New trends in parallel and distributed simulation: From many-cores to Cloud Computing

In this paper, the rationale and some advantages for multiaccess broadcast packet communication using satellite and ground radio channels are discussed. A mathematical model is formulated for a slotted ALOHA random access system. Using this model, a theory is put forth which gives a coherent qualitative interpretation of the system stability behavior which leads to the definition of a stability measure. Quantitative estimates for the relative instability of unstable channels are obtained. Numerical results are shown illustrating the trading relations among channel stability, throughput, and delay. These results provide tools for the performance evaluation and design of an uncontrolled slotted ALOHA system. Adaptive channel control schemes are studied in a companion paper.

Packet Switching in a Multiaccess Broadcast Channel: Performance Evaluation

In this tutorial paper, we will firstly review some basic simulation concepts and then introduce the parallel and distributed simulation techniques in view of some new challenges of today and tomorrow. More in particular, in the last years there has been a wide diffusion of many cores architectures and we can expect this trend to continue. On the other hand, the success of cloud computing is strongly promoting the “everything as a service” paradigm. Is parallel and distributed simulation ready for these new challenges? The current approaches present many limitations in terms of usability and adaptivity: there is a strong need for new evaluation metrics and for revising the currently implemented mechanisms. In the last part of the paper, we propose a new approach based on multi-agent systems for the simulation of complex systems. It is possible to implement advanced techniques such as the migration of simulated entities in order to build mechanisms that are both adaptive and very easy to use. Adaptive mechanisms are able to significantly reduce the communication cost in the parallel/distributed architectures, to implement load-balance techniques and to cope with execution environments that are both variable and dynamic.

Parallel and distributed simulation from many cores to the public cloud

http://cell-devs.sce.carleton.ca/publications/2013/JLW13/j4-JLW13.pdf

Synchronization Methods in Parallel and Distributed Discrete-Event Simulation

—In this tutorial paper, we will ﬁrstly review somebasic simulation concepts and then introduce the parallel anddistributed simulation techniques in view of some new challengesof today and tomorrow. More in particular, in the last yearsthere has been a wide diffusion of many cores architectures andwe can expect this trend to continue. On the other hand, thesuccess of cloud computing is strongly promoting the “everythingas a service” paradigm. Is parallel and distributed simulationready for these new challenges? The current approaches presentmany limitations in terms of usability and adaptivity: there isa strong need for new evaluation metrics and for revising thecurrently implemented mechanisms. In the last part of the paper,we propose a new approach based on multi-agent systems forthe simulation of complex systems. It is possible to implementadvanced techniques such as the migration of simulated entitiesin order to build mechanisms that are both adaptive and veryeasy to use. Adaptive mechanisms are able to signiﬁcantly re ducethe communication cost in the parallel/distributed architectures,to implement load-balance techniques and to cope with executionenvironments that are both variable and dynamic. Finally, suchmechanisms will be used to build simulations on top of unreliablecloud services.Index Terms—Simulation; Parallel and Distributed Simulation;Cloud Computing; Adaptive Systems; Middleware

Parallel and Distributed Simulation from Many Cores to the Public Cloud (Extended Version)

The performance of a conservative time management algorithm in a distributed simulation system degrade s significantly if a large number of null messages are exchanged across the logical processes in order to avoid deadlock. This situation gets more severe when the exchange of null messages is increased due to the poor selection of key parameters such as lookahead values. However, with a mathematical model that can approximate the optimal values of parameters that are directly involved in the performance of a time management algorithm, we can limit the exchange of null messages. The reduction in the exchange of null messages greatly improves the performance of the time management algorithm by both minimizing the transmission overhead and maintaining a consistent parallelization. This paper presents a generic mathematical model that can be effectively used to evaluate the performance of a conservative distributed simulation system that uses null messages to avoid deadlock. Since the proposed mathematical model is generic, the performance of any conservative synchronization algorithm can be approximated. In addition, we develop a performance model that demonstrates that how a conservative distributed simulation system performs with the null message algorithm (NMA). The simulation results show that the performance of a conservative distributed system degrades if the NMA generates an excessive number of null messages due to the improper selection of parameters. In addition, the proposed mathematical model presents the critical role of lookahead which may increase or decrease the amount of null messages across the logical processes. Furthermore, the proposed mathematical model is not limited to NMA. It can also be used with any conservative synchronization algorithm to approximate the optimal values of parameters.

