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FA-67281 / Railway interlocking logic / Open access

Flank protection selection: indirect protection availability · case 01

A route is protected by a flank signal that cannot actually be held.

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

ROOT CAUSE

Any existing flank signal is assumed holdable.

THE FAILURE

Any existing flank signal is assumed holdable.

Unsuccessful approach: Checking only that some signal is holdable appends missing or unholdable signals.

Case contract

For each route point (sorted) in its lie, the flank table (key point+lie) lists flank points with the protecting lie and an optional flank signal. A flank point is set to its protecting lie if it is free, locked in that lie by another route, or already demanded in that lie by this route; if it is unavailable, its flank signal is held at danger when the signal exists and is holdable; otherwise the route is refused (refused:<flank point>, nothing set or held). Held signals are returned sorted and unique.

Why this case matters

Interlocking logic decides whether trains may be given authority; a wrong decision at this point either grants unsafe movements or strands traffic.

1 / The failure

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

N = 1
observations = []
def solve(x):
    set_pts = {}
    held = []
    locks = x['point_locks']
    for p, pos in sorted(x['route_points'].items()):
        for fp, fpos, fsig in x['flank'].get(p + pos, []):
            lk = locks.get(fp, set_pts.get(fp))
            if lk is None or lk == fpos:
                set_pts[fp] = fpos
            elif fsig is not None:
                held.append(fsig)
            else:
                return {'result': 'refused:' + fp, 'set_points': {}, 'held_signals': []}
    return {'result': 'protected', 'set_points': set_pts, 'held_signals': sorted(set(held))}
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[('regression: flank signal not holdable', {'route_points': {'P1': 'R'}, 'flank': {'P1N': [['P7', 'R', 'S20'], ['P8', 'N', None]], 'P1R': [['P7', 'N', 'S21']], 'P2N': [['P8', 'R', 'S22'], ['P9', 'R', 'S20']], 'P2R': [['P9', 'N', 'S23'], ['P7', 'N', None]], 'P3N': [['P9', 'R', None]], 'P3R': [['P8', 'N', 'S24']]}, 'point_locks': {'P7': 'R'}, 'holdable': []}, {'result': 'refused:P7', 'set_points': {}, 'held_signals': []}), ('boundary: no flank signal available', {'route_points': {'P3': 'N'}, 'flank': {'P1N': [['P7', 'R', 'S20'], ['P8', 'N', None]], 'P1R': [['P7', 'N', 'S21']], 'P2N': [['P8', 'R', 'S22'], ['P9', 'R', 'S20']], 'P2R': [['P9', 'N', 'S23'], ['P7', 'N', None]], 'P3N': [['P9', 'R', None]], 'P3R': [['P8', 'N', 'S24']]}, 'point_locks': {'P9': 'N'}, 'holdable': ['S20', 'S21', 'S22', 'S23', 'S24']}, {'result': 'refused:P9', 'set_points': {}, 'held_signals': []}), ('sampled regression 11', {'route_points': {'P1': 'N', 'P2': 'R'}, 'flank': {'P1N': [['P7', 'R', 'S20'], ['P8', 'N', None]], 'P1R': [['P7', 'N', 'S21']], 'P2N': [['P8', 'R', 'S22'], ['P9', 'R', 'S20']], 'P2R': [['P9', 'N', 'S23'], ['P7', 'N', None]], 'P3N': [['P9', 'R', None]], 'P3R': [['P8', 'N', 'S24']]}, 'point_locks': {'P7': 'N', 'P9': 'R'}, 'holdable': ['S20', 'S21', 'S22', 'S24']}, {'result': 'refused:P9', 'set_points': {}, 'held_signals': []}), ('boundary: own conflicting demand without a signal', {'route_points': {'P1': 'N', 'P2': 'R'}, 'flank': {'P1N': [['P7', 'R', 'S20'], ['P8', 'N', None]], 'P1R': [['P7', 'N', 'S21']], 'P2N': [['P8', 'R', 'S22'], ['P9', 'R', 'S20']], 'P2R': [['P9', 'N', 'S23'], ['P7', 'N', None]], 'P3N': [['P9', 'R', None]], 'P3R': [['P8', 'N', 'S24']]}, 'point_locks': {}, 'holdable': ['S20', 'S21', 'S22', 'S23', 'S24']}, {'result': 'refused:P7', 'set_points': {}, 'held_signals': []}), ('boundary: flank point locked in the protecting lie', {'route_points': {'P1': 'N'}, 'flank': {'P1N': [['P7', 'R', 'S20'], ['P8', 'N', None]], 'P1R': [['P7', 'N', 'S21']], 'P2N': [['P8', 'R', 'S22'], ['P9', 'R', 'S20']], 'P2R': [['P9', 'N', 'S23'], ['P7', 'N', None]], 'P3N': [['P9', 'R', None]], 'P3R': [['P8', 'N', 'S24']]}, 'point_locks': {'P7': 'R'}, 'holdable': ['S20', 'S21', 'S22', 'S23', 'S24']}, {'result': 'protected', 'set_points': {'P7': 'R', 'P8': 'N'}, 'held_signals': []}), ('control 1', {'route_points': {'P3': 'N'}, 'flank': {'P1N': [['P7', 'R', 'S20'], ['P8', 'N', None]], 'P1R': [['P7', 'N', 'S21']], 'P2N': [['P8', 'R', 'S22'], ['P9', 'R', 'S20']], 'P2R': [['P9', 'N', 'S23'], ['P7', 'N', None]], 'P3N': [['P9', 'R', None]], 'P3R': [['P8', 'N', 'S24']]}, 'point_locks': {'P7': 'R', 'P9': 'N'}, 'holdable': ['S23', 'S24']}, {'result': 'refused:P9', 'set_points': {}, 'held_signals': []}), ('control 4', {'route_points': {'P2': 'R'}, 'flank': {'P1N': [['P7', 'R', 'S20'], ['P8', 'N', None]], 'P1R': [['P7', 'N', 'S21']], 'P2N': [['P8', 'R', 'S22'], ['P9', 'R', 'S20']], 'P2R': [['P9', 'N', 'S23'], ['P7', 'N', None]], 'P3N': [['P9', 'R', None]], 'P3R': [['P8', 'N', 'S24']]}, 'point_locks': {}, 'holdable': ['S21', 'S22']}, {'result': 'protected', 'set_points': {'P9': 'N', 'P7': 'N'}, 'held_signals': []}), ('control 8', {'route_points': {'P1': 'N'}, 'flank': {'P1N': [['P7', 'R', 'S20'], ['P8', 'N', None]], 'P1R': [['P7', 'N', 'S21']], 'P2N': [['P8', 'R', 'S22'], ['P9', 'R', 'S20']], 'P2R': [['P9', 'N', 'S23'], ['P7', 'N', None]], 