Multiprocessor scheduling of processes with release times,deadlines, precedence, and exclusion relations

The author presents a scheduling algorithm that solves the problem of finding a feasible nonpreemptive schedule whenever one exists on M identical processors for a given set of processes such that each process starts executing after its release time and completes its computation before its deadline. A given set of precedence relations and a given set of exclusion relations defined on ordered pairs of process segments are satisfied. This algorithm can be applied to the important problem of automated pre-run-time scheduling of processes with arbitrary precedence and exclusion relations on multiprocessors in hard-real-time systems     

一种进程调度的预处理算法

有预处理的Xu-scheduling算法能有效地对硬实时系统中的一组进程进行静态调度,以得到一种可行性调度,使得在单个处理器上,每个进程都在发布时间之后运行,在截止时间之前结束,并且满足每对进程上的优先关系和排斥关系。     

A pre-run-time scheduling algorithm for hard real-time systems

Process scheduling, an important issue in the design and maintenance of hard real-time systems, is discussed. A pre-run-time scheduling algorithm that addresses the problem of process sequencing is presented. The algorithm is designed for multiprocessor applications with preemptable processes having release times, computation times, deadlines and arbitrary precedence and exclusion constraints. The algorithm uses a branch-and-bound implicit enumeration technique to generate a feasible schedule for each processor. The set of feasible schedules ensures that the timing specifications of the processes are observed and that all the precedence and exclusion constraints between pairs of processes are satisfied. the algorithm was tested using a model derived from the F-18 mission computer operational flight program     

求解广义优先关系下多技能人员项目调度问题的改进布谷鸟搜索算法

为解决传统的完成-开始时序不能满足描述真实项目调度顺序要求的问题,引入广义优先关系(GPRs)及改进的AON描述任务的时序约束。提出将布谷鸟搜索算法应用于求解广义优先关系下的多技能人力资源项目调度问题(MS-RCPSP/GPRs)中的构想,建立了基于改进布谷鸟搜索算法(ICS)的求解方法,采用Powell局部改进技术和精英保留策略,并给出了算法流程。基于相关案例生成器生成该问题的数据集,实验结果表明ICS是一种求解MS-RCPSP/GPRs的有效方法,对解决实际问题具有重要意义。     

Genetic algorithm for balancing reconfigurable machining lines

We consider the problem of designing a reconfigurable machining line. Such a line is composed of a sequence of workstations performing specific sets of operations. Each workstation is comprised of several identical CNC machines (machining centers). The line is required to satisfy the given precedence order, inclusion, exclusion and accessibility constraints on the given set of operations. Inclusion and exclusion are zoning constraints which oblige or forbid certain operations to be performed on the same workstation. The accessibility constraints imply that each operation has a set of possible part positions under which it can be performed. All the operations performed on the same workstation must have a common part position. Workstation times are computed taking into account processing and setup times for operations and must not exceed a given bound. The number of CNC machines at one workstation is limited, and the total number of machines must be minimized. A genetic algorithm is proposed. This algorithm is based on the permutation representation of solutions. A heuristic decoder is suggested to construct a solution from a permutation, so that the output solution is feasible w.r.t. precedence, accessibility, cycle time, and exclusion constraints. The other constraints are treated with a penalty approach. For a local improvement of solutions, a mixed integer programming model is suggested for an optimal design of workstations if the order of operations is fixed. An experimental evaluation of the proposed GA on large scale test instances is performed.     

A Token-Based Distributed Group Mutual Exclusion Algorithm with Quorums

The group mutual exclusion problem is a generalization of mutual exclusion problem such that a set of processes in the same group can enter critical section simultaneously. In this paper, we propose a distributed algorithm for the group mutual exclusion problem in asynchronous message passing distributed systems. Our algorithm is based on tokens, and a process that obtains a token can enter critical section. For reducing message complexity, it uses coterie as a communication structure when a process sends a request messages. Informally, coterie is a set of quorums, each of which is a subset of the process set, and any two quorums share at least one process. The message complexity of our algorithm is $O(|Q|)$ in the worst case, where $|Q|$ is a quorum size that the algorithm adopts. Performance of the proposed algorithm is presented by analysis and discrete event simulation. Especially, the proposed algorithm achieves high concurrency, which is a performance measure for the number of processes that can be in critical section simultaneously.     

