Slow Consistency

1990 · Hutto, Ahamad · theoretical, formal · axiomatic formalism

A read must return some value previously written to the location, and once a value has been read no earlier write to that location by the same writer may be returned; a process sees its own writes immediately. Strictly weaker than both PRAM and cache consistency; strictly stronger than local consistency.

Properties

Property vector author-extrapolated — set only where the model’s definition pins the cell down (unknown cells are omitted); cells citing a specific source are marked.

Reasoning guarantees: no Coherence
Atomicity guarantees: no Multicopy atomic

Ordering relationships

Strictly weaker than: PRAM (Pipelined RAM) Consistency — Slow consistency is strictly weaker than PRAM consistency (Hutto & Ahamad 1990; Steinke & Nutt 2004).
Cache Coherence — Slow consistency is strictly weaker than cache consistency (Hutto & Ahamad 1990; Steinke & Nutt 2004).
Strictly stronger than: Local Consistency — Local consistency is the weakest model, strictly weaker than slow consistency (Bataller & Bernabeu-Auban 1997; Steinke & Nutt 2004).

References

Phillip W. Hutto, Mustaque Ahamad. Slow Memory: Weakening Consistency to Enhance Concurrency in Distributed Shared Memories. Proc. 10th International Conference on Distributed Computing Systems (ICDCS), 1990.
Robert C. Steinke, Gary J. Nutt. A Unified Theory of Shared Memory Consistency. Journal of the ACM 51(5), 2004. arxiv.org/abs/cs/0208027

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