'P3N': [['P9', 'R', None]], 'P3R': [['P8', 'N', 'S24']]}, 'point_locks': {'P7': 'R'}, 'holdable': ['S21', 'S24']}, {'result': 'protected', 'set_points': {'P7': 'R', 'P8': 'N'}, 'held_signals': []})], [('regression: flank signal not holdable', {'route_points': {'P1': 'R'}, 'flank': {'P1N': [['P7', 'R', 'S20'], ['P8', 'N', None]], 'P1R': [['P7', 'N', 'S21']], 'P2N': [['P8', 'R', 'S22'], ['P9', 'R', 'S20']], 'P2R': [['P9', 'N', 'S23'], ['P7', 'N', None]], 'P3N': [['P9', 'R', None]], 'P3R': [['P8', 'N', 'S24']]}, 'point_locks': {'P7': 'R'}, 'holdable': []}, {'result': 'refused:P7', 'set_points': {}, 'held_signals': []}), ('boundary: own conflicting demand without a signal', {'route_points': {'P1': 'N', 'P2': 'R'}, 'flank': {'P1N': [['P7', 'R', 'S20'], ['P8', 'N', None]], 'P1R': [['P7', 'N', 'S21']], 'P2N': [['P8', 'R', 'S22'], ['P9', 'R', 'S20']], 'P2R': [['P9', 'N', 'S23'], ['P7', 'N', None]], 'P3N': [['P9', 'R', None]], 'P3R': [['P8', 'N', 'S24']]}, 'point_locks': {}, 'holdable': ['S20', 'S21', 'S22', 'S23', 'S24']}, {'result': 'refused:P7', 'set_points': {}, 'held_signals': []}), ('sampled regression 50', {'route_points': {'P2': 'R'}, 'flank': {'P1N': [['P7', 'R', 'S20'], ['P8', 'N', None]], 'P1R': [['P7', 'N', 'S21']], 'P2N': [['P8', 'R', 'S22'], ['P9', 'R', 'S20']], 'P2R': [['P9', 'N', 'S23'], ['P7', 'N', None]], 'P3N': [['P9', 'R', None]], 'P3R': [['P8', 'N', 'S24']]}, 'point_locks': {'P9': 'R'}, 'holdable': ['S22', 'S24']}, {'result': 'refused:P9', 'set_points': {}, 'held_signals': []}), ('sampled regression 14', {'route_points': {'P2': 'N', 'P3': 'N', 'P1': 'R'}, 'flank': {'P1N': [['P7', 'R', 'S20'], ['P8', 'N', None]], 'P1R': [['P7', 'N', 'S21']], 'P2N': [['P8', 'R', 'S22'], ['P9', 'R', 'S20']], 'P2R': [['P9', 'N', 'S23'], ['P7', 'N', None]], 'P3N': [['P9', 'R', None]], 'P3R': [['P8', 'N', 'S24']]}, 'point_locks': {'P7': 'R', 'P8': 'N'}, 'holdable': ['S20', 'S23', 'S24']}, {'result': 'refused:P7', 'set_points': {}, 'held_signals': []}), ('boundary: two route points disagree on a flank point', {'route_points': {'P1': 'R', 'P2': 'R'}, 'flank': {'P1N': [['P7', 'R', 'S20'], ['P8', 'N', None]], 'P1R': [['P7', 'N', 'S21']], 'P2N': [['P8', 'R', 'S22'], ['P9', 'R', 'S20']], 'P2R': [['P9', 'N', 'S23'], ['P7', 'N', None]], 'P3N': [['P9', 'R', None]], 'P3R': [['P8', 'N', 'S24']]}, 'point_locks': {}, 'holdable': ['S20', 'S21', 'S22', 'S23', 'S24']}, {'result': 'protected', 'set_points': {'P7': 'N', 'P9': 'N'}, 'held_signals': []}), ('control 17', {'route_points': {'P3': 'N', 'P2': 'N'}, 'flank': {'P1N': [['P7', 'R', 'S20'], ['P8', 'N', None]], 'P1R': [['P7', 'N', 'S21']], 'P2N': [['P8', 'R', 'S22'], ['P9', 'R', 'S20']], 'P2R': [['P9', 'N', 'S23'], ['P7', 'N', None]], 'P3N': [['P9', 'R', None]], 'P3R': [['P8', 'N', 'S24']]}, 'point_locks': {}, 'holdable': ['S20', 'S21', 'S23', 'S24']}, {'result': 'protected', 'set_points': {'P8': 'R', 'P9': 'R'}, 'held_signals': []}), ('sampled regression 20', {'route_points': {'P1': 'R', 'P2': 'N', 'P3': 'R'}, 'flank': {'P1N': [['P7', 'R', 'S20'], ['P8', 'N', None]], 'P1R': [['P7', 'N', 'S21']], 'P2N': [['P8', 'R', 'S22'], ['P9', 'R', 'S20']], 'P2R': [['P9', 'N', 'S23'], ['P7', 'N', None]], 'P3N': [['P9', 'R', None]], 'P3R': [['P8', 'N', 'S24']]}, 'point_locks': {}, 'holdable': []}, {'result': 'refused:P8', 'set_points': {}, 'held_signals': []}), ('control 23', {'route_points': {'P1': 'R', 'P2': 'N', 'P3': 'R'}, 'flank': {'P1N': [['P7', 'R', 'S20'], ['P8', 'N', None]], 'P1R': [['P7', 'N', 'S21']], 'P2N': [['P8', 'R', 'S22'], ['P9', 'R', 'S20']], 'P2R': [['P9', 'N', 'S23'], ['P7', 'N', None]], 'P3N': [['P9', 'R', None]], 'P3R': [['P8', 'N', 'S24']]}, 'point_locks': {}, 'holdable': ['S20', 'S21', 'S22', 'S24']}, {'result': 'protected', 'set_points': {'P7': 'N', 'P8': 'R', 'P9': 'R'}, 'held_signals': ['S24']})], [('regression: flank signal not holdable', {'route_points': {'P1': 'R'}, 'flank': {'P1N': [['P7', 'R', 'S20'], ['P8', 'N', None]], 'P1R': [['P7', 'N', 'S21']], 'P2N': [['P8', 'R', 'S22'], ['P9', 'R', 'S20']], 'P2R': [['P9', 'N', 'S23'], ['P7', 'N', None]], 'P3N': [['P9', 'R', None]], 'P3R': [['P8', 'N', 'S24']]}, 'point_locks': {'P7': 'R'}, 'holdable': []}, {'result': 'refused:P7', 'set_points': {}, 'held_signals': []}), ('boundary: no flank signal available', {'route_points': {'P3': 'N'}, 'flank': {'P1N': [['P7', 'R', 'S20'], ['P8', 'N', None]], 'P1R': [['P7', 'N', 'S21']], 'P2N': [['P8', 'R', 'S22'], ['P9', 'R', 'S20']], 'P2R': [['P9', 'N', 'S23'], ['P7', 'N', None]], 'P3N': [['P9', 'R', None]], 'P3R': [['P8', 'N', 'S24']]}, 'point_locks': {'P9': 'N'}, 'holdable': ['S20', 'S21', 'S22', 'S23', 'S24']}, {'result': 'refused:P9', 'set_points': {}, 'held_signals': []}), ('sampled regression 11', {'route_points': {'P1': 'N', 'P2': 'R'}, 'flank': {'P1N': [['P7', 'R', 'S20'], ['P8', 'N', None]], 'P1R': [['P7', 'N', 'S21']], 'P2N': [['P8', 'R', 'S22'], ['P9', 'R', 'S20']], 'P2R': [['P9', 'N', 'S23'], ['P7', 'N', None]], 'P3N': [['P9', 'R', None]], 'P3R': [['P8', 'N', 'S24']]}, 'point_locks': {'P7': 'N', 'P9': 'R'}, 'holdable': ['S20', 'S21', 'S22', 'S24']}, {'result': 'refused:P9', 'set_points': {}, 'held_signals': []}), ('control 36', {'route_points': {'P3': 'R', 'P2': 'R', 'P1': 'N'}, 'flank': {'P1N': [['P7', 'R', 'S20'], ['P8', 'N', None]], 'P1R': [['P7', 'N', 'S21']], 'P2N': [['P8', 'R', 