transition of a memory block form transactional to non-transactional space; we compare word and object transactional grain units; and evaluate the cost of consistent state validation, arguing that this cost can be minimized by performing partial validation on problematic code regions.

Dias, R. J., J. M. Lourenço, and G. Cunha, "Developing libraries using software transactional memory", Comput. Sci. Inf. Syst., vol. 5, issue 2, no. 2, pp. 103–117, 2008. Abstractcomsis_final.pdf

Software transactional memory is a promising programming model that adapts many concepts borrowed from the databases world to control concurrent accesses to main memory (RAM). This paper discusses how to support revertible operations, such as memory allocation and release, within software libraries that will be used in software memory transactional contexts. The proposal is based in the extension of the transaction life cycle state diagram with new states associated to the execution of user-defined handlers. The proposed approach is evaluated in terms of functionality and performance by way of a use case study and performance tests. Results demonstrate that the proposal and its current implementation are flexible, generic and efficient

Dias, R. J., J. Lourenço, and G. Cunha, "Developing Libraries Using Software Transactional Memory", CoRTA 2008: Proceedings of the Conference on Compilers, Related Technologies and Applications, Bragança, Portugal, Instituto Politécnico de Bragança - ESTG, 2008. Abstractcorta_2008.pdf

Software transactional memory (STM) is a promising programming model that adapts many concepts borrowed from the databases world to control concurrent accesses to main memory (RAM) locations. This paper aims at discussing how to support apparently irreversible operations within a memory transaction.

2007
Lourenço, J. M., and G. Cunha, "Testing patterns for software transactional memory engines", Proceedings of the 5th Workshop on Parallel and Distributed Systems: Testing, Analysis, and Debugging (PADTAD'07), New York, NY, USA, ACM, pp. 36–42, 2007. Abstractpadtad21s.pdf

The emergence of multi-core processors is promoting the use of concurrency and multithreading. To raise the abstraction level of synchronization constructs is fundamental to ease the development of concurrent software, and Software Transactional Memory (STM) is a good approach towards such goal. However, execution environment issues such as the processor instruction set, caching policy, and memory model, may have strong influence upon the reliability of STM engines. This paper addresses the testing of STM engines aiming at improving their reliability and independence from execution environment. From our experience with porting and extending a specific STM engine, we report on some of the bugs found and synthesize some testing patterns that proved to be useful at testing STM engines.

2005
Cunha, J. C., W. Fleischman, J. M. Lourenço, and V. K. Proulx, Proceedings of the 10th Annual SIGCSE Conference on Innovation and Technology in Computer Science Education (ITiCSE'05), , New York, NY, USA, ACM, 2005. Abstract

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2004
Lourenço, J. M., "A Debugging Engine for Parallel and Distributed Programs", Universidade Nova de Lisboa: Faculdade de Ciências e Tecnologia, 2004. Abstractfiddle-thesis.pdf

In the last decade a considerable amount of research work has focused on distributed debugging, one of the crucial fields in the parallel software development cycle. The productivity of the software development process strongly depends on the adequate definition of what debugging tools should be provided, and what debugging methodologies and functionalities should these tools support. The work described in this dissertation was initiated in 1995, in the context of two research projects, the SEPP (Software Engineering for Parallel Processing) and HPCTI (High-Performance Computing Tools for Industry), both sponsored by the European Union in the Copernicus program, which aimed at the design and implementation of an integrated parallel software development environment. In the context of these projects, two independent toolsets have been developed, the GRADE and EDPEPPS parallel software development environments. Our contribution to these projects was in the debugging support. We have designed a debugging engine and developed a prototype, which was integrated the both toolsets (it was the only tool developed in the context of the SEPP and HPCTI projects which achieved such a result). Even after the closing of those research projects, further research work on distributed debugger has been carried on, which conducted to the re-design and re-implementation of the debugging engine. This dissertation describes the debugging engine according to its most up-to-date design and implementation stages. It also reposts some of the experimental work made with both the initial and the current implementations, and how it contributed to validate the design and implementations of the debugging engine.

