FA-67546 / Elevator dispatch scheduling / Open access

Hall call ETA with intermediate stops: return leg stops · case 01

The ETA of calls behind the car ignores stops made on the way back.

Verified by executionVariant 1 · 8 checks per implementationDownload source bundle ↓JSON ↗

ROOT CAUSE

Stops between the target and the car on the return leg are not counted.

VERIFIED REPAIR

Add the stops strictly between target and current floor on the return leg.

Unsuccessful approach: Counting stops up to the reversal floor double-counts the stops ahead.

Case contract

A moving car at floor with direction and car stops estimates its arrival at a hall call (target, call direction). Work in the car direction (mirror floors for down). If the target is strictly ahead and the call is in the car direction, the car goes straight there, stopping at stops strictly between. Otherwise it runs to the farthest of its stops ahead and the target, reverses and returns to the target, stopping at every stop ahead plus stops strictly between target and floor behind. A stop at the target floor is not extra. ETA = floors travelled * per_floor_s + stops * stop_s.

Why this case matters

Lift group controllers make these decisions many times per minute; a wrong answer strands passengers, wastes trips or overrides a safety rule.

1 / The failure

Exit 1

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

N = 1
observations = []
def solve(x):
    sg = 1 if x['dir'] == 'up' else -1
    f = x['floor'] * sg
    t = x['target'] * sg
    stops = [s * sg for s in x['stops'] if s * sg != t]
    same = x['call_dir'] == x['dir']
    if t > f and same:
        path = t - f
        n = len([s for s in stops if f < s < t])
    else:
        ahead = [s for s in stops if s > f]
        far = max(ahead + [t, f])
        path = (far - f) + (far - t)
        n = len(ahead)
    return path * x['per_floor_s'] + n * x['stop_s']
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[('regression: stops behind served on return', {'floor': 6, 'dir': 'up', 'target': 1, 'call_dir': 'up', 'stops': [9, 3], 'per_floor_s': 2, 'stop_s': 10}, 42), ('boundary: call behind a down car', {'floor': 10, 'dir': 'down', 'target': 12, 'call_dir': 'up', 'stops': [6], 'per_floor_s': 2, 'stop_s': 10}, 30), ('sampled regression 9', {'floor': 15, 'dir': 'up', 'target': 9, 'call_dir': 'down', 'stops': [13, 11, 12], 'per_floor_s': 2, 'stop_s': 10}, 42), ('boundary: call ahead but opposite direction', {'floor': 2, 'dir': 'up', 'target': 8, 'call_dir': 'down', 'stops': [5, 11], 'per_floor_s': 2, 'stop_s': 10}, 44), ('boundary: down car mirrored', {'floor': 10, 'dir': 'down', 'target': 4, 'call_dir': 'down', 'stops': [7], 'per_floor_s': 2, 'stop_s': 10}, 22), ('control 1', {'floor': 