'S22'], ['P9', 'R', 'S20']], 'P2R': [['P9', 'N', 'S23'], ['P7', 'N', None]], 'P3N': [['P9', 'R', None]], 'P3R': [['P8', 'N', 'S24']]}, 'point_locks': {'P8': 'N'}, 'holdable': ['S20', 'S21', 'S22', 'S24']}, {'result': 'refused:P7', 'set_points': {}, 'held_signals': []}), ('boundary: reverse lie flank entry', {'route_points': {'P2': 'R'}, 'flank': {'P1N': [['P7', 'R', 'S20'], ['P8', 'N', None]], 'P1R': [['P7', 'N', 'S21']], 'P2N': [['P8', 'R', 'S22'], ['P9', 'R', 'S20']], 'P2R': [['P9', 'N', 'S23'], ['P7', 'N', None]], 'P3N': [['P9', 'R', None]], 'P3R': [['P8', 'N', 'S24']]}, 'point_locks': {'P9': 'R'}, 'holdable': ['S20', 'S21', 'S22', 'S23', 'S24']}, {'result': 'protected', 'set_points': {'P7': 'N'}, 'held_signals': ['S23']}), ('control 26', {'route_points': {'P3': 'N'}, 'flank': {'P1N': [['P7', 'R', 'S20'], ['P8', 'N', None]], 'P1R': [['P7', 'N', 'S21']], 'P2N': [['P8', 'R', 'S22'], ['P9', 'R', 'S20']], 'P2R': [['P9', 'N', 'S23'], ['P7', 'N', None]], 'P3N': [['P9', 'R', None]], 'P3R': [['P8', 'N', 'S24']]}, 'point_locks': {'P7': 'R', 'P8': 'N'}, 'holdable': ['S20', 'S21', 'S22', 'S23', 'S24']}, {'result': 'protected', 'set_points': {'P9': 'R'}, 'held_signals': []}), ('control 29', {'route_points': {'P1': 'R', 'P2': 'R'}, 'flank': {'P1N': [['P7', 'R', 'S20'], ['P8', 'N', None]], 'P1R': [['P7', 'N', 'S21']], 'P2N': [['P8', 'R', 'S22'], ['P9', 'R', 'S20']], 'P2R': [['P9', 'N', 'S23'], ['P7', 'N', None]], 'P3N': [['P9', 'R', None]], 'P3R': [['P8', 'N', 'S24']]}, 'point_locks': {'P9': 'R'}, 'holdable': ['S20', 'S23']}, {'result': 'protected', 'set_points': {'P7': 'N'}, 'held_signals': ['S23']}), ('control 32', {'route_points': {'P1': 'N'}, 'flank': {'P1N': [['P7', 'R', 'S20'], ['P8', 'N', None]], 'P1R': [['P7', 'N', 'S21']], 'P2N': [['P8', 'R', 'S22'], ['P9', 'R', 'S20']], 'P2R': [['P9', 'N', 'S23'], ['P7', 'N', None]], 'P3N': [['P9', 'R', None]], 'P3R': [['P8', 'N', 'S24']]}, 'point_locks': {'P8': 'R'}, 'holdable': ['S23']}, {'result': 'refused:P8', 'set_points': {}, 'held_signals': []})], [('regression: flank signal not holdable', {'route_points': {'P1': 'R'}, 'flank': {'P1N': [['P7', 'R', 'S20'], ['P8', 'N', None]], 'P1R': [['P7', 'N', 'S21']], 'P2N': [['P8', 'R', 'S22'], ['P9', 'R', 'S20']], 'P2R': [['P9', 'N', 'S23'], ['P7', 'N', None]], 'P3N': [['P9', 'R', None]], 'P3R': [['P8', 'N', 'S24']]}, 'point_locks': {'P7': 'R'}, 'holdable': []}, {'result': 'refused:P7', 'set_points': {}, 'held_signals': []}), ('boundary: own conflicting demand without a signal', {'route_points': {'P1': 'N', 'P2': 'R'}, 'flank': {'P1N': [['P7', 'R', 'S20'], ['P8', 'N', None]], 'P1R': [['P7', 'N', 'S21']], 'P2N': [['P8', 'R', 'S22'], ['P9', 'R', 'S20']], 'P2R': [['P9', 'N', 'S23'], ['P7', 'N', None]], 'P3N': [['P9', 'R', None]], 'P3R': [['P8', 'N', 'S24']]}, 'point_locks': {}, 'holdable': ['S20', 'S21', 'S22', 'S23', 'S24']}, {'result': 'refused:P7', 'set_points': {}, 'held_signals': []}), ('sampled regression 50', {'route_points': {'P2': 'R'}, 'flank': {'P1N': [['P7', 'R', 'S20'], ['P8', 'N', None]], 'P1R': [['P7', 'N', 'S21']], 'P2N': [['P8', 'R', 'S22'], ['P9', 'R', 'S20']], 'P2R': [['P9', 'N', 'S23'], ['P7', 'N', None]], 'P3N': [['P9', 'R', None]], 'P3R': [['P8', 'N', 'S24']]}, 'point_locks': {'P9': 'R'}, 'holdable': ['S22', 'S24']}, {'result': 'refused:P9', 'set_points': {}, 'held_signals': []}), ('sampled regression 53', {'route_points': {'P2': 'N', 'P3': 'R'}, 'flank': {'P1N': [['P7', 'R', 'S20'], ['P8', 'N', None]], 'P1R': [['P7', 'N', 'S21']], 'P2N': [['P8', 'R', 'S22'], ['P9', 'R', 'S20']], 'P2R': [['P9', 'N', 'S23'], ['P7', 'N', None]], 'P3N': [['P9', 'R', None]], 'P3R': [['P8', 'N', 'S24']]}, 'point_locks': {'P9': 'N'}, 'holdable': ['S20', 'S21', 'S22', 'S23']}, {'result': 'refused:P8', 'set_points': {}, 'held_signals': []}), ('boundary: same signal held twice', {'route_points': {'P1': 'N', 'P2': 'N'}, 'flank': {'P1N': [['P7', 'R', 'S20'], ['P8', 'N', None]], 'P1R': [['P7', 'N', 'S21']], 'P2N': [['P8', 'R', 'S22'], ['P9', 'R', 'S20']], 'P2R': [['P9', 'N', 'S23'], ['P7', 'N', None]], 'P3N': [['P9', 'R', None]], 'P3R': [['P8', 'N', 'S24']]}, 'point_locks': {'P7': 'N', 'P8': 'N', 'P9': 'N'}, 'holdable': ['S20', 'S22']}, {'result': 'protected', 'set_points': {'P8': 'N'}, 'held_signals': ['S20', 'S22']}), ('control 37', {'route_points': {'P2': 'N', 'P1': 'R', 'P3': 'N'}, 'flank': {'P1N': [['P7', 'R', 'S20'], ['P8', 'N', None]], 'P1R': [['P7', 'N', 'S21']], 'P2N': [['P8', 'R', 'S22'], ['P9', 'R', 'S20']], 'P2R': [['P9', 'N', 'S23'], ['P7', 'N', None]], 'P3N': [['P9', 'R', None]], 'P3R': [['P8', 'N', 'S24']]}, 'point_locks': {'P8': 'R'}, 'holdable': ['S21', 'S24']}, {'result': 'protected', 'set_points': {'P7': 'N', 'P8': 'R', 'P9': 'R'}, 'held_signals': []}), ('control 41', {'route_points': {'P2': 'R', 'P1': 'R', 'P3': 'N'}, 'flank': {'P1N': [['P7', 'R', 'S20'], ['P8', 'N', None]], 'P1R': [['P7', 'N', 'S21']], 'P2N': [['P8', 'R', 'S22'], ['P9', 'R', 'S20']], 'P2R': [['P9', 'N', 'S23'], ['P7', 'N', None]], 'P3N': [['P9', 'R', None]], 'P3R': [['P8', 'N', 'S24']]}, 'point_locks': {}, 'holdable': ['S20', 'S21', 'S22']}, {'result': 'refused:P9', 'set_points': {}, 'held_signals': []}), ('control 46', {'route_points': {'P2': 'N'}, 'flank': {'P1N': [['P7', 'R', 'S20'], ['P8', 'N', None]], 'P1R': [['P7', 'N', 'S21']], 'P2N': [['P8', 'R', 'S22'], ['P9', 'R', 