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FA-46701 / Bounded deques / Open access

Deque split traversal skips the first suffix element · case 01

Deque split traversal skips the first suffix element.

Verified by executionVariant 1 · 7 checks per implementationDownload source bundle ↓JSON ↗

ROOT CAUSE

Deque split traversal skips the first suffix element.

THE FAILURE

Deque split traversal skips the first suffix element.

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

Case contract

Split an iterator range into disjoint prefix and suffix if its length meets a positive minimum. Both halves retain the same captured deque epoch and cover every original element exactly once.

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,start,stop,minimum,epoch=x
    length=stop-start
    if length<minimum:return [None,[start,stop,epoch],a[start:stop]]
    middle=start+length//2
    prefix=[start,middle,epoch]
    suffix=[middle,stop,epoch]
    visited=a[start:middle]+a[middle+1:stop]
    return [prefix,suffix,visited]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('0', solve([[N,N+1,N+2,N+3,N+4],1,5,2,7]), {1: [[1, 3, 7], [3, 5, 7], [2, 3, 4, 5]], 2: [[1, 3, 7], [3, 5, 7], [3, 4, 5, 6]], 3: [[1, 3, 7], [3, 5, 7], [4, 5, 6, 7]], 4: [[1, 3, 7], [3, 5, 7], [5, 6, 7, 8]], 5: [[1, 3, 7], [3, 5, 7], [6, 7, 8, 9]]}[N])
check('1', solve([[N,N+1,N+2],0,3,2,4]), {1: [[0, 1, 4], [1, 3, 4], [1, 2, 3]], 2: [[0, 1, 4], [1, 3, 4], [2, 3, 4]], 3: [[0, 1, 4], [1, 3, 4], [3, 4, 5]], 4: [[0, 1, 4], [1, 3, 4], [4, 5, 6]], 5: [[0, 1, 4], [1, 3, 4], [5, 6, 7]]}[N])
check('2', solve([[N],0,1,2,3]), {1: [None, [0, 1, 3], [1]], 2: [None, [0, 1, 3], [2]], 3: [None, [0, 1, 3], [3]], 4: [None, [0, 1, 3], [4]], 5: [None, [0, 1, 3], [5]]}[N])
check('3', solve([[],0,0,1,0]), {1: [None, [0, 0, 0], []], 2: [None, [0, 0, 0], []], 3: [None, [0, 0, 0], []], 4: [None, [0, 0, 0], []], 5: [None, [0, 0, 0], []]}[N])
check('4', solve([[N,N+1,N+2,N+3],2,4,2,8]), {1: [[2, 3, 8], [3, 4, 8], [3, 4]], 2: [[2, 3, 8], [3, 4, 8], [4, 5]], 3: [[2, 3, 8], [3, 4, 8], [5, 6]], 4: [[2, 3, 8], [3, 4, 8], [6, 7]], 5: [[2, 3, 8], [3, 4, 8], [7, 8]]}[N])
check('5', solve([[N,N+1,N+2,N+3,N+4],0,5,3,1]), {1: [[0, 2, 1], [2, 5, 1], [1, 2, 3, 4, 5]], 2: [[0, 2, 1], [2, 5, 1], [2, 3, 4, 5, 6]], 3: [[0, 2, 1], [2, 5, 1], [3, 4, 5, 6, 7]], 4: [[0, 2, 1], [2, 5, 1], [4, 5, 6, 7, 8]], 5: [[0, 2, 1], [2, 5, 1], [5, 6, 7, 8, 9]]}[N])
check('short shifted remainder', solve([[N,N+1,N+2],2,3,2,6]), [None,[2,3,6],[N+2]])
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, 3, 7], [3, 5, 7], [2, 3, 5]][[1, 3, 7], [3, 5, 7], [2, 3, 4, 5]]Failed
1[[0, 1, 4], [1, 3, 4], [1, 3]][[0, 1, 4], [1, 3, 4], [1, 2, 3]]Failed
2[None, [0, 1, 3], [1]][None, [0, 1, 3], [1]]Passed
3[None, [0, 0, 0], []][None, [0, 0, 0], []]Passed
4[[2, 3, 8], [3, 4, 8], [3]][[2, 3, 8], [3, 4, 8], [3, 4]]Failed
5[[0, 2, 1], [2, 5, 1], [1, 2, 4, 5]][[0, 2, 1], [2, 5, 1], [1, 2, 3, 4, 5]]Failed
short shifted remainder[None, [2, 3, 6], [3]][None, [2, 3, 6], [3]]Passed

