Atomic Snapshots of Shared Memory

This paper introduces a general formulation of atomic snapshot memory, a sharedmemory partitioned into words written1993 by individual processes, orinstantaneously read (scanned) in itsentirety. This paper presents three wait-free implementations of atomicsnapshot memory. The first implementation in this paper uses unbounded(integer) fields in these registers, and is particularly easy tounderstand. The second implementation uses bounded registers. Itscorrectness proof follows the ideas of the unbounded implementation.Both constructions implement a single-writer snapshot memory, in whicheach word may be updated by only one process, from single-writer, n-reader registers. The thirdalgorithm implements a multi-writer snapshot memory from atomic n-writer, n-reader registers, again echoing keyideas from the earlier constructions. All operations require (n²) readsand writes to the component shared registers in the worst case.