2003
Lourenço, J. M., J. C. Cunha, and V. Moreira, "Control and Debugging of Distributed Programs Using Fiddle", CoRR, vol. cs.DC/0309049, pp. 143–157, 2003. Abstractaadebug.pdfWebsite

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Duarte, V., J. M. Lourenço, and J. C. Cunha, "Supporting on-line distributed monitoring and debugging", On-Line Monitoring Systems and Computer Tool Interoperability, Commack, NY, USA, Nova Science Publishers, Inc., pp. 43–59, 2003. Abstractpdcp.pdf

Monitoring systems have traditionally been developed with rigid objectives and functionalities, and tied to specific languages, libraries and run-time environments. There is a need for more flexible monitoring systems which can be easily adapted to distinct requirements. On-line monitoring has been considered as increasingly important for observation and control of a distributed application. In this paper we discuss monitoring interfaces and architectures which support more extensible monitoring and control services. We describe our work on the development of a distributed monitoring infrastructure, and illustrate how it eases the implementation of a complex distributed debugging architecture. We also discuss several issues concerning support for tool interoperability and illustrate how the cooperation among multiple concurrent tools can ease the task of distributed debugging.

2001
Cunha, J. C., J. M. Lourenço, and V. Duarte, "The DDBG distributed debugger", Parallel Program Development for Cluster Computing, Commack, NY, USA, Nova Science Publishers, Inc., pp. 279–290, 2001. Abstractcap13.pdf

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Cunha, J. C., J. M. Lourenço, and V. Duarte, "Debugging of parallel and distributed programs", Parallel Program Development for Cluster Computing, Commack, NY, USA, Nova Science Publishers, Inc., pp. 97–129, 2001. Abstractcap03.pdf

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Lourenço, J. M., and J. C. Cunha, "Fiddle: A Flexible Distributed Debugging Architecture", Proceedings of the International Conference on Computational Science-Part II, London, UK, Springer-Verlag, pp. 821–830, 2001. Abstracticcs01.pdf

In the recent past, multiple techniques and tools have been proposed and contributed to improve the distributed debugging functionalities, in several distinct aspects, such as handling the non-determinism, allowing cyclic interactive debugging of parallel programs, and providing more user-friendly interfaces. However, most of these tools are tied to a specific programming language and provide rigid graphical user interfaces. So they cannot easily adapt to support distinct abstraction levels or user interfaces. They also don't provide adequate support for cooperation with other tools in a software engineering environment. In this paper we discuss several dimensions which may contribute to develop more flexible distributed debuggers. We describe Fiddle, a distributed debugging tool which aims at overcoming some of the above limitations.

1999
Cunha, J. C., J. M. Lourenço, and T. Antão, "An experiment in tool integration: the {DDBG} parallel and distributed debugger", J. Syst. Archit., vol. 45, New York, NY, USA, Elsevier North-Holland, Inc., pp. 897–907, may, 1999. Abstractjsa99.pdfWebsite

Most known teaching experiences focus on parallel computing courses only, but some teaching experiences on distributed computing courses have also been reported. In this paper we describe a course on Parallel and Distributed Processing that is taught at undergraduate level in the Computer Science degree of our University.This course presents an integrated approach concerning concurrency, parallelism, and distribution issues. It's a breadth-first course addressing a wide spectrum of abstractions: the theoretical component focus on the fundamental abstractions to model concurrent systems, including process cooperation schemes, concurrent programming models, data and control distribution, concurrency control and recovery in transactional systems, and parallel processing models; the practical component illustrates the design and implementation issues involved in selected topics such as a data and control distribution problem, a distributed transaction-based support system and a parallel algorithm.We also discuss how this approach has been contributing to prepare the student to further actions regarding research and development of concurrent, distributed, or parallel systems.

Cunha, J. C., P. D. Medeiros, V. Duarte, J. Lourenço, and C. Gomes, "An Experience in Building a Parallel and Distributed Problem-Solving Environment", Proceedings of the International Conference on Parallel and Distributed Processing Techniques and Applications (PDPTA'99): CSREA Press, pp. 1804–1809, 1999. Abstractpdpta99.pdf

We describe our experimentation with the design and implementation of specific environments, consisting of heterogeneous computational, visualization, and control components. We illustrate the approach with the design of a problem–solving environment supporting the execution of genetic algorithms. We describe a prototype supporting parallel execution, visualization, and steering. A life cycle for the development of applications based on genetic algorithms is proposed.

1998
Cunha, J. C., P. D. Medeiros, J. M. Lourenço, V. Duarte, J. Vieira, B. Moscão, D. Pereira, and R. Vaz, "The DOTPAR Project: Towards a Framework Supporting Domain Oriented Tools for Parallel and Distributed Processing", Proceedings of the International Conference and Exhibition on High-Performance Computing and Networking (HPCN'98), London, UK, Springer-Verlag, pp. 952–954, 1998. Abstractdotpar98.pdf

We discuss the problem of building domain oriented environments by a composition of heterogeneous application components and tools. We describe several individual tools that support such environments, namely a distributed monitoring and control tool (DAMS), a process-based distributed debugger (PDBG) and a heterogeneous interconnection model (PHIS). We discuss our experience with the development of a Problem Oriented Environment in the domain of genetic algorithms, obtained by a composition of heterogeneous tools and application components.