SHA-256 / b5255c4a24fcbd2c24049593cadbc1a0aaeda7cc691b9f6b8164f6d673050d7e

2 / The unsuccessful fix

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

N = 1
observations = []
def solve(x):
    a,start,stop,minimum,epoch=x
    length=stop-start
    if length<minimum:return [None,[start,stop,epoch],a[start:stop]]
    middle=start+length//2
    prefix=[start,middle,epoch]
    suffix=[middle,stop,epoch]
    visited=a[start:middle]+a[middle:stop] if length<=2 else a[start:middle]+a[middle+1:stop]
    return [prefix,suffix,visited]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('0', solve([[N,N+1,N+2,N+3,N+4],1,5,2,7]), {1: [[1, 3, 7], [3, 5, 7], [2, 3, 4, 5]], 2: [[1, 3, 7], [3, 5, 7], [3, 4, 5, 6]], 3: [[1, 3, 7], [3, 5, 7], [4, 5, 6, 7]], 4: [[1, 3, 7], [3, 5, 7], [5, 6, 7, 8]], 5: [[1, 3, 7], [3, 5, 7], [6, 7, 8, 9]]}[N])
check('1', solve([[N,N+1,N+2],0,3,2,4]), {1: [[0, 1, 4], [1, 3, 4], [1, 2, 3]], 2: [[0, 1, 4], [1, 3, 4], [2, 3, 4]], 3: [[0, 1, 4], [1, 3, 4], [3, 4, 5]], 4: [[0, 1, 4], [1, 3, 4], [4, 5, 6]], 5: [[0, 1, 4], [1, 3, 4], [5, 6, 7]]}[N])
check('2', solve([[N],0,1,2,3]), {1: [None, [0, 1, 3], [1]], 2: [None, [0, 1, 3], [2]], 3: [None, [0, 1, 3], [3]], 4: [None, [0, 1, 3], [4]], 5: [None, [0, 1, 3], [5]]}[N])
check('3', solve([[],0,0,1,0]), {1: [None, [0, 0, 0], []], 2: [None, [0, 0, 0], []], 3: [None, [0, 0, 0], []], 4: [None, [0, 0, 0], []], 5: [None, [0, 0, 0], []]}[N])
check('4', solve([[N,N+1,N+2,N+3],2,4,2,8]), {1: [[2, 3, 8], [3, 4, 8], [3, 4]], 2: [[2, 3, 8], [3, 4, 8], [4, 5]], 3: [[2, 3, 8], [3, 4, 8], [5, 6]], 4: [[2, 3, 8], [3, 4, 8], [6, 7]], 5: [[2, 3, 8], [3, 4, 8], [7, 8]]}[N])
check('5', solve([[N,N+1,N+2,N+3,N+4],0,5,3,1]), {1: [[0, 2, 1], [2, 5, 1], [1, 2, 3, 4, 5]], 2: [[0, 2, 1], [2, 5, 1], [2, 3, 4, 5, 6]], 3: [[0, 2, 1], [2, 5, 1], [3, 4, 5, 6, 7]], 4: [[0, 2, 1], [2, 5, 1], [4, 5, 6, 7, 8]], 5: [[0, 2, 1], [2, 5, 1], [5, 6, 7, 8, 9]]}[N])
check('short shifted remainder', solve([[N,N+1,N+2],2,3,2,6]), [None,[2,3,6],[N+2]])
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, 3, 7], [3, 5, 7], [2, 3, 5]][[1, 3, 7], [3, 5, 7], [2, 3, 4, 5]]Failed
1[[0, 1, 4], [1, 3, 4], [1, 3]][[0, 1, 4], [1, 3, 4], [1, 2, 3]]Failed
2[None, [0, 1, 3], [1]][None, [0, 1, 3], [1]]Passed
3[None, [0, 0, 0], []][None, [0, 0, 0], []]Passed
4[[2, 3, 8], [3, 4, 8], [3, 4]][[2, 3, 8], [3, 4, 8], [3, 4]]Passed
5[[0, 2, 1], [2, 5, 1], [1, 2, 4, 5]][[0, 2, 1], [2, 5, 1], [1, 2, 3, 4, 5]]Failed
short shifted remainder[None, [2, 3, 6], [3]][None, [2, 3, 6], [3]]Passed

SHA-256 / e22d8e625d77be79e3ecda4ac2954b781c5e933a5cf4d873b81090f81e2ad744

HELD IN THE MEMBER ARCHIVE

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

This mechanism has 7 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 2026-09-29T14:44:34.584630+00:00.

Case digest / b2c4b51f0259686f29d1e234b83851ea90805c5de0d7d03c2c135dbb436f3f62