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FA-67306 / Railway interlocking logic / Open access

Automatic route setting arbitration: conflict symmetry · case 01

Two conflicting routes are both granted when the conflict is listed in the other order.

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

ROOT CAUSE

Conflict pairs are only stored in their listed orientation.

THE FAILURE

Conflict pairs are only stored in their listed orientation.

Unsuccessful approach: Mirroring only pairs listed in sorted order still misses reverse-listed pairs.

Case contract

Trains whose eta is at most lookahead_s after now are candidates, including overdue trains (eta before now). Candidates are ordered by class (1 highest), then scheduled time, then id. Routes are granted greedily in that order; a candidate is skipped if its route equals or conflicts with (conflict pairs are unordered) any route already granted. Return granted train ids in grant order.

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):
    now = x['now']
    cand = [t for t in x['trains'] if t['eta'] - now <= x['lookahead_s']]
    cand.sort(key=lambda t: (t['cls'], t['sched'], t['id']))
    pairs = set()
    for a, b in x['conflicts']:
        pairs.add((a, b))
    granted = []
    routes = []
    for t in cand:
        if any(t['route'] == r or (t['route'], r) in pairs for r in routes):
            continue
        granted.append(t['id'])
        routes.append(t['route'])
    return granted
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[('regression: reverse-listed conflict granted in reverse', {'now': 100, 'lookahead_s': 60, 'conflicts': [['R3', 'R2']], 'trains': [{'id': '1A01', 'cls': 1, 'sched': 100, 'eta': 110, 'route': 'R3'}, {'id': '1A02', 'cls': 1, 'sched': 120, 'eta': 120, 'route': 'R2'}]}, ['1A01']), ('sampled regression 4', {'now': 100, 'lookahead_s': 120, 'trains': [{'id': '2A00', 'cls': 2, 'sched': 200, 'eta': 220, 'route': 'R3'}, {'id': '8A01', 'cls': 1, 'sched': 100, 'eta': 80, 'route': 'R5'}, {'id': '7A02', 'cls': 3, 'sched': 100, 'eta': 80, 'route': 'R2'}], 'conflicts': [['R1', 'R5'], ['R1', 'R2'], ['R3', 'R2'], ['R4', 'R5']]}, ['8A01', '2A00']), ('boundary: eta exactly at the lookahead', {'now': 100, 'lookahead_s': 60, 'conflicts': [], 'trains': [{'id': '1A01', 'cls': 1, 'sched': 100, 'eta': 160, 'route': 'R1'}]}, ['1A01']), ('boundary: overdue train', {'now': 100, 'lookahead_s': 60, 'conflicts': [], 'trains': [{'id': '2A01', 'cls': 2, 'sched': 60, 'eta': 70, 'route': 'R2'}]}, ['2A01']), ('boundary: class beats schedule', {'now': 100, 'lookahead_s': 60, 'conflicts': [['R1', 'R2']], 'trains': [{'id': '2A01', 'cls': 2, 'sched': 100, 'eta': 110, 'route': 'R1'}, {'id': '1A02', 'cls': 1, 'sched': 150, 'eta': 150, 'route': 'R2'}]}, ['1A02']), ('control 1', {'now': 100, 'lookahead_s': 60, 'trains': [{'id': '6A00', 'cls': 1, 'sched': 120, 'eta': 400, 'route': 'R1'}, {'id': '7A01', 'cls': 1, 'sched': 120, 'eta': 220, 'route': 'R2'}], 'conflicts': [['R4', 'R3'], ['R2', 'R3'], ['R4', 'R5'], ['R2', 'R1']]}, []), ('control 7', {'now': 100, 'lookahead_s': 80, 'trains': [{'id': '2A00', 'cls': 1, 'sched': 150, 'eta': 220, 'route': 'R5'}, {'id': '9A01', 'cls': 3, 'sched': 100, 'eta': 160, 'route': 'R1'}], 'conflicts': [['R3', 'R2']]}, ['9A01']), ('control 10', {'now': 100, 'lookahead_s': 120, 'trains': [{'id': '1A00', 'cls': 1, 'sched': 200, 'eta': 220, 'route': 'R1'}, {'id': '6A01', 'cls': 3, 'sched': 150, 'eta': 160, 'route': 'R5'}, {'id': '7A02', 'cls': 1, 'sched': 120, 'eta': 400, 'route': 'R2'}, {'id': '4A03', 'cls': 3, 'sched': 100, 'eta': 220, 'route': 'R4'}, {'id': '1A04', 'cls': 1, 'sched': 150, 'eta': 220, 'route': 'R4'}, {'id': '8A05', 'cls': 3, 'sched': 150, 'eta': 400, 'route': 'R4'}], 'conflicts': [['R2', 'R1'], ['R3', 'R4'], ['R5', 'R4']]}, ['1A04', '1A00'])], [('regression: conflict with an earlier grant', {'now': 100, 'lookahead_s': 