Abstract
Reasoning about a distributed algorithm is simplified if we can ignore the time needed to send and deliver messages and can instead pretend that a process sends a collection of messages as a single atomic action, with the messages delivered instantaneously as part of the action. A theorem is derived that proves the validity of such reasoning for a large class of algorithms. It generalizes and corrects a well-known folk theorem about when an operation in a multiprocess program can be considered atomic.
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Abbreviations
- A :
-
The set of program actions
- A :
-
The algorithm under consideration
- A :
-
The reduced version of algorithmA
- 〈A〉:
-
The action obtained by executing the operationA as an atomic action
- C :
-
The set of state components
- d[i]:
-
A variable of the Distance-Finding Algorithm
- L :
-
An operation ofA, as in C2
- Ľ :
-
The operation obtained by adding toL the actions that deliver messages sent byL
- N p(S):
-
The set of possible next actions of processp from states
- P :
-
The correctness property
- R :
-
An operation ofA, as in C2
- S :
-
The set of states
- S 0 :
-
The set of initial states
- S c :
-
The range of values of state componentc
- 〈X〉:
-
An action ofA, as in C2
- Φ:
-
Usually denotes an execution ofA
- ∑:
-
The execution ofA that corresponds to an execution Φ ofA
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When snow conditions are poor,Dr. L. Lamport works at Digital Equipment Corporation's Systems Research Center. As an undergraduate, he took a course in atomic physics.
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Lamport, L. A theorem on atomicity in distributed algorithms. Distrib Comput 4, 59–68 (1990). https://doi.org/10.1007/BF01786631
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DOI: https://doi.org/10.1007/BF01786631