6, 'dir': 'down', 'target': 12, 'call_dir': 'down', 'stops': [3, 4], 'per_floor_s': 2, 'stop_s': 12}, 48), ('sampled regression 4', {'floor': 1, 'dir': 'down', 'target': 14, 'call_dir': 'down', 'stops': [3, 10, 5], 'per_floor_s': 2, 'stop_s': 12}, 62), ('control 7', {'floor': 7, 'dir': 'up', 'target': 11, 'call_dir': 'up', 'stops': [1, 13, 9, 2], 'per_floor_s': 3, 'stop_s': 12}, 24)], [('regression: stops behind served on return', {'floor': 6, 'dir': 'up', 'target': 1, 'call_dir': 'up', 'stops': [9, 3], 'per_floor_s': 2, 'stop_s': 10}, 42), ('boundary: call ahead but opposite direction', {'floor': 2, 'dir': 'up', 'target': 8, 'call_dir': 'down', 'stops': [5, 11], 'per_floor_s': 2, 'stop_s': 10}, 44), ('sampled regression 59', {'floor': 15, 'dir': 'up', 'target': 2, 'call_dir': 'down', 'stops': [14, 13], 'per_floor_s': 3, 'stop_s': 10}, 59), ('control 3', {'floor': 13, 'dir': 'up', 'target': 9, 'call_dir': 'up', 'stops': [2, 15, 4, 6], 'per_floor_s': 3, 'stop_s': 8}, 32), ('boundary: call at the current floor', {'floor': 5, 'dir': 'up', 'target': 5, 'call_dir': 'up', 'stops': [9], 'per_floor_s': 2, 'stop_s': 10}, 26), ('control 12', {'floor': 12, 'dir': 'down', 'target': 11, 'call_dir': 'down', 'stops': [4, 8, 7, 15], 'per_floor_s': 3, 'stop_s': 10}, 3), ('control 15', {'floor': 15, 'dir': 'up', 'target': 11, 'call_dir': 'down', 'stops': [3], 'per_floor_s': 3, 'stop_s': 12}, 12), ('sampled regression 18', {'floor': 1, 'dir': 'down', 'target': 4, 'call_dir': 'down', 'stops': [8, 2, 11, 1], 'per_floor_s': 2, 'stop_s': 10}, 16)], [('regression: stops behind served on return', {'floor': 6, 'dir': 'up', 'target': 1, 'call_dir': 'up', 'stops': [9, 3], 'per_floor_s': 2, 'stop_s': 10}, 42), ('boundary: call at the current floor', {'floor': 5, 'dir': 'up', 'target': 5, 'call_dir': 'up', 'stops': [9], 'per_floor_s': 2, 'stop_s': 10}, 26), ('sampled regression 9', {'floor': 15, 'dir': 'up', 'target': 9, 'call_dir': 'down', 'stops': [13, 11, 12], 'per_floor_s': 2, 'stop_s': 10}, 42), ('sampled regression 18', {'floor': 1, 'dir': 'down', 'target': 4, 'call_dir': 'down', 'stops': [8, 2, 11, 1], 'per_floor_s': 2, 'stop_s': 10}, 16), ('boundary: stop at the target floor', {'floor': 2, 'dir': 'up', 'target': 8, 'call_dir': 'up', 'stops': [8, 5], 'per_floor_s': 2, 'stop_s': 10}, 22), ('control 23', {'floor': 4, 'dir': 'up', 'target': 13, 'call_dir': 'up', 'stops': [], 'per_floor_s': 2, 'stop_s': 12}, 18), ('control 26', {'floor': 14, 'dir': 'up', 'target': 15, 'call_dir': 'down', 'stops': [1, 14], 'per_floor_s': 2, 'stop_s': 8}, 2), ('control 29', {'floor': 8, 'dir': 'down', 'target': 6, 'call_dir': 'down', 'stops': [14, 15, 3], 'per_floor_s': 3, 'stop_s': 10}, 6)], [('regression: stops behind served on return', {'floor': 