Monthly Archives: May 2015

A Scalable Prescriptive Parallel Debugging Model

A Scalable Prescriptive Parallel Debugging Model

  • Nicklas Bo Jensen, Niklas Quarfot Nielsen, Gregory L. Lee, Sven Karlsson, Matthew LeGendre, Martin Schulz, and Dong H. Ahn. A Scalable Prescriptive Parallel Debugging Model. In Proceedings of IEEE International Parallel and Distributed Processing Symposium, pages 473-483, Hyderabad, India, 2015. doi:10.1109/IPDPS.2015.15
    [BibTeX] [Abstract]

    Debugging is a critical step in the development of any parallel program. However, the traditional interactive debugging model, where users manually step through code and inspect their application, does not scale well even for current supercomputers due its centralized nature. While lightweight debugging models, which have been proposed as an alternative, scale well, they can currently only debug a subset of bug classes. We therefore propose a new model, which we call prescriptive debugging, to fill this gap between these two approaches. This user-guided model allows programmers to express and test their debugging intuition in a way that helps to reduce the error space. Based on this debugging model we introduce a prototype implementation embodying this model, the DySectAPI, allowing programmers to construct probe trees for automatic, event-driven debugging at scale. In this paper we introduce the concepts behind DySectAPI and, using both experimental results and analytical modelling, we show that the DySectAPI implementation can run with a low overhead on current systems. We achieve a logarithmic scaling of the prototype and show predictions that even for a large system the overhead of the prescriptive debugging model will be small.

    @InProceedings{2015-05-JENSEN-1,
    author = {Nicklas Bo Jensen and Niklas Quarfot Nielsen and Gregory L. Lee and Sven Karlsson and Matthew LeGendre and Martin Schulz and Dong H. Ahn},
    title = {{A Scalable Prescriptive Parallel Debugging Model}},
    booktitle = {{Proceedings of IEEE International Parallel and Distributed Processing Symposium}},
    date = {2015-05-25/2015-05-27},
    address = {Hyderabad, India},
    doi = {10.1109/IPDPS.2015.15},
    pages = {473-483},
    abstract = {Debugging is a critical step in the development of any parallel program. However, the traditional interactive debugging model, where users manually step through code and inspect their application, does not scale well even for current supercomputers due its centralized nature. While lightweight debugging models, which have been proposed as an alternative, scale well, they can currently only debug a subset of bug classes. We therefore propose a new model, which we call prescriptive debugging, to fill this gap between these two approaches. This user-guided model allows programmers to express and test their debugging intuition in a way that helps to reduce the error space. Based on this debugging model we introduce a prototype implementation embodying this model, the DySectAPI, allowing programmers to construct probe trees for automatic, event-driven debugging at scale. In this paper we introduce the concepts behind DySectAPI and, using both experimental results and analytical modelling, we show that the DySectAPI implementation can run with a low overhead on current systems. We achieve a logarithmic scaling of the prototype and show predictions that even for a large system the overhead of the prescriptive debugging model will be small.},
    year = {2015}
    }

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Experiences with Compiler Support for Processors with Exposed Pipelines

Experiences with Compiler Support for Processors with Exposed Pipelines

  • Nicklas Bo Jensen, Pascal Schleuniger, Andreas Hindborg, Maxwell Walter, and Sven Karlsson. Experiences with Compiler Support for Processors with Exposed Pipelines. In Proceedings of the 22nd Reconfigurable Architectures Workshop (RAW 2015), pages 137-143, Hyderabad, India, 2015. doi:10.1109/IPDPSW.2015.9
    [BibTeX] [Abstract]

    Field programmable gate arrays, FPGAs, have become an attractive implementation technology for a broad range of computing systems. We recently proposed a processor architecture, Tinuso, which achieves high performance by moving complexity from hardware to the compiler tool chain. This means that the compiler tool chain must handle the increased complexity. However, it is not clear if current production compilers can successfully meet the strict constraints on instruction order and generate efficient object code. In this paper, we present our experiences developing a compiler backend using the GNU Compiler Collection, GCC. For a set of C benchmarks, we show that a Tinuso implementation with our GCC backend reaches a relative speedup of up to 1.73 over a similar Xilinx Micro Blaze configuration while using 30% fewer hardware resources. While our experiences are generally positive, we expose some limitations in GCC that need to be addressed to achieve the full performance potential of Tinuso.

