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<p>The authors present a data-race-free-1, shared-memory model that unifies four earliermodels: weak ordering, release consistency (with sequentially consistent specialoperations), the VAX memory model, and data-race-free-0. Data-race-free-1 unifies themodels of weak ordering, release consistency, the VAX, and data-race-free-0 byformalizing the intuition that if programs synchronize explicitly and correctly, thensequential consistency can be guaranteed with high performance in a manner that retainsthe advantages of each of the four models. Data-race-free-1 expresses the programmer'sinterface more explicitly and formally than weak ordering and the VAX, and allows animplementation not allowed by weak ordering, release consistency, or data-race-free-0.The implementation proposal for data-race-free-1 differs from earlier implementations bypermitting the execution of all synchronization operations of a processor even whileprevious data operations of the processor are in progress. To ensure sequentialconsistency, two sychronizing processors exchange information to delay later operationsof the second processor that conflict with an incomplete data operation of the firstprocessor.</p>
Index Termsmultiprocessors; formalization; shared-memory models; data-race-free-1; weak ordering;release consistency; data-race-free-0; sequential consistency; hazards and raceconditions; shared memory systems

J. Aggarwal and S. Adve, "A Unified Formalization of Four Shared-Memory Models," in IEEE Transactions on Parallel & Distributed Systems, vol. 4, no. , pp. 613-624, 1993.
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