Dipali Shah’s research while affiliated with University of Bridgeport and other places

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Publications (1)


Fig.1. Representation of transient message problem between two LPs and the controller. X-axis represents the global current simulation time of the system. The first two messages are transmitted from controller (indicated by full dotted lines) to initiate GVT computation. LP A and LP B compute its LBTS values as 15 and 20, respectively and reported to the controller (indicated by partially cut lines). A transient message arrived with the time stamp 10 at LP A. If this time stamp is not considered, the value of GVT will be incorrectly computed as 15 rather than 10.
Fig.5. Tree implementation with Samadi's algorithm, Number of rounds versus latency for N=10.
Implementation of Tree and Butterfly Barriers with Optimistic Time Management Algorithms for Discrete Event Simulation
  • Conference Paper
  • Full-text available

January 2008

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455 Reads

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1 Citation

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Dipali Shah

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Aasia Riasat

The Time Wrap algorithm [3] offers a run time recovery mechanism that deals with the causality errors. These run time recovery mechanisms consists of rollback, anti-message, and Global Virtual Time (GVT) techniques. For rollback, there is a need to compute GVT which is used in discrete-event simulation to reclaim the memory, commit the output, detect the termination, and handle the errors. However, the computation of GVT requires dealing with transient message problem and the simultaneous reporting problem. These problems can be dealt in an efficient manner by the Samadi’s algorithm [8] which works fine in the presence of causality errors. However, the performance of both Time Wrap and Samadi’s algorithms depends on the latency involve in GVT computation. Both algorithms give poor latency for large simulation systems especially in the presence of causality errors. To improve the latency and reduce the processor ideal time, we implement tree and butterflies barriers with the optimistic algorithm. Our analysis shows that the use of synchronous barriers such as tree and butterfly with the optimistic algorithm not only minimizes the GVT latency but also minimizes the processor idle time.

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Citations (1)


... Consequently, the use of matrix with the Mattern's algorithm provides several advantages such as it reduces the number of memory fetches, saves memory, increases the processor speed, and improves the latency. We incorporated the butterfly barrier as it has great performance when compared to the other broadcast and the centralized barriers [7,19,20]. ...

Reference:

A Use of Matrix with GVT Computation in Optimistic Time Warp Algorithm for Parallel Simulation
Implementation of Tree and Butterfly Barriers with Optimistic Time Management Algorithms for Discrete Event Simulation