Relaxed Memory Model Zoo

A living survey of published weak memory models

The Relaxed Memory Model Zoo is a living survey of weak memory models: 101 models spanning 47 years — hardware, programming language, distributed and transactional — and 145 relations between them, ordered by the inclusion of the behaviours they allow. A time slider makes the chronological development of the field explorable, and the dataset behind the map is machine-readable.

A recording of the Zoo in use: the map of memory-model nodes ordered by strength, with every arrow descending from a stronger model to a weaker one; selecting C11 opens its definition, tags and neighbours; an edge's evidence expands to the herd7 litmus test that separates the two models; the category, cat-specifiability and property filters narrow the map; the year slider sweeps from 1979 to 2026; search matches names, descriptions and references; and the theme switches from light to dark.
The Zoo's map, from overview to the litmus test behind a single edge. [fig1]

Every model and every edge carries provenance naming the original publication, and every ordering claim states how it is known: a litmus test in the repository that runs and produces the verdict, an argument by construction, or a citation to the primary source. 65 herd7 checks run on every push against a pinned herdtools7, and an edge that contradicts the transitive closure of the others fails the consistency gate before it can ship.

The dataset lives in rmm-zoo-dataset, which is where corrections and additions go.