The Utilitarian parallel Simulator (U.P.S.) extends parallelism to the CSIM sequential simulation tool by providing several new modeling constructs. Using conservative synchronization techniques, these constructs auto...
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The Utilitarian parallel Simulator (U.P.S.) extends parallelism to the CSIM sequential simulation tool by providing several new modeling constructs. Using conservative synchronization techniques, these constructs automatically support time-synchronized communications between CSIM submodels running on different processors. This paper describes extensions to U.P.S. that allow the user to assist U.P.S. by providing additional 'process lookahead,' thereby reducing the frequency of synchronizations. The use and effect on performance of process lookahead is described for several models. In a mobile cellular communications model, the use of process lookahead results in up to a 60% improvement in speedup on 32 nodes of the IBM SP2. A factor of 3 improvement is obtained on a closed queueing network simulation running on 32 nodes of the Intel Paragon.
This paper describes two forms of feedback in the simulation runtime of VHDL circuits that greatly influences performance. While circuit feedback and strongly connected components have been observed and documented as ...
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This paper describes two forms of feedback in the simulation runtime of VHDL circuits that greatly influences performance. While circuit feedback and strongly connected components have been observed and documented as detrimental influences to conservative parallel discrete event simulation (PDES) efficiency, that influence has never been quantified. Moreover, in this study, the phenomenon of induced feedback [1] was observed to diminish speedup to the same degree as explicit feedback. In this paper the influence of feedback on simulation runtime is analyzed and an O(n) algorithm for its elimination is presented. In addition, a metric for the quantification of feedback is introduced. By measuring feedback, it is possible to balance its influence on simulation runtime with that of other factors (e.g. load balance, number of processors, machine granularity, etc.) through the use of a cost-based partitioning approach. This paper reports significant improvements in runtime for three circuits due to the prevention of feedback using the partitioning algorithm presented. In addition, strong correlation between the feedback metric and conservative parallelsimulation overhead is demonstrated.
One of the promises of parallelized discrete-event simulation is that it might provide significant speedups over sequential simulation. In reality, high performance cannot be achieved unless the system is fine-tuned t...
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One of the promises of parallelized discrete-event simulation is that it might provide significant speedups over sequential simulation. In reality, high performance cannot be achieved unless the system is fine-tuned to balance computation, communication, and synchronization requirements. In this paper, we discuss our experiments in automated load balancing using the SPEEDES simulation framework. Specifically, we examine three mapping algorithms that use run-time measurements. Using simulation models of queuing networks and the National Airspace System, we investigate (i) the use of run-time data to guide mapping, (ii) the utility of considering communication costs in a mapping algorithm, (iii) the degree to which computational 'hot-spots' ought to be broken up in the linearization, and (iv) the relative execution costs of the different algorithms. We compare the performance of the three algorithms using results from the Intel Paragon.
The simulation of computational fluid dynamics problems in two and more dimensions involves computations of multiple degrees of freedom, such as the components of velocity, which are an obvious source of parallelism. ...
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A load distribution system is proposed to enable a single Time Warp program to execute in background, spreading over a collection of possibly heterogeneous workstations (including multiprocessor hosts), utilizing what...
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A load distribution system is proposed to enable a single Time Warp program to execute in background, spreading over a collection of possibly heterogeneous workstations (including multiprocessor hosts), utilizing whatever otherwise unused CPU cycles are available. The system uses a simple processor allocation policy to dynamically add or delete hosts from the set of processors utilized by the Time Warp program during its execution. A load balancing algorithm is used that allocates logical processes (LPs) to processors, taking into account other computations executing on the host from the system or other user applications. A clustering mechanism is used to group collections of logical processes together, reducing process migration overheads and helping to retain locality of communication for simulations containing large number of LPs. An initial, prototype implementation of the load distribution system is described that executes on a homogeneous network of Silicon Graphics workstations. Initial experiments indicate this approach shows promise in enabling efficient execution of Time Warp programs 'in background' on distributed computing platforms.
We present an Incremental State Saving technique for which the state saving calls are inserted automatically by directly editing the application executable. This method has the advantage of being easy to use since it ...
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We present an Incremental State Saving technique for which the state saving calls are inserted automatically by directly editing the application executable. This method has the advantage of being easy to use since it is fully automatic, and has good performance since it adds overhead only where state is being modified. Since the editing happens on executable code, the method is independent of the compiler, and allows third party libraries to be used. None of the previous incremental state saving methods have both of these features. We find that it is beneficial to use Automatic Incremental State Saving if less than 15% of the state is modified in each event as compared to copy state saving. This technique allows us to efficiently parallelize existing simulations, and makes Time Warp more accessible to non-Time Warp experts.
The proceedings contain 45 papers. The topics discussed include: use case maps for attributing behavior to system architecture;modeling real-time distributed software systems;the integration of real-time applications ...
ISBN:
(纸本)0818675152
The proceedings contain 45 papers. The topics discussed include: use case maps for attributing behavior to system architecture;modeling real-time distributed software systems;the integration of real-time applications into the global command and control system;implementing distributed real-time control systems in a functional programming language;modeling and simulation in reactive systems;entity-life modeling in a distributed environment;an environment for incremental development of distributed extensible asynchronous real-time systems;development and validation of network clock measurement techniques;inter- and intra-processor synchronizations in multiprocessor real-time kernel;and behavior analysis of parallel, real-time and embedded sytems for monitoring and optimizing industrial processes.
The event horizon is a very important concept that applies to both parallel and sequential discrete-event simulations. By exploiting the event horizon, parallelsimulations can processes events optimistically in a ris...
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The event horizon is a very important concept that applies to both parallel and sequential discrete-event simulations. By exploiting the event horizon, parallelsimulations can processes events optimistically in a risk-free manner (i.e., without requiring antimessages) using adaptable 'breathing' time cycles with variable time widths. Additionally, by exploiting the event horizon, one can significantly reduce the overhead of event list management that is common to virtually every discrete-event simulation. This paper is a continuation of work previously reported at PADS94. In that report, a complete mathematical formulation of the event horizon was derived under equilibrium conditions using the hold model. Various forms of the beta density function were consequently used to verify the predicted results of the analytic model. This second report describes how the concept of the event horizon can also be applied to event list management. By exploiting the event horizon, the performance of several priority queue data structures are improved including: linked lists, various binary trees, and heaps. A somewhat detailed description of these modified data structures along with other relevant background information is provided for completeness. Performance results for each priority queue data structure is presented.
For the performability evaluation of complex soft realtime systems simulation often remains the only feasible method. simulation experiments tend to be very time consuming if rare events have to be considered. This pa...
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