60, 'conflicts': [['R1', 'R5']], 'trains': [{'id': '1A01', 'cls': 1, 'sched': 100, 'eta': 110, 'route': 'R1'}, {'id': '1A02', 'cls': 1, 'sched': 110, 'eta': 120, 'route': 'R4'}, {'id': '1A03', 'cls': 1, 'sched': 130, 'eta': 130, 'route': 'R5'}]}, ['1A01', '1A02']), ('regression: reverse-listed conflict granted in reverse', {'now': 100, 'lookahead_s': 60, 'conflicts': [['R3', 'R2']], 'trains': [{'id': '1A01', 'cls': 1, 'sched': 100, 'eta': 110, 'route': 'R3'}, {'id': '1A02', 'cls': 1, 'sched': 120, 'eta': 120, 'route': 'R2'}]}, ['1A01']), ('sampled regression 40', {'now': 100, 'lookahead_s': 60, 'trains': [{'id': '2A00', 'cls': 2, 'sched': 120, 'eta': 180, 'route': 'R4'}, {'id': '2A01', 'cls': 1, 'sched': 100, 'eta': 400, 'route': 'R4'}, {'id': '8A02', 'cls': 1, 'sched': 150, 'eta': 100, 'route': 'R3'}, {'id': '1A03', 'cls': 2, 'sched': 200, 'eta': 100, 'route': 'R3'}, {'id': '8A04', 'cls': 2, 'sched': 100, 'eta': 130, 'route': 'R4'}, {'id': '3A05', 'cls': 3, 'sched': 120, 'eta': 130, 'route': 'R5'}], 'conflicts': [['R1', 'R5'], ['R2', 'R3'], ['R1', 'R2'], ['R3', 'R4']]}, ['8A02', '3A05']), ('sampled regression 63', {'now': 100, 'lookahead_s': 120, 'trains': [{'id': '7A00', 'cls': 3, 'sched': 100, 'eta': 80, 'route': 'R3'}, {'id': '3A01', 'cls': 2, 'sched': 200, 'eta': 130, 'route': 'R4'}, {'id': '6A02', 'cls': 1, 'sched': 120, 'eta': 130, 'route': 'R5'}, {'id': '3A03', 'cls': 2, 'sched': 120, 'eta': 400, 'route': 'R1'}, {'id': '2A04', 'cls': 2, 'sched': 100, 'eta': 130, 'route': 'R1'}, {'id': '2A05', 'cls': 2, 'sched': 150, 'eta': 220, 'route': 'R2'}], 'conflicts': [['R1', 'R2'], ['R5', 'R1'], ['R2', 'R3'], ['R4', 'R3']]}, ['6A02', '2A05', '3A01']), ('boundary: class beats schedule', {'now': 100, 'lookahead_s': 60, 'conflicts': [['R1', 'R2']], 'trains': [{'id': '2A01', 'cls': 2, 'sched': 100, 'eta': 110, 'route': 'R1'}, {'id': '1A02', 'cls': 1, 'sched': 150, 'eta': 150, 'route': 'R2'}]}, ['1A02']), ('control 12', {'now': 100, 'lookahead_s': 120, 'trains': [{'id': '8A00', 'cls': 1, 'sched': 100, 'eta': 180, 'route': 'R3'}, {'id': '8A01', 'cls': 2, 'sched': 100, 'eta': 220, 'route': 'R2'}], 'conflicts': [['R3', 'R4']]}, ['8A00', '8A01']), ('control 15', {'now': 100, 'lookahead_s': 60, 'trains': [{'id': '2A00', 'cls': 2, 'sched': 200, 'eta': 180, 'route': 'R5'}, {'id': '6A01', 'cls': 3, 'sched': 150, 'eta': 80, 'route': 'R2'}, {'id': '7A02', 'cls': 3, 'sched': 100, 'eta': 130, 'route': 'R5'}, {'id': '5A03', 'cls': 3, 'sched': 120, 'eta': 160, 'route': 'R1'}], 'conflicts': [['R2', 'R1'], ['R4', 'R5'], ['R1', 'R5']]}, ['7A02', '6A01']), ('sampled regression 18', {'now': 100, 'lookahead_s': 120, 'trains': [{'id': '9A00', 'cls': 1, 'sched': 150, 'eta': 220, 'route': 'R4'}, {'id': '8A01', 'cls': 2, 'sched': 100, 'eta': 80, 'route': 'R3'}], 'conflicts': [['R5', 'R4'], ['R1', 'R2'], ['R4', 'R3']]}, ['9A00'])], [('regression: late running train keeps schedule order', {'now': 100, 'lookahead_s': 60, 'conflicts': [['R1', 'R2']], 'trains': [{'id': '1A01', 'cls': 1, 'sched': 100, 'eta': 150, 'route': 'R1'}, {'id': '1A02', 'cls': 1, 'sched': 120, 'eta': 105, 'route': 'R2'}]}, ['1A01']), ('regression: reverse-listed conflict granted in reverse', {'now': 100, 'lookahead_s': 60, 'conflicts': [['R3', 'R2']], 'trains': [{'id': '1A01', 'cls': 1, 'sched': 100, 'eta': 110, 'route': 'R3'}, {'id': '1A02', 'cls': 1, 'sched': 120, 'eta': 120, 'route': 'R2'}]}, ['1A01']), ('sampled regression 14', {'now': 100, 'lookahead_s': 60, 'trains': [{'id': '3A00', 'cls': 2, 'sched': 200, 'eta': 180, 'route': 'R2'}, {'id': '5A01', 'cls': 3, 'sched': 100, 'eta': 100, 'route': 'R4'}, {'id': '1A02', 'cls': 2, 'sched': 150, 'eta': 180, 'route': 'R3'}, {'id': '6A03', 'cls': 3, 'sched': 200, 'eta': 400, 'route': 'R1'}, {'id': '3A04', 'cls': 2, 'sched': 200, 'eta': 130, 'route': 'R5'}], 'conflicts': [['R1', 'R2'], ['R2', 'R3'], ['R5', 'R4']]}, ['3A04']), ('boundary: two trains