• 제목/요약/키워드: Preemptive

검색결과 415건 처리시간 0.052초

竝列處理機械상에서 總作業完了時間의 最小化解法에 관한 硏究 (A Study on Approximate and Exact Algorithms to Minimize Makespan on Parallel Processors)

  • 안상형;이송근
    • 한국경영과학회지
    • /
    • 제16권2호
    • /
    • pp.14-35
    • /
    • 1991
  • The purpose of this study is to develop an efficient exact algorithm for the problem of scheduling n in dependent jobs on m unequal parallel processors to minimize makespan. Efficient solutions are already known for the preemptive case. But for the non-preemptive case, this problem belongs to a set of strong NP-complete problems. Hence, it is unlikely that the polynomial time algorithm can be found. This is the reason why most investigations have bben directed toward the fast approximate algorithms and the worst-case analysis of algorithms. Recently, great advances have been made in mathematical theories regarding Lagrangean relaxation and the subgradient optimization procedure which updates the Lagrangean multipliers. By combining and the subgradient optimization procedure which updates the Lagrangean multipliers. By combining these mathematical tools with branch-and-bound procedures, these have been some successes in constructing pseudo-polynomial time algorithms for solving previously unsolved NP-complete problems. This study applied similar methodologies to the unequal parallel processor problem to find the efficient exact algorithm.

  • PDF

병렬처리리례 상에서 동작업완료시간의 최소화해법에 관한 연구 (A Study on Approximate and Exact Algorithms to Minimize Makespan on Parallel Processors)

  • 안상형;이송근
    • 한국경영과학회지
    • /
    • 제16권2호
    • /
    • pp.13-35
    • /
    • 1991
  • The purpose of this study is to develop an efficient exact algorithm for the problem of scheduling n in dependent jobs on m unequal parallel processors to minimize makespan. Efficient solutions are already known for the preemptive case. But for the non-preemptive case, this problem belongs to a set of strong NP-complete problems. Hence, it is unlikely that the polynomial time algorithm can be found. This is the reason why most investigations have bben directed toward the fast approximate algorithms and the worst-case analysis of algorithms. Recently, great advances have been made in mathematical theories regarding Lagrangean relaxation and the subgradient optimization procedure which updates the Lagrangean multipliers. By combining and the subgradient optimization procedure which updates the Lagrangean multipliers. By combining these mathematical tools with branch-and-bound procedures, these have been some successes in constructing pseudo-polynomial time algorithms for solving previously unsolved NP-complete problems. This study applied similar methodologies to the unequal parallel processor problem to find the efficient exact algorithm.

  • PDF

Improved Schedulability Analysis of Real-Time Sporadic Tasks with EDF Preemptive Scheduling

  • Darbandi, Armaghan;Kim, Myung-Kyun
    • Journal of information and communication convergence engineering
    • /
    • 제10권4호
    • /
    • pp.396-404
    • /
    • 2012
  • This paper proposes an analysis method to check the schedulability of a set of sporadic tasks under earliest deadline first (EDF) scheduler. The sporadic task model consists of subtasks with precedence constraints, arbitrary arrival times and deadlines. In order to determine the schedulability, we present an approach to find exact worst case response time (WCRT) of subtatsks. With the technique presented in this paper, we exploit the precedence relations between subtasks in an accurate way while taking advantage of the deadline of different subtasks. Another nice feature of our approach is that it avoids calculation time overhead by exploiting the concept of deadline busy period. Experimental results show that this consideration leads to a significant improvement compared with existing work.

IEC 61850 프로토콜의 실시간성 향상을 위한 선점형 이더넷 컨트롤러 (Preemptive Ethernet Controller to Improve Real-Time Characteristics of IEC 61850 Protocol)

  • 이범용;박태림;박재현
    • 전기학회논문지
    • /
    • 제59권10호
    • /
    • pp.1923-1928
    • /
    • 2010
  • The IEC 61850 protocol proposed for the interoperability between IEDs(intelligent electronic devices) adopts the prioritized switched ethernet as its communication channel because substation bus is utilized to exchange both real-time and non real-time messages. The prioritized switched ethernet uses IEEE 802.1Q/p QoS(Quality of Service) in addition to IEEE 802.3 ethernet to enhance the real-time characteristics. However, IEEE 802.1Q/p QoS has priority-blocking problem that occurs when higher-priority frame transmission request during lower-priority frame transmission. To resolve this problem, this paper proposes P(Preemptive)-Ethernet. P-Ethernet uses the modified IEEE 802.1Q/p frame format and new priority preemption mechanism. This paper also implements P-Ethernet controller using FPGA (Virtex-4) and MicroBlaze processor. From the implementation results, P-Ethernet controller shows a improved latency and jitter of transmission period compare to the normal ethernet controller.

TWO-CLASS M/PH,G/1 QUEUE WITH IMPATIENCE OF HIGH-PRIORITY CUSTOMERS

  • Kim, Jeongsim
    • Journal of applied mathematics & informatics
    • /
    • 제30권5_6호
    • /
    • pp.749-757
    • /
    • 2012
  • We consider the M/PH,G/1 queue with two classes of customers in which class-1 customers have deterministic impatience time and have preemptive priority over class-2 customers who are assumed to be infinitely patient. The service times of class-1 and class-2 customers have a phase-type distribution and a general distribution, respectively. We obtain performance measures of class-2 customers such as the queue length distribution, the waiting time distribution and the sojourn time distribution, by analyzing the busy period of class-1 customers. We also compute the moments of the queue length and the waiting and sojourn times.

