Reiher, P. L., and Jefferson, D. Dynamic load management in the Time Warp operating system. Transactions of The Society for Computer Simulation 7, 2 (June 1990), 91--120.  Home/Search   Document Not in Database   Summary   Related Articles   Check

.... mechanisms in the warped simulator and classified the factors that influence the aggregation decisions namely: Aggregation Optimistic 1 Note that delaying the messages may improve the performance of the receiving process by improving the effective work as defined by Reiher and Jefferson [52]. 2 While each application message arrives at the destination LP in a shorter time on average, the simulation progress rate is also faster at the receiving LP because it spends less time communicating. Thus, the proportionality between the time that a message is delayed and the potential harm to ....

Reiher, P. L., and Jefferson, D. Dynamic load management in the Time Warp operating system. Transactions of The Society for Computer Simulation 7, 2 (June 1990), 91--120.

.... affect the efficiency of the synchronisation mechanism (e.g. amount of roll backed computation) As a result, load balancing has been studied extensively in the special context of both conservative and optimistic parallel simulation (Burdorf Marti 1993, Glazer Tropper 1993, Goldberg 1992, Reiher Jefferson 1990, Schlagenhaft, Ruhwandl, Sporrer Bauer 1995, Carothers Fujimoto 1996) However, the issue of dynamic load balancing has received very little attention in relation to interest management and work in this area to date is only preliminary (Morse 1996, Messina, Davis, Brunette, Gottshock, ....

Reiher, P. L. & Jefferson, D. (1990), `Dynamic load management in the Time-Warp operating system', Transactions of the Society for Computer Simulation 7(2), 91--120.

.... affect the efficiency of the synchronisation mechanism (e.g. amount of roll backed computation) As a result, load balancing has been studied extensively in the special context of both conservative and optimistic parallel simulation (Burdorf Marti 1993, Glazer Tropper 1993, Goldberg 1992, Reiher Jefferson 1990, Schlagenhaft, Ruhwandl, Sporrer Bauer 1995, Carothers Fujimoto 1996) However, the issue of dynamic load balancing has received very little attention in relation to interest management and work in this area to date is only preliminary (Morse 1996, Messina, Davis, Brunette, Gottshock, ....

Reiher, P. L. & Jefferson, D. (1990), `Dynamic load management in the time-warp operating system', Transactions of the Society for Computer Simulation 7(2), 91--120.

....shared state so that bottlenecks and broadcast communication are minimised. In addition, our approach aims to exploit this decomposition in order to perform load balancing. Although load balancing has been studied extensively in the context of conventional distributed simulations [32] 33] 34] [35], 36] 37] it has received very little attention in relation to Interest Management, and work in this area to date is only preliminary [17] 38] 39] 40] V. SPHERES OF INFLUENCE We assume that each ALP ELP is capable of generating and responding to a finite number of event types, and a ....

P. L. Reiher and D. Jefferson, "Dynamic load management in the TimeWarp operating system," Transactions of the Society for Computer Simulation, vol. 7, no. 2, pp. 91--120, 1990.

....scope of this thesis. The excellent paper by Norman and Thanisch [Norm93] provides a comprehensive list of references concerning the subject. The mapping problem has been investigated within the context of parallel simulation too, for both conservative [Nand92] Bouk94] and optimistic approaches [Reih90a] [Glaz92] The static nature of the occam language requires that the mapping of the occam process graph on the transputer network is specified in advance by the application developer, though a number of tools have been developed to automate various steps of this task [Boil87] Murt87] Lau88] ....

Reiher, P.L., Jefferson, D., "Dynamic Load Management in the Time Warp Operating System", Transactions of the Society for Computer Simulation, 7, 2, June 1990, pp. 91-120.

....Warp simulations. Dynamic load management of Time Warp programs has been studied by others. Reiher and Jefferson propose a new metric called effective processor utilization which is defined as the fraction of the time during which a processor is executing computations that are eventually committed [15]. Based on this metric, they propose a strategy that migrates processes from processors with high effective utilization to those with low utilization. Reiher and Jefferson also propose splitting a logical process into phases to reduce the amount of process state that must be moved when an LP ....

....execution. A well known problem in migrating Time Warp LPs (and thus clusters of LPs) is the fact that each contains a large amount of state. Specifically, each LP maintains a history of state vectors, in case rollback is later required. While phases could be used to address this problem (see [15]) this necessitates implementation of a mechanism for rollbacks to span processor boundaries because a rollback may extend beyond the beginning point of a recently created phase. A simpler, though perhaps more radical, solution is used here. The entire simulation computation is rolled back at ....

