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  • Efficient OpenMP over sequentially consistent distributed shared memory systems  Open access

     Costa Prats, Juan Jose
    Department of Computer Architecture, Universitat Politècnica de Catalunya
    Theses

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    Nowadays clusters are one of the most used platforms in High Performance Computing and most programmers use the Message Passing Interface (MPI) library to program their applications in these distributed platforms getting their maximum performance, although it is a complex task. On the other side, OpenMP has been established as the de facto standard to program applications on shared memory platforms because it is easy to use and obtains good performance without too much effort. So, could it be possible to join both worlds? Could programmers use the easiness of OpenMP in distributed platforms? A lot of researchers think so. And one of the developed ideas is the distributed shared memory (DSM), a software layer on top of a distributed platform giving an abstract shared memory view to the applications. Even though it seems a good solution it also has some inconveniences. The memory coherence between the nodes in the platform is difficult to maintain (complex management, scalability issues, high overhead and others) and the latency of the remote-memory accesses which can be orders of magnitude greater than on a shared bus due to the interconnection network. Therefore this research improves the performance of OpenMP applications being executed on distributed memory platforms using a DSM with sequential consistency evaluating thoroughly the results from the NAS parallel benchmarks. The vast majority of designed DSMs use a relaxed consistency model because it avoids some major problems in the area. In contrast, we use a sequential consistency model because we think that showing these potential problems that otherwise are hidden may allow the finding of some solutions and, therefore, apply them to both models. The main idea behind this work is that both runtimes, the OpenMP and the DSM layer, should cooperate to achieve good performance, otherwise they interfere one each other trashing the final performance of applications. We develop three different contributions to improve the performance of these applications: (a) a technique to avoid false sharing at runtime, (b) a technique to mimic the MPI behaviour, where produced data is forwarded to their consumers and, finally, (c) a mechanism to avoid the network congestion due to the DSM coherence messages. The NAS Parallel Benchmarks are used to test the contributions. The results of this work shows that the false-sharing problem is a relative problem depending on each application. Another result is the importance to move the data flow outside of the critical path and to use techniques that forwards data as early as possible, similar to MPI, benefits the final application performance. Additionally, this data movement is usually concentrated at single points and affects the application performance due to the limited bandwidth of the network. Therefore it is necessary to provide mechanisms that allows the distribution of this data through the computation time using an otherwise idle network. Finally, results shows that the proposed contributions improve the performance of OpenMP applications on this kind of environments.

  • Transient congestion avoidance in software distributed shared memory systems

     Costa Prats, Juan Jose; Cortes Rossello, Antonio; Martorell Bofill, Xavier; Bueno Hedo, Javier; Ayguade Parra, Eduard
    International Conference on Parallel and Distributed Computing, Applications and Technologies
    p. 357-364
    DOI: 10.1109/PDCAT.2010.32
    Presentation's date: 2010-12
    Presentation of work at congresses

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  • Reducing data access latency in SDSM systems using runtime optimizations

     Bueno Hedo, Javier; Martorell Bofill, Xavier; Costa Prats, Juan Jose; Cortes Rossello, Antonio; Ayguade Parra, Eduard; Zhang, Guansong; Barton, Christopher; Silvera, Raul
    Conference of the Center for Advanced Studies on Collaborative Research (CASCON)
    p. 160-173
    DOI: 10.1145/1923947.1923965
    Presentation's date: 2010-11-01
    Presentation of work at congresses

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  • Validación de conceptos adquiridos en una asignatura de proyecto: experiencia en ProSO

     Becerra Fontal, Yolanda; Corbalan Gonzalez, Julita; Costa Prats, Juan Jose; Gil Gómez, Maria Luisa; Guitart Fernández, Jordi
    Jornades de Docència del Departament d'Arquitectura de Computadors
    Presentation's date: 2010-02-11
    Presentation of work at congresses

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  • MPEXPAR: MODELS DE PROGRAMACIO I ENTORNS D'EXECUCIO PARAL·LELS

     Nou Castell, Ramon; Becerra Fontal, Yolanda; Gonzalez Tallada, Marc; Tejedor Saavedra, Enric; Herrero Zaragoza, José Ramón; Navarro Mas, Nacho; Gil Gómez, Maria Luisa; Carrera Perez, David; Farreras Esclusa, Montserrat; Costa Prats, Juan Jose; Corbalan Gonzalez, Julita; Cortes Rossello, Antonio; Badia Sala, Rosa Maria; Torres Viñals, Jordi; Martorell Bofill, Xavier; Guitart Fernández, Jordi; Sirvent Pardell, Raül; Labarta Mancho, Jesus Jose; Alonso López, Javier; Ayguade Parra, Eduard
    Competitive project

