FA-65228 / Epidemic compartment models / Member archive

SIR with Erlang-distributed infectious period: interior stage chain · case 03

The last stage never fills and nobody reaches R through it.

Member previewVariant 3 · 3 implementations · 7 checks per implementation

Case contract

Infectious period split into k sequential stages each left at rate k*gamma; seeds start in stage 1; all stages transmit; Euler with dt=0.1 (10 substeps/day); return [total I at day ends including day 0 rounded 3, R rounded 3], None for k<1.

Why this case matters

Compartmental epidemic calculations drive outbreak forecasts, vaccine targets and hospital planning; a single wrong flow, rate conversion or boundary silently changes every downstream number.

One recorded failure

Sample boundary fixture

This sample comes from the broken implementation of a controlled reproducer.

Boundary fixture	Actual	Expected	Outcome
regression: three stages	`[[10.0, 14.62, 19.24, 24.537, 30.857, 38.401, 47.273], 0.0]`	`[[10.0, 15.964, 24.203, 35.419, 50.774, 71.593, 99.086], 25.589]`	Failed

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