예방 용접 overlay 가 밀림관 노즐 보수 용접부 잔류응력에 미치는 영향 (Effect of preemptive weld overlay on residual stress of repaired weldment in surge nozzle)

  • 오창영;송태광;배홍열;전윤배;김윤재;이경수;박치용
    • 대한기계학회:학술대회논문집
    • /
    • 대한기계학회 2008년도 추계학술대회A
    • /
    • pp.94-97
    • /
    • 2008
  • In the welding process, weldments usually include repair weld during the manufacturing process. Repair welds is supposed to cause strong tensile residual stress. Moreover weldments, usually made by Alloy 82/182, is susceptible to PWSCC. Therefore, mitigation of welding residual stress in weldments is important for reliable operating. PWOL is one of the methods for mitigation and verified for over twenty years. In this paper, residual stress distribution of repaired weldments and the effect of PWOL on mitigation is examined for surge nozzle.

  • PDF

일시(一時) 작업중단(作業中斷)을 허용(許容)하는 순서종속작업(順序從屬作業)을 병행기계(並行機械)로서 makespan 최소화(最小化)를 도모(圖謀)하는 발견적(發見的) 방법(方法) (Heuristic Procedure on Minimizing Makespan for Preemptive Sequence Dependent Job Scheduling with Parallel Identical Machines)

  • 원진희;김만식
    • 대한산업공학회지
    • /
    • 제13권2호
    • /
    • pp.35-46
    • /
    • 1987
  • To minimize makespan for preemptive sequence dependent job scheduling with parallel identical processors, fundamental results, as the basis of new algorithm to be presented, such as McNauton's algorithm for independent jobs, Hu's characterization for dependent jobs, and Muntz-Coffman's algorithm, were first introduced. Then a huristic procedure was presented applying those concepts of zoning of assembly line balancing and of resource leveling on CPM network scheduling with two or more of parallel machines in general. New procedure has eliminated presumative machine assignment using ${\rho}$, rate of resource capability (${\rho}$ < 1), for practical scheduling.

  • PDF

복합 태스크 모델에 대한 효율적인 실시간 스케쥴링 (Effective Real-Time Scheduling in Composite Task Model)

  • 김인국
    • 한국정보처리학회논문지
    • /
    • 제3권6호
    • /
    • pp.1568-1579
    • /
    • 1996
  • 이제까지의 실시간 스케쥴링은 대상이 되는 태스크들이 모두 선점가능하거나 모 두 선점불가능함을 가정하였다. 본 논문에서는 단일 프로세서 환경에서 선점가능한 서브태스크와 선점불가능한 서브태스크를 모두 포함하는 보다 일반적인 태스크 모델 에 대한 고정 우선순위 전략을 기반으로 하는 실시간 스케쥴링 방법을 제시하였다. 기존에 발표된 바 있는 Harbour등의 방법에 의해 스케쥴링이 가능하다고 판정된 태스 크 집합은 본 논문의 방법에 의해서도 스케쥴링이 가능하다고 판단되며 두 방법을 모 의실험을 통하여 비교해 본 결과 최대 45% 이상의 효율의 차이가 남이 보여지고 있 다.

  • PDF

Optimal Admission Control and State Space Reduction in Two-Class Preemptive Loss Systems

  • Kim, Bara;Ko, Sung-Seok
    • ETRI Journal
    • /
    • 제37권5호
    • /
    • pp.917-921
    • /
    • 2015
  • We consider a multiserver system with two classes of customers with preemption, which is a widely used system in the analysis of cognitive radio networks. It is known that the optimal admission control for this system is of threshold type. We express the expected total discounted profit using the total number of customers, thus reducing the stochastic optimization problem with a two-dimensional state space to a problem with a one-dimensional birth-and-death structure. An efficient algorithm is proposed for the calculation of the expected total discounted profit.

광 인터넷에서 버스트 손실 성능 향상을 위한 채널 선정 방식 (A Preemptive Channel Reservation Scheme for Improving Burst Loss Performance in Optical Burst Switching Networks)

  • 김은아;이강형;이수경
    • 한국정보과학회:학술대회논문집
    • /
    • 한국정보과학회 2005년도 한국컴퓨터종합학술대회 논문집 Vol.32 No.1 (A)
    • /
    • pp.457-459
    • /
    • 2005
  • OBS(Optical Burst Switching) 망에서 우선 순위를 보장해 주기 위해 채널 선정 방식(preemptive channel reservation scheme)이 제안되어 왔다. 채널 선점으로 인해 drop된 버스트의 크기가 OBS 망의 전체 성능에 영향을 끼치는 요소인데도 불구하고 기존의 채널 선점 방식은 선점될 채널 선택 시에 버스트의 채널 사용 시간(elapsed time)만을 고려하고 있다. 따라서 본 논문에서는 각 버스트의 채널 사용 시간과 버스트 길이의 합이 작은 채널을 선택하는 선점 방식으로써 Length-based Smallest Elapsed time Selection(LSE)을 제안한다 시뮬레이션을 통하여 제안하는 LSE 방식이 기존의 SE(Smallest Elapsed time)에 비해서 버스트 손실 성능 면에서 우수함을 알 수 있었다.

  • PDF