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FA-67171 / Railway interlocking logic / Open access

Signal lamp proving and aspect degradation: dark signal alarm · case 01

A completely dark signal raises no alarm.

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

ROOT CAUSE

The DARK state is excluded from alarming.

VERIFIED REPAIR

Always alarm a DARK signal.

Unsuccessful approach: Looking up lamps for DARK finds none and still does not alarm.

Case contract

Aspects need lamps: G needs G; YY needs Y1 and Y2; Y needs Y1; R needs R. A lamp is lit if its main or auxiliary filament works. If the requested aspect cannot be lit, show the next more restrictive aspect that can (G, YY, Y, R); if even R cannot be lit the signal is DARK. alarm is raised if the signal is DARK or any lamp used by the shown aspect runs on its auxiliary filament. degraded means shown != requested.

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):
    lamps = x['lamps']
    need = {'G': ['G'], 'YY': ['Y1', 'Y2'], 'Y': ['Y1'], 'R': ['R']}
    order = ['G', 'YY', 'Y', 'R']
    def lit(l):
        return lamps[l]['main'] or lamps[l]['aux']
    shown = 'DARK'
    for asp in order[order.index(x['requested']):]:
        if all(lit(l) for l in need[asp]):
            shown = asp
            break
    alarm = shown != 'DARK' and any(not lamps[l]['main'] for l in need[shown])
    return {'shown': shown, 'alarm': alarm, 'degraded': shown != x['requested']}
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[('regression: red lamp dead', {'requested': 'R', 'lamps': {'R': {'main': False, 'aux': False}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'DARK', 'alarm': True, 'degraded': True}), ('sampled regression 43', {'requested': 'R', 'lamps': {'R': {'main': False, 'aux': False}, 'Y1': {'main': False, 'aux': False}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': False, 'aux': False}}}, {'shown': 'DARK', 'alarm': True, 'degraded': True}), ('boundary: green on auxiliary filament', {'requested': 'G', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': False, 'aux': True}}}, {'shown': 'G', 'alarm': True, 'degraded': False}), ('boundary: red on auxiliary filament', {'requested': 'R', 'lamps': {'R': {'main': False, 'aux': True}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'R', 'alarm': True, 'degraded': False}), ('boundary: green lamp dead', {'requested': 'G', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': False, 'aux': False}}}, {'shown': 'YY', 'alarm': False, 'degraded': True}), ('control 1', {'requested': 'G', 'lamps': {'R': {'main': True, 'aux': False}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'G', 'alarm': False, 'degraded': False}), ('control 4', {'requested': 'G', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'G', 'alarm': False, 'degraded': False}), ('control 7', {'requested': 'R', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': True, 'aux': False}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'R', 'alarm': False, 'degraded': False})], [('regression: red lamp dead', {'requested': 'R', 'lamps': {'R': {'main': False, 'aux': False}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'DARK', 'alarm': True, 'degraded': True}), ('sampled regression 43', {'requested': 'R', 'lamps': {'R': {'main': False, 'aux': False}, 'Y1': {'main': False, 'aux': False}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': False, 'aux': False}}}, {'shown': 'DARK', 'alarm': True, 'degraded': True}), ('boundary: green lamp dead', {'requested': 'G', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': False, 'aux': False}}}, {'shown': 'YY', 'alarm': False, 'degraded': True}), ('boundary: lower yellow dead under double yellow', {'requested': 'YY', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': False, 'aux': False}, 'G': {'main': True, 'aux': True}}}, {'shown': 'Y', 'alarm': False, 'degraded': True}), ('boundary: upper yellow dead under double yellow', {'requested': 'YY', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': False, 'aux': False}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'R', 'alarm': False, 'degraded': True}), ('control 12', {'requested': 'YY', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': True, 'aux': False}, 'G': {'main': False, 'aux': True}}}, {'shown': 'YY', 'alarm': False, 'degraded': False}), ('control 15', {'requested': 'YY', 'lamps': {'R': {'main': True, 'aux': False}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': False, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'YY', 'alarm': True, 'degraded': False}), ('control 18', {'requested': 'Y', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': False, 'aux': True}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': False, 'aux': True}}}, {'shown': 'Y', 'alarm': True, 'degraded': False})], [('regression: red lamp dead', {'requested': 'R', 'lamps': {'R': {'main': False, 'aux': False}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'DARK', 'alarm': True, 'degraded': True}), ('sampled regression 70', {'requested': 'R', 'lamps': {'R': {'main': False, 'aux': False}, 'Y1': {'main': False, 'aux': True}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': True, 'aux': False}}}, {'shown': 'DARK', 'alarm': True, 'degraded': True}), ('boundary: upper yellow dead under double yellow', {'requested': 'YY', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': False, 'aux': False}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'R', 'alarm': False, 'degraded': True}), ('boundary: unused lamp on auxiliary', {'requested': 'Y', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': False, 'aux': True}}}, {'shown': 'Y', 'alarm': False, 'degraded': False}), ('boundary: second yellow on auxiliary', {'requested': 'YY', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': False, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'YY', 'alarm': True, 'degraded': False}), ('control 