| 摘要 |
In a distributed system comprising a plurality of processors coupled to one another, each processor comprises a controllable clock circuit which indicates a local time. Clock synchronization methods are based on the idea in which randomly selected M processors out of the total N processors cooperate to adjust the controllable clock circuits of all processors in the distributed system. Three types of methods are described. In a first one of the methods, all processors randomly selects M processors, respectively, at time instants which are different from one another, and each processor adjusts its own controllable clock circuit to an average of the local times of the selected M processors. In a second method, each processor transmits its own local time to randomly selected M processors and adjusts its own controllable clock circuit to the average of received local times. In a third method, all processors adjust their controllable clock circuits to the average of received local times issued by randomly selected M processors. Fault tolerance against each processor is taken into account in their methods. Their methods can be applied to a sufficient large distributed system because of a small number of messages exchanged among processors.
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