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FA-46396 / Bounded deques / Open access

Adjacent block merge ignores left block occupancy · case 01

Adjacent block merge ignores left block occupancy.

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

ROOT CAUSE

Adjacent block merge ignores left block occupancy.

THE FAILURE

Adjacent block merge ignores left block occupancy.

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

Case contract

Merge adjacent deque storage blocks if combined occupancy fits one block. Preserve the left block ID, retire the right ID once, and advance the directory epoch only on success.

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):
    a,b,aid,bid,cap,epoch=x
    fits=len(b)<=cap
    if not fits:return [a,b,False,aid,[],epoch]
    joined=a+b
    right=[]
    identity=aid
    retired=[bid]
    version=epoch+1
    return [joined,right,True,identity,retired,version]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('0', solve([[N,N+1],[N+2],4,5,3,0]), {1: [[1, 2, 3], [], True, 4, [5], 1], 2: [[2, 3, 4], [], True, 4, [5], 1], 3: [[3, 4, 5], [], True, 4, [5], 1], 4: [[4, 5, 6], [], True, 4, [5], 1], 5: [[5, 6, 7], [], True, 4, [5], 1]}[N])
check('1', solve([[N,N+1],[N+2,N+3],4,5,3,2]), {1: [[1, 2], [3, 4], False, 4, [], 2], 2: [[2, 3], [4, 5], False, 4, [], 2], 3: [[3, 4], [5, 6], False, 4, [], 2], 4: [[4, 5], [6, 7], False, 4, [], 2], 5: [[5, 6], [7, 8], False, 4, [], 2]}[N])
check('2', solve([[],[N,N+1],7,8,4,3]), {1: [[1, 2], [], True, 7, [8], 4], 2: [[2, 3], [], True, 7, [8], 4], 3: [[3, 4], [], True, 7, [8], 4], 4: [[4, 5], [], True, 7, [8], 4], 5: [[5, 6], [], True, 7, [8], 4]}[N])
check('3', solve([[N],[],2,6,3,4]), {1: [[1], [], True, 2, [6], 5], 2: [[2], [], True, 2, [6], 5], 3: [[3], [], True, 2, [6], 5], 4: [[4], [], True, 2, [6], 5], 5: [[5], [], True, 2, [6], 5]}[N])
check('4', solve([[],[],1,3,2,8]), {1: [[], [], True, 1, [3], 9], 2: [[], [], True, 1, [3], 9], 3: [[], [], True, 1, [3], 9], 4: [[], [], True, 1, [3], 9], 5: [[], [], True, 1, [3], 9]}[N])
check('5', solve([[N],[N+1,N+2],6,9,5,1]), {1: [[1, 2, 3], [], True, 6, [9], 2], 2: [[2, 3, 4], [], True, 6, [9], 2], 3: [[3, 4, 5], [], True, 6, [9], 2], 4: [[4, 5, 6], [], True, 6, [9], 2], 5: [[5, 6, 7], [], True, 6, [9], 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], [], True, 4, [5], 1][[1, 2, 3], [], True, 4, [5], 1]Passed
1[[1, 2, 3, 4], [], True, 4, [5], 3][[1, 2], [3, 4], False, 4, [], 2]Failed
2[[1, 2], [], True, 7, [8], 4][[1, 2], [], True, 7, [8], 4]Passed
3[[1], [], True, 2, [6], 5][[1], [], True, 2, [6], 5]Passed
4[[], [], True, 1, [3], 9][[], [], True, 1, [3], 9]Passed
5[[1, 2, 3], [], True, 6, [9], 2][[1, 2, 3], [], True, 6, [9], 2]Passed

SHA-256 / 831872c550a4030ec1cb462d2d3931d1543490052b9efc1f4bc18a38911c34e7

2 / The unsuccessful fix

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

N = 1
observations = []
def solve(x):
    a,b,aid,bid,cap,epoch=x
    fits=len(a)+len(b)<=cap if not a else len(b)<=cap
    if not fits:return [a,b,False,aid,[],epoch]
    joined=a+b
    right=[]
    identity=aid
    retired=[bid]
    version=epoch+1
    return [joined,right,True,identity,retired,version]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('0', solve([[N,N+1],[N+2],4,5,3,0]), {1: [[1, 2, 3], [], True, 4, [5], 1], 2: [[2, 3, 4], [], True, 4, [5], 1], 3: [[3, 4, 5], [], True, 4, [5], 1], 4: [[4, 5, 6], [], True, 4, [5], 1], 5: [[5, 6, 7], [], True, 4, [5], 1]}[N])
check('1', solve([[N,N+1],[N+2,N+3],4,5,3,2]), {1: [[1, 2], [3, 4], False, 4, [], 2], 2: [[2, 3], [4, 5], False, 4, [], 2], 3: [[3, 4], [5, 6], False, 4, [], 2], 4: [[4, 5], [6, 7], False, 4, [], 2], 5: [[5, 6], [7, 8], False, 4, [], 2]}[N])
check('2', solve([[],[N,N+1],7,8,4,3]), {1: [[1, 2], [], True, 7, [8], 4], 2: [[2, 3], [], True, 7, [8], 4], 3: [[3, 4], [], True, 7, [8], 4], 4: [[4, 5], [], True, 7, [8], 4], 5: [[5, 6], [], True, 7, [8], 4]}[N])
check('3', solve([[N],[],2,6,3,4]), {1: [[1], [], True, 2, [6], 5], 2: [[2], [], True, 2, [6], 5], 3: [[3], [], True, 2, [6], 5], 4: [[4], [], True, 2, [6], 5], 5: [[5], [], True, 2, [6], 5]}[N])
check('4', solve([[],[],1,3,2,8]), {1: [[], [], True, 1, [3], 9], 2: [[], [], True, 1, [3], 9], 3: [[], [], True, 1, [3], 9], 4: [[], [], True, 1, [3], 9], 5: [[], [], True, 1, [3], 9]}[N])
check('5', solve([[N],[N+1,N+2],6,9,5,1]), {1: [[1, 2, 3], [], True, 6, [9], 2], 2: [[2, 3, 4], [], True, 6, [9], 2], 3: [[3, 4, 5], [], True, 6, [9], 2], 4: [[4, 5, 6], [], True, 6, [9], 2], 5: [[5, 6, 7], [], True, 6, [9], 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], [], True, 4, [5], 1][[1, 2, 3], [], True, 4, [5], 1]Passed
1[[1, 2, 3, 4], [], True, 4, [5], 3][[1, 2], [3, 4], False, 4, [], 2]Failed
2[[1, 2], [], True, 7, [8], 4][[1, 2], [], True, 7, [8], 4]Passed
3[[1], [], True, 2, [6], 5][[1], [], True, 2, [6], 5]Passed
4[[], [], True, 1, [3], 9][[], [], True, 1, [3], 9]Passed
5[[1, 2, 3], [], True, 6, [9], 2][[1, 2, 3], [], True, 6, [9], 2]Passed

SHA-256 / ac1deea6e553e08d64574d041690d9c0272575ed617a3e5d4c0fd0d112251a5d

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 2026-09-29T14:44:31.883260+00:00.

Case digest / 5194f3f8b19e9c5cbeef6330f5cc6b9faf4332908d5766a3eab62e48c5d6d1da