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43 Implementation simulation time and also the Transaction chain itself. The SimulationEngine class will be implemented as part of the Basic GPSS Simulation Engine implementation phase detailed in section 5.2.2 and a description of how the scheduling was implemented can be found in 5.<strong>3.1</strong>. 5.1.3 Generation and Termination of Transactions Performing transaction-oriented simulation in a parallel simulator also has an influence on how Transactions are generated and how they are terminated. Generating Transactions Transactions are generated in the GENERATE blocks of the simulation. During the generation each Transaction receives a unique numerical ID that identifies the Transaction during the rest of the simulation. In a parallel transaction-oriented simulator GENERATE blocks can exist in any of the model partitions and therefore in any of the LPs. This requires a scheme, which ensures that the Transaction IDs generated in each LP are unique across the overall parallel simulation. Ideally such a scheme requires as little communication between the LPs as possible. The scheme used for this parallel simulator will generate unique Transaction IDs without any additional communication overhead. This is achieved by partitioning the value range of the numeric IDs according to the number of partitions in the simulation model. The only requirement of this scheme is that all LPs are aware of the total number of partitions and LPs within the simulation. This information will be passed to them during the initialisation. The used scheme is based on an offset that depends on the total number of LPs. Each LP has its own counter that is used to generate unique Transaction IDs. These counters are initialised with different starting values and the same offset is used for incrementing the counters when one of their values has been used for a Transaction ID. A simulation with n LPs (i.e. n partitions) will use the offset n to increment the local Transaction ID counters and each LP will initialise its counter with its own number in the list of LPs. In a simulation with 3 LPs, LP1 would initialise its counter to the value 1, LP2 to 2 and LP3 to 3 and the increment offset used would be the total number of LPs which is 3. The sequence of IDs generated by these LPs would be LP1: 1, 4, 7, … and by LP2: 2, 5, 8, … and by LP3: 3, 6, 9, … and so forth. Further advantages of this scheme are that it partitions the possible ID value range into equally
44 Implementation large numerical partitions independent of the total size of the value range and it also makes it possible to determine in which partition a Transaction was generated using their ID. Terminating Transactions The termination of Transactions raises similar problems like their generation. According to GPSS Transactions are terminated in TERMINATE blocks. Each time a Transaction is terminated a global Termination Counter is decremented by the decrement parameter of the TERMINATE block involved. A GPSS simulation initialises the Termination Counter with a positive value at the start of the simulation and the counter is then used to detect the end of the simulation, which is reached as soon as the Termination Counter has a value of zero or less. The required global Termination Counter could be located in one of the LPs but accessing it form other LPs would require additional synchronisation. The problem of accessing such a Termination Counter is the same like accessing other objects from different LPs as outlined in 4.1.2. In order to avoid the additional complexity and communication overhead of implementing a global Termination Counter the parallel simulator will use a separate local Termination Counter in each LP. This solution will perform simulations that don’t require a global Termination Counter without additional communication overhead. For simulations that do require a global Termination Counter the problem can be reduced to the synchronisation and the movement of Transactions between LPs as solved by the synchronisation algorithm. In this case all TERMINATE blocks of such a simulation need to be located within the same partition. This will result in additional communication and synchronisation when Transactions are moved from other LPs to the one containing the TERMINATE blocks. Figure 12 below shows how a simulation model with two partitions that needs a single Termination Counter can be converted into equivalent simulation models so that the simulation will effectively use a single Termination Counter.
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
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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
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Page 93 and 94: 6.4 Validation 4 84 Validation of t
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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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