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PN-Counter with local floor: the floor check ignores decrements already applied · case 05

Repeated decrements drive a replica's observed value below zero.

Member previewVariant 5 · 3 implementations · 9 checks per implementation

Case contract

Replicas keep a positive map and a negative map (replica->total). ["inc", r, k] and ["dec", r, k] need k > 0, otherwise the event index is rejected. A decrement is also rejected when r's locally observed value is below k. ["sync", src, dst] merges both maps of src into dst by pointwise maximum. Return values and rejected indices.

Why this case matters

Positive/negative counters are the standard way to support decrements in a state-based counter.

One recorded failure

Sample boundary fixture

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

Boundary fixture	Actual	Expected	Outcome
second decrement cannot pass the floor	`{"rejected": [], "values": [-1, 0, 0]}`	`{"rejected": [2], "values": [1, 0, 0]}`	Failed

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