Scheduling the production of rolling ingots: industrial context, model, and solution method

We study a real‐world scheduling problem arising in the context of a rolling ingots production. First we review the production process and discuss peculiarities that have to be observed when scheduling a given set of production orders on the production facilities. We then show how to model this scheduling problem using prescribed time lags between operations, different kinds of resources, and sequence‐dependent changeovers. A branch‐and‐bound solution procedure is presented in the second part. The basic principle is to relax the resource constraints by assuming infinite resource availability. Resulting resource conflicts are then stepwise resolved by introducing precedence relationships among operations competing for the same resources. The algorithm has been implemented as a beam search heuristic enumerating alternative sets of precedence relationships.     

Hard real-time tasks' scheduling considering voltage scaling, precedence and exclusion relations

Several scheduling approaches have been developed to address DVS in time-critical systems, however, overheads, precedence and exclusion relations have been neglected. This paper presents a pre-runtime scheduling method for hard real-time systems considering DVS, overheads as well as inter-task relations. The proposed method adopts a formal model based on time Petri nets in order to find a feasible schedule that satisfies timing and energy constraints.     

带流水作业工程项目调度问题的遗传算法

介绍了带流水作业的工程项目调度问题，这是项目网络中带有流水作业子网络的项目调度问题。它不仅带有常规的时序和资源约束，还带有流水作业所带来的特殊约束。首先给出了带流水作业工程项目调度问题的描述；进而提出一种解决该问题的遗传算法。该算法引入了基于项目划分的编码方式，将个体划分为流水基因段和非流水基因段，并分别进行遗传操作。最后对提出的算法进行了数值计算验证，结果表明了算法的有效性。     

Synthesis of mutual exclusion solutions based on binary semaphores

A graphical form of the mutual exclusion problem is considered in which each vertex represents a process and each edge represents a mutual exclusion constraint between the critical sections of the processes associated with its endpoints. An edge semaphore solution for mutual exclusion problems is defined, and those graphs which are edge solvable are characterized in terms of both a forbidden subgraph and a graph grammar. Finally, an efficient algorithm is given which generates the entry and exit sections for all processes in an edge-solvable problem     

一种RB-RBAC模型规则冲突消解算法

RB-RBAC(Rule-Based RBAC)模型克服了RBAC模型的一些局限,提供了基于用户属性自动指派角色的机制。RB-RBAC模型允许进行否定授权,可能在进行授权的过程中出现冲突。在研究RB-RBAC模型冲突规则间关系的基础上,提出了一种基于否定优先的冲突消解算法,能够在保持原有语义的条件下,自动改写RB-RBAC模型中冲突的授权规则来消解冲突。     

基于模拟谐振子算法的多项目调度

针对资源受限多项目调度问题(RCMPSP),介绍了一种模拟谐振子算法。算法通过模拟简谐振动系统中势能状态的变化,从经典简谐振动阶段过渡到量子振动阶段,从而实现全局搜索到局部搜索的变化过程;同时,两阶段的搜索形式使算法的收敛精度和搜索效率得到了保证。采用基于排列的方法和串行项目进度生成机制,结合多项目的任务列表,可以保证所得调度方案满足项目优先关系约束。运用标准测试函数对算法进行了测试,结果表明算法具有高质量的搜索效率和精度。最后给出了三组多项目调度算例。     

Exact and heuristic algorithms for balancing transfer lines when a set of available spindle heads is given

A balancing problem for paced tandem transfer lines with several spindle heads at each station is considered. A spindle head executes a block of operations. The set of all available spindle heads as well as the operations executed by each spindle head, the spindle head times and costs are known. There are operations with several spindle head candidates. The problem at the line design stage consists in the choice of spindle heads from the given set and their assignment to workstations. The goal is to minimize the line cost while satisfying the precedence, inclusion and exclusion constraints. An exact algorithm based on a mixed integer programming approach is developed. Two types of new heuristic algorithms are also suggested. One of them step‐by‐step assigns randomly spindle heads to a current workstation. The second uses depth‐first search techniques. Experimental results are reported.     

The total completion time open shop scheduling problem with a given sequence of jobs on one machine

This paper addresses the open shop scheduling problem to minimize the total completion time, provided that one of the machines has to process the jobs in a given sequence. The problem is NP-hard in the strong sense even for the two-machine case. A lower bound is derived based on the optimal solution of a relaxed problem in which the operations on every machine may overlap except for the machine with a given sequence of jobs. This relaxed problem is NP-hard in the ordinary sense, however it can be quickly solved via a decomposition into subset-sum problems. Both heuristic and branch-and-bound algorithm are proposed. Experimental results show that the heuristic is efficient for solving large-scaled problems, and the branch-and-bound algorithm performs well on small-scaled problems.Scope and purposeShop scheduling problems, widely used in the modeling of industrial production processes, are receiving an increasing amount of attention from researchers. To model practical production processes more closely, additional processing restrictions can be introduced, e.g., the resource constraints, the no-wait in process requirement, the precedence constraints, etc. This paper considers the total completion time open shop scheduling problem with a given sequence of jobs on one machine. This model belongs to a new class of shop scheduling problems under machine-dependent precedence constraints. This problem is NP-hard in the strong sense. A heuristic is proposed to efficiently solve large-scaled problems and a branch-and-bound algorithm is presented to optimally solve small-scaled problems. Computational experience is also reported.     