'S20']], 'P2R': [['P9', 'N', 'S23'], ['P7', 'N', None]], 'P3N': [['P9', 'R', None]], 'P3R': [['P8', 'N', 'S24']]}, 'point_locks': {'P7': 'N'}, 'holdable': ['S20', 'S21']}, {'result': 'protected', 'set_points': {'P8': 'R', 'P9': 'R'}, 'held_signals': []})], [('regression: flank signal not holdable', {'route_points': {'P1': 'R'}, 'flank': {'P1N': [['P7', 'R', 'S20'], ['P8', 'N', None]], 'P1R': [['P7', 'N', 'S21']], 'P2N': [['P8', 'R', 'S22'], ['P9', 'R', 'S20']], 'P2R': [['P9', 'N', 'S23'], ['P7', 'N', None]], 'P3N': [['P9', 'R', None]], 'P3R': [['P8', 'N', 'S24']]}, 'point_locks': {'P7': 'R'}, 'holdable': []}, {'result': 'refused:P7', 'set_points': {}, 'held_signals': []}), ('boundary: no flank signal available', {'route_points': {'P3': 'N'}, 'flank': {'P1N': [['P7', 'R', 'S20'], ['P8', 'N', None]], 'P1R': [['P7', 'N', 'S21']], 'P2N': [['P8', 'R', 'S22'], ['P9', 'R', 'S20']], 'P2R': [['P9', 'N', 'S23'], ['P7', 'N', None]], 'P3N': [['P9', 'R', None]], 'P3R': [['P8', 'N', 'S24']]}, 'point_locks': {'P9': 'N'}, 'holdable': ['S20', 'S21', 'S22', 'S23', 'S24']}, {'result': 'refused:P9', 'set_points': {}, 'held_signals': []}), ('sampled regression 11', {'route_points': {'P1': 'N', 'P2': 'R'}, 'flank': {'P1N': [['P7', 'R', 'S20'], ['P8', 'N', None]], 'P1R': [['P7', 'N', 'S21']], 'P2N': [['P8', 'R', 'S22'], ['P9', 'R', 'S20']], 'P2R': [['P9', 'N', 'S23'], ['P7', 'N', None]], 'P3N': [['P9', 'R', None]], 'P3R': [['P8', 'N', 'S24']]}, 'point_locks': {'P7': 'N', 'P9': 'R'}, 'holdable': ['S20', 'S21', 'S22', 'S24']}, {'result': 'refused:P9', 'set_points': {}, 'held_signals': []}), ('control 70', {'route_points': {'P3': 'N', 'P1': 'R', 'P2': 'R'}, 'flank': {'P1N': [['P7', 'R', 'S20'], ['P8', 'N', None]], 'P1R': [['P7', 'N', 'S21']], 'P2N': [['P8', 'R', 'S22'], ['P9', 'R', 'S20']], 'P2R': [['P9', 'N', 'S23'], ['P7', 'N', None]], 'P3N': [['P9', 'R', None]], 'P3R': [['P8', 'N', 'S24']]}, 'point_locks': {'P8': 'N'}, 'holdable': ['S20', 'S21']}, {'result': 'refused:P9', 'set_points': {}, 'held_signals': []}), ('boundary: own conflicting demand without a signal', {'route_points': {'P1': 'N', 'P2': 'R'}, 'flank': {'P1N': [['P7', 'R', 'S20'], ['P8', 'N', None]], 'P1R': [['P7', 'N', 'S21']], 'P2N': [['P8', 'R', 'S22'], ['P9', 'R', 'S20']], 'P2R': [['P9', 'N', 'S23'], ['P7', 'N', None]], 'P3N': [['P9', 'R', None]], 'P3R': [['P8', 'N', 'S24']]}, 'point_locks': {}, 'holdable': ['S20', 'S21', 'S22', 'S23', 'S24']}, {'result': 'refused:P7', 'set_points': {}, 'held_signals': []}), ('control 51', {'route_points': {'P3': 'N', 'P2': 'R'}, 'flank': {'P1N': [['P7', 'R', 'S20'], ['P8', 'N', None]], 'P1R': [['P7', 'N', 'S21']], 'P2N': [['P8', 'R', 'S22'], ['P9', 'R', 'S20']], 'P2R': [['P9', 'N', 'S23'], ['P7', 'N', None]], 'P3N': [['P9', 'R', None]], 'P3R': [['P8', 'N', 'S24']]}, 'point_locks': {'P9': 'R'}, 'holdable': ['S20', 'S21', 'S22', 'S23', 'S24']}, {'result': 'protected', 'set_points': {'P7': 'N', 'P9': 'R'}, 'held_signals': ['S23']}), ('control 54', {'route_points': {'P3': 'N', 'P1': 'R'}, 'flank': {'P1N': [['P7', 'R', 'S20'], ['P8', 'N', None]], 'P1R': [['P7', 'N', 'S21']], 'P2N': [['P8', 'R', 'S22'], ['P9', 'R', 'S20']], 'P2R': [['P9', 'N', 'S23'], ['P7', 'N', None]], 'P3N': [['P9', 'R', None]], 'P3R': [['P8', 'N', 'S24']]}, 'point_locks': {}, 'holdable': ['S20', 'S21', 'S22']}, {'result': 'protected', 'set_points': {'P7': 'N', 'P9': 'R'}, 'held_signals': []}), ('control 57', {'route_points': {'P2': 'R'}, 'flank': {'P1N': [['P7', 'R', 'S20'], ['P8', 'N', None]], 'P1R': [['P7', 'N', 'S21']], 'P2N': [['P8', 'R', 'S22'], ['P9', 'R', 'S20']], 'P2R': [['P9', 'N', 'S23'], ['P7', 'N', None]], 'P3N': [['P9', 'R', None]], 'P3R': [['P8', 'N', 'S24']]}, 'point_locks': {}, 'holdable': ['S21', 'S22']}, {'result': 'protected', 'set_points': {'P9': 'N', 'P7': 'N'}, 'held_signals': []})]]
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 fixtureActualExpectedOutcome
regression: flank signal not holdable{'held_signals': ['S21'], 'result': 'protected', 'set_points': {}}{'held_signals': [], 'result': 'refused:P7', 'set_points': {}}Failed
boundary: no flank signal available{'held_signals': [], 'result': 'refused:P9', 'set_points': {}}{'held_signals': [], 'result': 'refused:P9', 'set_points': {}}Passed
sampled regression 11{'held_signals': ['S20', 'S23'], 'result': 'protected', 'set_points': {'P7': 'N', 'P8': 'N'}}{'held_signals': [], 'result': 'refused:P9', 'set_points': {}}Failed
boundary: own conflicting demand without a signal{'held_signals': [], 'result': 'refused:P7', 'set_points': {}}{'held_signals': [], 'result': 'refused:P7', 'set_points': {}}Passed
boundary: flank point locked in the protecting lie{'held_signals': [], 'result': 'protected', 'set_points': {'P7': 'R', 'P8': 'N'}}{'held_signals': [], 'result': 'protected', 'set_points': {'P7': 'R', 'P8': 'N'}}Passed
control 1{'held_signals': [], 'result': 'refused:P9', 'set_points': {}}{'held_signals': [], 'result': 'refused:P9', 'set_points': {}}Passed
control 4{'held_signals': [], 'result': 'protected', 'set_points': {'P7': 'N', 'P9': 'N'}}{'held_signals': [], 'result': 'protected', 'set_points': {'P7': 'N', 'P9': 'N'}}Passed
control 8{'held_signals': [], 'result': 'protected', 'set_points': {'P7': 'R', 'P8': 'N'}}{'held_signals': [], 'result': 'protected', 'set_points': {'P7': 'R', 'P8': 'N'}}Passed