for one route', {'now': 100, 'lookahead_s': 60, 'conflicts': [], 'trains': [{'id': '1A01', 'cls': 1, 'sched': 100, 'eta': 110, 'route': 'R3'}, {'id': '1A02', 'cls': 1, 'sched': 120, 'eta': 120, 'route': 'R3'}]}, ['1A01']), ('regression: conflict with an earlier grant', {'now': 100, 'lookahead_s': 60, 'conflicts': [['R1', 'R5']], 'trains': [{'id': '1A01', 'cls': 1, 'sched': 100, 'eta': 110, 'route': 'R1'}, {'id': '1A02', 'cls': 1, 'sched': 110, 'eta': 120, 'route': 'R4'}, {'id': '1A03', 'cls': 1, 'sched': 130, 'eta': 130, 'route': 'R5'}]}, ['1A01', '1A02']), ('control 23', {'now': 100, 'lookahead_s': 80, 'trains': [{'id': '9A00', 'cls': 1, 'sched': 200, 'eta': 180, 'route': 'R4'}, {'id': '1A01', 'cls': 2, 'sched': 200, 'eta': 220, 'route': 'R2'}, {'id': '5A02', 'cls': 2, 'sched': 120, 'eta': 160, 'route': 'R5'}, {'id': '2A03', 'cls': 2, 'sched': 150, 'eta': 80, 'route': 'R2'}], 'conflicts': [['R1', 'R5'], ['R2', 'R1']]}, ['9A00', '5A02', '2A03']), ('control 26', {'now': 100, 'lookahead_s': 80, 'trains': [{'id': '9A00', 'cls': 1, 'sched': 120, 'eta': 160, 'route': 'R2'}, {'id': '7A01', 'cls': 2, 'sched': 100, 'eta': 220, 'route': 'R4'}, {'id': '2A02', 'cls': 1, 'sched': 150, 'eta': 180, 'route': 'R2'}, {'id': '1A03', 'cls': 3, 'sched': 150, 'eta': 130, 'route': 'R1'}, {'id': '7A04', 'cls': 2, 'sched': 120, 'eta': 100, 'route': 'R1'}, {'id': '1A05', 'cls': 2, 'sched': 150, 'eta': 400, 'route': 'R3'}], 'conflicts': [['R1', 'R5']]}, ['9A00', '7A04']), ('control 29', {'now': 100, 'lookahead_s': 80, 'trains': [{'id': '6A00', 'cls': 2, 'sched': 200, 'eta': 80, 'route': 'R5'}, {'id': '8A01', 'cls': 2, 'sched': 120, 'eta': 220, 'route': 'R1'}, {'id': '6A02', 'cls': 1, 'sched': 120, 'eta': 400, 'route': 'R1'}, {'id': '2A03', 'cls': 1, 'sched': 200, 'eta': 400, 'route': 'R3'}], 'conflicts': [['R5', 'R4'], ['R4', 'R3'], ['R2', 'R1'], ['R3', 'R2']]}, ['6A00'])], [('regression: reverse-listed conflict granted in reverse', {'now': 100, 'lookahead_s': 60, 'conflicts': [['R3', 'R2']], 'trains': [{'id': '1A01', 'cls': 1, 'sched': 100, 'eta': 110, 'route': 'R3'}, {'id': '1A02', 'cls': 1, 'sched': 120, 'eta': 120, 'route': 'R2'}]}, ['1A01']), ('sampled regression 33', {'now': 100, 'lookahead_s': 120, 'trains': [{'id': '7A00', 'cls': 1, 'sched': 200, 'eta': 130, 'route': 'R2'}, {'id': '1A01', 'cls': 2, 'sched': 120, 'eta': 400, 'route': 'R3'}, {'id': '9A02', 'cls': 2, 'sched': 120, 'eta': 100, 'route': 'R3'}], 'conflicts': [['R2', 'R3'], ['R4', 'R3'], ['R4', 'R5']]}, ['7A00']), ('regression: conflict with an earlier grant', {'now': 100, 'lookahead_s': 60, 'conflicts': [['R1', 'R5']], 'trains': [{'id': '1A01', 'cls': 1, 'sched': 100, 'eta': 110, 'route': 'R1'}, {'id': '1A02', 'cls': 1, 'sched': 110, 'eta': 120, 'route': 'R4'}, {'id': '1A03', 'cls': 1, 'sched': 130, 'eta': 130, 'route': 'R5'}]}, ['1A01', '1A02']), ('regression: late running train keeps schedule order', {'now': 100, 'lookahead_s': 60, 'conflicts': [['R1', 'R2']], 'trains': [{'id': '1A01', 'cls': 1, 'sched': 100, 'eta': 150, 'route': 'R1'}, {'id': '1A02', 'cls': 1, 'sched': 120, 'eta': 105, 'route': 'R2'}]}, ['1A01']), ('boundary: eta exactly at the lookahead', {'now': 100, 'lookahead_s': 60, 'conflicts': [], 'trains': [{'id': '1A01', 'cls': 1, 'sched': 100, 'eta': 160, 'route': 'R1'}]}, ['1A01']), ('control 34', {'now': 100, 'lookahead_s': 80, 'trains': [{'id': '2A00', 'cls': 2, 'sched': 150, 'eta': 160, 'route': 'R5'}, {'id': '6A01', 'cls': 2, 'sched': 200, 'eta': 130, 'route': 'R5'}], 'conflicts': [['R4', 'R3']]}, ['2A00']), ('control 37', {'now': 100, 'lookahead_s': 60, 'trains': [{'id': '4A00', 'cls': 3, 'sched': 120, 'eta': 400, 'route': 'R4'}, {'id': '1A01', 'cls': 1, 'sched': 150, 'eta': 100, 'route': 'R4'}, {'id': '6A02', 'cls': 2, 'sched': 100, 'eta': 130, 'route': 'R4'}, {'id': '3A03', 'cls': 2, 'sched': 150, 'eta': 220, 'route': 'R5'}, {'id': '1A04', 'cls': 3, 'sched': 120, 'eta': 