Cunha, J. C., J. M. Lourenço, J. Vieira, B. Moscão, and D. Pereira, "A Framework to Support Parallel and Distributed Debugging", Proceedings of the International Conference and Exhibition on High-Performance Computing and Networking (HPCN'98), London, UK, Springer-Verlag, pp. 708–717, 1998. Abstracthpcn98.pdf

We discuss debugging prototypes that can easily support new functionalities, depending on the requirements of high-level computational models, and allowing a coherent integration with other tools in a software engineering environment. Concerning the first aspect, we propose a framework that identifies two distinct levels of functionalities that should be supported by a parallel and distributed debugger using: a process and thread-level, and a coordination level concerning sets of processes or threads. An incremental approach is used to effectively develop prototypes that support both functionalities. Concerning the second aspect, we discuss how the interfacing with other tools has influenced the design of a process-level debugging interface (PDBG) and a distributed monitoring and control layer called (DAMS).

Cunha, J. C., and J. M. Lourenço, "An Integrated Course on Parallel and Distributed Processing", SIGCSE Bull., vol. 30, New York, NY, USA, ACM, pp. 217–221, 1998. Abstractsigcse98.pdfWebsite

Most known teaching experiences focus on parallel computing courses only, but some teaching experiences on distributed computing courses have also been reported. In this paper we describe a course on Parallel and Distributed Processing that is taught at undergraduate level in the Computer Science degree of our University.This course presents an integrated approach concerning concurrency, parallelism, and distribution issues. It's a breadth-first course addressing a wide spectrum of abstractions: the theoretical component focus on the fundamental abstractions to model concurrent systems, including process cooperation schemes, concurrent programming models, data and control distribution, concurrency control and recovery in transactional systems, and parallel processing models; the practical component illustrates the design and implementation issues involved in selected topics such as a data and control distribution problem, a distributed transaction-based support system and a parallel algorithm.We also discuss how this approach has been contributing to prepare the student to further actions regarding research and development of concurrent, distributed, or parallel systems.

Lourenço, J. M., and J. C. Cunha, "The PDBG Process-Level Debugger for Parallel and Distributed Programs", Proceedings of the SIGMETRICS symposium on Parallel and Distributed Tools, New York, NY, USA, ACM, pp. 154, 1998. Abstractspdt-asbt98.pdf

In this paper we discuss several issues concerning the design and implementation of a debugger for parallel and distributed applications. This debugger uses a client-server approach to isolate the debugging user-interface from the debugging services, by way of a two-level structured approach: the component-level to observe and act upon individual processes; and the coordination-level to observe the interprocess relations and act upon them.

Lourenço, J. M., and J. C. Cunha, "Replaying Distributed Applications with RPVM", Proceeding of the 2nd Austrian-Hungarian Workshop on Distributed and Parallel Systems (DAPSYS'98): University of Vienna, 1998. Abstractdapsys98.pdf

Parallel debugging is complex and difficult. Complex because the programmer has to deal with multiple program flows and process interactions, and difficult due to the very limited choice on effective and easy-to-use debugging tools for parallel programming. Simple and necessary features for parallel debugging are absent even from commercial debuggers, such as a record-replay feature, that allows to re-execute multiple times a parallel application assuring that during each re-execution the internal race conditions are solved in the same way they were in the first time. Some work has been done on record-replay techniques for parallel and distributed applications, but just a few have been applied to specific systems (such as PVM or MPI), and even less have produced working prototypes. In this paper we describe a method designed to work with the PVM system and how it was implemented to provide a working prototype.

Lourenço, J. M., and J. C. Cunha, "A Thread-Level Distributed Debugger", Proceedings of the 3rd International Conference on Vector and Parallel Processing (VecPar'98), Porto, Portugal, Universidade do Porto, pp. 359–366, 1998. Abstractvecpar98.pdf

In order to address the diversity of existing parallel programming models, it is important to provide development environments that can be incrementally extended with new services. Concerning the debugging of process based models, we have previously designed and implemented a basic interface that can be accessed by other tools as well as by debugging modules associated with high-level programming languages.