6, 'dir': 'up', 'target': 1, 'call_dir': 'up', 'stops': [9, 3], 'per_floor_s': 2, 'stop_s': 10}, 42), ('sampled regression 59', {'floor': 15, 'dir': 'up', 'target': 2, 'call_dir': 'down', 'stops': [14, 13], 'per_floor_s': 3, 'stop_s': 10}, 59), ('control 52', {'floor': 6, 'dir': 'down', 'target': 13, 'call_dir': 'down', 'stops': [1, 2, 0, 15], 'per_floor_s': 2, 'stop_s': 12}, 74), ('boundary: stops beyond the target', {'floor': 2, 'dir': 'up', 'target': 6, 'call_dir': 'up', 'stops': [4, 10], 'per_floor_s': 2, 'stop_s': 10}, 18), ('boundary: down car mirrored', {'floor': 10, 'dir': 'down', 'target': 4, 'call_dir': 'down', 'stops': [7], 'per_floor_s': 2, 'stop_s': 10}, 22), ('control 34', {'floor': 7, 'dir': 'down', 'target': 7, 'call_dir': 'up', 'stops': [10, 7], 'per_floor_s': 2, 'stop_s': 8}, 0), ('sampled regression 37', {'floor': 14, 'dir': 'up', 'target': 11, 'call_dir': 'up', 'stops': [7, 4, 13, 1], 'per_floor_s': 2, 'stop_s': 10}, 16), ('control 40', {'floor': 10, 'dir': 'down', 'target': 11, 'call_dir': 'down', 'stops': [4, 10, 12, 5], 'per_floor_s': 3, 'stop_s': 10}, 59)], [('regression: stops behind served on return', {'floor': 6, 'dir': 'up', 'target': 1, 'call_dir': 'up', 'stops': [9, 3], 'per_floor_s': 2, 'stop_s': 10}, 42), ('boundary: call behind a down car', {'floor': 10, 'dir': 'down', 'target': 12, 'call_dir': 'up', 'stops': [6], 'per_floor_s': 2, 'stop_s': 10}, 30), ('sampled regression 9', {'floor': 15, 'dir': 'up', 'target': 9, 'call_dir': 'down', 'stops': [13, 11, 12], 'per_floor_s': 2, 'stop_s': 10}, 42), ('sampled regression 63', {'floor': 5, 'dir': 'down', 'target': 13, 'call_dir': 'down', 'stops': [4, 11, 7, 9], 'per_floor_s': 2, 'stop_s': 8}, 52), ('boundary: call ahead but opposite direction', {'floor': 2, 'dir': 'up', 'target': 8, 'call_dir': 'down', 'stops': [5, 11], 'per_floor_s': 2, 'stop_s': 10}, 44), ('control 45', {'floor': 2, 'dir': 'down', 'target': 0, 'call_dir': 'down', 'stops': [3, 12, 7, 11], 'per_floor_s': 2, 'stop_s': 8}, 4), ('control 48', {'floor': 8, 'dir': 'down', 'target': 2, 'call_dir': 'up', 'stops': [8, 7, 4, 6], 'per_floor_s': 3, 'stop_s': 8}, 42), ('control 51', {'floor': 11, 'dir': 'up', 'target': 4, 'call_dir': 'down', 'stops': [], 'per_floor_s': 3, 'stop_s': 12}, 21)]]
for label, args, expected in fixtures[N-1]:
    check(label, solve(args), expected)
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
regression: stops behind served on return	`32`	`42`	Failed
boundary: call behind a down car	`30`	`30`	Passed
sampled regression 9	`12`	`42`	Failed
boundary: call ahead but opposite direction	`44`	`44`	Passed
boundary: down car mirrored	`22`	`22`	Passed
control 1	`48`	`48`	Passed
sampled regression 4	`26`	`62`	Failed
control 7	`24`	`24`	Passed