220, 'route': 'R2'}, {'id': '6A05', 'cls': 3, 'sched': 120, 'eta': 180, 'route': 'R1'}], 'conflicts': [['R1', 'R5'], ['R2', 'R1'], ['R3', 'R4']]}, ['1A01']), ('sampled regression 40', {'now': 100, 'lookahead_s': 60, 'trains': [{'id': '2A00', 'cls': 2, 'sched': 120, 'eta': 180, 'route': 'R4'}, {'id': '2A01', 'cls': 1, 'sched': 100, 'eta': 400, 'route': 'R4'}, {'id': '8A02', 'cls': 1, 'sched': 150, 'eta': 100, 'route': 'R3'}, {'id': '1A03', 'cls': 2, 'sched': 200, 'eta': 100, 'route': 'R3'}, {'id': '8A04', 'cls': 2, 'sched': 100, 'eta': 130, 'route': 'R4'}, {'id': '3A05', 'cls': 3, 'sched': 120, 'eta': 130, 'route': 'R5'}], 'conflicts': [['R1', 'R5'], ['R2', 'R3'], ['R1', 'R2'], ['R3', 'R4']]}, ['8A02', '3A05'])], [('regression: conflict with an earlier grant', {'now': 100, 'lookahead_s': 60, 'conflicts': [['R1', 'R5']], 'trains': [{'id': '1A01', 'cls': 1, 'sched': 100, 'eta': 110, 'route': 'R1'}, {'id': '1A02', 'cls': 1, 'sched': 110, 'eta': 120, 'route': 'R4'}, {'id': '1A03', 'cls': 1, 'sched': 130, 'eta': 130, 'route': 'R5'}]}, ['1A01', '1A02']), ('regression: reverse-listed conflict granted in reverse', {'now': 100, 'lookahead_s': 60, 'conflicts': [['R3', 'R2']], 'trains': [{'id': '1A01', 'cls': 1, 'sched': 100, 'eta': 110, 'route': 'R3'}, {'id': '1A02', 'cls': 1, 'sched': 120, 'eta': 120, 'route': 'R2'}]}, ['1A01']), ('sampled regression 50', {'now': 100, 'lookahead_s': 80, 'trains': [{'id': '9A00', 'cls': 3, 'sched': 100, 'eta': 130, 'route': 'R5'}, {'id': '4A01', 'cls': 3, 'sched': 200, 'eta': 180, 'route': 'R4'}, {'id': '6A02', 'cls': 1, 'sched': 120, 'eta': 400, 'route': 'R3'}, {'id': '4A03', 'cls': 3, 'sched': 100, 'eta': 180, 'route': 'R3'}, {'id': '7A04', 'cls': 3, 'sched': 120, 'eta': 400, 'route': 'R1'}, {'id': '2A05', 'cls': 1, 'sched': 100, 'eta': 160, 'route': 'R4'}], 'conflicts': [['R1', 'R2'], ['R1', 'R5'], ['R4', 'R3']]}, ['2A05', '9A00']), ('boundary: eta exactly at the lookahead', {'now': 100, 'lookahead_s': 60, 'conflicts': [], 'trains': [{'id': '1A01', 'cls': 1, 'sched': 100, 'eta': 160, 'route': 'R1'}]}, ['1A01']), ('boundary: overdue train', {'now': 100, 'lookahead_s': 60, 'conflicts': [], 'trains': [{'id': '2A01', 'cls': 2, 'sched': 60, 'eta': 70, 'route': 'R2'}]}, ['2A01']), ('control 45', {'now': 100, 'lookahead_s': 60, 'trains': [{'id': '6A00', 'cls': 3, 'sched': 150, 'eta': 180, 'route': 'R1'}, {'id': '2A01', 'cls': 3, 'sched': 120, 'eta': 80, 'route': 'R1'}, {'id': '2A02', 'cls': 1, 'sched': 120, 'eta': 400, 'route': 'R1'}, {'id': '5A03', 'cls': 1, 'sched': 120, 'eta': 160, 'route': 'R2'}, {'id': '9A04', 'cls': 3, 'sched': 200, 'eta': 130, 'route': 'R1'}, {'id': '5A05', 'cls': 1, 'sched': 120, 'eta': 130, 'route': 'R1'}], 'conflicts': [['R5', 'R4'], ['R3', 'R2'], ['R1', 'R5'], ['R3', 'R4']]}, ['5A03', '5A05']), ('control 48', {'now': 100, 'lookahead_s': 80, 'trains': [{'id': '5A00', 'cls': 2, 'sched': 120, 'eta': 100, 'route': 'R1'}, {'id': '2A01', 'cls': 3, 'sched': 100, 'eta': 100, 'route': 'R3'}], 'conflicts': [['R4', 'R5'], ['R3', 'R4'], ['R1', 'R2']]}, ['5A00', '2A01']), ('control 51', {'now': 100, 'lookahead_s': 80, 'trains': [{'id': '5A00', 'cls': 3, 'sched': 150, 'eta': 220, 'route': 'R4'}, {'id': '6A01', 'cls': 1, 'sched': 120, 'eta': 400, 'route': 'R2'}, {'id': '3A02', 'cls': 2, 'sched': 120, 'eta': 160, 'route': 'R4'}, {'id': '6A03', 'cls': 2, 'sched': 100, 'eta': 400, 'route': 'R2'}], 'conflicts': [['R3', 'R2'], ['R4', 'R5']]}, ['3A02'])]]
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: reverse-listed conflict granted in reverse['1A01', '1A02']['1A01']Failed
sampled regression 4['8A01', '2A00', '7A02']['8A01', '2A00']Failed
boundary: eta exactly at the lookahead['1A01']['1A01']Passed
boundary: overdue train['2A01']['2A01']Passed
boundary: class beats schedule['1A02']['1A02']Passed
control 1[][]Passed
control 7['9A01']['9A01']Passed
control 10['1A04', '1A00']['1A04', '1A00']Passed