SHA-256 / 3e9efad9c650b2f533ee134836bc9fcc9d855db041e48675655c9cb25f73e59c

2 / The unsuccessful fix

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

N = 1
observations = []
def solve(x):
    set_pts = {}
    held = []
    locks = x['point_locks']
    for p, pos in sorted(x['route_points'].items()):
        for fp, fpos, fsig in x['flank'].get(p + pos, []):
            lk = locks.get(fp, set_pts.get(fp))
            if lk is None or lk == fpos:
                set_pts[fp] = fpos
            elif x['holdable']:
                held.append(fsig)
            else:
                return {'result': 'refused:' + fp, 'set_points': {}, 'held_signals': []}
    return {'result': 'protected', 'set_points': set_pts, 'held_signals': sorted(set(held))}
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[('regression: flank signal not holdable', {'route_points': {'P1': 'R'}, 'flank': {'P1N': [['P7', 'R', 'S20'], ['P8', 'N', None]], 'P1R': [['P7', 'N', 'S21']], 'P2N': [['P8', 'R', 'S22'], ['P9', 'R', 'S20']], 'P2R': [['P9', 'N', 'S23'], ['P7', 'N', None]], 'P3N': [['P9', 'R', None]], 'P3R': [['P8', 'N', 'S24']]}, 'point_locks': {'P7': 'R'}, 'holdable': []}, {'result': 'refused:P7', 'set_points': {}, 'held_signals': []}), ('boundary: no flank signal available', {'route_points': {'P3': 'N'}, 'flank': {'P1N': [['P7', 'R', 'S20'], ['P8', 'N', None]], 'P1R': [['P7', 'N', 'S21']], 'P2N': [['P8', 'R', 'S22'], ['P9', 'R', 'S20']], 'P2R': [['P9', 'N', 'S23'], ['P7', 'N', None]], 'P3N': [['P9', 'R', None]], 'P3R': [['P8', 'N', 'S24']]}, 'point_locks': {'P9': 'N'}, 'holdable': ['S20', 'S21', 'S22', 'S23', 'S24']}, {'result': 'refused:P9', 'set_points': {}, 'held_signals': []}), ('sampled regression 11', {'route_points': {'P1': 'N', 'P2': 'R'}, 'flank': {'P1N': [['P7', 'R', 'S20'], ['P8', 'N', None]], 'P1R': [['P7', 'N', 'S21']], 'P2N': [['P8', 'R', 'S22'], ['P9', 'R', 'S20']], 'P2R': [['P9', 'N', 'S23'], ['P7', 'N', None]], 'P3N': [['P9', 'R', None]], 'P3R': [['P8', 'N', 'S24']]}, 'point_locks': {'P7': 'N', 'P9': 'R'}, 'holdable': ['S20', 'S21', 'S22', 'S24']}, {'result': 'refused:P9', 'set_points': {}, 'held_signals': []}), ('boundary: own conflicting demand without a signal', {'route_points': {'P1': 'N', 'P2': 'R'}, 'flank': {'P1N': [['P7', 'R', 'S20'], ['P8', 'N', None]], 'P1R': [['P7', 'N', 'S21']], 'P2N': [['P8', 'R', 'S22'], ['P9', 'R', 'S20']], 'P2R': [['P9', 'N', 'S23'], ['P7', 'N', None]], 'P3N': [['P9', 'R', None]], 'P3R': [['P8', 'N', 'S24']]}, 'point_locks': {}, 'holdable': ['S20', 'S21', 'S22', 'S23', 'S24']}, {'result': 'refused:P7', 'set_points': {}, 'held_signals': []}), ('boundary: flank point locked in the protecting lie', {'route_points': {'P1': 'N'}, 'flank': {'P1N': [['P7', 'R', 'S20'], ['P8', 'N', None]], 'P1R': [['P7', 'N', 'S21']], 'P2N': [['P8', 'R', 'S22'], ['P9', 'R', 'S20']], 'P2R': [['P9', 'N', 'S23'], ['P7', 'N', None]], 'P3N': [['P9', 'R', None]], 'P3R': [['P8', 'N', 'S24']]}, 'point_locks': {'P7': 'R'}, 'holdable': ['S20', 'S21', 'S22', 'S23', 'S24']}, {'result': 'protected', 'set_points': {'P7': 'R', 'P8': 'N'}, 'held_signals': []}), ('control 1', {'route_points': {'P3': 'N'}, 'flank': {'P1N': [['P7', 'R', 'S20'], ['P8', 'N', None]], 'P1R': [['P7', 'N', 'S21']], 'P2N': [['P8', 'R', 'S22'], ['P9', 'R', 'S20']], 'P2R': [['P9', 'N', 'S23'], ['P7', 'N', None]], 'P3N': [['P9', 'R', None]], 'P3R': [['P8', 'N', 'S24']]}, 'point_locks': {'P7': 'R', 'P9': 'N'}, 'holdable': ['S23', 'S24']}, {'result': 'refused:P9', 'set_points': {}, 'held_signals': []}), ('control 4', {'route_points': {'P2': 'R'}, 'flank': {'P1N': [['P7', 'R', 'S20'], ['P8', 'N', None]], 'P1R': [['P7', 'N', 'S21']], 'P2N': [['P8', 'R', 'S22'], ['P9', 'R', 'S20']], 'P2R': [['P9', 'N', 'S23'], ['P7', 'N', None]], 'P3N': [['P9', 'R', None]], 'P3R': [['P8', 'N', 'S24']]}, 'point_locks': {}, 'holdable': ['S21', 'S22']}, {'result': 'protected', 'set_points': {'P9': 'N', 'P7': 'N'}, 'held_signals': []}), ('control 8', {'route_points': {'P1': 'N'}, 'flank': {'P1N': [['P7', 'R', 'S20'], ['P8', 'N', None]], 'P1R': [['P7', 'N', 'S21']], 'P2N': [['P8', 'R', 'S22'], ['P9', 'R', 'S20']], 'P2R': [['P9', 'N', 'S23'], ['P7', 'N', None]], 'P3N': [['P9', 'R', None]], 'P3R': [['P8', 'N', 'S24']]}, 'point_locks': {'P7': 'R'}, 'holdable': ['S21', 'S24']}, {'result': 'protected', 'set_points': {'P7': 'R', 'P8': 'N'}, 'held_signals': []})], [('regression: flank signal not holdable', {'route_points': {'P1': 'R'}, 'flank': {'P1N': [['P7', 'R', 'S20'], ['P8', 'N', None]], 'P1R': [['P7', 'N', 'S21']], 'P2N': [['P8', 'R', 'S22'], ['P9', 'R', 'S20']], 'P2R': [['P9', 'N', 'S23'], ['P7', 'N', None]], 'P3N': [['P9', 'R', None]], 'P3R': [['P8', 'N', 'S24']]}, 'point_locks': {'P7': 'R'}, 'holdable': []}, {'result': 'refused:P7', 'set_points': {}, 'held_signals': []}), ('boundary: own conflicting demand without a signal', {'route_points': {'P1': 'N', 'P2': 'R'}, 'flank': {'P1N': [['P7', 'R', 'S20'], ['P8', 'N', None]], 'P1R': [['P7', 'N', 'S21']], 'P2N': [['P8', 'R', 'S22'], ['P9', 'R', 'S20']], 'P2R': [['P9', 'N', 'S23'], ['P7', 'N', None]], 'P3N': [['P9', 'R', None]], 'P3R': [['P8', 'N', 'S24']]}, 'point_locks': {}, 'holdable': ['S20', 'S21', 