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Publications

Publications by CSE

2017

On scaling dynamic programming problems with a multithreaded tabling, Prolog system

Authors
Areias, M; Rocha, R;

Publication
JOURNAL OF SYSTEMS AND SOFTWARE

Abstract
Tabling is a powerful implementation technique that improves the declarativeness and expressiveness of traditional Prolog systems in dealing with recursion and redundant computations. It can be viewed as a natural tool to implement dynamic programming problems, where a general recursive strategy divides a problem in simple sub-problems that are often the same. When tabling is combined with multithreading, we have the best of both worlds, since we can exploit the combination of higher declarative semantics with higher procedural control. However, at the engine level, such combination for dynamic programming problems is very difficult to exploit in order to achieve execution scalability as we increase the number of running threads. In this work, we focus on two well-known dynamic programming problems, the Knapsack and the Longest Common Subsequence problems, and we discuss how we were able to scale their execution by using the multithreaded tabling engine of the Yap Prolog system. To the best of our knowledge, this is the first work showing a Prolog system to be able to scale the execution of multithreaded dynamic programming problems. Our experiments also show that our system can achieve comparable or even better speedup results than other parallel implementations of the same problems.

2017

Generation of Customized Accelerators for Loop Pipelining of Binary Instruction Traces

Authors
Paulino, NMC; Ferreira, JC; Cardoso, JMP;

Publication
IEEE TRANSACTIONS ON VERY LARGE SCALE INTEGRATION (VLSI) SYSTEMS

Abstract
Many embedded applications process large amounts of data using regular computational kernels, amenable to acceleration by specialized hardware coprocessors. To reduce the significant design effort, the dedicated hardware may be automatically generated, usually starting from the application's source or binary code. This paper presents a moduloscheduled loop accelerator capable of executing multiple loops and a supporting toolchain. A generation/scheduling procedure, which fully relies on MicroBlaze instruction traces, produces accelerator instances, customized in terms of functional units and interconnections. The accelerators support integer and single-precision floating-point arithmetic, and exploit instruction-level parallelism, loop pipelining, and memory access parallelism via two read/write ports. A complete implementation of the proposed architecture is evaluated in a Virtex-7 device. Augmenting a MicroBlaze processor with a tailored accelerator achieves a geometric mean speedup, over software-only execution, of 6.61x for 13 floating-point kernels from the Livermore Loops set, and of 4.08x for 11 integer kernels from Texas Instruments' IMGLIB. The proposed customized accelerators are compared with ALU-based ones. The average specialized accelerator requires only 0.47x the number of field-programmable gate array slices of an accelerator with four ALUs. A geometric mean speedup of 1.78x over a four-issue very long instruction word (without floating-point support) was obtained for the integer kernels.

2017

Context-aware HDR video distribution for mobile devices

Authors
Melo, M; Barbosa, L; Bessa, M; Debattista, K; Chalmers, A;

Publication
MULTIMEDIA TOOLS AND APPLICATIONS

Abstract
HDR video on mobile devices is in its infancy and there are no solutions yet that can achieve full HDR video reproduction due to computational power limitations. In this paper we present a novel and versatile solution that allows the delivery of HDR video on mobile devices by taking into account contextual information and retro-compatibility for devices that do not have the computational power to decode HDR video. The proposed solution also enables the remote transmission of HDR video to mobile devices in real-time. This context-aware HDR video distribution solution for mobile devices is evaluated and discussed by considering the impact of HDR videos over conventional low dynamic range videos on mobile devices as well as the challenge of playing HDR videos directly locally or remotely.

2017

DDFlasks: Deduplicated Very Large Scale Data Store

Authors
Maia, F; Paulo, J; Coelho, F; Neves, F; Pereira, J; Oliveira, R;

Publication
Distributed Applications and Interoperable Systems - 17th IFIP WG 6.1 International Conference, DAIS 2017, Held as Part of the 12th International Federated Conference on Distributed Computing Techniques, DisCoTec 2017, Neuchâtel, Switzerland, June 19-22, 2017, Proceedings

Abstract
With the increasing number of connected devices, it becomes essential to find novel data management solutions that can leverage their computational and storage capabilities. However, developing very large scale data management systems requires tackling a number of interesting distributed systems challenges, namely continuous failures and high levels of node churn. In this context, epidemic-based protocols proved suitable and effective and have been successfully used to build DataFlasks, an epidemic data store for massive scale systems. Ensuring resiliency in this data store comes with a significant cost in storage resources and network bandwidth consumption. Deduplication has proven to be an efficient technique to reduce both costs but, applying it to a large-scale distributed storage system is not a trivial task. In fact, achieving significant space-savings without compromising the resiliency and decentralized design of these storage systems is a relevant research challenge. In this paper, we extend DataFlasks with deduplication to design DDFlasks. This system is evaluated in a real world scenario using Wikipedia snapshots, and the results are twofold. We show that deduplication is able to decrease storage consumption up to 63% and decrease network bandwidth consumption by up to 20%, while maintaining a fullydecentralized and resilient design. © IFIP International Federation for Information Processing 2017.

2017

A multisensory virtual experience model for thematic tourism: A Port wine tourism application proposal

Authors
Martins, J; Goncalves, R; Branco, F; Barbosa, L; Melo, M; Bessa, M;

Publication
JOURNAL OF DESTINATION MARKETING & MANAGEMENT

Abstract
Technological evolution has led to a significant transformation in tourism organizations, particularly in those who focus their activities on particular themes or segments, such as wine tourism. This can be transposed to Portuguese wine tourism organizations because the majority lack the necessary information and communication technologies (and inherent technologies) to become globally competitive. As highlighted in the literature, for a tourism experience to become memorable it must be emotional and immersive in such a way that the tourist becomes fully involved with the existing surroundings. This leads to the notion of using virtual reality experiences as triggers for the development of wine tourism. Considering the relevance of Portugal's Douro Valley to the country's wine tourism segment, a theoretical model that supports the implementation of multisensory (hence more immersive) virtual wine tourism experiences is developed. While considering the international success of Port wine tourism, this paper also presents a conceptualization of a multisensory virtual Port wine experience that includes a conceptual perspective and a technological solution proposal.

2017

Enriching Mental Health Mobile Assessment and Intervention with Situation Awareness

Authors
Teles, AS; Rocha, A; da Silva e Silva, FJDE; Lopes, JC; O'Sullivan, D; Van de Ven, P; Endler, M;

Publication
SENSORS

Abstract
Current mobile devices allow the execution of sophisticated applications with the capacity for identifying the user situation, which can be helpful in treatments of mental disorders. In this paper, we present SituMan, a solution that provides situation awareness to MoodBuster, an ecological momentary assessment and intervention mobile application used to request self-assessments from patients in depression treatments. SituMan has a fuzzy inference engine to identify patient situations using context data gathered from the sensors embedded in mobile devices. Situations are specified jointly by the patient and mental health professional, and they can represent the patient's daily routine (e.g., "studying", "at work", "working out"). MoodBuster requests mental status self-assessments from patients at adequate moments using situation awareness. In addition, SituMan saves and displays patient situations in a summary, delivering them for consultation by mental health professionals. A first experimental evaluation was performed to assess the user satisfaction with the approaches to define and identify situations. This experiment showed that SituMan was well evaluated in both criteria. A second experiment was performed to assess the accuracy of the fuzzy engine to infer situations. Results from the second experiment showed that the fuzzy inference engine has a good accuracy to identify situations.

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