Causal memory

We define and implement one member of a family of causal memories that we have developed. Causal memories are weakly consistent and admit more executions, hence allowing more concurrency, than either atomic or sequentially consistent memories. Informally, causal memories require the apparent order of writes to respect a shared memory analog of Lamport's potential causality. In this paper we:motivate weakly consistent memories, particularly their use as distributed shared memories;precisely and formally characterize one causal memory;demonstrate that our causal memory can be effectively programmed;present a simple implementation using reliable, “FIFO” message passing, and prove it correct;present a fault-tolerant causal memory implementation that tolerates lossy channels and stopping failures and prove it correct.