SHA-256 / bde8a746fc73bd50d405259f610d2095b7ed5137c277c1990ac66cec98f5aa9a

2 / The unsuccessful fix

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

N = 1
observations = []
def solve(x):
    now = x['now']
    cand = [t for t in x['trains'] if t['eta'] - now <= x['lookahead_s']]
    cand.sort(key=lambda t: (t['cls'], t['sched'], t['id']))
    pairs = set()
    for a, b in x['conflicts']:
        pairs.add((a, b))
        if a < b:
            pairs.add((b, a))
    granted = []
    routes = []
    for t in cand:
        if any(t['route'] == r or (t['route'], r) in pairs for r in routes):
            continue
        granted.append(t['id'])
        routes.append(t['route'])
    return granted
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[('regression: reverse-listed conflict granted in reverse', {'now': 100, 'lookahead_s': 60, 'conflicts': [['R3', 'R2']], 'trains': [{'id': '1A01', 'cls': 1, 'sched': 100, 'eta': 110, 'route': 'R3'}, {'id': '1A02', 'cls': 1, 'sched': 120, 'eta': 120, 'route': 'R2'}]}, ['1A01']), ('sampled regression 4', {'now': 100, 'lookahead_s': 120, 'trains': [{'id': '2A00', 'cls': 2, 'sched': 200, 'eta': 220, 'route': 'R3'}, {'id': '8A01', 'cls': 1, 'sched': 100, 'eta': 80, 'route': 'R5'}, {'id': '7A02', 'cls': 3, 'sched': 100, 'eta': 80, 'route': 'R2'}], 'conflicts': [['R1', 'R5'], ['R1', 'R2'], ['R3', 'R2'], ['R4', 'R5']]}, ['8A01', '2A00']), ('boundary: eta exactly at the lookahead', {'now': 100, 'lookahead_s': 60, 'conflicts': [], 'trains': [{'id': '1A01', 'cls': 1, 'sched': 100, 'eta': 160, 'route': 'R1'}]}, ['1A01']), ('boundary: overdue train', {'now': 100, 'lookahead_s': 60, 'conflicts': [], 'trains': [{'id': '2A01', 'cls': 2, 'sched': 60, 'eta': 70, 'route': 'R2'}]}, ['2A01']), ('boundary: class beats schedule', {'now': 100, 'lookahead_s': 60, 'conflicts': [['R1', 'R2']], 'trains': [{'id': '2A01', 'cls': 2, 'sched': 100, 'eta': 110, 'route': 'R1'}, {'id': '1A02', 'cls': 1, 'sched': 150, 'eta': 150, 'route': 'R2'}]}, ['1A02']), ('control 1', {'now': 100, 'lookahead_s': 60, 'trains': [{'id': '6A00', 'cls': 1, 'sched': 120, 'eta': 400, 'route': 'R1'}, {'id': '7A01', 'cls': 1, 'sched': 120, 'eta': 220, 'route': 'R2'}], 'conflicts': [['R4', 'R3'], ['R2', 'R3'], ['R4', 'R5'], ['R2', 'R1']]}, []), ('control 7', {'now': 100, 'lookahead_s': 80, 'trains': [{'id': '2A00', 'cls': 1, 'sched': 150, 'eta': 220, 'route': 'R5'}, {'id': '9A01', 'cls': 3, 'sched': 100, 'eta': 160, 'route': 'R1'}], 'conflicts': [['R3', 'R2']]}, ['9A01']), ('control 10', {'now': 100, 'lookahead_s': 120, 'trains': [{'id': '1A00', 'cls': 1, 'sched': 200, 'eta': 220, 'route': 'R1'}, {'id': '6A01', 'cls': 3, 'sched': 150, 'eta': 160, 'route': 'R5'}, {'id': '7A02', 'cls': 1, 'sched': 120, 'eta': 400, 'route': 'R2'}, {'id': '4A03', 'cls': 3, 'sched': 100, 'eta': 220, 'route': 'R4'}, {'id': '1A04', 'cls': 1, 'sched': 150, 'eta': 220, 'route': 'R4'}, {'id': '8A05', 'cls': 3, 'sched': 150, 'eta': 400, 'route': 'R4'}], 'conflicts': [['R2', 'R1'], ['R3', 'R4'], ['R5', 'R4']]}, ['1A04', '1A00'])], [('regression: conflict with an earlier grant', {'now': 100, 'lookahead_s': 60, 'conflicts': [['R1', 'R5']], 'trains': [{'id': '1A01', 'cls': 1, 'sched': 100, 'eta': 110, 'route': 'R1'}, {'id': '1A02', 'cls': 1, 'sched': 110, 'eta': 120, 'route': 'R4'}, {'id': '1A03', 'cls': 1, 'sched': 130, 'eta': 130, 'route': 'R5'}]}, ['1A01', '1A02']), ('regression: reverse-listed conflict granted in reverse', {'now': 100, 'lookahead_s': 60, 'conflicts': [['R3', 'R2']], 'trains': [{'id': '1A01', 'cls': 1, 'sched': 100, 'eta': 110, 'route': 'R3'}, {'id': '1A02', 'cls': 1, 'sched': 120, 'eta': 120, 'route': 'R2'}]}, ['1A01']), ('sampled regression 40', {'now': 100, 'lookahead_s': 60, 'trains': [{'id': '2A00', 'cls': 2, 'sched': 120, 'eta': 180, 'route': 'R4'}, {'id': '2A01', 