Solving a real-time allocation problem with constraint programming

In this paper, we present an original approach (CPRTA for “Constraint Programming for solving Real-Time Allocation”) based on constraint programming to solve a static allocation problem of hard real-time tasks. This problem consists in assigning periodic tasks to distributed processors in the context of fixed priority preemptive scheduling. CPRTA is built on dynamic constraint programming together with a learning method to find a feasible processor allocation under constraints. Two efficient new approaches are proposed and validated with experimental results. Moreover, CPRTA exhibits very interesting properties. It is complete (if a problem has no solution, the algorithm is able to prove it); it is non-parametric (it does not require specific tuning) thus allowing a large diversity of models to be easily considered. Finally, thanks to its capacity to explain failures, it offers attractive perspectives for guiding the architectural design process.     

On a batch arrival Poisson queue with a random setup time and vacation period

The single server queue with vacation has been extended to include several types of extensions and generalisations, to which attention has been paid by several researchers (e.g. see Doshi, B. T., Single server queues with vacations — a servey. Queueing Systems, 1986, 1, 29–66; Takagi, H., Queueing Analysis: A Foundation of Performance evaluation, Vol. 1, Vacation and Priority systems, Part. 1. North Holland, Amsterdam, 1991; Medhi, J., Extensions and generalizations of the classical single server queueing system with Poisson input. J. Ass. Sci. Soc., 1994, 36, 35–41, etc.). The interest in such types of queues have been further enhanced in resent years because of their theoretical structures as well as their application in many real life situations such as computer, telecommunication, airline scheduling as well as production/inventory systems. This paper concerns the model building of such a production/inventory system, where machine undergoes extra operation (such as machine repair, preventive maintenance, gearing up machinery, etc.) before the processing of raw material is to be started. To be realistic, we also assume that raw materials arrive in batch. This production system can be formulated as an M^x/M/1 queues with a setup time. Further, from the utility point of view of idle time this model can also be formulated as a case of multiple vacation model, where vacation begins at the end of each busy period. Besides, the production/inventory systems, such a model is generally fitted to airline scheduling problems also. In this paper an attempt has been made to study the steady state behavior of such an M^x/M/1 queueing system with a view to provide some system performance measures, which lead to remarkable simplification when solving other similar types of queueing models.This paper deals with the steady state behaviour of a single server batch arrival Poisson queue with a random setup time and a vacation period. The service of the first customer in each busy period is preceded by a random setup period, on completion of which service starts. As soon as the system becomes empty the server goes on vacation for a random length of time. On return from vacation, if he finds customer(s) waiting, the server starts servicing the first customer in the queue. Otherwise it takes another vacation and so on. We study the steady state behaviour of the queue size distribution at random (stationary) point of time as well as at departure point of time and try to show that departure point queue size distribution can be decomposed into three independent random variables, one of which is the queue size of the standard M^x/M/1 queue. The interpretation of the other two random variables will also be provided. Further, we derive analytically explicit expressions for the system state (number of customers in the system) probabilities and provide their appropriate interpretations. Also, we derive some system performance measures. Finally, we develop a procedure to find mean waiting time of an arbitrary customer.     

同构计算环境中一种新的静态任务调度算法

延伸了TTIG模型并提出新的算法．在模拟实验中，将此算法与MATE和其它同构环境中基于DAG的调度算法，在不同测试条件下进行了比较，结果显示该算法性能明显优于MATE，与基于DAG模型的调度算法比较而言，在性能方面各有千秋，但在算法时间复杂度方面具有显著的优势．     

实时多处理器系统的动态分批优化调度算法

提出了一种实时多处理器系统的新的高效动态调度算法--动态分批优化调度算法,该算法突破了以往算法中一次只安排一项任务的做法,采用在每次扩充当前局部调度时,按一定规则在待调度的任务集中选取一批任务,对该批任务中的每项任务在每个处理器上运行构造目标函数,将问题转化为非平衡分配问题,一次性为这些任务都安排一个处理器或为每个处理器安排一项任务,使得这种安排具有最好的"合适性",以增大未安排任务的可行性.这种方法极大地提高了算法的调度成功率.同时,为了研究该算法的有效性,对其进行了大量的模拟,分析了一些任务参数的变化对算法调度成功率的影响,并与节约算法的调度成功率进行了比较.模拟结果显示,在节约算法的调度成功率小于10%的约束条件下,该算法的调度成功率大于90%,说明新算法的优势是非常明显的.     

船闸运调系统模型的建立

船闸实现基于C／S的运调系统,不仅是船闸现代化管理的需要,而且能够极大程度地提高船闸的工作效率。本文主要应用关系数据库理论分析了系统的用户需求,运用E—R图设计了该系统的数据库,保证了数据库的冗余度和完整性;应用面向对象的理论用UML建模语言分别建立了系统的用例图、类图、顺序图。     

一类单机动态调度问题的改进滚动时域方法

将滚动时域方法用于一类单机动态调度问题,对其调度子问题进行改进.在子问题的目标函数中增加一个终端惩罚项,在优化局部目标的同时兼顾全局目标,证明了已有分枝定界算法经适当修正可用于求解改进的调度子问题.仿真计算结果表明,在绝大多数情况下,改进滚动时域方法的调度质量优于最好的规则调度方法.     

一种新型实时调度算法研究

在许多片上特定应用系统中，任务多且切换频繁，任务切换开销大，有时甚至严重影响系统的可调度性．研究了动态可抢占门限调度算法，它通过初始门限值、动态门限值的计算和优化线程分配，实现了在处理器高利用率下，有效降低任务切换开销的目的，并相应地减少了对内存的需求．动态可抢占门限调度算法是将静态抢占门限算法与动态调度算法有机地结合在一起。完成了由静态到动态无缝转换．     

并行工程环境下设计任务调度原理与实现方法的研究

并行工程ＣＥ环境下,设计任务被分解为若干子任务,然后进行协同求解,因此各子任务的调度是实现产 品并行设计的关键．该文提出了设计任务调度的“均衡一适度”法,分析了其调度策略,研究了其算法实现,最后给出 了应用实例。     

Loop Shifting for Loop Compaction

The idea of decomposed software pipelining is to decouple the software pipelining problem into a cyclic scheduling problem without resource constraints and an acyclic scheduling problem with resource constraints. In terms of loop transformation and code motion, the technique can be formulated as a combination of loop shifting and loop compaction. Loop shifting amounts to moving statements between iterations thereby changing some loop independent dependences into loop carried dependences and vice versa. Then, loop compaction schedules the body of the loop considering only loop independent dependences, but taking into account the details of the target architecture. In this paper, we show how loop shifting can be optimized so as to minimize both the length of the critical path and the number of dependences for loop compaction. The first problem is well-known and can be solved by an algorithm due to Leiserson and Saxe. We show that the second optimization (and the combination with the first one) is also polynomially solvable with a fast graph algorithm, variant of minimum-cost flow algorithms. Finally, we analyze the improvements obtained on loop compaction by experiments on random graphs.     

具有约束条件的单机JIT调度问题

具有约束条件的单机ＪＩＴ调度问题齐向彤陈秋双涂生（南开大学计算机与系统科学系天津３０００７１）关键词Ｅ／Ｔ调度,优化,分支定界法．１）国家“八六三”ＣＩＭＳ主题和国家自然科学基金资助课题．收稿日期１９９５－０９－１８１引言近年来,随着Ｊｕｓｔ－ｉｎ...