Sharif Digital Repository

In this paper a lower bounding method for the flowshop sequence dependentgroups scheduling problems by minimization of makespan criterion (Fm|fmls, Sijkprmu|Cmax) is proposed. Theperformance of the proposed lower bound (LB) is compared with the availablelower bounding methods in literature. In order to do this, the performance ofthe proposed LB and the one available in literature are compared with theavailable upper bound in literature based on solving the available testproblems. The results show that the proposed LB has a superior performancecompared to the available ones in literature. The average percentage error ofthe proposed LB for the test problems is 1.1% and 1.4% for three and six... 

Scheduling of the maintenance activities is considered, in which the duration of activities is uncertain, delivery date of the maintenance shutdown is predefined, and activities are multi-mode. The problem is a multi-mode time-constrained project scheduling problem (MTCPSP). The glycol regeneration unit in a gas refinery is as the case study. Based on the effect of equipment or sub-equipment on the system reliability, the importance value of equipment and sub-equipment within the system is determined, and these values are used in a heuristic algorithm as a priority rule for choosing activities in the schedule. Outcomes demonstrate the performance of the algorithm in early or on time delivery... 

Corner-case analysis is a well-known technique to cope with occasional deviations occurring during the manufacturing process of semiconductors. However, the increasing amount of process variation in nanometer technologies has made it inevitable to move toward statistical analysis methods, instead of deterministic worst-case-based techniques, at all design levels. We show that by statically considering statistical effects of random and systematic process variation on performance and power consumption of a Multiprocessor System-on-Chip (MPSoC), significant power improvement can be achieved by static software-level optimizations such as task and communication scheduling. Moreover, we analyze... 

In this paper, we present a new Start-time Fair Queuing (SFQ) algorithm called Weighted Start-time Fair Queuing (WSFQ) which is more efficient and achieves better fairness than SFQ in the presence of small and huge elastic traffic flows. WSFQ scheduler, like SFQ uses a start time eligibility criterion to select packets and when the start-time of two packets in two flows are the same, it acts like Weighted Fair Queuing (WFQ) which selects the smallest virtual finish time first. Afterward, we compared the performance of our model with that of the applied scheduling algorithms such as First-In-First-Out (FIFO), SFQ as well as WFQ on the end-to-end delay and the throughput in small and... 

Hidden-terminal is one of the main problems in ad hoc wireless networks. In addition, there are scenarios where the desired destination is located in the range of other transmitters, so that the efforts on setting up communication with this terminal will fail due to collisions that may occur between transmitted control frames and undesired received control and data frames. This phenomenon becomes a bottleneck when most of data transmissions experience packet fragmentation. In such scenarios, the desired destination becomes unreachable during the data transfer of neighboring nodes. Using the same PHY of IEEE 802.11 and making slight modifications in its MAC, a new medium access control scheme... 

Job scheduling in MapReduce plays a vital role in Hadoop performance. In recent years, many researchers have presented job scheduler algorithms to improve Hadoop performance. Designing a job scheduler that minimizes job execution time with maximum resource utilization is not a straightforward task. The primary purpose of this paper is to investigate agents affecting job scheduler efficiency and present a novel classification for job schedulers based on these factors. We provide a comprehensive overview of existing job schedulers in each group, evaluating their approaches, their effects on Hadoop performance, and comparing their advantages and disadvantages. Finally, we provide... 

Data aggregation is a key, yet time-consuming functionality in wireless sensor networks (WSNs). Multi-channel design is a promising technique to alleviate interference as a primary reason for long latency of TDMA aggregation scheduling. Indeed, it provides more potential of parallel transmissions over different frequency channels, thus minimizing time latency. In this paper, we focus on designing a multi-channel minimum latency aggregation scheduling protocol, named MC-MLAS, using a new joint approach for tree construction, channel assignment, and transmission scheduling. To our best knowledge, this is the first work in the literature which combines orthogonal channels and partially... 

In this research, two scheduling problems i.e., single machine scheduling problem with minimizing the number of tardy jobs (1∥∑Uj) and two machine flow shop scheduling problem with a common due date and minimizing the number of tardy jobs (F2{pipe}dj=d{pipe}∑Uj) are investigated in a stochastic setting in the class of non-preemptive static list policies. It is assumed that the processing times of jobs are independent random variables. The stochastic problems are solved based on chance constrained programming. An equivalent deterministic problem is generated for each stochastic problem by linearization of the chance constraints. Then, the generated deterministic problems are solved using... 

Multiprocessor systems have been widely used for the execution of parallel applications. Task scheduling is crucial for the right operation of multiprocessor systems, where the aim is shortening the length of schedules. Fault tolerance is becoming a necessary attribute in multiprocessor systems as the number of processing elements is getting larger. This paper presents a fault tolerant scheduling algorithm for task graph applications in multiprocessor systems. The algorithm is an extension of a previously proposed algorithm with a reduced communications scheme. Simulation results show the efficiency of the proposed algorithm despite its simplicity  

In nanometer-scale process technologies, the effects of process variations are observed in Multiprocessor System-on-Chips (MPSoC) in terms of variations in frequencies and leakage powers among the processors on the same chip as well as across different chips of the same design. Traditionally, worst-case values are assumed for these parameters and then a deterministic optimization technique is applied to the MPSoC application under design. We show that such worst-case-based approaches are not optimal with the increasing variation observed at system-level, and instead, statistical approaches should be employed. We consider the problem of simultaneously choosing MPSoC architecture and task... 

