Atomic semantics

Atomic semantics is a term which describes the guarantees provided by a data register shared by several processors in a parallel machine or in a network of computers working together.

The read and write registers are one of the important and basic objects encountered in distributed theory systems. Atomic semantics are very strong. An atomic register provides strong guarantees even when there is concurrency and failures.A register R could be accessed by two base operations: R.Read ,and R.write(v).The R.Read will return the value of R and R.write(v) writes a new value into R.

A register is called atomic if it satisfies the two following properties:

1) Each invocation operation(op) of a read or write operation :

• Should become visible just as if it was executed already at a point τ(op) of the timeline.

• τ (op) works as follow: τb(op) ≤ τ (op) ≤ τe(op): where τb(op) and τe(op) indicate the time where exactly the operation op started and finished.

• If op1 ≠ op2 ⇒τ (op1)≠τ (op2)

See also

• Regular semantics
• Safe semantics

References

• Atomic semantics are defined formally in Lamport's "On Interprocess Communication" Distributed Computing 1, 2 (1986), 77-101. (Also appeared as SRC Research Report 8).