/pdf/minimizing-the-null-message-exchange-in-conservative-388op20cfl.pdf

Minimizing the Null Message Exchange in Conservative Distributed Simulation

Time Wrap algorithm is a well-known mechanism of optimistic synchronization in a parallel discrete-event simulation (PDES) system. It offers a run time recovery mechanism that deals with the causality errors. For an efficient use of rollback, the global virtual time (GVT) computation is performed to reclaim the memory, commit the output, detect the termination, and handle the errors. This paper presents a new unacknowledged message list (UML) scheme for an efficient and accurate GVT computation. The proposed UML scheme is based on the assumption that certain variables are accessible by all processors. In addition to GVT computation, the proposed UML scheme provides an effective solution for both simultaneous reporting and transient message problems in the context of synchronous algorithm. To support the proposed UML approach, two algorithms are presented in details, with a proof of its correctness. Empirical evidence from an experimental study of the proposed UML scheme on PHOLD benchmark fully confirms the theoretical outcomes of this paper. (Received in June 2009, accepted in April 2010. This paper was with the authors 5 months for 3 revisions.)

/pdf/an-efficient-optimistic-time-management-algorithm-for-4stcm09i68.pdf

An efficient optimistic time management algorithm for discrete-event simulation system

With the tremendous applications of the wireless sensor network, self-localization has become one of the challenging subject matter that has gained attention of many researchers in the field of wireless sensor network. Localization is the process of assigning or computing the location of the sensor nodes in a sensor network. As the sensor nodes are deployed randomly, we do not have any knowledge about their location in advance. As a result, this becomes very important that they localize themselves as manual deployment of sensor node is not feasible. Also, in WSN the main problem is the power as the sensor nodes have very limited power source. This paper provides a novel solution for localizing the sensor nodes using controlled power of the beacon nodes such that we will have longer life of the beacon nodes which plays a vital role in the process of localization as it is the only special nodes that has the information about its location when they are deployed such that the remaining ordinary nodes can localize themselves in accordance with these beacon node. We develop a novel model that first finds the distance of the sensor nodes then it finds the location of the unknown sensor nodes in power efficient manner. Our simulation results show the effectiveness of the proposed methodology in terms of controlled and reduced power.

Power efficient scheme for self localization in wireless sensor networks

Multiuser detection is an important technology in wireless CDMA systems for improving both data rate as well as user capacity. However, the computational complexity of multiuser detection prevents the widespread use of this technique. Most of the CDMA systems today and in the near future will continue to use the conventional matched filter with its comparatively low user capacity and a slow data rate. However, if we could lower the computational complexity of multiuser detectors, most of the CDMA systems would be likely to take advantage of this technique in order to gain increased system capacity and a better data rate. In this paper, a novel approach for reducing the computational complexity of multiuser receivers is proposed. It utilizes the transformation matrix technique to improve the performance of multiuser detectors. We show that the mathematical computations of the implementation complexity can turn in overall less complex system that has strong impact on the system's signal to noise ratio (SNR) and the bit error rate (BER). The performance measure adopted in this paper is the achievable bit rate for a fixed probability of error (10-7) and consistent values of SNR.

Transformation matrix algorithm for reducing the computational complexity of multiuser receivers for DS-CDMA wireless systems

Null message algorithm is an important conservative time management protocol in parallel discrete event simulation systems for providing synchronization between the distributed computers with the capability of both avoiding and resolving the deadlock. However, the excessive generation of null messages prevents the widespread use of this algorithm. The excessive generation of null messages results due to an improper use of some of the critical parameters such as frequency of transmission and Lookahead values. However, if we could minimize the generation of null messages, most of the parallel discrete event simulation systems would be likely to take advantage of this algorithm in order to gain increased system throughput and minimum transmission delays. In this paper, a new mathematical model for optimizing the performance of parallel and distributed simulation systems is proposed. The proposed mathematical model utilizes various optimization techniques such as variance of null message elimination to improve the performance of parallel and distributed simulation systems. For the sake of simulation results, we consider both uniform and non-uniform distribution of Lookahead values across multiple output lines of an LP. Our experimental verifications demonstrate that an optimal NMA offers better scalability in parallel discrete event simulation systems if it is used with the proper selection of critical parameters.

Aasia Riasat

Papers

Minimizing the Null Message Exchange in Conservative Distributed Simulation

An efficient optimistic time management algorithm for discrete-event simulation system

Power efficient scheme for self localization in wireless sensor networks

Transformation matrix algorithm for reducing the computational complexity of multiuser receivers for DS-CDMA wireless systems

A new mathematical model for optimizing the performance of parallel and discrete event simulation systems