Algorithms and implementation of a set partitioning approach for modular machining line design

A transfer line design problem is considered. Transfer lines are sequences of workstations equipped with processing modules called blocks each of which performs specific operations. These lines are used for mass production of one type of product and thus execute repetitively a given set of operations. The machine parts move along the stations in the same direction. An identical cost is associated with each station and differing costs are associated with the blocks. The problem is to determine the number of stations, select a set of blocks and assign selected blocks to the stations so that operations of the selected blocks constitute the original set of operations and the total cost is minimized. A distinct feature of the problem is that operations at the same station are performed in parallel. Plus, there are inclusion, exclusion and precedence relations that restrict the assignment of the blocks and operations to the same station as well as the processing order of the operations on the transfer line. We implement a novel set partitioning formulation of this design problem with pre-processing procedures and heuristics. The presented approach has the best performance among the existing methods in terms of solution time and quality.     

Generating Processes from Specifications using the Relation Manipulation System RelView

In this paper we present an algorithm generating a bundle of processes from a given safety specification. The specification is given by a formula in a process logic, i.e. a modal logic with a set of possibility operators induced by the possible actions of the underlying transition system. This logic is a finite sublanguage, in the sense that only finite conjunctions are allowed, of the language introduced by R. Milner in [3]. Furthermore, we present an implementation of the algorithm using the functional language HASKELL and the internal language of the RelView system. Within the system processes are modelled by relations as shown in [8,9].     

A simple local-spin group mutual exclusion algorithm

This paper presents a new solution to the group mutual exclusion problem recently posed by Joung. In this problem, processes repeatedly request access to various “sessions.” It is required that distinct processes are not in different sessions concurrently, that multiple processes may be in the same session concurrently, and that each process that tries to enter a session is eventually able to do so. This problem is a generalization of the mutual exclusion and readers-writers problems. Our algorithm and its correctness proof are substantially simpler than Joung's. This simplicity is achieved by building upon known solutions to the more specific mutual exclusion problem. Our algorithm also has various advantages over Joung's, depending on the choice of mutual exclusion algorithm used. These advantages include admitting a process to its session in constant time in the absence of contention, spinning locally in Cache Coherent (CC) and Nonuniform Memory Access (NUMA) systems, and improvements in the complexity measures proposed by Joung     

分布式系统进程互斥算法的研究与改进

本文分析比较了传统互斥算法，提出了一种新的基于令牌的算法，并详细阐述算法的设计思想及其数据结构。本算法最主要的特点是在分布式互斥中引入了优先级和树的概念，能有效的降低进程问的通信量，以及保证互斥和预防死锁。     

Converging to periodic schedules for cyclic scheduling problems with resources and deadlines

Cyclic scheduling has been widely studied because of the importance of applications in manufacturing systems and in computer science. For this class of problems, a finite set of tasks with precedence relations and resource constraints must be executed repetitively while maximizing the throughput. Many applications also require that execution schedules be periodic i.e. the execution of each task is repeated with a fixed global period w.The present paper develops a new method to build periodic schedules with cumulative resource constraints, periodic release dates and deadlines. The main idea is to fix the period w, to unwind the cyclic scheduling problem for some number of iterations, and to add precedence relations so that the minimum time lag between two successive executions of any task equals w. Then, using any usual (not cyclic) scheduling algorithm to compute task starting times for the unwound problem, we prove that either the method converges to a periodic schedule of period w or it fails to compute a schedule. A non-polynomial upper bound on the number of iterations to unwind in order to guarantee that cyclic precedence relations and resource constraints are fulfilled is also provided. This method is successfully applied to a real-life problem, namely the software pipelining of inner loops on an embedded VLIW processor core by using a Graham list scheduling algorithm.     

Fixed priority scheduling of tasks with arbitrary precedence constraints in distributed hard real-time systems

This paper considers the schedulability analysis of real-time distributed applications where tasks may present arbitrary precedence relations. It is assumed that tasks are periodic or sporadic and dynamically released. They have fixed priorities and hard end-to-end deadlines that are equal to or less than the respective period. We develop a method to transform arbitrary precedence relations into release jitter. By eliminating all precedence relations in the task set one can apply any available schedulability test that is valid for independent task sets.