FAILURE MAP
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FA-46851 / Bounded deques / Open access

Deque block rebalance concatenates right before left · case 01

Deque block rebalance concatenates right before left.

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

ROOT CAUSE

Deque block rebalance concatenates right before left.

THE FAILURE

Deque block rebalance concatenates right before left.

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

Case contract

Redistribute two adjacent deque blocks to a requested left occupancy without changing element order or block identities. Return signed left-to-right transfer count and new directory lengths.

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,target,aid,bid=x
    joined=b+a
    left=joined[:target]
    right=joined[target:]
    left_id=aid
    right_id=bid
    transfer=len(a)-target
    directory=[[left_id,len(left)],[right_id,len(right)]]
    return [left,right,left_id,right_id,transfer,directory]
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],2,3,8]), {1: [[1, 2], [3, 4], 3, 8, 1, [[3, 2], [8, 2]]], 2: [[2, 3], [4, 5], 3, 8, 1, [[3, 2], [8, 2]]], 3: [[3, 4], [5, 6], 3, 8, 1, [[3, 2], [8, 2]]], 4: [[4, 5], [6, 7], 3, 8, 1, [[3, 2], [8, 2]]], 5: [[5, 6], [7, 8], 3, 8, 1, [[3, 2], [8, 2]]]}[N])
check('1', solve([[N],[N+1,N+2,N+3],3,4,9]), {1: [[1, 2, 3], [4], 4, 9, -2, [[4, 3], [9, 1]]], 2: [[2, 3, 4], [5], 4, 9, -2, [[4, 3], [9, 1]]], 3: [[3, 4, 5], [6], 4, 9, -2, [[4, 3], [9, 1]]], 4: [[4, 5, 6], [7], 4, 9, -2, [[4, 3], [9, 1]]], 5: [[5, 6, 7], [8], 4, 9, -2, [[4, 3], [9, 1]]]}[N])
check('2', solve([[N,N+1],[N+2,N+3],2,5,10]), {1: [[1, 2], [3, 4], 5, 10, 0, [[5, 2], [10, 2]]], 2: [[2, 3], [4, 5], 5, 10, 0, [[5, 2], [10, 2]]], 3: [[3, 4], [5, 6], 5, 10, 0, [[5, 2], [10, 2]]], 4: [[4, 5], [6, 7], 5, 10, 0, [[5, 2], [10, 2]]], 5: [[5, 6], [7, 8], 5, 10, 0, [[5, 2], [10, 2]]]}[N])
check('3', solve([[],[N,N+1],1,2,7]), {1: [[1], [2], 2, 7, -1, [[2, 1], [7, 1]]], 2: [[2], [3], 2, 7, -1, [[2, 1], [7, 1]]], 3: [[3], [4], 2, 7, -1, [[2, 1], [7, 1]]], 4: [[4], [5], 2, 7, -1, [[2, 1], [7, 1]]], 5: [[5], [6], 2, 7, -1, [[2, 1], [7, 1]]]}[N])
check('4', solve([[N,N+1],[],0,4,6]), {1: [[], [1, 2], 4, 6, 2, [[4, 0], [6, 2]]], 2: [[], [2, 3], 4, 6, 2, [[4, 0], [6, 2]]], 3: [[], [3, 4], 4, 6, 2, [[4, 0], [6, 2]]], 4: [[], [4, 5], 4, 6, 2, [[4, 0], [6, 2]]], 5: [[], [5, 6], 4, 6, 2, [[4, 0], [6, 2]]]}[N])
check('5', solve([[N],[N+1],2,1,5]), {1: [[1, 2], [], 1, 5, -1, [[1, 2], [5, 0]]], 2: [[2, 3], [], 1, 5, -1, [[1, 2], [5, 0]]], 3: [[3, 4], [], 1, 5, -1, [[1, 2], [5, 0]]], 4: [[4, 5], [], 1, 5, -1, [[1, 2], [5, 0]]], 5: [[5, 6], [], 1, 5, -1, [[1, 2], [5, 0]]]}[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[[4, 1], [2, 3], 3, 8, 1, [[3, 2], [8, 2]]][[1, 2], [3, 4], 3, 8, 1, [[3, 2], [8, 2]]]Failed
1[[2, 3, 4], [1], 4, 9, -2, [[4, 3], [9, 1]]][[1, 2, 3], [4], 4, 9, -2, [[4, 3], [9, 1]]]Failed
2[[3, 4], [1, 2], 5, 10, 0, [[5, 2], [10, 2]]][[1, 2], [3, 4], 5, 10, 0, [[5, 2], [10, 2]]]Failed
3[[1], [2], 2, 7, -1, [[2, 1], [7, 1]]][[1], [2], 2, 7, -1, [[2, 1], [7, 1]]]Passed
4[[], [1, 2], 4, 6, 2, [[4, 0], [6, 2]]][[], [1, 2], 4, 6, 2, [[4, 0], [6, 2]]]Passed
5[[2, 1], [], 1, 5, -1, [[1, 2], [5, 0]]][[1, 2], [], 1, 5, -1, [[1, 2], [5, 0]]]Failed