'cls': 1, 'sched': 100, 'eta': 400, 'route': 'R4'}, {'id': '8A02', 'cls': 1, 'sched': 150, 'eta': 100, 'route': 'R3'}, {'id': '1A03', 'cls': 2, 'sched': 200, 'eta': 100, 'route': 'R3'}, {'id': '8A04', 'cls': 2, 'sched': 100, 'eta': 130, 'route': 'R4'}, {'id': '3A05', 'cls': 3, 'sched': 120, 'eta': 130, 'route': 'R5'}], 'conflicts': [['R1', 'R5'], ['R2', 'R3'], ['R1', 'R2'], ['R3', 'R4']]}, ['8A02', '3A05']), ('sampled regression 63', {'now': 100, 'lookahead_s': 120, 'trains': [{'id': '7A00', 'cls': 3, 'sched': 100, 'eta': 80, 'route': 'R3'}, {'id': '3A01', 'cls': 2, 'sched': 200, 'eta': 130, 'route': 'R4'}, {'id': '6A02', 'cls': 1, 'sched': 120, 'eta': 130, 'route': 'R5'}, {'id': '3A03', 'cls': 2, 'sched': 120, 'eta': 400, 'route': 'R1'}, {'id': '2A04', 'cls': 2, 'sched': 100, 'eta': 130, 'route': 'R1'}, {'id': '2A05', 'cls': 2, 'sched': 150, 'eta': 220, 'route': 'R2'}], 'conflicts': [['R1', 'R2'], ['R5', 'R1'], ['R2', 'R3'], ['R4', 'R3']]}, ['6A02', '2A05', '3A01']), ('boundary: class beats schedule', {'now': 100, 'lookahead_s': 60, 'conflicts': [['R1', 'R2']], 'trains': [{'id': '2A01', 'cls': 2, 'sched': 100, 'eta': 110, 'route': 'R1'}, {'id': '1A02', 'cls': 1, 'sched': 150, 'eta': 150, 'route': 'R2'}]}, ['1A02']), ('control 12', {'now': 100, 'lookahead_s': 120, 'trains': [{'id': '8A00', 'cls': 1, 'sched': 100, 'eta': 180, 'route': 'R3'}, {'id': '8A01', 'cls': 2, 'sched': 100, 'eta': 220, 'route': 'R2'}], 'conflicts': [['R3', 'R4']]}, ['8A00', '8A01']), ('control 15', {'now': 100, 'lookahead_s': 60, 'trains': [{'id': '2A00', 'cls': 2, 'sched': 200, 'eta': 180, 'route': 'R5'}, {'id': '6A01', 'cls': 3, 'sched': 150, 'eta': 80, 'route': 'R2'}, {'id': '7A02', 'cls': 3, 'sched': 100, 'eta': 130, 'route': 'R5'}, {'id': '5A03', 'cls': 3, 'sched': 120, 'eta': 160, 'route': 'R1'}], 'conflicts': [['R2', 'R1'], ['R4', 'R5'], ['R1', 'R5']]}, ['7A02', '6A01']), ('sampled regression 18', {'now': 100, 'lookahead_s': 120, 'trains': [{'id': '9A00', 'cls': 1, 'sched': 150, 'eta': 220, 'route': 'R4'}, {'id': '8A01', 'cls': 2, 'sched': 100, 'eta': 80, 'route': 'R3'}], 'conflicts': [['R5', 'R4'], ['R1', 'R2'], ['R4', 'R3']]}, ['9A00'])], [('regression: late running train keeps schedule order', {'now': 100, 'lookahead_s': 60, 'conflicts': [['R1', 'R2']], 'trains': [{'id': '1A01', 'cls': 1, 'sched': 100, 'eta': 150, 'route': 'R1'}, {'id': '1A02', 'cls': 1, 'sched': 120, 'eta': 105, 'route': 'R2'}]}, ['1A01']), ('regression: reverse-listed conflict granted in reverse', {'now': 100, 'lookahead_s': 60, 'conflicts': [['R3', 'R2']], 'trains': [{'id': '1A01', 'cls': 1, 'sched': 100, 'eta': 110, 'route': 'R3'}, {'id': '1A02', 'cls': 1, 'sched': 120, 'eta': 120, 'route': 'R2'}]}, ['1A01']), ('sampled regression 14', {'now': 100, 'lookahead_s': 60, 'trains': [{'id': '3A00', 'cls': 2, 'sched': 200, 'eta': 180, 'route': 'R2'}, {'id': '5A01', 'cls': 3, 'sched': 100, 'eta': 100, 'route': 'R4'}, {'id': '1A02', 'cls': 2, 'sched': 150, 'eta': 180, 'route': 'R3'}, {'id': '6A03', 'cls': 3, 'sched': 200, 'eta': 400, 'route': 'R1'}, {'id': '3A04', 'cls': 2, 'sched': 200, 'eta': 130, 'route': 'R5'}], 'conflicts': [['R1', 'R2'], ['R2', 'R3'], ['R5', 'R4']]}, ['3A04']), ('boundary: two trains for one route', {'now': 100, 'lookahead_s': 60, 'conflicts': [], 'trains': [{'id': '1A01', 'cls': 1, 'sched': 100, 'eta': 110, 'route': 'R3'}, {'id': '1A02', 'cls': 1, 'sched': 120, 'eta': 120, 'route': 'R3'}]}, ['1A01']), ('regression: conflict with an earlier grant', {'now': 100, 'lookahead_s': 60, 'conflicts': [['R1', 'R5']], 'trains': [{'id': '1A01', 'cls': 1, 'sched': 100, 'eta': 110, 'route': 'R1'}, {'id': '1A02', 'cls': 1, 'sched': 110, 'eta': 120, 'route': 'R4'}, {'id': '1A03', 'cls': 1, 'sched': 130, 'eta': 130, 'route': 'R5'}]}, ['1A01', '1A02']), ('control 23', {'now': 100, 