2816777
Compiler-Directed Dynamic Frequency and Voltage Scheduling
Dynamic voltage and frequency scaling has been identified as one of the most effective ways to reduce power dissipation. This paper discusses a compilation strategy that identifies opportunities for dynamic voltage and frequency scaling of the CPU without significant increase in overall program execution time. The paper introduces a simple, yet effective performance model to determine an efficient CPU slowdown factor for memory bound loop computations. Simulation results of a superscalar target architecture and a program kernel compiled at different optimizations levels show the potential benefit of the proposed compiler optimization. The energy savings are reported for a hypothetical target machine with power dissipation characteristics similar to Transmeta's Crusoe TM5400 processor.
6774277
The design, implementation, and evaluation of a compiler algorithm for CPU energy reduction
This paper presents the design and implementation of a compiler algorithm that effectively optimizes programs for energy usage using dynamic voltage scaling (DVS). The algorithm identifies program regions where the CPU can be slowed down with negligible performance loss. It is implemented as a source-to-source level transformation using the SUIF2 compiler infrastructure. Physical measurements on a high-performance laptop show that total system (i.e., laptop) energy savings of up to 28% can be achieved with performance degradation of less than 5% for the SPECfp95 benchmarks. On average, the system energy and energy-delay product are reduced by 11% and 9%, respectively, with a performance slowdown of 2%. It was also discovered that the energy usage of the programs using our DVS algorithm is within 6% from the theoretical lower bound. To the best of our knowledge, this is one of the first work that evaluates DVS algorithms by physical measurements.
1883138
A Knowledge-Based Approach for Retrieving Images by Content
A knowledge based approach is introduced for retrieving images by content. It supports the answering of conceptual image queries involving similar-to predicates, spatial semantic operators, and references to conceptual terms. Interested objects in the images are represented by contours segmented from images. Image content such as shapes and spatial relationships are derived from object contours according to domain specific image knowledge. A three layered model is proposed for integrating image representations, extracted image features, and image semantics. With such a model, images can be retrieved based on the features and content specified in the queries. The knowledge based query processing is based on a query relaxation technique. The image features are classified by an automatic clustering algorithm and represented by Type Abstraction Hierarchies (TAHs) for knowledge based query processing. Since the features selected for TAH generation are based on context and user profile, and the TAHs can be generated automatically by a clustering algorithm from the feature database, our proposed image retrieval approach is scalable and context sensitive. The performance of the proposed knowledge based query processing is also discussed.
41295780
On deflection routing in optical burst-switched networks
This paper investigates the performance of deflection routing in optical burst-switched networks adopting Just-Enough-Time (JET) signaling mechanism. In general, buffer requirement is not vital for JET-based optical burst switching (OBS). However, if deflection routing is enabled, optical buffers are indispensable to prevent data bursts from overtaking associated control packets. Another solution, which can alleviate buffering, is to lengthen offset time in the beginning. As previous work indicated, a burst with extra offset time has higher priority than that without extra offset time and quality-of-service (QoS) can be accomplished in this way. In this paper, we consider the performance of deflection routing in both non-prioritized and prioritized JET-based optical burst-switched networks. For each case, a variant of priority queuing model is proposed to approximate burst loss probability respectively and the results show that the model provides an accurate estimation. We also evaluate the performance of deflection routing with and without QoS support in arpanet-2 topology.
5458216
Multicast traffic scheduling in single-hop WDM networks with arbitrary tuning latencies
To accommodate the demands of quality of service (QoS) and multicast applications, a multicast QoS traffic-scheduling algorithm with tuning latency consideration in wavelength-division multiplexing star-coupled networks is provided in this paper. To furnish different levels of QoS, two classes of traffic are considered: constant bit rate and available bit rate (ABR). An effective bandwidth-normalization scheme for ABR traffic is also derived. We define the slot scanning problem in the connection-setup process as the maximum assignable slots (MAS) problem. We prove that the optimal solution of the MAS problem can be obtained in polynomial time. Owing to its high-order time complexity, we also propose two heuristics for the MAS problem. The performance of these strategies are evaluated and compared by simulations under different system parameters, such as number of wavelengths, traffic load, and tuning latency.