We propose a new simulation method, called interval branching, which aims to facilitate efficient simulation studies of systems that involve temporal uncertainty. The method uses interval timestamps for events and exp...
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ISBN:
(纸本)9780769531595
We propose a new simulation method, called interval branching, which aims to facilitate efficient simulation studies of systems that involve temporal uncertainty. The method uses interval timestamps for events and explores different execution orders of overlapping events by branching the simulation. We first present a sequential version of interval branching, and then extend it to parallelsimulation using the logical process paradigm. The parallel interval branching algorithm uses the logical-process cloning technique for efficient computation of branches. Our preliminary experiments show its potential as an efficient method for discrete-event simulation studies.
The notion of temporal uncertainty, expressed as the possibility for an event to occur in an interval of simulation time, rather than at a specific instant, has been recently proposed and exploited in order to enhance...
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ISBN:
(纸本)0769521118
The notion of temporal uncertainty, expressed as the possibility for an event to occur in an interval of simulation time, rather than at a specific instant, has been recently proposed and exploited in order to enhance the performance of parallel/distributedsimulation systems. In this paper we propose the concept of "spatial uncertainty" expressed as the possibility for a simulation event to occur in one of a set of points within the simulated system space. How to handle/exploit space uncertain events in an optimistic simulation system is discussed. Also, experimental results for optimistic simulations of a Personal Communication System (PCS) modeled with space uncertain events are reported These results show the ability of spatial uncertainty to increase the performance of the parallelsimulation system by providing a more flexible approach to synchronization.
Several scheduling algorithms have been proposed to determine the ne,rr event to be executed on a processor in a Time Warp parallel discrete event simulation. However none of them is specifically designed for simulati...
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ISBN:
(纸本)0769506771
Several scheduling algorithms have been proposed to determine the ne,rr event to be executed on a processor in a Time Warp parallel discrete event simulation. However none of them is specifically designed for simulations where the execution time (or granularity)for different ty,pes of events has large variance. In this paper we present a grain sensitive scheduling algorithm which addresses this problem. In our solution, the scheduling decision depends on both timestamp and granularity values with the aim at giving higher priority, to small grain events even if their timestamp is not the lowest one (i.e. the closest one to the commitment horizon of the simulation). This implicitly limits the optimism of the execution of large grain events that, if rolled back, would produce large waste of CPU time. The algorithm is adaptive in that it relies on the dynamic recalculation of the length of a simulated time window within which the timestamp of ally good candidate event for the scheduling falls in. if the window length is set to Zeta, then the algorithm behaves like the standard Lowest-Timestamp-First (LTF) scheduling algorithm. simulation results of a classical benchmark in several different configurations are reported for a performance comparison with LTE These results demonstrate the effectiveness of our algorithm.
This paper describes Nops, a conservatively synchronized process-oriented parallelsimulation system. Nops is designed to support the programming model of the Telecommunications Description Language (TeD), with specia...
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This paper describes Nops, a conservatively synchronized process-oriented parallelsimulation system. Nops is designed to support the programming model of the Telecommunications Description Language (TeD), with special emphasis on scaling up to very large network models. We chronicle the decisions beyond Nops' design, describe that design, assess its raw performance relative to CSIM, Maisie, and GTW, and study its ability to scale to large models.
In this work we discuss the use and possible abuse of linear and inversive pseudorandom numbers (PRNs) in parallel and distributed environments. After an investigation of properties of PRNs which determine hour these ...
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ISBN:
(纸本)0818684577
In this work we discuss the use and possible abuse of linear and inversive pseudorandom numbers (PRNs) in parallel and distributed environments. After an investigation of properties of PRNs which determine hour these may be applied in such environments we introduce a software package which provides an unified and easy-to-use approach to the generating and handling of parallel streams of such PRNs. Experimental results are conducted which describe the features of the software package and compare the performance of two selected types of pseudorandom number *** this work we discuss the use and possible abuse of linear and inversive pseudorandom numbers (PRNs) in parallel and distributed environments. After an investigation of properties of PRNs which determine hour these may be applied in such environments we introduce a software package which provides an unified and easy-to-use approach to the generating and handling of parallel streams of such PRNs. Experimental results are conducted which describe the features of the software package and compare the performance of two selected types of pseudorandom number generators.
This paper proposes a critical path-like analyzer to predict the amount of memory consumed in a specific Chandy-Misra simulation: Segments of code are inserted into the existing sequential simulation program, and this...
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This paper proposes a critical path-like analyzer to predict the amount of memory consumed in a specific Chandy-Misra simulation: Segments of code are inserted into the existing sequential simulation program, and this modified simulation program is called a memory analyzer. The amount of memory needed in the corresponding Chandy-Misra simulation is computed along with the execution of the memory analyzer. Experiments to evaluate the analyzer are in progress.
A Motif based graphical tool XTracker is described. XTracker can show Gannt-like charts of the activities on each node or it can show the event messages as traffic between simulation objects. XTracker can take its dat...
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A Motif based graphical tool XTracker is described. XTracker can show Gannt-like charts of the activities on each node or it can show the event messages as traffic between simulation objects. XTracker can take its data from sequential simulation runs and simulate a parallel execution under a number of simulation methods. XTracker can act as a performance modeling tool.
In this paper we address the problem of efficiently performing parallel discrete-event simulation in the case that events elaboration is dependent of other processes' local states. We propose a parallelsimulation...
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ISBN:
(纸本)0818679654
In this paper we address the problem of efficiently performing parallel discrete-event simulation in the case that events elaboration is dependent of other processes' local states. We propose a parallelsimulation policy, called State Query Time Warp (SQTW), based on the Time Warp mechanism. We present experiments performed by means of a SQTW-based parallel simulator on a T-800 transputer machine for solving performance models based on state-dependent routing queueing network models. The experiments are used for assessing overheads and efficiency involved by SQTW;results show that high efficiency is achievable, and surprisingly reveal SQTW is able to globally reduce rollback overheads with respect to corresponding Time Warp simulations.
In this paper we revisit the notion of event simultaneity in the context of parallel and distributedsimulation. Although the simulation community has recognized this problem for years, it has focused mainly on the me...
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In this paper we revisit the notion of event simultaneity in the context of parallel and distributedsimulation. Although the simulation community has recognized this problem for years, it has focused mainly on the mechanics of breaking event-time ties and has neither measured its extent nor considered its implications. Extant simulators (both serial and parallel) prohibit simultaneity either by user-specified event priorities or by an arbitrary (but well-documented) tie-breaking mechanism. We shall show, theoretically and empirically, that these strategies may lead to an invalid simulation. In doing so, we shall introduce the threshold of event simultaneity and use it to understand the semantics of simultaneity.
Data distribution management (DDM) is concerned with the problem of efficiently distributing state information among the entities in a distributedsimulation. While heavily studied in the DIS community for training ap...
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Data distribution management (DDM) is concerned with the problem of efficiently distributing state information among the entities in a distributedsimulation. While heavily studied in the DIS community for training applications using real-time synchronization, this problem has received considerably less attention for logical time simulations, and little performance data has appeared in this regard. This paper is concerned with evaluating the performance of a logical time synchronized.
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