'lookahead_s': 80, 'trains': [{'id': '9A00', 'cls': 1, 'sched': 200, 'eta': 180, 'route': 'R4'}, {'id': '1A01', 'cls': 2, 'sched': 200, 'eta': 220, 'route': 'R2'}, {'id': '5A02', 'cls': 2, 'sched': 120, 'eta': 160, 'route': 'R5'}, {'id': '2A03', 'cls': 2, 'sched': 150, 'eta': 80, 'route': 'R2'}], 'conflicts': [['R1', 'R5'], ['R2', 'R1']]}, ['9A00', '5A02', '2A03']), ('control 26', {'now': 100, 'lookahead_s': 80, 'trains': [{'id': '9A00', 'cls': 1, 'sched': 120, 'eta': 160, 'route': 'R2'}, {'id': '7A01', 'cls': 2, 'sched': 100, 'eta': 220, 'route': 'R4'}, {'id': '2A02', 'cls': 1, 'sched': 150, 'eta': 180, 'route': 'R2'}, {'id': '1A03', 'cls': 3, 'sched': 150, 'eta': 130, 'route': 'R1'}, {'id': '7A04', 'cls': 2, 'sched': 120, 'eta': 100, 'route': 'R1'}, {'id': '1A05', 'cls': 2, 'sched': 150, 'eta': 400, 'route': 'R3'}], 'conflicts': [['R1', 'R5']]}, ['9A00', '7A04']), ('control 29', {'now': 100, 'lookahead_s': 80, 'trains': [{'id': '6A00', 'cls': 2, 'sched': 200, 'eta': 80, 'route': 'R5'}, {'id': '8A01', 'cls': 2, 'sched': 120, 'eta': 220, 'route': 'R1'}, {'id': '6A02', 'cls': 1, 'sched': 120, 'eta': 400, 'route': 'R1'}, {'id': '2A03', 'cls': 1, 'sched': 200, 'eta': 400, 'route': 'R3'}], 'conflicts': [['R5', 'R4'], ['R4', 'R3'], ['R2', 'R1'], ['R3', 'R2']]}, ['6A00'])], [('regression: reverse-listed conflict granted in reverse', {'now': 100, 'lookahead_s': 60, 'conflicts': [['R3', 'R2']], 'trains': [{'id': '1A01', 'cls': 1, 'sched': 100, 'eta': 110, 'route': 'R3'}, {'id': '1A02', 'cls': 1, 'sched': 120, 'eta': 120, 'route': 'R2'}]}, ['1A01']), ('sampled regression 33', {'now': 100, 'lookahead_s': 120, 'trains': [{'id': '7A00', 'cls': 1, 'sched': 200, 'eta': 130, 'route': 'R2'}, {'id': '1A01', 'cls': 2, 'sched': 120, 'eta': 400, 'route': 'R3'}, {'id': '9A02', 'cls': 2, 'sched': 120, 'eta': 100, 'route': 'R3'}], 'conflicts': [['R2', 'R3'], ['R4', 'R3'], ['R4', 'R5']]}, ['7A00']), ('regression: conflict with an earlier grant', {'now': 100, 'lookahead_s': 60, 'conflicts': [['R1', 'R5']], 'trains': [{'id': '1A01', 'cls': 1, 'sched': 100, 'eta': 110, 'route': 'R1'}, {'id': '1A02', 'cls': 1, 'sched': 110, 'eta': 120, 'route': 'R4'}, {'id': '1A03', 'cls': 1, 'sched': 130, 'eta': 130, 'route': 'R5'}]}, ['1A01', '1A02']), ('regression: late running train keeps schedule order', {'now': 100, 'lookahead_s': 60, 'conflicts': [['R1', 'R2']], 'trains': [{'id': '1A01', 'cls': 1, 'sched': 100, 'eta': 150, 'route': 'R1'}, {'id': '1A02', 'cls': 1, 'sched': 120, 'eta': 105, 'route': 'R2'}]}, ['1A01']), ('boundary: eta exactly at the lookahead', {'now': 100, 'lookahead_s': 60, 'conflicts': [], 'trains': [{'id': '1A01', 'cls': 1, 'sched': 100, 'eta': 160, 'route': 'R1'}]}, ['1A01']), ('control 34', {'now': 100, 'lookahead_s': 80, 'trains': [{'id': '2A00', 'cls': 2, 'sched': 150, 'eta': 160, 'route': 'R5'}, {'id': '6A01', 'cls': 2, 'sched': 200, 'eta': 130, 'route': 'R5'}], 'conflicts': [['R4', 'R3']]}, ['2A00']), ('control 37', {'now': 100, 'lookahead_s': 60, 'trains': [{'id': '4A00', 'cls': 3, 'sched': 120, 'eta': 400, 'route': 'R4'}, {'id': '1A01', 'cls': 1, 'sched': 150, 'eta': 100, 'route': 'R4'}, {'id': '6A02', 'cls': 2, 'sched': 100, 'eta': 130, 'route': 'R4'}, {'id': '3A03', 'cls': 2, 'sched': 150, 'eta': 220, 'route': 'R5'}, {'id': '1A04', 'cls': 3, 'sched': 120, 'eta': 220, 'route': 'R2'}, {'id': '6A05', 'cls': 3, 'sched': 120, 'eta': 180, 'route': 'R1'}], 'conflicts': [['R1', 'R5'], ['R2', 'R1'], ['R3', 'R4']]}, ['1A01']), ('sampled regression 40', {'now': 100, 'lookahead_s': 60, 'trains': [{'id': '2A00', 'cls': 2, 'sched': 120, 'eta': 180, 'route': 'R4'}, {'id': '2A01', 'cls': 1, 'sched': 100, 'eta': 400, 'route': 'R4'}, {'id': '8A02', 'cls': 1, 'sched': 150, 'eta': 100, 'route': 'R3'}, {'id': '1A03', 'cls': 2, 'sched': 200, 'eta': 100, 'route': 