SHA-256 / eb1104d4de170222fa70a85efe1e1edbd09ec99c80bb93bacf23546d06ba39ed

2 / The unsuccessful fix

Exit 1

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

N = 1
observations = []
def solve(x):
    sg = 1 if x['dir'] == 'up' else -1
    f = x['floor'] * sg
    t = x['target'] * sg
    stops = [s * sg for s in x['stops'] if s * sg != t]
    same = x['call_dir'] == x['dir']
    if t > f and same:
        path = t - f
        n = len([s for s in stops if f < s < t])
    else:
        ahead = [s for s in stops if s > f]
        far = max(ahead + [t, f])
        path = (far - f) + (far - t)
        n = len(ahead) + len([s for s in stops if t < s <= far])
    return path * x['per_floor_s'] + n * x['stop_s']
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[('regression: stops behind served on return', {'floor': 6, 'dir': 'up', 'target': 1, 'call_dir': 'up', 'stops': [9, 3], 'per_floor_s': 2, 'stop_s': 10}, 42), ('boundary: call behind a down car', {'floor': 10, 'dir': 'down', 'target': 12, 'call_dir': 'up', 'stops': [6], 'per_floor_s': 2, 'stop_s': 10}, 30), ('sampled regression 9', {'floor': 15, 'dir': 'up', 'target': 9, 'call_dir': 'down', 'stops': [13, 11, 12], 'per_floor_s': 2, 'stop_s': 10}, 42), ('boundary: call ahead but opposite direction', {'floor': 2, 'dir': 'up', 'target': 8, 'call_dir': 'down', 'stops': [5, 11], 'per_floor_s': 2, 'stop_s': 10}, 44), ('boundary: down car mirrored', {'floor': 10, 'dir': 'down', 'target': 4, 'call_dir': 'down', 'stops': [7], 'per_floor_s': 2, 'stop_s': 10}, 22), ('control 1', {'floor': 6, 'dir': 'down', 'target': 12, 'call_dir': 'down', 'stops': [3, 4], 'per_floor_s': 2, 'stop_s': 12}, 48), ('sampled regression 4', {'floor': 1, 'dir': 'down', 'target': 14, 'call_dir': 'down', 'stops': [3, 10, 5], 'per_floor_s': 2, 'stop_s': 12}, 62), ('control 7', {'floor': 7, 'dir': 'up', 'target': 11, 'call_dir': 'up', 'stops': [1, 13, 9, 2], 'per_floor_s': 3, 'stop_s': 12}, 24)], [('regression: stops behind served on return', {'floor': 6, 'dir': 'up', 'target': 1, 'call_dir': 'up', 'stops': [9, 3], 'per_floor_s': 2, 'stop_s': 10}, 42), ('boundary: call ahead but opposite direction', {'floor': 2, 'dir': 'up', 'target': 8, 'call_dir': 'down', 'stops': [5, 11], 'per_floor_s': 2, 'stop_s': 10}, 44), ('sampled regression 59', {'floor': 15, 'dir': 'up', 'target': 2, 'call_dir': 'down', 'stops': [14, 13], 'per_floor_s': 3, 'stop_s': 10}, 59), ('control 3', {'floor': 13, 'dir': 'up', 'target': 9, 'call_dir': 'up', 'stops': [2, 15, 4, 6], 'per_floor_s': 3, 'stop_s': 8}, 32), ('boundary: call at the current floor', {'floor': 5, 'dir': 'up', 'target': 5, 'call_dir': 'up', 'stops': [9], 'per_floor_s': 2, 'stop_s': 10}, 26), ('control 12', {'floor': 12, 'dir': 'down', 'target': 11, 'call_dir': 'down', 'stops': [4, 8, 7, 15], 'per_floor_s': 3, 'stop_s': 10}, 3), ('control 15', {'floor': 15, 'dir': 'up', 'target': 11, 'call_dir': 'down', 'stops': [3], 'per_floor_s': 3, 'stop_s': 12}, 12), ('sampled regression 18', {'floor': 1, 'dir': 'down', 'target': 4, 'call_dir': 'down', 'stops': [8, 2, 11, 1], 'per_floor_s': 2, 'stop_s': 10}, 16)], [('regression: stops behind served on return', {'floor': 6, 'dir': 'up', 'target': 1, 'call_dir': 'up', 'stops': [9, 3], 'per_floor_s': 2, 'stop_s': 10}, 42), ('boundary: call at the current floor', {'floor': 5, 'dir': 'up', 'target': 5, 'call_dir': 'up', 'stops': [9], 'per_floor_s': 2, 'stop_s': 10}, 26), ('sampled regression 9', {'floor': 15, 'dir': 'up', 'target': 9, 'call_dir': 'down', 'stops': [13, 11, 12], 