1362947
Optimal Replication of Series-Parallel Graphs for Computation-Intensive Applications
Abstract We consider the replication problem of series-parallel (SP) task graphs where each task may run on more than one processor. The objective of the problem is to minimize the total cost of task execution and interprocessor communication. We call it the minimum cost replication problem for SP graphs (MCRP-SP). In this paper, we adopt a new communication model where the purpose of replication is to reduce the total cost. The class of applications we consider is computation-intensive applications in which the execution cost of a task is greater than its communication cost. The complexity of MCRP-SP for such applications is proved to be NP-complete. We present a branch-and-bound method to find an optimal solution as well as an approximation approach for a suboptimal solution. The numerical results show that such replication may lead to a lower cost than the optimal assignment problem (in which each task is assigned to only one processor) does. The proposed optimal solution has complexity O ( n 2 2 n M ), while the approximation solution has O ( n 4 M 2 ), where n is the number of processors in the system and M is the number of tasks in the graph.
14292166
A self-adjusting quality of service control scheme
We propose and analyze a self-adjusting Quality of Service (QoS) control scheme with the goal of optimizing the system reward as a result of servicing different priority clients with varying workload, QoS and reward/penalty requirements. Our scheme is based on resource partitioning and designated "degrade QoS areas" such that system resources are partitioned into priority areas each of which is reserved specifically to serve only clients in a corresponding class with no QoS degradation, plus one "degraded QoS area" into which all clients can be admitted with QoS adjustment being applied only to the lowest priority clients. We show that the best partition is dictated by the workload and the reward/penalty characteristics of clients in difference priority classes. The analysis results can be used by a QoS manager to optimize the system total rewawrd dynamically in response to changing workloads at run time. We demonstrate the validity of our scheme by means of simulation and comparing the proposed QoS self-adjusting scheme with those that do not use resource partitioning or designated degraded QoS area.
30645069
Backtrack Routing and Priority-Based Wavelength Assignment in WDM Networks
In this paper, we consider two key problems in the WDM networks: the wavelengh assignment and routing problems. The objective of the problems is to minimize the request blocking rate. We propose two priority-based methods for the wavelength assignment problem: static and dynamic strategies. Based on the priority of an incoming request, the proposed methods allocate a wavelength among the available wavelengths for the given priority. Analytic models and simulations are presented for the proposed wavelength assignment methods so as to analyse the link blocking rate. The simulation results show that the link blocking rate by the dynamic strategy is less than that by the assignment strategy. We also develop a routing algorithm that works together with the proposed wavelength assignment methods to reduce the overall blocking rates. The proposed routing method maintains a routing tree for a given connection request. Based on the routing tree, the algorithm finds a route with one available wavelength for each link along the route. We compare the proposed routing method with the fixed routing and fixed alternate routing algorithms. The experiments show that the proposed routing algorithm performs better than the fixed routing and the alternate routing methods.
6666618
Low-Power Design for Real-Time Systems
Real-time Systems often are located in the special environments where the power consumption is a big concern. Upon presence of timing constraints, the low power design on the real-time systems has significant impact on the performance as well as the schedulability of the systems. The system developers are facing the challenges for reducing the power consumption and meeting the timing constraints in the real-time systems.This paper represents one of few attempts to address the issue of the low power design on real-time systems. We present two power reduction methods: one is at the software compilation level and the other at the operating system level. Given a real-time program, an inter-instruction power reduction technique is proposed to transform the program to another one with lower power consumption. In addition, a scheduling algorithm for real-time operating systems is proposed to reschedule real-time programs when the execution time of the programs is changed. Therefore, the proposed scheduling algorithm works together with the proposed power reduction technique to make sure all programs meet their deadlines and to improve the system schedulability. We also evaluate the performance of the proposed inter-instruction reduction method by comparing it with the cold scheduling algorithm and show that the proposed method outperforms the cold scheduling algorithm and reduces more energy power.
10474032
Dynamic quota-based admission control with sub-rating in multimedia servers
Abstract. An admission control algorithm for a multimedia server is responsible for determining if a new request can be accepted without violating the Quality of Service (QoS) requirements of the existing requests in the system. A novel quota-based admission control algorithm with sub-rating for two priority classes of requests is proposed in this study. The server capacity is divided into three partitions based on the quota values: one for each class of requests and one common pool shared by two classes of requests. Reward and penalty are adopted in the proposed system model. High-priority requests are associated with higher values of reward as well as penalty than low-priority ones. Given the characteristics of the system workload, the proposed algorithm finds the best partitions, optimizing the system performance based on the objective function of the total reward minus the total penalty. The sub-rating mechanism will reduce the QoS requirements of several low- priority clients, by cutting out a small fraction of the assigned server capacity, to accept a new high- priority client and to achieve a higher net earning value. A stochastic Petri-Net model is used to find the optimal quota values and two approximation approaches are developed to find sub-optimal settings. The experiment results show that the proposed algorithm performs better than one without sub-rating mechanism, and that the sub-optimal solutions found by the proposed approximation approaches are very close to optimal ones. The approximation approaches enable the algorithm to dynamically adjust the quota values, based on the characteristics of the system workload, to achieve higher system performance.
