A scheduling heuristic for maximizing wirebonder throughput

Process planning and scheduling is an important part of managing the complex dynamic back end (i.e., test, assembly, and packaging) of the semiconductor manufacturing process. One of the most critical toolsets in the back end in terms of manufacturing capacity and product flow is the wirebonders that electrically connect bare silicon die to lead frames via thin metal wires. We develop two approaches for maximizing throughput on a group of wirebonders containing three different wirebonder types. Although our mathematical programming approach is capable of producing a near-optimal wirebonder schedule for any production day of interest, the computational requirements of this approach are unacceptable for implementation in a real-world back-end facility. Therefore, we develop a rule-based heuristic approach for wirebonder scheduling capable of producing high-quality schedules in a much shorter period of time.     

A time-domain physical optics heuristic approach to passiveintermodulation scattering

Passive intermodulation (PIM) is a phenomenon which often arises at junctions between different materials. This may be a major issue in tightly packed antenna farms as those typically present on communication satellites. Here, an heuristic nonlinear extension to the time-domain physical optics (TD-PO) is proposed, to take into account electromagnetic scattering at intermodulated frequencies when such a junction is illuminated by two impinging electromagnetic fields at different frequencies. Simulation results are compared with measures to validate the model     

A heuristic approach to establishing punctuation convention in instant messaging

Instant Messaging (IM) features informal writing styles such as the omission of punctuation. Punctuation plays an important role in representing prosody and facilitating syntactic processing during communication. The discrepancy between the recognized importance and actual inadequate usage of punctuation in IM calls for establishing punctuation convention for more effective online communication. The research uniquely reported here addressed two research questions. The first was whether punctuation had an impact on the effectiveness of IM. The results of an empirical study showed that the majority of surveyed participants perceived punctuation to be somewhat important. This led to the investigation of the second research question: how to restore omitted punctuation in instant messaging to help develop punctuation convention effectively? We designed and implemented a technical solution for recovering punctuation based on heuristics rules and an evaluation of this approach showed satisfactory performance. A detailed analysis of punctuation in archived instant messages revealed several patterns of omitted punctuation. The findings of this research not only advance our understanding of the stylistic convention, but also provide positive evidence for establishing punctuation convention in IM. As IM continues to pervade daily communication, punctuation convention in IM deserves closer attention.     

A heuristic algorithm for lightpath scheduling in next-generation WDM optical networks

We study the routing and wavelength assignment (RWA) problem of scheduled lightpath demands (SLDs) in all-optical wavelength division multiplexing networks with no wavelength conversion capability. We consider the deterministic lightpath scheduling problem in which the whole set of lightpath demands is completely known in advance. The objective is to maximize the number of established lightpaths for a given number of wavelengths. Since this problem has been shown to be NP complete, various heuristic algorithms have been developed to solve it suboptimally. In this paper, we propose a novel heuristic RWA algorithm for SLDs based on the bee colony optimization (BCO) metaheuristic. BCO is a newborn swarm intelligence metaheuristic approach recently proposed to solve complex combinatorial optimization problems. We compare the efficiency of the proposed algorithm with three simple greedy algorithms for the same problem. Numerical results obtained by numerous simulations performed on the widely used realistic European Optical Network topology indicate that the proposed algorithm produces better-quality solutions compared to those obtained by greedy algorithms. In addition, we compare the results of the BCO–RWA–SLD algorithm with four other heuristic/metaheuristic algorithms proposed in literature to solve the RWA problem in the case of permanent (static) traffic demands.     

A formal approach to context scheduling for multicontextreconfigurable architectures

In this paper, we analyze the main issues in context scheduling for multicontext reconfigurable architectures from a formal point of view. We first provide an intuitive approach. which is later supported by a detailed analysis of the mathematical relations that express the reconfiguration process. This enables us to deduce a methodology for the minimization of context loading overhead, which considers the tradeoff between achievable system performance and algorithm efficiency. In this respect, the optimality necessary conditions are established in order to contrive an optimal search. However, as this approach is very time consuming we propose some heuristic techniques that reduce the algorithm complexity and accomplish very good results in relatively short execution time. This work has been developed as a part of an automated design environment for reconfigurable systems. A set of experiments has been developed so as to validate the theoretical results     

A new heuristic approach for redundancy optimization problem

The present paper describes a simple heuristic approach to solve redundancy optimization problem without much of computation to help reliability designers choose an appropriate configuration. The solution technique is simpler than all previous methods and offers optimal results with a high success rate.     