Data aggregation is a key, yet time-consuming functionality introduced to conserve energy in wireless sensor networks (WSNs). In this paper, to minimize time latency, we focus on aggregation scheduling problem and propose an efficient distributed algorithm that generates a collision-free schedule with the least number of time slots. In contrast to others, our approach named FAST mainly contributes to both tree construction, where the former studies employ Connected 2-hop Dominating Sets, and aggregation scheduling that was previously addressed through the Competitor Sets computation. We prove that the latency of FAST under the protocol interference model is upper-bounded by 12R+Δ-2, where R... 

An important approach to reduce power dissipation is reducing the number of instructions executed by the processor. To achieve this goal, this paper introduces a novel instruction scheduling algorithm that executes an instruction only when its result is required by another instruction. In this manner, it not only does not execute useless instructions, but also reduces the number of instructions executed after a mispredicted branch. The cost of the extra hardware is 161 bytes for 128 instruction window size. Measurements done using SPEC CPU 2000 benchmarks show that the average number of executed instructions is reduced by 13.5% while the average IPC is not affected. Copyright 2008 ACM  

In this paper, a new approach to formulate a class of scheduling problems is introduced, which can be applied to many other discrete problems with complicated structures. The concept of graph circular coloring is applied to develop a model for the special case of an open shop scheduling problem. In this problem, there are some independent jobs to be processed in a shop with dedicated renewable resources. Each job consists of several tasks with no precedence restriction. Each task is processed without preemption. The processing time of the tasks is given. Processing each task requires using some multiple specified types of resource, while no more than one task can use each resource,... 

The authors consider the Multi-Skilled Project Scheduling Problem (MSPSP) as a version of the Multi-mode Resource-Constrained Project Scheduling Problem (MRCPSP), which extends the well-known NP-hard Resource-Constrained Project Scheduling Problem (RCPSP). In the MSPSP, it is made up of activities, which require specific skills to be done. Moreover, resources are staff members who master fixed skill(s). Thus, each resource requirement of an activity corresponds to the number of persons doing the corresponding skill that must be assigned to the activity during its whole processing time. The authors focus on taking into account the setup times when performing work, depending on the appointment... 

In this research the parallel machine scheduling problem with preemption by considering a constant transportation delay for migrated jobs and minimization of makespan as the criterion i.e., Pm|pmtn(delay)|Cmax is investigated. It is assumed that when a preempted job resumes on another machine, it is required a delay between the processing time of the job on these two machines. This delay is called transportation delay. We criticize an existing mathematical model for the research problem in the literature [Boudhar M, Haned A. Preemptive scheduling in the presence of transportation times. Computers & Operations Research 2009; 36(8):2387-93]. Then, we prove that there exists an optimal schedule... 

In this paper, we show that by considering the factor of usage in instruction bundles in VLIW processors and using the slots filled with NOPs in bundles, we can improve the overall performance by reducing the total execution time of the program. By our proposed scheme, Combined Bundle Scheduling (CBS), we have gained better performance compared to that for the PDT scheme (Predicted Decision Tree scheduling) which is the best scheduling strategy known so far. © 2006 IEEE  

The aim of this paper is to propose a scheduling method to consider reliability along with makespan in grid computing systems. The reliability of task execution is considered in the proposed method to increase the chance of running large-scale and computationally intensive workflows successfully. To handle situations in which a resource failure in a possible scheduling solution occurs, the proposed method finds a collection of scheduling solutions instead of only one solution to run the workflow. It leads to have chance to run an alternative scheduling solution that is not using the failed resource. To find the most optimized scheduling solutions, we exploit the lately developed... 

Most of the research works conducted on Project Scheduling Problem (PSP) especially Resource Constrain Project Scheduling Problem (RCPSP) either ignore equipment planning or schedule the activities first, and then plan for the required equipment. Moreover, little works that consider simultaneous PSP and Equipment Planning (EP) are based on the assumption that the equipment is continuously available. However, in reality, equipment is subject to either random breakdowns or deterministic maintenance programs that make it not being available all the time. In this paper, the PSP and EP problems are simultaneously considered in closer to reality situations in which the equipment is not always... 

The problem of this paper deals with the multi-mode project scheduling problem under uncertainty of activity duration where only the renewable resources are taken into account and a given deadline has to be met at the cost of recruiting additional resources. A heuristic algorithm is employed to solve this problem, and to maintain the robustness of the baseline schedule, the concept of critical chain project management (CCPM) is applied in which a new definition to resource buffer is considered. A simulation methodology is used to determine the size and location of resource buffers in the schedules in which three different buffer sizes and three different uncertainty levels are considered.... 

While IEEE 802.16 standardizes the PHY and MAC layers of Wireless Metropolitan Area Networks (MAN), optimal scheduling which is crucial in providing QoS, remains to be an open issue. In this paper, we propose an optimization based uplink scheduling algorithm which aims at maximizing the throughput while guaranteeing the negotiated QoS parameters for all connections. Unlike typical strict priority schedulers the proposed scheduler is able to satisfy the requirements of higher priority connections while not letting the lower priority connections to be neglected. Additionally, a parameter is defined to ensure fairness among rtPS connections. The scheduler's performance is then evaluated through...