FA-231 / Runtime and resources / Open access
A bounded queue admits only part of a logical batch · case 01
A queue exceeds capacity or silently drops a suffix after accepting a batch.
ROOT CAUSE
Admission checks a single item or truncates work instead of reserving capacity for the complete batch.
VERIFIED REPAIR
Admit the complete batch only when its full size fits; otherwise preserve the existing queue unchanged.
Unsuccessful approach: Truncating the resulting queue enforces a size bound but violates all-or-nothing admission.
Case contract
Capacity is nonnegative and the initial queue fits. Return [new queue,accepted]. A batch is atomic: all items append in order or none do. An empty batch succeeds even at zero capacity. The check and append are one serialized state transition in this model.
Why this case matters
Models bounded work admission for a logically indivisible request, isolating capacity reservation from the separate problem of locking a concurrent implementation.
1 / The failure
Exit 1"""Failure Map reference implementation. Python standard library only."""
import json
N = 1
observations = []
def solve(capacity, queue, batch):
allowed = len(queue) < capacity
return [list(queue)+list(batch), True] if allowed else [list(queue), False]
def check(label, actual, expected):
observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
queue = list(range(N))
check('oversize batch is rejected intact', solve(N+1, queue, ['a', 'b']), [queue, False])
check('exact fit admitted', solve(N+2, queue, ['a', 'b']), [queue+['a', 'b'], True])
check('empty batch on full queue', solve(N, queue, []), [queue, True])
check('zero capacity empty batch', solve(0, [], []), [[], True])
check('zero capacity nonempty batch', solve(0, [], [N]), [[], False])
check('oversize from empty', solve(N, [], list(range(N+1))), [[], False])
check('room for small batch', solve(3*N, queue, [N]), [queue+[N], True])
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 fixture | Actual | Expected | Outcome |
|---|---|---|---|
| oversize batch is rejected intact | [[0, 'a', 'b'], True] | [[0], False] | Failed |
| exact fit admitted | [[0, 'a', 'b'], True] | [[0, 'a', 'b'], True] | Passed |
| empty batch on full queue | [[0], False] | [[0], True] | Failed |
| zero capacity empty batch | [[], False] | [[], True] | Failed |
| zero capacity nonempty batch | [[], False] | [[], False] | Passed |
| oversize from empty | [[0, 1], True] | [[], False] | Failed |
| room for small batch | [[0, 1], True] | [[0, 1], True] | Passed |
SHA-256 / db9dcd1f8250c598cbc3620002ca710e050422c1fa0338874b7cfdf639fb0530
2 / The unsuccessful fix
Exit 1"""Failure Map reference implementation. Python standard library only."""
import json
N = 1
observations = []
def solve(capacity, queue, batch):
return [(list(queue)+list(batch))[:capacity], len(queue) < capacity]
def check(label, actual, expected):
observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
queue = list(range(N))
check('oversize batch is rejected intact', solve(N+1, queue, ['a', 'b']), [queue, False])
check('exact fit admitted', solve(N+2, queue, ['a', 'b']), [queue+['a', 'b'], True])
check('empty batch on full queue', solve(N, queue, []), [queue, True])
check('zero capacity empty batch', solve(0, [], []), [[], True])
check('zero capacity nonempty batch', solve(0, [], [N]), [[], False])
check('oversize from empty', solve(N, [], list(range(N+1))), [[], False])
check('room for small batch', solve(3*N, queue, [N]), [queue+[N], True])
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 fixture | Actual | Expected | Outcome |
|---|---|---|---|
| oversize batch is rejected intact | [[0, 'a'], True] | [[0], False] | Failed |
| exact fit admitted | [[0, 'a', 'b'], True] | [[0, 'a', 'b'], True] | Passed |
| empty batch on full queue | [[0], False] | [[0], True] | Failed |
| zero capacity empty batch | [[], False] | [[], True] | Failed |
| zero capacity nonempty batch | [[], False] | [[], False] | Passed |
| oversize from empty | [[0], True] | [[], False] | Failed |
| room for small batch | [[0, 1], True] | [[0, 1], True] | Passed |
SHA-256 / 8aacaf2519b78db462dc45f7b0c038c97404be88ff0cacb3401df75fd67d1fbb
3 / The verified repair
Exit 0"""Failure Map reference implementation. Python standard library only."""
import json
N = 1
observations = []
def solve(capacity, queue, batch):
allowed = len(queue)+len(batch) <= capacity
return [list(queue)+list(batch), True] if allowed else [list(queue), False]
def check(label, actual, expected):
observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
queue = list(range(N))
check('oversize batch is rejected intact', solve(N+1, queue, ['a', 'b']), [queue, False])
check('exact fit admitted', solve(N+2, queue, ['a', 'b']), [queue+['a', 'b'], True])
check('empty batch on full queue', solve(N, queue, []), [queue, True])
check('zero capacity empty batch', solve(0, [], []), [[], True])
check('zero capacity nonempty batch', solve(0, [], [N]), [[], False])
check('oversize from empty', solve(N, [], list(range(N+1))), [[], False])
check('room for small batch', solve(3*N, queue, [N]), [queue+[N], True])
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 fixture | Actual | Expected | Outcome |
|---|---|---|---|
| oversize batch is rejected intact | [[0], False] | [[0], False] | Passed |
| exact fit admitted | [[0, 'a', 'b'], True] | [[0, 'a', 'b'], True] | Passed |
| empty batch on full queue | [[0], True] | [[0], True] | Passed |
| zero capacity empty batch | [[], True] | [[], True] | Passed |
| zero capacity nonempty batch | [[], False] | [[], False] | Passed |
| oversize from empty | [[], False] | [[], False] | Passed |
| room for small batch | [[0, 1], True] | [[0, 1], True] | Passed |
SHA-256 / 4d00dc0b66bb0bfce854cf6097284955f5a8b2c5e4bf4d00230992e32c229a9b
Verification & scope
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 2026-09-29T14:36:51.526279+00:00.
Case digest / 4f6f61999399feaa472ee8c35febc3de42c1f0fb5355be178771558870043f85