'per_floor_s': 2, 'stop_s': 10}, 42), ('sampled regression 18', {'floor': 1, 'dir': 'down', 'target': 4, 'call_dir': 'down', 'stops': [8, 2, 11, 1], 'per_floor_s': 2, 'stop_s': 10}, 16), ('boundary: stop at the target floor', {'floor': 2, 'dir': 'up', 'target': 8, 'call_dir': 'up', 'stops': [8, 5], 'per_floor_s': 2, 'stop_s': 10}, 22), ('control 23', {'floor': 4, 'dir': 'up', 'target': 13, 'call_dir': 'up', 'stops': [], 'per_floor_s': 2, 'stop_s': 12}, 18), ('control 26', {'floor': 14, 'dir': 'up', 'target': 15, 'call_dir': 'down', 'stops': [1, 14], 'per_floor_s': 2, 'stop_s': 8}, 2), ('control 29', {'floor': 8, 'dir': 'down', 'target': 6, 'call_dir': 'down', 'stops': [14, 15, 3], 'per_floor_s': 3, 'stop_s': 10}, 6)], [('regression: stops behind served on return', {'floor': 6, 'dir': 'up', 'target': 1, 'call_dir': 'up', 'stops': [9, 3], 'per_floor_s': 2, 'stop_s': 10}, 42), ('sampled regression 59', {'floor': 15, 'dir': 'up', 'target': 2, 'call_dir': 'down', 'stops': [14, 13], 'per_floor_s': 3, 'stop_s': 10}, 59), ('control 52', {'floor': 6, 'dir': 'down', 'target': 13, 'call_dir': 'down', 'stops': [1, 2, 0, 15], 'per_floor_s': 2, 'stop_s': 12}, 74), ('boundary: stops beyond the target', {'floor': 2, 'dir': 'up', 'target': 6, 'call_dir': 'up', 'stops': [4, 10], 'per_floor_s': 2, 'stop_s': 10}, 18), ('boundary: down car mirrored', {'floor': 10, 'dir': 'down', 'target': 4, 'call_dir': 'down', 'stops': [7], 'per_floor_s': 2, 'stop_s': 10}, 22), ('control 34', {'floor': 7, 'dir': 'down', 'target': 7, 'call_dir': 'up', 'stops': [10, 7], 'per_floor_s': 2, 'stop_s': 8}, 0), ('sampled regression 37', {'floor': 14, 'dir': 'up', 'target': 11, 'call_dir': 'up', 'stops': [7, 4, 13, 1], 'per_floor_s': 2, 'stop_s': 10}, 16), ('control 40', {'floor': 10, 'dir': 'down', 'target': 11, 'call_dir': 'down', 'stops': [4, 10, 12, 5], 'per_floor_s': 3, 'stop_s': 10}, 59)], [('regression: stops behind served on return', {'floor': 6, 'dir': 'up', 'target': 1, 'call_dir': 'up', 'stops': [9, 3], 'per_floor_s': 2, 'stop_s': 10}, 42), ('boundary: call behind a down car', {'floor': 10, 'dir': 'down', 'target': 12, 'call_dir': 'up', 'stops': [6], 'per_floor_s': 2, 'stop_s': 10}, 30), ('sampled regression 9', {'floor': 15, 'dir': 'up', 'target': 9, 'call_dir': 'down', 'stops': [13, 11, 12], 'per_floor_s': 2, 'stop_s': 10}, 42), ('sampled regression 63', {'floor': 5, 'dir': 'down', 'target': 13, 'call_dir': 'down', 'stops': [4, 11, 7, 9], 'per_floor_s': 2, 'stop_s': 8}, 52), ('boundary: call ahead but opposite direction', {'floor': 2, 'dir': 'up', 'target': 8, 'call_dir': 'down', 'stops': [5, 11], 'per_floor_s': 2, 'stop_s': 10}, 44), ('control 45', {'floor': 2, 'dir': 'down', 'target': 0, 'call_dir': 'down', 'stops': [3, 12, 7, 11], 'per_floor_s': 2, 'stop_s': 8}, 4), ('control 48', {'floor': 8, 'dir': 'down', 'target': 2, 'call_dir': 'up', 'stops': [8, 7, 4, 6], 'per_floor_s': 3, 'stop_s': 8}, 42), ('control 51', {'floor': 11, 'dir': 'up', 'target': 4, 'call_dir': 'down', 'stops': [], 'per_floor_s': 3, 'stop_s': 12}, 21)]]
for label, args, expected in fixtures[N-1]:
    check(label, solve(args), expected)
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
regression: stops behind served on return	`52`	`42`	Failed
boundary: call behind a down car	`40`	`30`	Failed
sampled regression 9	`42`	`42`	Passed
boundary: call ahead but opposite direction	`54`	`44`	Failed
boundary: down car mirrored	`22`	`22`	Passed
control 1	`72`	`48`	Failed
sampled regression 4	`62`	`62`	Passed
control 7	`24`	`24`	Passed