'S22', 'S23', 'S24']}, {'result': 'refused:P7', 'set_points': {}, 'held_signals': []}), ('sampled regression 50', {'route_points': {'P2': 'R'}, 'flank': {'P1N': [['P7', 'R', 'S20'], ['P8', 'N', None]], 'P1R': [['P7', 'N', 'S21']], 'P2N': [['P8', 'R', 'S22'], ['P9', 'R', 'S20']], 'P2R': [['P9', 'N', 'S23'], ['P7', 'N', None]], 'P3N': [['P9', 'R', None]], 'P3R': [['P8', 'N', 'S24']]}, 'point_locks': {'P9': 'R'}, 'holdable': ['S22', 'S24']}, {'result': 'refused:P9', 'set_points': {}, 'held_signals': []}), ('sampled regression 14', {'route_points': {'P2': 'N', 'P3': 'N', 'P1': 'R'}, 'flank': {'P1N': [['P7', 'R', 'S20'], ['P8', 'N', None]], 'P1R': [['P7', 'N', 'S21']], 'P2N': [['P8', 'R', 'S22'], ['P9', 'R', 'S20']], 'P2R': [['P9', 'N', 'S23'], ['P7', 'N', None]], 'P3N': [['P9', 'R', None]], 'P3R': [['P8', 'N', 'S24']]}, 'point_locks': {'P7': 'R', 'P8': 'N'}, 'holdable': ['S20', 'S23', 'S24']}, {'result': 'refused:P7', 'set_points': {}, 'held_signals': []}), ('boundary: two route points disagree on a flank point', {'route_points': {'P1': 'R', 'P2': 'R'}, 'flank': {'P1N': [['P7', 'R', 'S20'], ['P8', 'N', None]], 'P1R': [['P7', 'N', 'S21']], 'P2N': [['P8', 'R', 'S22'], ['P9', 'R', 'S20']], 'P2R': [['P9', 'N', 'S23'], ['P7', 'N', None]], 'P3N': [['P9', 'R', None]], 'P3R': [['P8', 'N', 'S24']]}, 'point_locks': {}, 'holdable': ['S20', 'S21', 'S22', 'S23', 'S24']}, {'result': 'protected', 'set_points': {'P7': 'N', 'P9': 'N'}, 'held_signals': []}), ('control 17', {'route_points': {'P3': 'N', 'P2': 'N'}, 'flank': {'P1N': [['P7', 'R', 'S20'], ['P8', 'N', None]], 'P1R': [['P7', 'N', 'S21']], 'P2N': [['P8', 'R', 'S22'], ['P9', 'R', 'S20']], 'P2R': [['P9', 'N', 'S23'], ['P7', 'N', None]], 'P3N': [['P9', 'R', None]], 'P3R': [['P8', 'N', 'S24']]}, 'point_locks': {}, 'holdable': ['S20', 'S21', 'S23', 'S24']}, {'result': 'protected', 'set_points': {'P8': 'R', 'P9': 'R'}, 'held_signals': []}), ('sampled regression 20', {'route_points': {'P1': 'R', 'P2': 'N', 'P3': 'R'}, 'flank': {'P1N': [['P7', 'R', 'S20'], ['P8', 'N', None]], 'P1R': [['P7', 'N', 'S21']], 'P2N': [['P8', 'R', 'S22'], ['P9', 'R', 'S20']], 'P2R': [['P9', 'N', 'S23'], ['P7', 'N', None]], 'P3N': [['P9', 'R', None]], 'P3R': [['P8', 'N', 'S24']]}, 'point_locks': {}, 'holdable': []}, {'result': 'refused:P8', 'set_points': {}, 'held_signals': []}), ('control 23', {'route_points': {'P1': 'R', 'P2': 'N', 'P3': 'R'}, 'flank': {'P1N': [['P7', 'R', 'S20'], ['P8', 'N', None]], 'P1R': [['P7', 'N', 'S21']], 'P2N': [['P8', 'R', 'S22'], ['P9', 'R', 'S20']], 'P2R': [['P9', 'N', 'S23'], ['P7', 'N', None]], 'P3N': [['P9', 'R', None]], 'P3R': [['P8', 'N', 'S24']]}, 'point_locks': {}, 'holdable': ['S20', 'S21', 'S22', 'S24']}, {'result': 'protected', 'set_points': {'P7': 'N', 'P8': 'R', 'P9': 'R'}, 'held_signals': ['S24']})], [('regression: flank signal not holdable', {'route_points': {'P1': 'R'}, 'flank': {'P1N': [['P7', 'R', 'S20'], ['P8', 'N', None]], 'P1R': [['P7', 'N', 'S21']], 'P2N': [['P8', 'R', 'S22'], ['P9', 'R', 'S20']], 'P2R': [['P9', 'N', 'S23'], ['P7', 'N', None]], 'P3N': [['P9', 'R', None]], 'P3R': [['P8', 'N', 'S24']]}, 'point_locks': {'P7': 'R'}, 'holdable': []}, {'result': 'refused:P7', 'set_points': {}, 'held_signals': []}), ('boundary: no flank signal available', {'route_points': {'P3': 'N'}, 'flank': {'P1N': [['P7', 'R', 'S20'], ['P8', 'N', None]], 'P1R': [['P7', 'N', 'S21']], 'P2N': [['P8', 'R', 'S22'], ['P9', 'R', 'S20']], 'P2R': [['P9', 'N', 'S23'], ['P7', 'N', None]], 'P3N': [['P9', 'R', None]], 'P3R': [['P8', 'N', 'S24']]}, 'point_locks': {'P9': 'N'}, 'holdable': ['S20', 'S21', 'S22', 'S23', 'S24']}, {'result': 'refused:P9', 'set_points': {}, 'held_signals': []}), ('sampled regression 11', {'route_points': {'P1': 'N', 'P2': 'R'}, 'flank': {'P1N': [['P7', 'R', 'S20'], ['P8', 'N', None]], 'P1R': [['P7', 'N', 'S21']], 'P2N': [['P8', 'R', 'S22'], ['P9', 'R', 'S20']], 'P2R': [['P9', 'N', 'S23'], ['P7', 'N', None]], 'P3N': [['P9', 'R', None]], 'P3R': [['P8', 'N', 'S24']]}, 'point_locks': {'P7': 'N', 'P9': 'R'}, 'holdable': ['S20', 'S21', 'S22', 'S24']}, {'result': 'refused:P9', 'set_points': {}, 'held_signals': []}), ('control 36', {'route_points': {'P3': 'R', 'P2': 'R', 'P1': 'N'}, 'flank': {'P1N': [['P7', 'R', 'S20'], ['P8', 'N', None]], 'P1R': [['P7', 'N', 'S21']], 'P2N': [['P8', 'R', 'S22'], ['P9', 'R', 'S20']], 'P2R': [['P9', 'N', 'S23'], ['P7', 'N', None]], 'P3N': [['P9', 'R', None]], 'P3R': [['P8', 'N', 'S24']]}, 'point_locks': {'P8': 'N'}, 'holdable': ['S20', 'S21', 'S22', 'S24']}, {'result': 'refused:P7', 'set_points': {}, 'held_signals': []}), ('boundary: reverse lie flank entry', {'route_points': {'P2': 'R'}, 'flank': {'P1N': [['P7', 'R', 'S20'], ['P8', 'N', None]], 'P1R': [['P7', 'N', 'S21']], 'P2N': [['P8', 'R', 'S22'], ['P9', 'R', 'S20']], 'P2R': [['P9', 'N', 'S23'], ['P7', 'N', None]], 'P3N': [['P9', 'R', None]], 'P3R': [['P8', 'N', 'S24']]}, 'point_locks': {'P9': 'R'}, 'holdable': ['S20', 'S21', 'S22', 'S23', 'S24']}, {'result': 'protected', 'set_points': {'P7': 'N'}, 'held_signals': ['S23']}), ('control 26', {'route_points': {'P3': 'N'}, 'flank': {'P1N': [['P7', 'R', 'S20'], ['P8', 'N', None]], 'P1R': [['P7', 'N', 'S21']], 