SHA-256 / d54ee609d8c5ebf19155b3ddb71686dd907a83dd9c7c080b3fb1eddd99d94339

2 / The unsuccessful fix

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

N = 1
observations = []
def solve(x):
    a,b,target,aid,bid=x
    joined=a+b if not a else b+a
    left=joined[:target]
    right=joined[target:]
    left_id=aid
    right_id=bid
    transfer=len(a)-target
    directory=[[left_id,len(left)],[right_id,len(right)]]
    return [left,right,left_id,right_id,transfer,directory]
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],2,3,8]), {1: [[1, 2], [3, 4], 3, 8, 1, [[3, 2], [8, 2]]], 2: [[2, 3], [4, 5], 3, 8, 1, [[3, 2], [8, 2]]], 3: [[3, 4], [5, 6], 3, 8, 1, [[3, 2], [8, 2]]], 4: [[4, 5], [6, 7], 3, 8, 1, [[3, 2], [8, 2]]], 5: [[5, 6], [7, 8], 3, 8, 1, [[3, 2], [8, 2]]]}[N])
check('1', solve([[N],[N+1,N+2,N+3],3,4,9]), {1: [[1, 2, 3], [4], 4, 9, -2, [[4, 3], [9, 1]]], 2: [[2, 3, 4], [5], 4, 9, -2, [[4, 3], [9, 1]]], 3: [[3, 4, 5], [6], 4, 9, -2, [[4, 3], [9, 1]]], 4: [[4, 5, 6], [7], 4, 9, -2, [[4, 3], [9, 1]]], 5: [[5, 6, 7], [8], 4, 9, -2, [[4, 3], [9, 1]]]}[N])
check('2', solve([[N,N+1],[N+2,N+3],2,5,10]), {1: [[1, 2], [3, 4], 5, 10, 0, [[5, 2], [10, 2]]], 2: [[2, 3], [4, 5], 5, 10, 0, [[5, 2], [10, 2]]], 3: [[3, 4], [5, 6], 5, 10, 0, [[5, 2], [10, 2]]], 4: [[4, 5], [6, 7], 5, 10, 0, [[5, 2], [10, 2]]], 5: [[5, 6], [7, 8], 5, 10, 0, [[5, 2], [10, 2]]]}[N])
check('3', solve([[],[N,N+1],1,2,7]), {1: [[1], [2], 2, 7, -1, [[2, 1], [7, 1]]], 2: [[2], [3], 2, 7, -1, [[2, 1], [7, 1]]], 3: [[3], [4], 2, 7, -1, [[2, 1], [7, 1]]], 4: [[4], [5], 2, 7, -1, [[2, 1], [7, 1]]], 5: [[5], [6], 2, 7, -1, [[2, 1], [7, 1]]]}[N])
check('4', solve([[N,N+1],[],0,4,6]), {1: [[], [1, 2], 4, 6, 2, [[4, 0], [6, 2]]], 2: [[], [2, 3], 4, 6, 2, [[4, 0], [6, 2]]], 3: [[], [3, 4], 4, 6, 2, [[4, 0], [6, 2]]], 4: [[], [4, 5], 4, 6, 2, [[4, 0], [6, 2]]], 5: [[], [5, 6], 4, 6, 2, [[4, 0], [6, 2]]]}[N])
check('5', solve([[N],[N+1],2,1,5]), {1: [[1, 2], [], 1, 5, -1, [[1, 2], [5, 0]]], 2: [[2, 3], [], 1, 5, -1, [[1, 2], [5, 0]]], 3: [[3, 4], [], 1, 5, -1, [[1, 2], [5, 0]]], 4: [[4, 5], [], 1, 5, -1, [[1, 2], [5, 0]]], 5: [[5, 6], [], 1, 5, -1, [[1, 2], [5, 0]]]}[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[[4, 1], [2, 3], 3, 8, 1, [[3, 2], [8, 2]]][[1, 2], [3, 4], 3, 8, 1, [[3, 2], [8, 2]]]Failed
1[[2, 3, 4], [1], 4, 9, -2, [[4, 3], [9, 1]]][[1, 2, 3], [4], 4, 9, -2, [[4, 3], [9, 1]]]Failed
2[[3, 4], [1, 2], 5, 10, 0, [[5, 2], [10, 2]]][[1, 2], [3, 4], 5, 10, 0, [[5, 2], [10, 2]]]Failed
3[[1], [2], 2, 7, -1, [[2, 1], [7, 1]]][[1], [2], 2, 7, -1, [[2, 1], [7, 1]]]Passed
4[[], [1, 2], 4, 6, 2, [[4, 0], [6, 2]]][[], [1, 2], 4, 6, 2, [[4, 0], [6, 2]]]Passed
5[[2, 1], [], 1, 5, -1, [[1, 2], [5, 0]]][[1, 2], [], 1, 5, -1, [[1, 2], [5, 0]]]Failed

SHA-256 / a8482e9917f359a7fba86fbada53182cd170ef969417768cd6ffc30c35523eed

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 2026-09-29T14:44:36.288319+00:00.

Case digest / fe83adf5eac32fc7f0d774ee6423a766c3cb70354899cafb14bf435fa810e85e