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  • Measuring TCP bandwidth on top of a Gigabit and Myrinet network

     Costa Prats, Juan Jose; Bueno Hedo, Javier; Martorell Bofill, Xavier; Cortes Rossello, Antonio
    Date: 2009
    Report

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  • Overlapping communication with computation on NAS BT benchmark

     Costa Prats, Juan Jose; Bueno Hedo, Javier; Cortes Rossello, Antonio; Martorell Bofill, Xavier; Ayguade Parra, Eduard
    Advanced Computer Architecture and Compilation for Embedded Systems
    p. 55-58
    Presentation's date: 2009-07
    Presentation of work at congresses

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  • Experiencia e-Learning en una Asignatura de Proyecto

     Chacin Martinez, Pablo Jesus; Corbalan Gonzalez, Julita; Costa Prats, Juan Jose; Gil Gómez, Maria Luisa; Guitart Fernández, Jordi; Llorente Viejo, Silvia
    Congreso Nacional de Informática Educativa - Simposio Nacional de Tecnologías de la Información y las Comunicaciones en la Educación
    p. 189-196
    Presentation's date: 2007-09-11
    Presentation of work at congresses

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  • Improving Data Locality in NAS BT Benchmark

     Vaquero, Jordi; Gonzalez Tallada, Marc; Costa Prats, Juan Jose; Javier, Bueno; Martorell Bofill, Xavier; Cortes Rossello, Antonio; Ayguade Parra, Eduard
    Third International Summer School on Advanced Computer Architecture and Compilation for Embedded Systems (ACACES 2007)
    p. 199-202
    Presentation's date: 2007-07
    Presentation of work at congresses

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  • A proposal for error handling in OpenMP

     Duran González, Alejandro; Ferrer, Roger; Costa Prats, Juan Jose; Gonzalez Tallada, Marc; Martorell Bofill, Xavier; Ayguade Parra, Eduard; Labarta Mancho, Jesus Jose
    International journal of parallel programming
    Vol. 35, num. 4, p. 393-416
    Date of publication: 2007-08
    Journal article

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  • A Proposal for Error Handling in OpenMP

     Duran González, Alejandro; Ferrer, Roger; Costa Prats, Juan Jose; Gonzalez Tallada, Marc; Martorell Bofill, Xavier; Ayguade Parra, Eduard; Labarta Mancho, Jesus Jose
    International Workshops, IWOMP 2005 and IWOMP 2006. OpenMP Shared Memory Parallel Programming
    p. 422-434
    Presentation of work at congresses

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  • A proposal for error handling in OpenMP

     Duran González, Alejandro; Ferrer, Roger; Costa Prats, Juan Jose; Gonzalez Tallada, Marc; Martorell Bofill, Xavier; Ayguade Parra, Eduard; Labarta Mancho, Jesus Jose
    2nd International Workshop on OpenMP (IWOMP 2006)
    p. 1
    Presentation of work at congresses

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  • Running OpenMP application efficiently on an everything-shared SDSM

     Costa Prats, Juan Jose; Cortes Rossello, Antonio; Martorell Bofill, Xavier; Ayguade Parra, Eduard; Labarta Mancho, Jesus Jose
    Journal of parallel and distributed computing
    Vol. 66, num. 5, p. 647-658
    Date of publication: 2006-05
    Journal article

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  • A Proposal for Error Handling in OpenMP

     Duran González, Alejandro; Ferrer, Roger; Costa Prats, Juan Jose; Gonzalez Tallada, Marc; Martorell Bofill, Xavier; Ayguade Parra, Eduard; Labarta Mancho, Jesus Jose
    Lecture notes in computer science
    Vol. 4315, num. 1, p. 422-434
    Date of publication: 2006-06
    Journal article

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  • Running OpenMp applications efficiently on an everything-shared SDSM

     Costa Prats, Juan Jose; Cortes Rossello, Antonio; Martorell Bofill, Xavier; Ayguade Parra, Eduard; Labarta Mancho, Jesus Jose
    IEEE International Parallel and Distributed Processing Symposium
    p. 35
    Presentation's date: 2004-04
    Presentation of work at congresses

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