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FA-46336 / Bounded deques / Open access

Deque uniqueness clears seen identities after each item · case 01

Deque uniqueness clears seen identities after each item.

Verified by executionVariant 1 · 6 checks per implementationDownload source bundle ↓JSON ↗

ROOT CAUSE

Deque uniqueness clears seen identities after each item.

THE FAILURE

Deque uniqueness clears seen identities after each item.

Unsuccessful approach: The partial repair still applies the incorrect transition to an admitted boundary or multi-element case.

Case contract

Keep the first occurrence of each deque payload and return survivor values plus original positions removed. Payload equality is integer equality; zero is a valid value.

Why this case matters

Controlled bounded deque implementation model with explicit storage and lifecycle observations.

1 / The failure

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

N = 1
observations = []
def solve(x):
    items=x
    seen=set()
    keep=[]
    removed=[]
    for i,v in enumerate(items):
        if v in seen:removed.append(i)
        else:
            keep.append(v)
            seen={v}
    return [keep,removed]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('0', solve([N,N+1,N,N+2,N+1]), {1: [[1, 2, 3], [2, 4]], 2: [[2, 3, 4], [2, 4]], 3: [[3, 4, 5], [2, 4]], 4: [[4, 5, 6], [2, 4]], 5: [[5, 6, 7], [2, 4]]}[N])
check('1', solve([0,N,0,N]), {1: [[0, 1], [2, 3]], 2: [[0, 2], [2, 3]], 3: [[0, 3], [2, 3]], 4: [[0, 4], [2, 3]], 5: [[0, 5], [2, 3]]}[N])
check('2', solve([N,N,N]), {1: [[1], [1, 2]], 2: [[2], [1, 2]], 3: [[3], [1, 2]], 4: [[4], [1, 2]], 5: [[5], [1, 2]]}[N])
check('3', solve([]), {1: [[], []], 2: [[], []], 3: [[], []], 4: [[], []], 5: [[], []]}[N])
check('4', solve([N,N+1,N+2]), {1: [[1, 2, 3], []], 2: [[2, 3, 4], []], 3: [[3, 4, 5], []], 4: [[4, 5, 6], []], 5: [[5, 6, 7], []]}[N])
check('5', solve([N+2,N,N+2,N+1]), {1: [[3, 1, 2], [2]], 2: [[4, 2, 3], [2]], 3: [[5, 3, 4], [2]], 4: [[6, 4, 5], [2]], 5: [[7, 5, 6], [2]]}[N])
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
0[[1, 2, 1, 3, 2], []][[1, 2, 3], [2, 4]]Failed
1[[0, 1, 0, 1], []][[0, 1], [2, 3]]Failed
2[[1], [1, 2]][[1], [1, 2]]Passed
3[[], []][[], []]Passed
4[[1, 2, 3], []][[1, 2, 3], []]Passed
5[[3, 1, 3, 2], []][[3, 1, 2], [2]]Failed

SHA-256 / 9cb5e13994d5509a89ce49b62aef96af1538990245b7b3a0711c997fd3c8eccb

2 / The unsuccessful fix

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

N = 1
observations = []
def solve(x):
    items=x
    seen=set()
    keep=[]
    removed=[]
    for i,v in enumerate(items):
        if v in seen:removed.append(i)
        else:
            keep.append(v)
            seen.add(v) if not seen else None
    return [keep,removed]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('0', solve([N,N+1,N,N+2,N+1]), {1: [[1, 2, 3], [2, 4]], 2: [[2, 3, 4], [2, 4]], 3: [[3, 4, 5], [2, 4]], 4: [[4, 5, 6], [2, 4]], 5: [[5, 6, 7], [2, 4]]}[N])
check('1', solve([0,N,0,N]), {1: [[0, 1], [2, 3]], 2: [[0, 2], [2, 3]], 3: [[0, 3], [2, 3]], 4: [[0, 4], [2, 3]], 5: [[0, 5], [2, 3]]}[N])
check('2', solve([N,N,N]), {1: [[1], [1, 2]], 2: [[2], [1, 2]], 3: [[3], [1, 2]], 4: [[4], [1, 2]], 5: [[5], [1, 2]]}[N])
check('3', solve([]), {1: [[], []], 2: [[], []], 3: [[], []], 4: [[], []], 5: [[], []]}[N])
check('4', solve([N,N+1,N+2]), {1: [[1, 2, 3], []], 2: [[2, 3, 4], []], 3: [[3, 4, 5], []], 4: [[4, 5, 6], []], 5: [[5, 6, 7], []]}[N])
check('5', solve([N+2,N,N+2,N+1]), {1: [[3, 1, 2], [2]], 2: [[4, 2, 3], [2]], 3: [[5, 3, 4], [2]], 4: [[6, 4, 5], [2]], 5: [[7, 5, 6], [2]]}[N])
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
0[[1, 2, 3, 2], [2]][[1, 2, 3], [2, 4]]Failed
1[[0, 1, 1], [2]][[0, 1], [2, 3]]Failed
2[[1], [1, 2]][[1], [1, 2]]Passed
3[[], []][[], []]Passed
4[[1, 2, 3], []][[1, 2, 3], []]Passed
5[[3, 1, 2], [2]][[3, 1, 2], [2]]Passed

SHA-256 / 83c26520292d4fb25d3e6f62bed9c28c528825be1c4f3a4b08984a11099a04af

HELD IN THE MEMBER ARCHIVE

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

This mechanism has 6 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

Offline finite deterministic model; no claim of production implementation or concurrent memory-model conformance. 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 2026-09-29T14:44:31.228873+00:00.

Case digest / 11e1e253d0fa57bf978295bd920f337f452d45d645df2c11faf5ad72fa8f48b3