FA-65054 / Epidemic compartment models / Member archive

Final epidemic size by bisection: case count rounding · case 04

Expected case counts are one lower than the nearest integer.

Member previewVariant 4 · 3 implementations · 7 checks per implementation

Case contract

Attack fraction z is the positive root of z = 1-exp(-R0*z) found by bisection on (1e-9, 1] until the bracket is narrower than tol; for R0<=1 return [0.0, 0, 0.0]; return [z rounded 6, round(z*pop), overshoot z-(1-1/R0) rounded 6].

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: measles-like R0 12	`[0.999994, 999, 0.083327]`	`[0.999994, 1000, 0.083327]`	Failed

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