SHA-256 / 0dbd5ddf60238af922b9f03ebf549ac69e5a4d6e47d1ddb6ddfb4050310368c8

3 / The verified repair

Exit 0

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

N = 1
observations = []
def solve(x):
    sg = 1 if x['dir'] == 'up' else -1
    f = x['floor'] * sg
    t = x['target'] * sg
    stops = [s * sg for s in x['stops'] if s * sg != t]
    same = x['call_dir'] == x['dir']
    if t > f and same:
        path = t - f
        n = len([s for s in stops if f < s < t])
    else:
        ahead = [s for s in stops if s > f]
        far = max(ahead + [t, f])
        path = (far - f) + (far - t)
        n = len(ahead) + len([s for s in stops if t < s < f])
    return path * x['per_floor_s'] + n * x['stop_s']
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[('regression: stops behind served on return', {'floor': 6, 'dir': 'up', 'target': 1, 'call_dir': 'up', 'stops': [9, 3], 'per_floor_s': 2, 'stop_s': 10}, 42), ('boundary: call behind a down car', {'floor': 10, 'dir': 'down', 'target': 12, 'call_dir': 'up', 'stops': [6], 'per_floor_s': 2, 'stop_s': 10}, 30), ('sampled regression 9', {'floor': 15, 'dir': 'up', 'target': 9, 'call_dir': 'down', 'stops': [13, 11, 12], 'per_floor_s': 2, 'stop_s': 10}, 42), ('boundary: call ahead but opposite direction', {'floor': 2, 'dir': 'up', 'target': 8, 'call_dir': 'down', 'stops': [5, 11], 'per_floor_s': 2, 'stop_s': 10}, 44), ('boundary: down car mirrored', {'floor': 10, 'dir': 'down', 'target': 4, 'call_dir': 'down', 'stops': [7], 'per_floor_s': 2, 'stop_s': 10}, 22), ('control 1', {'floor': 6, 'dir': 'down', 'target': 12, 'call_dir': 'down', 'stops': [3, 4], 'per_floor_s': 2, 'stop_s': 12}, 48), ('sampled regression 4', {'floor': 1, 'dir': 'down', 'target': 14, 'call_dir': 'down', 'stops': [3, 10, 5], 'per_floor_s': 2, 'stop_s': 12}, 62), ('control 7', {'floor': 7, 'dir': 'up', 'target': 11, 'call_dir': 'up', 'stops': [1, 13, 9, 2], 'per_floor_s': 3, 'stop_s': 12}, 24)], [('regression: stops behind served on return', {'floor': 6, 'dir': 'up', 'target': 1, 'call_dir': 'up', 'stops': [9, 3], 'per_floor_s': 2, 'stop_s': 10}, 42), ('boundary: call ahead but opposite direction', {'floor': 2, 'dir': 'up', 'target': 8, 'call_dir': 'down', 'stops': [5, 11], 'per_floor_s': 2, 'stop_s': 10}, 44), ('sampled regression 59', {'floor': 15, 'dir': 'up', 'target': 2, 'call_dir': 'down', 'stops': [14, 13], 'per_floor_s': 3, 'stop_s': 10}, 59), ('control 3', {'floor': 13, 'dir': 'up', 'target': 9, 'call_dir': 'up', 'stops': [2, 15, 4, 6], 'per_floor_s': 3, 'stop_s': 8}, 32), ('boundary: call at the current floor', {'floor': 5, 'dir': 'up', 'target': 5, 'call_dir': 'up', 'stops': [9], 'per_floor_s': 2, 'stop_s': 10}, 26), ('control 12', {'floor': 12, 'dir': 'down', 'target': 11, 'call_dir': 'down', 'stops': [4, 8, 7, 15], 'per_floor_s': 3, 'stop_s': 10}, 3), ('control 15', {'floor': 15, 'dir': 'up', 'target': 11, 'call_dir': 'down', 'stops': [3], 'per_floor_s': 3, 'stop_s': 12}, 12), ('sampled regression 18', {'floor': 1, 'dir': 'down', 'target': 4, 'call_dir': 'down', 'stops': [8, 2, 11, 1], 'per_floor_s': 2, 'stop_s': 10}, 16)], [('regression: stops behind served on return', {'floor': 6, 'dir': 'up', 'target': 1, 'call_dir': 'up', 'stops': [9, 3], 'per_floor_s': 2, 'stop_s': 10}, 42), ('boundary: call at the current floor', {'floor': 5, 'dir': 'up', 'target': 5, 'call_dir': 'up', 'stops': [9], 'per_floor_s': 2, 'stop_s': 10}, 26), ('sampled regression 9', {'floor': 15, 'dir': 'up', 'target': 9, 'call_dir': 'down', 'stops': [13, 11, 12], 'per_floor_s': 2, 'stop_s': 10}, 42), ('sampled regression 18', {'floor': 1, 'dir': 'down', 'target': 4, 'call_dir': 'down', 'stops': [8, 2, 11, 1], 'per_floor_s': 2, 'stop_s': 10}, 16), ('boundary: stop at the target