Living Worlds

Research · Scale · Oct 5, 2026

A replayable world: one million lives, ten years

Checkable by anyone1,000,000 lives, 120 months

The test at a glance

What it tests
Correctness: that the world replays exactly and keeps its own rules. Not realism: partnership, separation and leaving-home rates are placeholders.
Data
1,000,000 simulated lives over 120 months on UK 2019 death and birth tables; seed 20261005.
Held out
Nothing held out: the open checker rebuilds every event from the published trace without the engine.
Compared against
An independent recomputation by the open checker, and a second run from the same seed.
Bar
Every death, birth, baby's sex and separation recomputed exactly; every partnership within the rules; two runs byte-identical.
Result
PASS: 156,543 deaths, 93,221 births, 168,907 partnerships and 14,724 separations, all reproduced.

One million lives over ten years on UK 2019 death and birth rates, replayable by anyone: 156,543 deaths, 93,221 births, 168,907 partnerships and 14,724 separations. The open checker rebuilds the world without our engine, recomputes every death, birth, baby's sex and separation exactly and checks every partnership against the rules: PASS. Two runs from the same seed are byte-identical. Tested: the download holds the starting population, every event in order and the sha256 of each file. The partnership, separation and leaving-home rates in this run are placeholders, not fitted to any data: this test checks that the world replays exactly, not that it is realistic.

Protocol, result and scorer

Trace (8.3 MB zip) Checker Manifest

Scale

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