A Comparison Study of Eleven Static Heuristics for Mapping a Class of Independent Tasks onto Ileterogeneous Distributed Computing Systems

ABSTRACT Il\u27lixed-machine heterogeneous computing (HC) environments utilize a distributed suite of different high-performance machines, interconnected with high-speed links to perform different computationally intensive applications that have diverse comput ational requirements. HC environments are well suited to meet thl: computational dell-tands of large, diverse groups of tasks. The problem of mapping (defined as matching and scheduling) these tasks onto the machines of a distributed HC environment has been shown, in general, to be NP-complete, requiring the development of heuristic techniques. Selecting the best heuristic to use in a given enviroi~menth, owever, remains a difficult problem, because comparisons are often clouded by different underlying assumptions in the original studies of each heuristic. There~fore; a collection of eleven heuristics from the literature has been selected: a,dapted, in~plementeda, nd anaiyzed under one set of common assumptions. It is assumed that the heuristics derive a, mapping statically (i.e., off-line). It is also assumed that a meta-task (i.e., a set of independent, non-communicating tasks) is being mapped, and that the goal is to minimize the total execution time of the metla-task. The eleven heuristics examined are Opportunistic Load Balancing, Minimum Execution Time, MininLlum Clompletion Time, Min-min, hllax-min, Duplex? Genetic i-Ilgorithm, Simulated Annealing, Genetic Simulat.ed .Annealing, Tabu, and Ax. This study provides one even basis for comparisor] and insights into circumstances where one technique will out perform another. The evaluation procedure is specified, the heuristics are defined, and then comparison results are discussed. It is shown that for the ca.ses studied here, the relat,ively simple Min-min heuristic performs well in comparison to the other techniques

Sex- and Diet-Specific Changes of Imprinted Gene Expression and DNA Methylation in Mouse Placenta under a High-Fat Diet

Changes in imprinted gene dosage in the placenta may compromise the prenatal control of nutritional resources. Indeed monoallelic behaviour and sensitivity to changes in regional epigenetic state render imprinted genes both vulnerable and adaptable

Adaptive Utility Based Scheduling

This work proposes a new general-purpose framework for adaptive scheduling of entities that interact in an environment. The framework developed was employed for scheduling packets in a packet switching network (PSN) and focuses on determining the order in which packets should be forwarded from a queue based on the everchanging state of the network. A scheduling system has to constantly adapt to various network states (the changing network parameters) in order to achieve maximum policy compliance. The framework presented in this paper attempts to maximize policy compliance while minimizing overhead, implementation difficulty, and computational complexity. The utility assessment of forwarding a packet in a network and the quantification of its impact, on the overall policy compliance of the network is very difficult to achieve. The problem of relevant utility assignment with minimal computational complexity is achieved using a well-known utility assignment technique in operational research, Multi Attribute Utility Theory (MAUT). Adaptability to various network states is achieved by a state aware neural network, which helps in relevant utility assignment for a given state of the network

Evaluation of Heuristics in a Distributed Data Staging Network

Providing up-to-date input to users\u27 applications is an important data management problem for a distributed computing environment, where each data storage location and intermediate node may have specific data available, storage limitations, and communication links available. Sites in the network request data items and each request has an associated deadline and priority. In a military situation, the data staging problem involves positioning data for facilitating a faster access time when it is needed by programs that will aid in decision making. This work concentrates on solving a basic version of the data staging problem in which all parameter values for the communication system and the data request information represent the best known information collected so far and stay fixed throughout the scheduling process. The network is assumed to be oversubscribed and not all requests for data items can be satisfied. A mathematical model for the basic data staging problem is reviewed. Then, three multiple-source shortest-path algorithm based procedures for finding a near-optimal schedule of the communication steps for staging the data are described. Each procedure can be used with each of seven cost criteria developed. A subset of the 21 possible resulting heuristics that are expected to perform well (based on earlier experiments) are evaluated in simulation studies considering different priority weightings schemes, different average number of links used to satisfy each data request, and different network loadings. Finally, an approach considering data items with more desirable and less desirable available versions is evaluated using a variable time, variable accuracy algorithm, and simulation results are presented. The proposed heuristics are shown to perform well with respect to upper and lower bounds. Furthermore, the heuristics using a complex cost criterion allow more highest priority messages to be received than a simple-cost-based heuristic that schedules all highest priority messages first