P. L. Reiher and D. Jefferson. Dynamic load management in the Time Warp Operating System. Transactions of the Society for Computer Simulation, 7(2):91--120, June 1990.

....take into account processors that are experiencing an excessive amount of rollback, or are advancing too far ahead of other processors. In both cases, the processor should receive more of the simulation workload, even though its utilization may be very high. Metrics such as effective utilization [26] account for rolled back computation, but not overly optimistic execution. Further, it is an open question as to whether standard load balancing algorithms (modified to utilize different metrics) are effective for optimistic simulators, or whether entirely new algorithms are required. We will ....

P. L. Reiher and D. Jefferson. Dynamic load management in the Time Warp Operating System. Transactions of the Society for Computer Simulation, 7(2):91--120, June 1990.

....make a good initial assignment of objects to Time Warp nodes, such that most nodes have an equal share of the work for most of the simulation. Dynamic load management monitors the course of the run and shifts objects or phases (see below) from node to node to equalize load. Reiher and Jefferson [21] have shown how the dynamic load management facility produces good performance improvements. To balance the load on TWOS dynamically, it is necessary to determine periodically the load on each node of the network. The basic metric used to calculate the relative load on the nodes in a TWOS run is ....

P. Reiher and D. Jefferson. Dynamic Load Management in the Time Warp Operating System. Trans. Society for Computer Simulation, 7(2):91--120, 1990.

....cycles to the computations that are constantly being rolled back. To address this issue, Reiher and Jefferson propose a new metric called effective processor utilization which is defined as the fraction of the time during which a processor is executing computations that are eventually committed [82]. This effectively treats time spent executing wrong computations as idle time. Based on this metric, they propose a strategy that migrates processes from processors with high effective utilization to those with low utilization. An algorithm that is similar in spirit is proposed in [37] This ....

....state is initialized to the state of process when the migration occurs. Reiher and Jefferson demonstrate that phase splitting and the effective utilization metric are useful to dynamically balance the load in simulations of a communication network, a system of colliding pucks, and a combat models [82]. Goldberg describes an interesting approach to the load distribution problem [38] If a process becomes a bottleneck, it is replicated to form two or more identical copies, each able to execute concurrently with the others. Read requests are sent to one replica, while write requests are sent to ....

P. L. Reiher and D. Jefferson. Dynamic load management in the Time Warp Operating System. Transactions of the Society for Computer Simulation, 7(2):91--120, June 1990.

....The termination detection is part of the task queue abstraction, because there are states in which a tasks may be in transit, and therefore no work is visible in the queue. Time Warp State The notion of a time warp system for doing speculative simulation was introduced by Reiher and Jefferson [9]. The essential data structure is the simulation state, which is partitioned and distributed across processors. For example, in circuit simulator, the circuit is partitioned into subcircuits based on connectivity defined by direct voltage connections [11] Although the contents of the state, its ....

Peter Reiher and David Jefferson. Dynamic load management in the time warp operating system. Transactions of the Society for Computer Simulation, 7(2):91--120, June 1990.

....system, so much remains to be learned in this area. 3.2.2.3 Load Management and Migration Like many other distributed systems, optimistic synchronization systems can sometimes benefit from dynamic load management. TWOS uses dynamic load management to deal with irregularities in its applications [Reiher 90b] There are several characteristics of optimistic synchronization that can complicate dynamic load management. First, many dynamic load management policies shift processes from machine to machine on the basis of the utilizations of the various machines. Simple utilization is not a good choice of ....

....times, even though much of the work it does might be rolled back. Thus, few processors in optimistic synchronization systems will ever have low utilization. One policy parameter that can take the place of simple utilization is effective utilization. Effective utilization is fully discussed in [Reiher 90b] but, briefly, it is an estimate of the proportion of time each processor spends doing work that is eventually committed. Only such work is of benefit to the application, so processors with low effective utilization are relatively underloaded, even if their simple utilization is quite high. Load ....

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Peter Reiher and David Jefferson, "Dynamic Load Management In the Time Warp Operating System," Transactions of the Society For Computer Simulation, Vol. 7 No. 2, Jun. 1990.

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P. L. Reiher and D. Jefferson. Dynamic load management in the Time Warp Operating System. Transactions of the Society for Computer Simulation, 7(2):91--120, June 1990.

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P. L. Reiher and D. Jefferson. "Dynamic Load Management in the Time Warp Operating System". Transactions of the Society for Computer Simulation, Vol. 7, No. 2, pp. 91--120, June 1990.

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