FAILURE MAP
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FA-036 / Data systems / Open access

Adjacent windows count a boundary twice · case 01

A sample on a shared boundary is counted in both adjacent windows.

Verified by executionVariant 1 · 3 checks per implementationDownload source bundle ↓JSON ↗

ROOT CAUSE

Both ends of every interval are inclusive.

THE FAILURE

Both ends of every interval are inclusive.

Unsuccessful approach: Making both ends exclusive drops samples at window starts.

Case contract

Use half-open intervals consistently across adjacent windows.

Why this case matters

A compact reasoning and repair task with executable evidence.

1 / The failure

Exit 1
"""Failure Map reference implementation. Python standard library only."""
import json

N = 1
observations = []
def solve(windows, t):
    return sum(start <= t <= end for start, end in windows)
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
windows = [[0, N], [N, 2*N]]
check('shared boundary', solve(windows, N), 1)
check('first boundary', solve(windows, 0), 1)
check('outside final boundary', solve(windows, 2*N), 0)
print(json.dumps({"observations": observations, "passed": all(x["passed"] for x in observations)}, ensure_ascii=False))
raise SystemExit(0 if all(x["passed"] for x in observations) else 1)
Boundary fixtureActualExpectedOutcome
shared boundary21Failed
first boundary11Passed
outside final boundary10Failed

SHA-256 / 283ae8306240a405ef37f7797d43d6eca20467b8a3f5c85a6e0cd551545f09af

2 / The unsuccessful fix

Exit 1
"""Failure Map reference implementation. Python standard library only."""
import json

N = 1
observations = []
def solve(windows, t):
    return sum(start < t < end for start, end in windows)
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
windows = [[0, N], [N, 2*N]]
check('shared boundary', solve(windows, N), 1)
check('first boundary', solve(windows, 0), 1)
check('outside final boundary', solve(windows, 2*N), 0)
print(json.dumps({"observations": observations, "passed": all(x["passed"] for x in observations)}, ensure_ascii=False))
raise SystemExit(0 if all(x["passed"] for x in observations) else 1)
Boundary fixtureActualExpectedOutcome
shared boundary01Failed
first boundary01Failed
outside final boundary00Passed

SHA-256 / cc4a5e9cd2a3aa6a3b1223e024c4d8250a7b07c038dd4b579313b6fbd90eb539

HELD IN THE MEMBER ARCHIVE

The verified repair and its recorded checks are member-only.

This mechanism has 3 recorded checks per implementation. The open-access tier publishes the failure and the unsuccessful fix; the repaired source that passes every check, and the observations that prove it, are available to members.

Every case sharing this mechanism uses the same contract and the same repair, so this one record is held back for all of them.

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Verification & scope

This reproducer isolates one failure mechanism. Results cover the supplied fixtures. Variants within a family share a test contract and should remain grouped when constructing evaluation splits. Related mechanisms with a shared evaluation_group must also remain together; these controlled models are not independent production incidents.

Observations recorded using Python 3.12.14 at 2026-09-29T14:36:49.871757+00:00.

Case digest / bc275c6b72b276e92d94f77d1be2ce11aec0ee5660fef8fe2301750b69770729