floor', {'floor': 2, 'dir': 'up', 'target': 8, 'call_dir': 'up', 'stops': [8, 5], 'per_floor_s': 2, 'stop_s': 10}, 22), ('control 23', {'floor': 4, 'dir': 'up', 'target': 13, 'call_dir': 'up', 'stops': [], 'per_floor_s': 2, 'stop_s': 12}, 18), ('control 26', {'floor': 14, 'dir': 'up', 'target': 15, 'call_dir': 'down', 'stops': [1, 14], 'per_floor_s': 2, 'stop_s': 8}, 2), ('control 29', {'floor': 8, 'dir': 'down', 'target': 6, 'call_dir': 'down', 'stops': [14, 15, 3], 'per_floor_s': 3, 'stop_s': 10}, 6)], [('regression: stops behind served on return', {'floor': 6, 'dir': 'up', 'target': 1, 'call_dir': 'up', 'stops': [9, 3], 'per_floor_s': 2, 'stop_s': 10}, 42), ('sampled regression 59', {'floor': 15, 'dir': 'up', 'target': 2, 'call_dir': 'down', 'stops': [14, 13], 'per_floor_s': 3, 'stop_s': 10}, 59), ('control 52', {'floor': 6, 'dir': 'down', 'target': 13, 'call_dir': 'down', 'stops': [1, 2, 0, 15], 'per_floor_s': 2, 'stop_s': 12}, 74), ('boundary: stops beyond the target', {'floor': 2, 'dir': 'up', 'target': 6, 'call_dir': 'up', 'stops': [4, 10], 'per_floor_s': 2, 'stop_s': 10}, 18), ('boundary: down car mirrored', {'floor': 10, 'dir': 'down', 'target': 4, 'call_dir': 'down', 'stops': [7], 'per_floor_s': 2, 'stop_s': 10}, 22), ('control 34', {'floor': 7, 'dir': 'down', 'target': 7, 'call_dir': 'up', 'stops': [10, 7], 'per_floor_s': 2, 'stop_s': 8}, 0), ('sampled regression 37', {'floor': 14, 'dir': 'up', 'target': 11, 'call_dir': 'up', 'stops': [7, 4, 13, 1], 'per_floor_s': 2, 'stop_s': 10}, 16), ('control 40', {'floor': 10, 'dir': 'down', 'target': 11, 'call_dir': 'down', 'stops': [4, 10, 12, 5], 'per_floor_s': 3, 'stop_s': 10}, 59)], [('regression: stops behind served on return', {'floor': 6, 'dir': 'up', 'target': 1, 'call_dir': 'up', 'stops': [9, 3], 'per_floor_s': 2, 'stop_s': 10}, 42), ('boundary: call behind a down car', {'floor': 10, 'dir': 'down', 'target': 12, 'call_dir': 'up', 'stops': [6], 'per_floor_s': 2, 'stop_s': 10}, 30), ('sampled regression 9', {'floor': 15, 'dir': 'up', 'target': 9, 'call_dir': 'down', 'stops': [13, 11, 12], 'per_floor_s': 2, 'stop_s': 10}, 42), ('sampled regression 63', {'floor': 5, 'dir': 'down', 'target': 13, 'call_dir': 'down', 'stops': [4, 11, 7, 9], 'per_floor_s': 2, 'stop_s': 8}, 52), ('boundary: call ahead but opposite direction', {'floor': 2, 'dir': 'up', 'target': 8, 'call_dir': 'down', 'stops': [5, 11], 'per_floor_s': 2, 'stop_s': 10}, 44), ('control 45', {'floor': 2, 'dir': 'down', 'target': 0, 'call_dir': 'down', 'stops': [3, 12, 7, 11], 'per_floor_s': 2, 'stop_s': 8}, 4), ('control 48', {'floor': 8, 'dir': 'down', 'target': 2, 'call_dir': 'up', 'stops': [8, 7, 4, 6], 'per_floor_s': 3, 'stop_s': 8}, 42), ('control 51', {'floor': 11, 'dir': 'up', 'target': 4, 'call_dir': 'down', 'stops': [], 'per_floor_s': 3, 'stop_s': 12}, 21)]]
for label, args, expected in fixtures[N-1]:
    check(label, solve(args), expected)
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
regression: stops behind served on return	`42`	`42`	Passed
boundary: call behind a down car	`30`	`30`	Passed
sampled regression 9	`42`	`42`	Passed
boundary: call ahead but opposite direction	`44`	`44`	Passed
boundary: down car mirrored	`22`	`22`	Passed
control 1	`48`	`48`	Passed
sampled regression 4	`62`	`62`	Passed
control 7	`24`	`24`	Passed

SHA-256 / 995c3172675353cece0887ebb03802e72e2326469b94d6809ff70720c0827152

Verification & scope

Stipulated toy lift-control contract for a bounded teaching model; it makes no claim of conformance to any lift code or vendor dispatcher and omits real safety cases. 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 2026-09-29T14:47:53.911038+00:00.

Case digest / f0ad9f8d9717e92e3d0ecff99ddca55158ccc92b513af73e4749dc549e396525