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FA-46046 / Bounded deques / Open access

Self-splice retains the final moved node in its old location · case 01

Self-splice retains the final moved node in its old location.

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

ROOT CAUSE

Self-splice retains the final moved node in its old location.

THE FAILURE

Self-splice retains the final moved node in its old location.

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

Case contract

Move a range within one bounded deque, preserving size and stable element identity. Gaps inside or at either boundary of the range are no-ops.

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,gap = x
    if start <= gap <= stop: return a
    piece = a[start:stop]
    rest = a[:start]+a[max(start,stop-1):]
    new_gap = gap - (stop-start) if gap > stop else gap
    return rest[:new_gap]+piece+rest[new_gap:]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('move left', solve([[N,N+1,N+2,N+3,N+4],2,4,0]), {1: [3, 4, 1, 2, 5], 2: [4, 5, 2, 3, 6], 3: [5, 6, 3, 4, 7], 4: [6, 7, 4, 5, 8], 5: [7, 8, 5, 6, 9]}[N])
check('move right', solve([[N,N+1,N+2,N+3,N+4],0,2,5]), {1: [3, 4, 5, 1, 2], 2: [4, 5, 6, 2, 3], 3: [5, 6, 7, 3, 4], 4: [6, 7, 8, 4, 5], 5: [7, 8, 9, 5, 6]}[N])
check('inside no op', solve([[N,N+1,N+2,N+3],1,3,2]), {1: [1, 2, 3, 4], 2: [2, 3, 4, 5], 3: [3, 4, 5, 6], 4: [4, 5, 6, 7], 5: [5, 6, 7, 8]}[N])
check('end boundary', solve([[N,N+1,N+2,N+3],1,3,3]), {1: [1, 2, 3, 4], 2: [2, 3, 4, 5], 3: [3, 4, 5, 6], 4: [4, 5, 6, 7], 5: [5, 6, 7, 8]}[N])
check('empty range', solve([[N,N+1,N+2],1,1,3]), {1: [1, 2, 3], 2: [2, 3, 4], 3: [3, 4, 5], 4: [4, 5, 6], 5: [5, 6, 7]}[N])
check('interior right', solve([[N,N+1,N+2,N+3,N+4,N+5],1,3,5]), {1: [1, 4, 5, 2, 3, 6], 2: [2, 5, 6, 3, 4, 7], 3: [3, 6, 7, 4, 5, 8], 4: [4, 7, 8, 5, 6, 9], 5: [5, 8, 9, 6, 7, 10]}[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
move left[3, 4, 1, 2, 4, 5][3, 4, 1, 2, 5]Failed
move right[2, 3, 4, 1, 2, 5][3, 4, 5, 1, 2]Failed
inside no op[1, 2, 3, 4][1, 2, 3, 4]Passed
end boundary[1, 2, 3, 4][1, 2, 3, 4]Passed
empty range[1, 2, 3][1, 2, 3]Passed
interior right[1, 3, 4, 2, 3, 5, 6][1, 4, 5, 2, 3, 6]Failed

SHA-256 / eb317162b7f3966a4f17c00397f07886d7c582cb588294247de4ec962875dcc8

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,gap = x
    if start <= gap <= stop: return a
    piece = a[start:stop]
    rest = a[:start]+a[stop:] if stop-start<=1 else a[:start]+a[stop-1:]
    new_gap = gap - (stop-start) if gap > stop else gap
    return rest[:new_gap]+piece+rest[new_gap:]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('move left', solve([[N,N+1,N+2,N+3,N+4],2,4,0]), {1: [3, 4, 1, 2, 5], 2: [4, 5, 2, 3, 6], 3: [5, 6, 3, 4, 7], 4: [6, 7, 4, 5, 8], 5: [7, 8, 5, 6, 9]}[N])
check('move right', solve([[N,N+1,N+2,N+3,N+4],0,2,5]), {1: [3, 4, 5, 1, 2], 2: [4, 5, 6, 2, 3], 3: [5, 6, 7, 3, 4], 4: [6, 7, 8, 4, 5], 5: [7, 8, 9, 5, 6]}[N])
check('inside no op', solve([[N,N+1,N+2,N+3],1,3,2]), {1: [1, 2, 3, 4], 2: [2, 3, 4, 5], 3: [3, 4, 5, 6], 4: [4, 5, 6, 7], 5: [5, 6, 7, 8]}[N])
check('end boundary', solve([[N,N+1,N+2,N+3],1,3,3]), {1: [1, 2, 3, 4], 2: [2, 3, 4, 5], 3: [3, 4, 5, 6], 4: [4, 5, 6, 7], 5: [5, 6, 7, 8]}[N])
check('empty range', solve([[N,N+1,N+2],1,1,3]), {1: [1, 2, 3], 2: [2, 3, 4], 3: [3, 4, 5], 4: [4, 5, 6], 5: [5, 6, 7]}[N])
check('interior right', solve([[N,N+1,N+2,N+3,N+4,N+5],1,3,5]), {1: [1, 4, 5, 2, 3, 6], 2: [2, 5, 6, 3, 4, 7], 3: [3, 6, 7, 4, 5, 8], 4: [4, 7, 8, 5, 6, 9], 5: [5, 8, 9, 6, 7, 10]}[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
move left[3, 4, 1, 2, 4, 5][3, 4, 1, 2, 5]Failed
move right[2, 3, 4, 1, 2, 5][3, 4, 5, 1, 2]Failed
inside no op[1, 2, 3, 4][1, 2, 3, 4]Passed
end boundary[1, 2, 3, 4][1, 2, 3, 4]Passed
empty range[1, 2, 3][1, 2, 3]Passed
interior right[1, 3, 4, 2, 3, 5, 6][1, 4, 5, 2, 3, 6]Failed

SHA-256 / 7eaa35087c5a4784713575a3b0359b2bd62726a4ab40a46c45120fae01a01717

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 2026-09-29T14:44:28.482589+00:00.

Case digest / 9550afc19241f648778bf46d66a209eb491b608b5c89972923955b95a3b333b5