Background Compensation and an Active-Camera Motion Tracking Algorithm

Abstract Introduction Motion tracking refers to a method of following a moving object and determining the exact location of the object relative to the observer at any given instant. There are several methods for performing motion trackihg. The simplest is to use a static camera. In this approach, the observer (camera) is held stationary and each frame is subtracted from the next frame. In this manner, information about the objects that are moving can be extracted. The simplicity of this algorithm prevents the system from tracking objects once they move outside the field of view of the camera. The advantage of such a tracking system is that high frame rates can be achieved without using special-purpose hardware. Another method, active motion tracking, involves using a camera mounted on a moving platform. Images from the camera are processed and the camera is then repositioned to keep the target in the center of the field of view. Tracking objects using an active camera necessitates high-speed processing so that fast moving targets can be tracked. In an attempt to study the effects of data layout, mode of parallelism, and machine size on computation and communication times, parallel implementations of an existing serial motion tracking algorithm were executed on three parallel machines: the PASM prototype [ 131, the MasPar MP-1 [ l l ] , and the Intel Paragon XP/S [l]. A distinguishing feature of this application study is that the portion of each image frame that is relevant changes from one frame to the next based on the camera motion. This impacts the effect of the chosen data layout on the needed inter-processor data transfers and the way in which work is distributed among the processors. In Section 2, background information, definitions, and related work associated with motion tracking are presented. An overview of the serial algorithm appears in Section 3. Section 4 contains implementation details of the background compensation portion of the tracking algorithm. This computationally intensive section of the overall algorithm was the focus of this study. Edge detection is examined in Section 5 so that the entire algorithm can be analyzed for each machine. In Section 6, results are compared and summarized from the three machines used in this study. Motion Tracking 2.1 Background Information There are two classifications into which a number of the present methods of motion tracking fall: recognition-based and motion-based [lo]. In recognition-based motion tracking, the object being tracked is first recognized and then the position of the object is determined. This allows tracking to be done in three dimensions and also allows the estimation of rotation and translation of the object. A limitation of this method is that it can only be used to track recognizable objects. Furthermore, recognition is a computationally complex task and, hence, the overall speed of the algorithm is reduced compared to motion-based tracking. Motion-based tracking is a less computationally complex alternative. In motion-based tracking systems, the object being tracked does not need to be recognized. Instead, motion within a frame is detected using a temporal derivative of the images to find areas of motion. If the sampling rate is high, the derivative can be approximated by a simple difference operation between successive frames followed by a thresholding operation. If it is assumed that motion is uniform within discrete objects, then only the edges of objects are important. Tracking only edges, rather than entire objects, decreases the computational burden, if finding the edges of objects i

Electrical and Electronic Engineers and the Association for Computing Machinery established the Joint Task Force on

Computing Curricula 2001 (CC2001) to undertake a major review of curriculum guidelines for undergraduate programs in computing. A separate task force was created to focus specifically on Computer Engineering (CPE) and develop a separate CPE volume for the CC2001 report. Computer engineering focuses on the design of computer components and computer-based systems, integrating hardware and software to produce systems that solve realworld problems. With this in mind, the CPE volume includes an outline of the body of knowledge appropriate for undergraduate study in CPE. This paper discusses the Computer Architecture and Organization (CAO) body of knowledge defined in the CPE volume, including a discussion of which CAO topics were selected as "core", i.e. to be included in every CPE program, vs. "elective", to be included or excluded according to individual program objectives