FA-71229 / Weather index computation / Member archive

Antecedent precipitation index: chronological ordering · case 04

Backfilled late reports make the API grow instead of decay.

Member previewVariant 4 · 3 implementations · 8 checks per implementation

Case contract

obs are [day, precip_mm] in any order; process in ascending day order (stable for equal days). Between observations API decays by k^(day gap); several reports on the same day accumulate without decay; negative precipitation is a sensor glitch treated as 0. Return API after each observation, rounded to 0.01.

Why this case matters

Flash-flood guidance and soil wetness models use API as a moisture state.

One recorded failure

Sample boundary fixture

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

Boundary fixture	Actual	Expected	Outcome
basin 16	`[30.0, 4.27, 45.66, 53.83]`	`[30.0, 45.66, 53.83, 28.1]`	Failed

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This record includes three runnable implementations, regression fixtures, execution results, and source hashes.

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