一种基于增量式时间序列和最佳任务调度的Web数据聚类算法

为了实现Web服务请求数据的快速聚类,并提高聚类的准确率,提出一种基于增量式时间序列和最佳任务调度的Web数据聚类算法。该算法进行了Web数据在时间序列上的聚类定义,并采用增量式时间序列聚类方法。先通过数据压缩形式降低Web数据的复杂性,再进行基于服务时间相似性的时间序列数据聚类;最后针对Web集群服务的最佳服务任务调度问题,通过以服务器执行能力为标准来分配服务任务。仿真实验结果表明,相比基于网格的高维数据层次聚类算法和基于增量学习的多目标模糊聚类算法,该文的算法在聚类时间、聚类精度、服务执行成功率、聚类失真度上均获得了更好的性能。     

Space communications scheduler: A rule-based approach to adaptive deadline scheduling

Job scheduling is a deceptively complex subfield of computer science. The highly combinatorial nature of the problem, which is NP-complete in nearly all cases, requires a scheduling program to intelligently traverse an immense search tree to create the best possible schedule in a minimal amount of time. In addition, the program must continually make adjustments to the initial schedule when faced with last-minute user requests, cancellations, unexpected device failures, etc. A good scheduler must be quick, flexible, and efficient, even at the expense of generating slightly less-than-optimal schedules.

The Space Communications Scheduler (SCS) is an intelligent rule-based scheduling system developed at GE's Advanced Technology Laboratories. SCS is an adaptive deadline scheduler, which allocates modular communications resources to meet an ordered set of user-specified job requests on board the NASA Space Station. SCS uses pattern-matching techniques to detect potential conflicts within a schedule, then resolves these conflicts through algorithmic and heuristic means. As a result, the system generates and maintains high-density schedules without relying heavily on backtracking or blind search techniques. SCS was designed to allocate communication devices on board the Space Station, but its general-purpose scheduling strategy is suitable for many common real-world applications.     

The synchronous approach to reactive and real-time systems

The state of the art in real-time programming is briefly reviewed. The synchronous approach is then introduced informally and its possible impact on the design of real-time and reactive systems is discussed. The authors present and discuss the application fields and the principles of synchronous programming. The major concern of the synchronous approach is to base synchronous programming languages on mathematical models. This makes it possible to handle compilation, logical correctness proofs, and verification of real-time programs in a formal way, leading to a clean and precise methodology for design and programming     

A genetic approach to joint routing and link scheduling for wireless mesh networks

Wireless mesh networks are an attractive technology for providing broadband connectivity to mobile clients who are just on the edge of wired networks, and also for building self-organized networks in places where wired infrastructures are not available or not deemed to be worth deploying. This paper investigates the joint link scheduling and routing issues involved in the delivery of a given backlog from any node of a wireless mesh network towards a specific node (which acts as a gateway), within a given deadline. Scheduling and routing are assumed to be aware of the physical interference among nodes, which is modeled in the paper by means of a signal-to-interference ratio. Firstly, we present a theoretical model which allows us to formulate the task of deriving joint routing and scheduling as an integer linear programming problem. Secondly, since the problem cannot be dealt with using exact methods, we propose and use a technique based on genetic algorithms. To the best of our knowledge, these algorithms have never been used before for working out these kinds of optimization problems in a wireless mesh environment. We show that our technique is suitable for this purpose as it provides a good trade-off between fast computation and the overall goodness of the solution found. Our experience has in fact shown that genetic algorithms would seem to be quite promising for solving more complex models than the one dealt with in this paper, such as those including multiple flows and multi-radio multi-channels.     

商覆盖立方体的一种增量维护策略

通过建立一种新的商覆盖立方体增量维护策略,将商覆盖立方体分成多个子集,在判断是否需要进行新增或修改操作时,不再需遍历整个商覆盖立方体而只需遍历部分子集,从而缩短了进行增量维护所需的时间。在实现这种策略中提出了基本表中新增记录时的算法Up-dateAddNew。实验结果表明,采用该算法时,需要访问的记录数仅为传统方法的85%。     

A heuristic approach to working and spare capacity optimization for survivable anycast streaming protected by p-cycles

Most of previous research in the field of network survivability has been focused on unicast transmissions. However, growing popularity of various concepts following the idea of content-oriented networks has triggered the need to develop new approaches to protect networks with other than unicast flows including multicast and anycast flows. In this paper, we consider the latter case and address the problem of working and spare capacity allocation in networks with anycast streaming, i.e., it is assumed that a set of replica servers is deployed in the network to serve streaming requests. To protect the network we propose to apply p-cycles—a relatively novel survivability approach combining capacity effectiveness of mesh restoration and ring-like restoration speed. To benefit from special properties of anycast flows, we use augmented version of p-cycles called Anycast-Protecting p-Cycles (APpC). We formulate the optimization problem as an ILP (Integer Linear Programming) model further applied to obtain optimal results using the GuRoBi solver. Due to high complexity of this optimization problem, we propose an effective heuristic algorithm based on the Simulated Annealing approach. Several versions of the algorithm are developed and examined—the best method yields on average results only 4.14 % worse than optimal ones. A wide range of experiments is conducted to verify performance of the proposed approach as a function of various network parameters including: p-cycle generator, p-cycle length, number of replica servers, number of clients. Moreover, we evaluate the Anycast-Protecting p-Cycles approach against classical p-cycle.     