'R3'}, {'id': '8A04', 'cls': 2, 'sched': 100, 'eta': 130, 'route': 'R4'}, {'id': '3A05', 'cls': 3, 'sched': 120, 'eta': 130, 'route': 'R5'}], 'conflicts': [['R1', 'R5'], ['R2', 'R3'], ['R1', 'R2'], ['R3', 'R4']]}, ['8A02', '3A05'])], [('regression: conflict with an earlier grant', {'now': 100, 'lookahead_s': 60, 'conflicts': [['R1', 'R5']], 'trains': [{'id': '1A01', 'cls': 1, 'sched': 100, 'eta': 110, 'route': 'R1'}, {'id': '1A02', 'cls': 1, 'sched': 110, 'eta': 120, 'route': 'R4'}, {'id': '1A03', 'cls': 1, 'sched': 130, 'eta': 130, 'route': 'R5'}]}, ['1A01', '1A02']), ('regression: reverse-listed conflict granted in reverse', {'now': 100, 'lookahead_s': 60, 'conflicts': [['R3', 'R2']], 'trains': [{'id': '1A01', 'cls': 1, 'sched': 100, 'eta': 110, 'route': 'R3'}, {'id': '1A02', 'cls': 1, 'sched': 120, 'eta': 120, 'route': 'R2'}]}, ['1A01']), ('sampled regression 50', {'now': 100, 'lookahead_s': 80, 'trains': [{'id': '9A00', 'cls': 3, 'sched': 100, 'eta': 130, 'route': 'R5'}, {'id': '4A01', 'cls': 3, 'sched': 200, 'eta': 180, 'route': 'R4'}, {'id': '6A02', 'cls': 1, 'sched': 120, 'eta': 400, 'route': 'R3'}, {'id': '4A03', 'cls': 3, 'sched': 100, 'eta': 180, 'route': 'R3'}, {'id': '7A04', 'cls': 3, 'sched': 120, 'eta': 400, 'route': 'R1'}, {'id': '2A05', 'cls': 1, 'sched': 100, 'eta': 160, 'route': 'R4'}], 'conflicts': [['R1', 'R2'], ['R1', 'R5'], ['R4', 'R3']]}, ['2A05', '9A00']), ('boundary: eta exactly at the lookahead', {'now': 100, 'lookahead_s': 60, 'conflicts': [], 'trains': [{'id': '1A01', 'cls': 1, 'sched': 100, 'eta': 160, 'route': 'R1'}]}, ['1A01']), ('boundary: overdue train', {'now': 100, 'lookahead_s': 60, 'conflicts': [], 'trains': [{'id': '2A01', 'cls': 2, 'sched': 60, 'eta': 70, 'route': 'R2'}]}, ['2A01']), ('control 45', {'now': 100, 'lookahead_s': 60, 'trains': [{'id': '6A00', 'cls': 3, 'sched': 150, 'eta': 180, 'route': 'R1'}, {'id': '2A01', 'cls': 3, 'sched': 120, 'eta': 80, 'route': 'R1'}, {'id': '2A02', 'cls': 1, 'sched': 120, 'eta': 400, 'route': 'R1'}, {'id': '5A03', 'cls': 1, 'sched': 120, 'eta': 160, 'route': 'R2'}, {'id': '9A04', 'cls': 3, 'sched': 200, 'eta': 130, 'route': 'R1'}, {'id': '5A05', 'cls': 1, 'sched': 120, 'eta': 130, 'route': 'R1'}], 'conflicts': [['R5', 'R4'], ['R3', 'R2'], ['R1', 'R5'], ['R3', 'R4']]}, ['5A03', '5A05']), ('control 48', {'now': 100, 'lookahead_s': 80, 'trains': [{'id': '5A00', 'cls': 2, 'sched': 120, 'eta': 100, 'route': 'R1'}, {'id': '2A01', 'cls': 3, 'sched': 100, 'eta': 100, 'route': 'R3'}], 'conflicts': [['R4', 'R5'], ['R3', 'R4'], ['R1', 'R2']]}, ['5A00', '2A01']), ('control 51', {'now': 100, 'lookahead_s': 80, 'trains': [{'id': '5A00', 'cls': 3, 'sched': 150, 'eta': 220, 'route': 'R4'}, {'id': '6A01', 'cls': 1, 'sched': 120, 'eta': 400, 'route': 'R2'}, {'id': '3A02', 'cls': 2, 'sched': 120, 'eta': 160, 'route': 'R4'}, {'id': '6A03', 'cls': 2, 'sched': 100, 'eta': 400, 'route': 'R2'}], 'conflicts': [['R3', 'R2'], ['R4', 'R5']]}, ['3A02'])]]
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: reverse-listed conflict granted in reverse['1A01', '1A02']['1A01']Failed
sampled regression 4['8A01', '2A00', '7A02']['8A01', '2A00']Failed
boundary: eta exactly at the lookahead['1A01']['1A01']Passed
boundary: overdue train['2A01']['2A01']Passed
boundary: class beats schedule['1A02']['1A02']Passed
control 1[][]Passed
control 7['9A01']['9A01']Passed
control 10['1A04', '1A00']['1A04', '1A00']Passed

SHA-256 / fc2cbe7f07a79d6a296928b1f4d388a192f79b78b3c6a54322b0cedf91546315

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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.

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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 2026-09-29T14:47:51.735633+00:00.

Case digest / ed8e71712c6f72e0d3e68efac738dfe27236808a07a9dc7f83f30bac9875b6b2