    @InProceedings{2015-05-JENSEN-2,
    author = {Nicklas Bo Jensen and Pascal Schleuniger and Andreas Hindborg and Maxwell Walter and Sven Karlsson},
    title = {{Experiences with Compiler Support for Processors with Exposed Pipelines}},
    booktitle = {{Proceedings of the 22nd Reconfigurable Architectures Workshop (RAW 2015)}},
    date = {2015-05-25},
    address = {Hyderabad, India},
    doi = {10.1109/IPDPSW.2015.9},
    pages = {137-143},
    abstract = {Field programmable gate arrays, FPGAs, have become an attractive implementation technology for a broad range of computing systems. We recently proposed a processor architecture, Tinuso, which achieves high performance by moving complexity from hardware to the compiler tool chain. This means that the compiler tool chain must handle the increased complexity. However, it is not clear if current production compilers can successfully meet the strict constraints on instruction order and generate efficient object code. In this paper, we present our experiences developing a compiler backend using the GNU Compiler Collection, GCC. For a set of C benchmarks, we show that a Tinuso implementation with our GCC backend reaches a relative speedup of up to 1.73 over a similar Xilinx Micro Blaze configuration while using 30% fewer hardware resources. While our experiences are generally positive, we expose some limitations in GCC that need to be addressed to achieve the full performance potential of Tinuso.},
    year = {2015}
    }

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Complexity Analysis of the Pawlak’s Flowgraph Extension for Re-Identification in Multi-Camera Surveillance System

Complexity Analysis of the Pawlak’s Flowgraph Extension for Re-Identification in Multi-Camera Surveillance System

  • Karol Lisowski and Andrzej Czyżewski. Complexity Analysis of the Pawlak’s Flowgraph Extension for Re-Identification in Multi-Camera Surveillance System. Multimedia Tools and Applications, 75(17):10495-10511, 2015. doi:10.1007/s11042-015-2652-z
    [BibTeX] [Abstract]

    The idea of Pawlak’s flowgraph turned out to be a useful and convenient container for a knowledge of objects’ behaviour and movements within the area observed with a multi-camera surveillance system. Utilization of the flowgraph for modelling behaviour admittedly requires certain extensions and enhancements, but it allows for combining many rules into a one data structure and for obtaining parameters describing how objects tend to move through the supervised area. The main aim of this article is presentation of the complexity analysis of proposed modification of flowgraphs. This analysis contains considerations of issues such as memory efficiency and computational complexity of operations on the flowgraph. The measures related to space and time efficiency were also included.

    @Article{2015-05-LISOWSKI,
    author = {Karol Lisowski and Andrzej Czy\.zewski},
    title = {{Complexity Analysis of the Pawlak's Flowgraph Extension for Re-Identification in Multi-Camera Surveillance System}},
    journal = {{Multimedia Tools and Applications}},
    date = {2015-05-26},
    volume = {75},
    number = {17},
    pages = {10495-10511},
    doi = {10.1007/s11042-015-2652-z},
    publisher = {Springer},
    abstract = {The idea of Pawlak's flowgraph turned out to be a useful and convenient container for a knowledge of objects’ behaviour and movements within the area observed with a multi-camera surveillance system. Utilization of the flowgraph for modelling behaviour admittedly requires certain extensions and enhancements, but it allows for combining many rules into a one data structure and for obtaining parameters describing how objects tend to move through the supervised area. The main aim of this article is presentation of the complexity analysis of proposed modification of flowgraphs. This analysis contains considerations of issues such as memory efficiency and computational complexity of operations on the flowgraph. The measures related to space and time efficiency were also included.},
    year = {2015}
    }

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Acoustic Direciton Finding Under High Reverberation

Acoustic Direciton Finding Under High Reverberation

  • Metin Aktas, Toygar Akgün, Duygu Büyükaydin, and Hüseyin Özkan. Acoustic Direciton Finding Under High Reverberation (Yüksek Yankilama Altinda Akustik Yön Bulma). In Proceedings of the 23nd IEEE Signal Processing and Communications Applications Conference (SIU 2015), pages 1533-1536, Inönü University, Malatya, Turkey, 2015. doi:10.1109/SIU.2015.7130138
    [BibTeX] [Abstract]