574471
Allocation and scheduling of real-time periodic tasks with relative timing constraints
Allocation problem has always been one of the fundamental issues of building the applications in real-time computing systems. For real-time applications, the allocation problem should directly address the issues of task and communication scheduling. In this context, the allocation of tasks has to fully utilize the available processors and the scheduling of tasks has to meet the specified timing constraints. Clearly, the execution of tasks under the allocation and schedule has to satisfy the precedence, resources, and other synchronization constraints among them. Recently, the timing requirements of the real-time systems emerge that the relative timing constraints are imposed on the consecutive executions of each task and the inter-task temporal relationships are specified across task periods. In this paper we consider the allocation and scheduling problem of the periodic tasks with such timing requirements. Given a set of periodic tasks, we consider the least common multiple (LCM) of the task periods. Each task is extended to several instances within the LCM. The scheduling window for each task instance is derived to satisfy the timing constraints. We develop a simulated annealing algorithm as the overall control algorithm. An example problem of the sanitized version of the Boeing 777 Aircraft Information Management System is solved by the algorithm. Experimental results show that the algorithm solves the problem in a reasonable time complexity.
1009077
An architecture for coordinating multiple self-management systems
A common approach to adding self-management capabilities to a system is to provide one or more external control modules, whose responsibility is to monitor system behavior, and adapt the system at run time to achieve various goals (configure the system, improve performance, recover from faults, etc.). An important problem arises when there is more than one such self-management module: how can one make sure that they are composed to provide consistent and complementary benefits? In this paper we describe a solution that introduces a self-management coordination architecture and infrastructure to support such composition. We focus on the problem of coordinating self-configuring and self-healing capabilities, particularly with respect to global configuration and incremental repair. We illustrate the approach in the context of a self-managing video teleconference system that composes two preexisting adaptation modules to achieve synergistic benefits of both.
7789266
LMT-skeleton heuristics for several new classes of optimal triangulations
Abstract Given a planar point set, we consider three classes of optimal triangulations: (1) the minimum weight triangulation with angular constraints (constraints on the minimum angle and the maximum angle in a triangulation), (2) the angular balanced triangulation which minimizes the sum of the ratios of the maximum angle to the minimum angle for each triangle, and (3) the area balanced triangulation which minimizes the variance of the areas of triangles in the triangulation. With appropriate definition of local optimality for each class, a simple unified method is established for the computation of the subgraphs of optimal triangulations. Computational experiments demonstrate that the method successfully identifies large portion of edges of the optimal triangulations of each class for all problem instances tested, and hence optimal triangulations for each class can be obtained from them by applying dynamic programming.
15323037
Successive refinement for the Wyner-Ziv problem and layered code design
We examine successive refinement for the Wyner-Ziv problem described in a recent paper by Steinberg and Merhav, where the authors showed that if the side information for all stages is identical, then the jointly Gaussian source with squared error distortion measure is successively refinable. We first extend this result to the case where the difference between the source and the side information is Gaussian and independent of the side information. As a byproduct, we give an alternative proof that the Wyner-Ziv problem for these sources has no rate loss-a result that was recently shown by Pradhan et al. through invoking the duality between the Gaussian Wyner-Ziv problem and the Costa problem. We then perform layered Wyner-Ziv code design for this general type of source based on nested scalar quantization, bit-plane coding, and low-density parity check (LDPC) code-based Slepian-Wolf coding (source coding with side information). We show that density evolution can be used to analyze the Slepian-Wolf code performance, provided that certain symmetry conditions, which have been dubbed dual symmetry, are satisfied by the hypothetical channel between the source and the side information. We also show that the dual symmetry condition is indeed satisfied by the hypothetical channel in our Slepian-Wolf coding setup. This justifies the use of density evolution in our LDPC code-based Slepian-Wolf code design for Wyner-Ziv coding. For the jointly Gaussian source, our layered coder performs 1.29 to 3.45 dB from the Wyner-Ziv bound for rates ranging from 0.47 to 4.68 bits per sample. When the side information is Laplacian and the source equals the side information plus an independent Gaussian noise term, our layered coder performs 1.33 to 3.90 dB from the Wyner-Ziv bound for rates ranging from 0.48 to 4.64 bits per sample.
15145046
A novel approach to diagnose diabetes based on the fractal characteristics of retinal images
A novel diagnostic scheme to develop quantitative indexes of diabetes is introduced in this paper. The fractal dimension of the vascular distribution is estimated because we discovered that the fractal dimension of a severe diabetic patient's retinal vascular distribution appears greater than that of a normal human's. The issue of how to yield an accurate fractal dimension is to use high-quality images. To achieve a better image-processing result, an appropriate image-processing algorithm is adopted in this paper. Another important fractal feature introduced in this paper is the measure of lacunarity, which describes the characteristics of fractals that have the same fractal dimension but different appearances. For those vascular distributions in the same fractal dimension, further classification can be made using the degree of lacunarity. In addition to the image-processing technique, the resolution of original image is also discussed here. In this paper, the influence of the image resolution upon the fractal dimension is explored. We found that a low-resolution image cannot yield an accurate fractal dimension. Therefore, an approach for examining the lower bound of image resolution is also proposed in this paper. As for the classification of diagnosis results, four different approaches are compared to achieve higher accuracy. In this study, the fractal dimension and the measure of lacunarity have shown their significance in the classification of diabetes and are adequate for use as quantitative indexes.
2623430
Manifold reconstruction from point samples
We present an algorithm to "reconstruct" a smooth <i>k</i>-dimensional manifold <i>M</i> embedded in an Euclidean space R<sup>d</sup> from a "sufficiently dense" point sample from the manifold. The algorithm outputs a simplicial manifold that is homeomorphic and geometrically close to <i>M.</i> The running time is <i>O</i>(<i>n</i> log <i>n</i>) where <i>n</i> is the number of points in the sample (the multiplicative constant depends exponentially on the dimension though).