SOSP '87 Proceedings of the eleventh ACM Symposium on Operating systems principles
Comparative analyses of parallel simulation protocols
WSC '89 Proceedings of the 21st conference on Winter simulation
GTW: a time warp system for shared memory multiprocessors
WSC '94 Proceedings of the 26th conference on Winter simulation
Time, clocks, and the ordering of events in a distributed system
Communications of the ACM
Fault-tolerant distributed simulation
PADS '98 Proceedings of the twelfth workshop on Parallel and distributed simulation
Unsynchronized parallel discrete event simulation
Proceedings of the 30th conference on Winter simulation
On event ordering in parallel discrete event simulation
PADS '99 Proceedings of the thirteenth workshop on Parallel and distributed simulation
Safe timestamps and large-scale modeling
PADS '00 Proceedings of the fourteenth workshop on Parallel and distributed simulation
Practical parallel simulation applied to aviation modeling
Proceedings of the fifteenth workshop on Parallel and distributed simulation
Consistent modeling of distributed mutual exclusion protocol using optimistic simulation
Proceedings of the fifteenth workshop on Parallel and distributed simulation
Lookback: a new way of exploiting parallelism in discrete event simulation
Proceedings of the sixteenth workshop on Parallel and distributed simulation
Parallel simulation: parallel and distributed simulation systems
Proceedings of the 33nd conference on Winter simulation
Proceedings of the 33nd conference on Winter simulation
A Delayed-Initiation Risk-Free Multiversion Temporally Correct Algorithm (Research Note)
Euro-Par '02 Proceedings of the 8th International Euro-Par Conference on Parallel Processing
Optimistic parallel simulation of a large-scale view storage system
Future Generation Computer Systems - Selected papers from CCGRID 2002
Large-Scale TCP Models Using Optimistic Parallel Simulation
Proceedings of the seventeenth workshop on Parallel and distributed simulation
Parallel simulation: distributed simulation systems
Proceedings of the 35th conference on Winter simulation: driving innovation
Optimistic Protocol Analysis in a Performance Analyzer and Prediction Tool
Proceedings of the 19th Workshop on Principles of Advanced and Distributed Simulation
Hierarchical Composite Synchronization
PADS '12 Proceedings of the 2012 ACM/IEEE/SCS 26th Workshop on Principles of Advanced and Distributed Simulation
Warp speed: executing time warp on 1,966,080 cores
Proceedings of the 2013 ACM SIGSIM conference on Principles of advanced discrete simulation
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This paper is a reminder of the danger of allowing ``risk'' when synchronizing a parallel discrete-event simulation: a simulation code that runs correctly on a serial machine may, when run in parallel, fail catastrophically. This can happen when Time Warp presents an ``inconsistent'' message to an LP, a message that makes absolutely no sense given the LP's state. Failure may result if the simulation modeler did not anticipate the possibility of this inconsistency. While the problem is not new, there has been little discussion of how to deal with it; furthermore the problem may not be evident to new users or potential users of parallel simulation. This paper shows how the problem may occur, and the damage it may cause. We show how one may eliminate inconsistencies due to lagging rollbacks and stale state, but then show that so long as risk is allowed it is still possible for an LP to be placed in a state that is inconsistent with model semantics, again making it vulnerable to failure. We finally show how simulation code can be tested to ensure safe execution under a risk-free protocol. Whether risky or risk-free, we conclude that under current practice the development of correct and safe parallel simulation code is not transparent to the modeler; certain protections must be included in model code or model testing that are not rigorously necessary if the simulation were executed only serially.