A scheduling approach for design activities in concurrentengineering

This paper presents an optimization scheduling approach for concurrent design projects, in which activities may be executed in more than one operating mode and renewable as well as nonrenewable resources exist. Research on the development of a scheduling approach for concurrent scheduling is expected to shorten development lead time, minimize cost, and eliminate unnecessary redesign periods. In this paper, an integrated criterion function is proposed to ensure optimal concurrent scheduling and effective utilization of resources along with fluent delivery of information. In the criterion function, some key factors such as time order, resources, lead time and overlapping time of activities, which can make concurrent activities execute successfully, are taken into account adequately. Besides, two cruxes in concurrent engineering-role allocation, prerelease, and feedback revision process are discussed in detail. The example is part of a certain product development process, and the scheduling results demonstrate that the proposed algorithm is feasible     

An object-oriented, constraint-based heuristic for a class ofpassenger-train scheduling problems

A constraint-based heuristic technique for predictive scheduling of passenger trains is presented in this paper. The algorithm, which is lookahead, has been designed using an object-oriented methodology and is suitable for a single-track railway with some double-track sections. It is shown that the heuristic tends to minimize total waiting time of the trains concerned. Simulation experiments with real data show the superiority of the schedules created to those by human experts with reference to data provided from predictive timetables and specifications of Iran Railways     

A Petri net based approach to modeling and scheduling for an FMSand a case study

In this paper, a timed-place Petri net (TPPN) model for flexible manufacturing systems (FMSs) is constructed, which contains two major submodels: the stationary transportation model; and the variable process flow model. For multiple automated guided vehicle (AGV) systems, the authors embed a simple rule and introduce a push-AGV strategy in a TPPN model to solve the collision and traffic jam problems of such vehicles. Since a firing sequence of the TPPN from the initial marking to the final marking can be seen as a schedule of the modeled FMS, by using an A^* based search algorithm, namely, the limited-expansion A algorithm, an effective schedule of the part processing can be obtained. To show the promising potential of the proposed work, a prototype FMS is used as a target system for implementation. The experiment results assert that the job-shop scheduling problem can always be satisfactorily solved     

A pipeline-based approach for maximal-sized matching scheduling ininput-buffered switches

This letter proposes an innovative pipeline-based maximal-sized matching scheduling approach, called PMM, for input-buffered switches. It dramatically relaxes the timing constraint for arbitration with a maximal matching scheme. In the PMM approach, arbitration operates in a pipelined manner. Each subscheduler is allowed to take more than one time slot for its matching. Every time slot, one of them provides the matching result. The subscheduler can adopt a pre-existing efficient round-robin-based maximal matching algorithm. We show that PMM provides 100% throughput under uniform traffic since it preserves a desynchronization effect of the round-robin pointers as in the preexisting algorithm. In addition, PMM maintains fairness for best-effort traffic due to the round-robin-based arbitration     

基于FCM与KKT条件的增量学习方法

增量学习方法的思想是仅利用部分相关的样本集参与训练,即能够保留历史样本知识,又能够不断地吸收新的知识,提高机器学习效率和精度,解决了大量样本训练时间长和存储空间不足的问题。因此,如何有效地丢弃大量无效的样本点是增量学习算法研究的重点。文中提出了一种FCM(Fuzzy C-Means)和KKT(Karush-KuhnTucker)条件结合的增量学习方法,分别从历史样本集和新增样本集两个阶段对无效样本进行过滤,利用余下的样本进行训练。最后,利用UCI数据库中的4组数据进行实验分析,结果证明训练精度与全数据样本的训练精度几乎完全拟合。     

Skeletonisation of binary patterns: a heuristic approach

Conventional algorithms which have been proposed for the skeletonisation of digital patterns or pictures suffer from basic problems (for example, endpoint identification, connectivity) deriving from the rigid application of fixed rules. This letter introduces a heuristic approach to the problem which overcomes such difficulties and may be tailored to suit different types of data.     

A problem reduction approach for scheduling semiconductor wafer fabrication facilities

Most scheduling procedures used in industry are based on the dispatching paradigm, where decisions are made based on the jobs available at the time the machine becomes free. While optimization-based scheduling procedures have repeatedly been shown to yield significantly better schedules under ideal circumstances, their practical implementation is hampered by high computational requirements. We present a problem reduction procedure that allows a workcenter-based global scheduling heuristic to be implemented in very low CPU times. The procedure partitions the workcenters in a fab into heavily loaded and lightly loaded classes and solves the global scheduling problem only for the heavily loaded workcenters. The proposed technique is tested on instances drawn from an International SEMATECH wafer fab model. The proposed problem reduction approach yields superior results with modest computational effort, enabling the practical use of the decomposition heuristic.     

A heuristic approach for designing hybrid PONs employing WDM and OCDMA with asymmetric traffic distribution

In this paper we examine the resource provisioning aspects in a passive optical network (PON) employing wavelength-division multiplexing (WDM) and optical code-division multiple access (OCDMA) techniques. A judicious resource allocation scheme is proposed for a given set of optical codes and wavelengths with due consideration to the traffic asymmetry between upstream and downstream transmissions. The proposed scheme employs some initial heuristic estimates, followed by a subsequent open search mode towards reaching an optimal solution. The search mechanism in the provisioning scheme is carried out by employing some network performance metrics and evaluated using the appropriate analytical models.