'P2N': [['P8', 'R', 'S22'], ['P9', 'R', 'S20']], 'P2R': [['P9', 'N', 'S23'], ['P7', 'N', None]], 'P3N': [['P9', 'R', None]], 'P3R': [['P8', 'N', 'S24']]}, 'point_locks': {'P7': 'R', 'P8': 'N'}, 'holdable': ['S20', 'S21', 'S22', 'S23', 'S24']}, {'result': 'protected', 'set_points': {'P9': 'R'}, 'held_signals': []}), ('control 29', {'route_points': {'P1': 'R', 'P2': 'R'}, 'flank': {'P1N': [['P7', 'R', 'S20'], ['P8', 'N', None]], 'P1R': [['P7', 'N', 'S21']], 'P2N': [['P8', 'R', 'S22'], ['P9', 'R', 'S20']], 'P2R': [['P9', 'N', 'S23'], ['P7', 'N', None]], 'P3N': [['P9', 'R', None]], 'P3R': [['P8', 'N', 'S24']]}, 'point_locks': {'P9': 'R'}, 'holdable': ['S20', 'S23']}, {'result': 'protected', 'set_points': {'P7': 'N'}, 'held_signals': ['S23']}), ('control 32', {'route_points': {'P1': 'N'}, 'flank': {'P1N': [['P7', 'R', 'S20'], ['P8', 'N', None]], 'P1R': [['P7', 'N', 'S21']], 'P2N': [['P8', 'R', 'S22'], ['P9', 'R', 'S20']], 'P2R': [['P9', 'N', 'S23'], ['P7', 'N', None]], 'P3N': [['P9', 'R', None]], 'P3R': [['P8', 'N', 'S24']]}, 'point_locks': {'P8': 'R'}, 'holdable': ['S23']}, {'result': 'refused:P8', 'set_points': {}, 'held_signals': []})], [('regression: flank signal not holdable', {'route_points': {'P1': 'R'}, 'flank': {'P1N': [['P7', 'R', 'S20'], ['P8', 'N', None]], 'P1R': [['P7', 'N', 'S21']], 'P2N': [['P8', 'R', 'S22'], ['P9', 'R', 'S20']], 'P2R': [['P9', 'N', 'S23'], ['P7', 'N', None]], 'P3N': [['P9', 'R', None]], 'P3R': [['P8', 'N', 'S24']]}, 'point_locks': {'P7': 'R'}, 'holdable': []}, {'result': 'refused:P7', 'set_points': {}, 'held_signals': []}), ('boundary: own conflicting demand without a signal', {'route_points': {'P1': 'N', 'P2': 'R'}, 'flank': {'P1N': [['P7', 'R', 'S20'], ['P8', 'N', None]], 'P1R': [['P7', 'N', 'S21']], 'P2N': [['P8', 'R', 'S22'], ['P9', 'R', 'S20']], 'P2R': [['P9', 'N', 'S23'], ['P7', 'N', None]], 'P3N': [['P9', 'R', None]], 'P3R': [['P8', 'N', 'S24']]}, 'point_locks': {}, 'holdable': ['S20', 'S21', 'S22', 'S23', 'S24']}, {'result': 'refused:P7', 'set_points': {}, 'held_signals': []}), ('sampled regression 50', {'route_points': {'P2': 'R'}, 'flank': {'P1N': [['P7', 'R', 'S20'], ['P8', 'N', None]], 'P1R': [['P7', 'N', 'S21']], 'P2N': [['P8', 'R', 'S22'], ['P9', 'R', 'S20']], 'P2R': [['P9', 'N', 'S23'], ['P7', 'N', None]], 'P3N': [['P9', 'R', None]], 'P3R': [['P8', 'N', 'S24']]}, 'point_locks': {'P9': 'R'}, 'holdable': ['S22', 'S24']}, {'result': 'refused:P9', 'set_points': {}, 'held_signals': []}), ('sampled regression 53', {'route_points': {'P2': 'N', 'P3': 'R'}, 'flank': {'P1N': [['P7', 'R', 'S20'], ['P8', 'N', None]], 'P1R': [['P7', 'N', 'S21']], 'P2N': [['P8', 'R', 'S22'], ['P9', 'R', 'S20']], 'P2R': [['P9', 'N', 'S23'], ['P7', 'N', None]], 'P3N': [['P9', 'R', None]], 'P3R': [['P8', 'N', 'S24']]}, 'point_locks': {'P9': 'N'}, 'holdable': ['S20', 'S21', 'S22', 'S23']}, {'result': 'refused:P8', 'set_points': {}, 'held_signals': []}), ('boundary: same signal held twice', {'route_points': {'P1': 'N', 'P2': 'N'}, 'flank': {'P1N': [['P7', 'R', 'S20'], ['P8', 'N', None]], 'P1R': [['P7', 'N', 'S21']], 'P2N': [['P8', 'R', 'S22'], ['P9', 'R', 'S20']], 'P2R': [['P9', 'N', 'S23'], ['P7', 'N', None]], 'P3N': [['P9', 'R', None]], 'P3R': [['P8', 'N', 'S24']]}, 'point_locks': {'P7': 'N', 'P8': 'N', 'P9': 'N'}, 'holdable': ['S20', 'S22']}, {'result': 'protected', 'set_points': {'P8': 'N'}, 'held_signals': ['S20', 'S22']}), ('control 37', {'route_points': {'P2': 'N', 'P1': 'R', 'P3': 'N'}, 'flank': {'P1N': [['P7', 'R', 'S20'], ['P8', 'N', None]], 'P1R': [['P7', 'N', 'S21']], 'P2N': [['P8', 'R', 'S22'], ['P9', 'R', 'S20']], 'P2R': [['P9', 'N', 'S23'], ['P7', 'N', None]], 'P3N': [['P9', 'R', None]], 'P3R': [['P8', 'N', 'S24']]}, 'point_locks': {'P8': 'R'}, 'holdable': ['S21', 'S24']}, {'result': 'protected', 'set_points': {'P7': 'N', 'P8': 'R', 'P9': 'R'}, 'held_signals': []}), ('control 41', {'route_points': {'P2': 'R', 'P1': 'R', 'P3': 'N'}, 'flank': {'P1N': [['P7', 'R', 'S20'], ['P8', 'N', None]], 'P1R': [['P7', 'N', 'S21']], 'P2N': [['P8', 'R', 'S22'], ['P9', 'R', 'S20']], 'P2R': [['P9', 'N', 'S23'], ['P7', 'N', None]], 'P3N': [['P9', 'R', None]], 'P3R': [['P8', 'N', 'S24']]}, 'point_locks': {}, 'holdable': ['S20', 'S21', 'S22']}, {'result': 'refused:P9', 'set_points': {}, 'held_signals': []}), ('control 46', {'route_points': {'P2': 'N'}, 'flank': {'P1N': [['P7', 'R', 'S20'], ['P8', 'N', None]], 'P1R': [['P7', 'N', 'S21']], 'P2N': [['P8', 'R', 'S22'], ['P9', 'R', 'S20']], 'P2R': [['P9', 'N', 'S23'], ['P7', 'N', None]], 'P3N': [['P9', 'R', None]], 'P3R': [['P8', 'N', 'S24']]}, 'point_locks': {'P7': 'N'}, 'holdable': ['S20', 'S21']}, {'result': 'protected', 'set_points': {'P8': 'R', 'P9': 'R'}, 'held_signals': []})], [('regression: flank signal not holdable', {'route_points': {'P1': 'R'}, 'flank': {'P1N': [['P7', 'R', 'S20'], ['P8', 'N', None]], 'P1R': [['P7', 'N', 'S21']], 'P2N': [['P8', 'R', 'S22'], ['P9', 'R', 'S20']], 'P2R': [['P9', 'N', 'S23'], ['P7', 'N', None]], 'P3N': [['P9', 'R', None]], 'P3R': [['P8', 'N', 'S24']]}, 'point_locks': {'P7': 'R'}, 'holdable': []}, {'result': 'refused:P7', 'set_points': {}, 'held_signals': []}), ('boundary: no flank signal