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Parallel Transaction-oriented Simulation LP1 just proceeds moving the Transactions in its Transaction chain according to their simulation time (Transaction priorities are ignored for this example). Apposed to that the rollback in aggressive cancellation would result in an anti-Transaction being sent out for x1 immediately which would cause a second rollback in LP2 and another anti- Transaction for x1’ being sent back to LP1. At the end both LPs will end up in the same state in which they were before x1 was moved by LP1. The same cycle of events would start again without any actual simulation progress. LP1 LP2 LP1 LP2 x1 x1 xy Lazy cancellation Aggressive cancellation xy- x1 x1 x2 x1 x2 x1 cycle 1 Transaction transferred to other LP Anti-Transaction for other LP Rollback x1' x1' simulations. This has also been explored by the authors of [33]. They concluded that the 37 x1 x1 x1- x1'- x1 x1' x1 x1 x2 repeat of cycle 1 time Figure 10: Cancellation in transaction-oriented simulation It can therefore be concluded that lazy cancellation needs to be used for a parallel transaction-oriented simulation based on an optimistic algorithm in order to avoid such endless loops. 4.6 Load Balancing Load balancing and the automatic migration of slow LPs to nodes or processors that have a lighter work load has been suggested in order to reduce the runtime of parallel x2 x1' ...
38 Parallel Transaction-oriented Simulation migration of LPs involves a “substantial amount of overheads in saving the process context, flushing the communication channels to prevent loss of messages”. And especially on loosely coupled systems with relatively slow communication channels sending the full process context of the LP from one node to another can add a significant performance penalty to the overall simulation. This penalty would depend on the size of the process context as well as the communication performance between the nodes involved in the migration. The gained performance on the other hand depends on the difference in processing performance and other workload on these nodes. To determine reliably when such an automatic migration is beneficial within a loosely coupled, dynamically changing Ad Hoc Grid environment would be difficult and it is likely that the performance penalty outweighs the gains. This work will therefore not investigate the load balancing and automatic LP migration for performance reasons but only support automatic LP migration as part of the fault tolerance functionality provided by ProActive and described in <strong>3.1</strong>.3. Manual LP migration will be supported by the parallel simulator using ProActive tools. 4.7 Model Partitioning Besides the chosen synchronisation algorithm the partitioning of the simulation model also has a large influence on the performance of the parallel simulation because the communication required between the Logical Processes depends to a large degree on how independent the partitions of a simulation model are. Looking at the requirements of a general-purpose transaction-oriented simulation system for Ad Hoc Grid environments in 4.2 the conclusion was drawn that the required communication needs to be kept to a minimum in order to reach acceptable performance results through parallelisation in such environments. The communication required for the exchange of Transactions between the Logical Processes is part of this overall communication. A simulation model that is supposed to be run in a Grid based parallel simulation system therefore needs to be partitioned in such a way that the expected amount of Transactions moved within the partitions is significantly larger than the amount of Transactions that need to be transferred between these partitions. This means that Grid based parallel
Page 1 and 2: TRANSACTION-ORIENTED SIMULATION IN
Page 3 and 4: Table of Content II Table of Conten
Page 5 and 6: IV Table of Content 6 VALIDATION OF
Page 7 and 8: Figures VI Figures Figure 1: Ad Hoc
Page 9 and 10: Tables VIII Tables Table 1: Change
Page 11 and 12: 2 Introduction synchronisation algo
Page 13 and 14: 2 Fundamental Concepts Fundamental
Page 15 and 16: Figure 1: Ad Hoc Grid architecture
Page 17 and 18: 8 Fundamental Concepts In continuou
Page 19 and 20: 10 Fundamental Concepts Two other a
Page 21 and 22: 12 Fundamental Concepts known as st
Page 23 and 24: 14 Fundamental Concepts event execu
Page 25 and 26: 3 Ad Hoc Grid Aspects 16 Ad Hoc Gri
Page 27 and 28: 18 Ad Hoc Grid Aspects resources an
Page 29 and 30: 20 Ad Hoc Grid Aspects means that a
Page 31 and 32: Parallel Transaction-oriented Simul
Page 33 and 34: 24 Parallel Transaction-oriented Si
Page 35 and 36: 4.2 Synchronisation algorithm 26 Pa
Page 45: 36 Parallel Transaction-oriented Si
Page 49 and 50: 5 Implementation 40 Implementation
Page 51 and 52: 42 Implementation confirm a provisi
Page 53 and 54: 44 Implementation large numerical p
Page 55 and 56: 46 Implementation A detailed descri
Page 57 and 58: 48 Implementation But in a parallel
Page 59 and 60: 50 Implementation GPSS test models
Page 61 and 62: Simulation Controller side 52 Imple
Page 63 and 64: 54 Implementation technique describ
Page 65 and 66: Implementation Euclidean distance b
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Page 69 and 70: 60 Implementation The algorithm wil
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Page 73 and 74: 5.3.2 GVT Calculation and End of Si
Page 75 and 76: 66 Implementation provisional simul
Page 77 and 78: Implementation relatively basic per
Page 79 and 80: 70 Implementation log4j.logger.para
Page 81 and 82: proactive-log4j 72 Implementation T
Page 83 and 84: 74 Implementation Memory Allocation
Page 85 and 86: 76 Validation of the Parallel Simul
Page 93 and 94: 6.4 Validation 4 84 Validation of t
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… LpccEnabled=true LpccClusterNum
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Validation 5.2 Validation of the Pa
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92 Validation of the Parallel Simul
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94 Validation of the Parallel Simul
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7 Conclusions 96 Conclusions Even s
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References 98 References [1] Amin K
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[19] Krafft G. Parallelisation of T
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Appendix A: Detailed GPSS Syntax 10
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Reserved word: DEPART Syntax: [] DE
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Reserved word: SEIZE Syntax: [] SEI
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Setting: LpccClusterNumber Default
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Appendix C: Simulator log4j loggers
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Logger: parallelJavaGpssSimulator.l
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114 Appendix D: Structure of the at
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Appendix E: Documentation of select
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!"#"$$%$&"'"(!))*+,-$"./#0$! 1$"))
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!/+/.7/8$ Appendix E: Documentation
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Returns: Appendix E: Documentation
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!"#$%&'()#%*+,"-*.# Appendix E: Doc
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Constructor Detail !"#$%&'$(#$)*$%+
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Validation 1.1, output of simulate:
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Validation 2, output of LP: Appendi
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Appendix F: Validation output logs
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Validation 2, output of simulate: A
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Validation 3.1, output of LP1: Appe
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Validation 4, output of LP1: Append
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simulation for time 2000) (628) 20:
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Validation 4, output of simulate: A
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(135) 19:37:56,477 Total transactio
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(68) 19:37:56,619 by the transactio
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(1295) 14:25:22,740 Simulation stop
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(68) 14:25:22,888 by the transactio
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Validation 6.2, output of LP2: (1)
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(32) (1,2) 0 765 Block: TRANSFER 0.
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