Simple atomic snapshots a linear complexity solution with unbounded time-stamps

Abstract

Let X ₁, ..., X _c be variables shared by a number of processes which operate in a totally asynchronous and wait-free manner. An operation by a process is either a write on one of the variables or a read of the values of all variables. All operations are assumed to be atomic, i.e. an execution of any number of them (including reads) must be serializable in a way compatible with the values returned by the reads. We give a new protocol implementing such operations for the case of a single-reader and one writer per variable. Our construction uses time-stamps that may take values as large as the number of operations performed. The advantagesof our construction over previous (bounded time-stamps) solutions are: (i) It has very simple semantics. (ii) The time complexity of an operation (i.e. the number of its sub-operations) and the space complexity of the construction (i.e. the number of subregisters used) are equal to the number of processes involved.

This research was partially supported by the ESPRIT II Basic Research Actions Program of the EC under contract no. 3075 (project ALCOM).