    One of the major challanges for acoustic source localization is to eliminate the multipath distortions due to the reverberation. In this paper, we propose a novel direction finding method that is robust to multipath distortions. Since we do not make any stochastic and sparseness assumptions regarding the underlying signal source, our method can be applied to a wide range of wideband acoustic signals. In particular, we introduce a novel approach to extract the signal portions that are not distorted with multipath signals and noise. Hence, the DOA estimation can be performed without being affected from the reverberation. Simulation results show that the proposed method reliably estimates the source direction even under the significantly high reverberation conditions.

    @InProceedings{2015-05-AKTAS,
    author = {Metin Aktas and Toygar Akg\"{u}n and Duygu B\"{u}y\"{u}kaydin and H\"{u}seyin \"{O}zkan},
    title = {{Acoustic Direciton Finding Under High Reverberation (Y\"{u}ksek Yankilama Altinda Akustik Y\"{o}n Bulma)}},
    booktitle = {{Proceedings of the 23nd IEEE Signal Processing and Communications Applications Conference (SIU 2015)}},
    date = {2015-05-16/2015-05-19},
    address = {In\"{o}n\"{u} University, Malatya, Turkey},
    doi = {10.1109/SIU.2015.7130138},
    pages = {1533-1536},
    abstract = {One of the major challanges for acoustic source localization is to eliminate the multipath distortions due to the reverberation. In this paper, we propose a novel direction finding method that is robust to multipath distortions. Since we do not make any stochastic and sparseness assumptions regarding the underlying signal source, our method can be applied to a wide range of wideband acoustic signals. In particular, we introduce a novel approach to extract the signal portions that are not distorted with multipath signals and noise. Hence, the DOA estimation can be performed without being affected from the reverberation. Simulation results show that the proposed method reliably estimates the source direction even under the significantly high reverberation conditions.},
    year = {2015}
    }

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Privacy in the era of always-on everywhere cameras

Privacy in the era of always-on everywhere cameras

  • Andrea Cavallaro. Privacy in the era of always-on everywhere cameras. Keynote lecture at Workshop on De-identification for privacy protection in multimedia in IEEE FG, 2015.
    [BibTeX] [Abstract]

    Video capturing devices are everywhere. Most of them are always on. Miniature high-quality cameras are increasingly worn by people, mounted on handlebars, dashboards and micro-drones, omnipresent in hallways, elevators, streets and stores; and in your smartphone. The pervasiveness of cameras in public places is offering incredible opportunities to improve our safety and quality of life, while at the same time posing important societal challenges. Enabling video-based applications and services while protecting privacy is a major interdisciplinary challenge that must be addressed to adapt to increased capabilities of technology and changing demands from citizens. In this talk I will cover multimedia applications that extract information from images, videos and camera networks as well as privacy constraints to be taken into account in the design of video-based systems. I will discuss basic principles and several application examples, and conclude with a set of open research questions.

    @Misc{2015-05-CAVALLARO,
    author = {Andrea Cavallaro},
    title = {{Privacy in the era of always-on everywhere cameras}},
    howpublished = {Keynote lecture at Workshop on De-identification for privacy protection in multimedia in IEEE FG},
    date = {2015-05-04},
    year = {2015},
    address = {Ljubljana, Slovenia},
    abstract = {Video capturing devices are everywhere. Most of them are always on. Miniature high-quality cameras are increasingly worn by people, mounted on handlebars, dashboards and micro-drones, omnipresent in hallways, elevators, streets and stores; and in your smartphone. The pervasiveness of cameras in public places is offering incredible opportunities to improve our safety and quality of life, while at the same time posing important societal challenges. Enabling video-based applications and services while protecting privacy is a major interdisciplinary challenge that must be addressed to adapt to increased capabilities of technology and changing demands from citizens. In this talk I will cover multimedia applications that extract information from images, videos and camera networks as well as privacy constraints to be taken into account in the design of video-based systems. I will discuss basic principles and several application examples, and conclude with a set of open research questions.}
    }

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