Cunha, J. C., J. M. Lourenço, and V. Duarte, "Tool Integration Issues for Parallel and Distributed Debugging", Proceedings of the 3rd SEIHPC Workshop, Braga, Portugal, University of Westminster, 1998. Abstractseihpc98.pdf

This paper describes our experience with the design and implementation of a distributed debugger for C/PVM programs within the scope of the SEPP and HPCTI Copernicus projects. These projects aimed at the development of an integrated parallel software engineering environment based on a high-level graphical parallel programming model (GRAPNEL) and a set of associated tools supporting graphical edition, compilation, simulated and real parallel execution, testing, debugging, performance monitoring, mapping, and load balancing. We discuss how the development of the debugging tool was strongly influenced by the requirements posed by other tools in the environment, namely support for high-level graphical debugging of GRAPNEL programs, and support for the integration of static and dynamic analysis tools. We describe the functionalities of the DDBG debugger and its internal architecture, and discuss its integration with two separate tools in the SEPP/HPCTI environment: the GRED graphical editor for GRAPNEL programs, and the STEPS testing tool for C/PVM programs.

Cunha, J. C., J. Lourenço, and V. Duarte, "Using DDBG to Support Testing and High-level Debugging Interfaces", Computers and Artificial Intelligence, vol. 17, no. 5, 1998. Abstractcaij98.pdfWebsite

This paper describes our experience with the design and implementation of a distributed debugger for C/PVM programs within the scope of the SEPP and HPCTI Copernicus projects. These projects aimed at the development of an integrated parallel software engineering environment based on a high-level graphical parallel programming model (GRAPNEL) and a set of associated tools supporting graphical edition, compilation, simulated and real parallel execution, testing, debugging, performance monitoring, mapping, and load balancing. We discuss how the development of the debugging tool was strongly influenced by the requirements posed by other tools in the environment, namely support for high-level graphical debugging of GRAPNEL programs, and support for the integration of static and dynamic analysis tools. We describe the functionalities of the DDBG debugger and its internal architecture, and discuss its integration with two separate tools in the SEPP/HPCTI environment: the GRED graphical editor for GRAPNEL programs, and the STEPS testing tool for C/PVM programs.

1997
Kacsuk, P., J. C. Cunha, G. Dózsa, J. M. Lourenço, T. Fadgyas, and T. Antão, "A graphical development and debugging environment for parallel programs", Parallel Comput., vol. 22, Amsterdam, The Netherlands, The Netherlands, Elsevier Science Publishers B. V., pp. 1747–1770, 1997. Abstractpar-comp97.pdfWebsite

To provide high-level graphical support for PVM (Parallel Virtual Machine) based program development, a complex programming environment (GRADE) is being developed. GRADE currently provides tools to construct, execute, debug, monitor and visualise message-passing parallel programs. It offers high-level graphical programming abstraction mechanism to construct parallel applications by introducing a new graphical language called GRAPNEL. GRADE also provides the programmer with the same graphical user interface during the program design and debugging stages. A distributed debugging engine (DDBG) assists the user in debugging GRAPNEL programs on distributed memory computer architectures. Tape/PVM and PROVE support the performance monitoring and visualization of parallel programs developed in the GRADE environment.

Lourenço, J. M., J. C. Cunha, H. Krawczyk, P. Kuzora, M. Neyman, and B. Wiszniewski, "An integrated testing and debugging environment for parallel and distributed programs", EUROMICRO Conference, Los Alamitos, CA, USA, IEEE Computer Society, pp. 291, 1997. Abstracteuromicro97.pdfWebsite

To achieve a certain degree of confidence that a given program follows its specification, a testing phase must be included in the program development process, and also a complementary debugging phase to help locating the program's bugs. This paper presents an environment which results of the composition and integration of two basic tools: STEPS (Structural TEsting of Parallel Software), which is a testing tool, and DDBG (Distributed DeBuGger), which is a debugging tool. The two tools are presented individually as stand-alone tools, and we describe how they were combined through the use of another intermediate tool: DEIPA (Deterministic re-Execution and Interactive Program Analysis). We claim that the result achieved is a very effective testing and debugging environment.

1996
Cunha, J. C., J. M. Lourenço, and T. Antão, "A Distributed Debugging Tool for a Parallel Software Engineering Environment", Proceedings of the 1st European Parallel Tools Meeting (EPTM'96), Paris, France, ONERA (French National Establishment for Aerospace Research), October, 1996. Abstracteptm96.pdf

We discuss issues in the design and implementation of a flexible debugging tool and its integration into a parallel software engineering environment.