available', {'route_points': {'P3': 'N'}, 'flank': {'P1N': [['P7', 'R', 'S20'], ['P8', 'N', None]], 'P1R': [['P7', 'N', 'S21']], 'P2N': [['P8', 'R', 'S22'], ['P9', 'R', 'S20']], 'P2R': [['P9', 'N', 'S23'], ['P7', 'N', None]], 'P3N': [['P9', 'R', None]], 'P3R': [['P8', 'N', 'S24']]}, 'point_locks': {'P9': 'N'}, 'holdable': ['S20', 'S21', 'S22', 'S23', 'S24']}, {'result': 'refused:P9', 'set_points': {}, 'held_signals': []}), ('sampled regression 11', {'route_points': {'P1': 'N', 'P2': 'R'}, 'flank': {'P1N': [['P7', 'R', 'S20'], ['P8', 'N', None]], 'P1R': [['P7', 'N', 'S21']], 'P2N': [['P8', 'R', 'S22'], ['P9', 'R', 'S20']], 'P2R': [['P9', 'N', 'S23'], ['P7', 'N', None]], 'P3N': [['P9', 'R', None]], 'P3R': [['P8', 'N', 'S24']]}, 'point_locks': {'P7': 'N', 'P9': 'R'}, 'holdable': ['S20', 'S21', 'S22', 'S24']}, {'result': 'refused:P9', 'set_points': {}, 'held_signals': []}), ('control 70', {'route_points': {'P3': 'N', 'P1': 'R', 'P2': 'R'}, 'flank': {'P1N': [['P7', 'R', 'S20'], ['P8', 'N', None]], 'P1R': [['P7', 'N', 'S21']], 'P2N': [['P8', 'R', 'S22'], ['P9', 'R', 'S20']], 'P2R': [['P9', 'N', 'S23'], ['P7', 'N', None]], 'P3N': [['P9', 'R', None]], 'P3R': [['P8', 'N', 'S24']]}, 'point_locks': {'P8': 'N'}, 'holdable': ['S20', 'S21']}, {'result': 'refused:P9', 'set_points': {}, 'held_signals': []}), ('boundary: own conflicting demand without a signal', {'route_points': {'P1': 'N', 'P2': 'R'}, 'flank': {'P1N': [['P7', 'R', 'S20'], ['P8', 'N', None]], 'P1R': [['P7', 'N', 'S21']], 'P2N': [['P8', 'R', 'S22'], ['P9', 'R', 'S20']], 'P2R': [['P9', 'N', 'S23'], ['P7', 'N', None]], 'P3N': [['P9', 'R', None]], 'P3R': [['P8', 'N', 'S24']]}, 'point_locks': {}, 'holdable': ['S20', 'S21', 'S22', 'S23', 'S24']}, {'result': 'refused:P7', 'set_points': {}, 'held_signals': []}), ('control 51', {'route_points': {'P3': 'N', 'P2': 'R'}, 'flank': {'P1N': [['P7', 'R', 'S20'], ['P8', 'N', None]], 'P1R': [['P7', 'N', 'S21']], 'P2N': [['P8', 'R', 'S22'], ['P9', 'R', 'S20']], 'P2R': [['P9', 'N', 'S23'], ['P7', 'N', None]], 'P3N': [['P9', 'R', None]], 'P3R': [['P8', 'N', 'S24']]}, 'point_locks': {'P9': 'R'}, 'holdable': ['S20', 'S21', 'S22', 'S23', 'S24']}, {'result': 'protected', 'set_points': {'P7': 'N', 'P9': 'R'}, 'held_signals': ['S23']}), ('control 54', {'route_points': {'P3': 'N', 'P1': 'R'}, 'flank': {'P1N': [['P7', 'R', 'S20'], ['P8', 'N', None]], 'P1R': [['P7', 'N', 'S21']], 'P2N': [['P8', 'R', 'S22'], ['P9', 'R', 'S20']], 'P2R': [['P9', 'N', 'S23'], ['P7', 'N', None]], 'P3N': [['P9', 'R', None]], 'P3R': [['P8', 'N', 'S24']]}, 'point_locks': {}, 'holdable': ['S20', 'S21', 'S22']}, {'result': 'protected', 'set_points': {'P7': 'N', 'P9': 'R'}, 'held_signals': []}), ('control 57', {'route_points': {'P2': 'R'}, 'flank': {'P1N': [['P7', 'R', 'S20'], ['P8', 'N', None]], 'P1R': [['P7', 'N', 'S21']], 'P2N': [['P8', 'R', 'S22'], ['P9', 'R', 'S20']], 'P2R': [['P9', 'N', 'S23'], ['P7', 'N', None]], 'P3N': [['P9', 'R', None]], 'P3R': [['P8', 'N', 'S24']]}, 'point_locks': {}, 'holdable': ['S21', 'S22']}, {'result': 'protected', 'set_points': {'P9': 'N', 'P7': 'N'}, 'held_signals': []})]]
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 fixtureActualExpectedOutcome
regression: flank signal not holdable{'held_signals': [], 'result': 'refused:P7', 'set_points': {}}{'held_signals': [], 'result': 'refused:P7', 'set_points': {}}Passed
boundary: no flank signal available{'held_signals': [None], 'result': 'protected', 'set_points': {}}{'held_signals': [], 'result': 'refused:P9', 'set_points': {}}Failed
sampled regression 11{'held_signals': ['S20', 'S23'], 'result': 'protected', 'set_points': {'P7': 'N', 'P8': 'N'}}{'held_signals': [], 'result': 'refused:P9', 'set_points': {}}Failed
boundary: own conflicting demand without a signal{'held_signals': [None], 'result': 'protected', 'set_points': {'P7': 'R', 'P8': 'N', 'P9': 'N'}}{'held_signals': [], 'result': 'refused:P7', 'set_points': {}}Failed
boundary: flank point locked in the protecting lie{'held_signals': [], 'result': 'protected', 'set_points': {'P7': 'R', 'P8': 'N'}}{'held_signals': [], 'result': 'protected', 'set_points': {'P7': 'R', 'P8': 'N'}}Passed
control 1{'held_signals': [None], 'result': 'protected', 'set_points': {}}{'held_signals': [], 'result': 'refused:P9', 'set_points': {}}Failed
control 4{'held_signals': [], 'result': 'protected', 'set_points': {'P7': 'N', 'P9': 'N'}}{'held_signals': [], 'result': 'protected', 'set_points': {'P7': 'N', 'P9': 'N'}}Passed
control 8{'held_signals': [], 'result': 'protected', 'set_points': {'P7': 'R', 'P8': 'N'}}{'held_signals': [], 'result': 'protected', 'set_points': {'P7': 'R', 'P8': 'N'}}Passed

SHA-256 / 25ebf212c11f01e5e70c32e6fb860f6291ed1e7304c613d06c92cb90b2edcc3f

HELD IN THE MEMBER ARCHIVE

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

This mechanism has 8 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

Stipulated toy interlocking contract for a bounded teaching model; it makes no claim of conformance to any railway signalling standard 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 2026-09-29T14:47:51.350702+00:00.

Case digest / 53f899c3dcdc7fb4c392d49e763b7ac7a5f99412de97d7b7aba5f07111e8d407