23', {'requested': 'Y', 'lamps': {'R': {'main': True, 'aux': False}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'Y', 'alarm': False, 'degraded': False}), ('control 26', {'requested': 'Y', 'lamps': {'R': {'main': True, 'aux': False}, 'Y1': {'main': True, 'aux': False}, 'Y2': {'main': True, 'aux': False}, 'G': {'main': True, 'aux': True}}}, {'shown': 'Y', 'alarm': False, 'degraded': False}), ('control 29', {'requested': 'R', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'R', 'alarm': False, 'degraded': False})], [('regression: red lamp dead', {'requested': 'R', 'lamps': {'R': {'main': False, 'aux': False}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'DARK', 'alarm': True, 'degraded': True}), ('sampled regression 43', {'requested': 'R', 'lamps': {'R': {'main': False, 'aux': False}, 'Y1': {'main': False, 'aux': False}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': False, 'aux': False}}}, {'shown': 'DARK', 'alarm': True, 'degraded': True}), ('boundary: unused lamp on auxiliary', {'requested': 'Y', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': False, 'aux': True}}}, {'shown': 'Y', 'alarm': False, 'degraded': False}), ('boundary: second yellow on auxiliary', {'requested': 'YY', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': False, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'YY', 'alarm': True, 'degraded': False}), ('boundary: all yellows dead', {'requested': 'YY', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': False, 'aux': False}, 'Y2': {'main': False, 'aux': False}, 'G': {'main': True, 'aux': True}}}, {'shown': 'R', 'alarm': False, 'degraded': True}), ('control 34', {'requested': 'R', 'lamps': {'R': {'main': False, 'aux': True}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': True, 'aux': False}, 'G': {'main': True, 'aux': True}}}, {'shown': 'R', 'alarm': True, 'degraded': False}), ('control 37', {'requested': 'R', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': False, 'aux': False}, 'Y2': {'main': False, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'R', 'alarm': False, 'degraded': False}), ('control 40', {'requested': 'YY', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': False, 'aux': False}}}, {'shown': 'YY', 'alarm': False, 'degraded': False})], [('regression: red lamp dead', {'requested': 'R', 'lamps': {'R': {'main': False, 'aux': False}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'DARK', 'alarm': True, 'degraded': True}), ('sampled regression 43', {'requested': 'R', 'lamps': {'R': {'main': False, 'aux': False}, 'Y1': {'main': False, 'aux': False}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': False, 'aux': False}}}, {'shown': 'DARK', 'alarm': True, 'degraded': True}), ('boundary: all yellows dead', {'requested': 'YY', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': False, 'aux': False}, 'Y2': {'main': False, 'aux': False}, 'G': {'main': True, 'aux': True}}}, {'shown': 'R', 'alarm': False, 'degraded': True}), ('boundary: green on auxiliary filament', {'requested': 'G', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': False, 'aux': True}}}, {'shown': 'G', 'alarm': True, 'degraded': False}), ('boundary: red on auxiliary filament', {'requested': 'R', 'lamps': {'R': {'main': False, 'aux': True}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'R', 'alarm': True, 'degraded': False}), ('control 45', {'requested': 'G', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': True, 'aux': False}, 'G': {'main': True, 'aux': False}}}, {'shown': 'G', 'alarm': False, 'degraded': False}), ('control 48', {'requested': 'G', 'lamps': {'R': {'main': False, 'aux': False}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': False, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'G', 'alarm': False, 'degraded': False}), ('control 51', {'requested': 'YY', 'lamps': {'R': {'main': False, 'aux': True}, 'Y1': {'main': True, 'aux': False}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'YY', 'alarm': False, 'degraded': False})]]
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: red lamp dead{'alarm': False, 'degraded': True, 'shown': 'DARK'}{'alarm': True, 'degraded': True, 'shown': 'DARK'}Failed
sampled regression 43{'alarm': False, 'degraded': True, 'shown': 'DARK'}{'alarm': True, 'degraded': True, 'shown': 'DARK'}Failed
boundary: green on auxiliary filament{'alarm': True, 'degraded': False, 'shown': 'G'}{'alarm': True, 'degraded': False, 'shown': 'G'}Passed
boundary: red on auxiliary filament{'alarm': True, 'degraded': False, 'shown': 'R'}{'alarm': True, 'degraded': False, 'shown': 'R'}Passed
boundary: green lamp dead{'alarm': False, 'degraded': True, 'shown': 'YY'}{'alarm': False, 'degraded': True, 'shown': 'YY'}Passed
control 1{'alarm': False, 'degraded': False, 'shown': 'G'}{'alarm': False, 'degraded': False, 'shown': 'G'}Passed
control 4{'alarm': False, 'degraded': False, 'shown': 'G'}{'alarm': False, 'degraded': False, 'shown': 'G'}Passed
control 7{'alarm': False, 'degraded': False, 'shown': 'R'}{'alarm': False, 'degraded': False, 'shown': 'R'}Passed

SHA-256 / 065ec759ccc4791e38d9e0586cf1ea4fe7938c6d9fa908c436f1b53b7ab306c2

2 / The unsuccessful fix

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

N = 1
observations = []
def solve(x):
    lamps = x['lamps']
    need = {'G': ['G'], 'YY': ['Y1', 'Y2'], 'Y': ['Y1'], 'R': ['R']}
    order = ['G', 'YY', 'Y', 'R']
    def lit(l):
        return lamps[l]['main'] or lamps[l]['aux']
    shown = 'DARK'
    for asp in order[order.index(x['requested']):]:
        if all(lit(l) for l in need[asp]):
            shown = asp
            break
    alarm = any(not lamps[l]['main'] for l in need.get(shown, []))
    return {'shown': shown, 'alarm': alarm, 'degraded': shown != x['requested']}
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[('regression: red lamp dead', {'requested': 'R', 'lamps': {'R': {'main': False, 'aux': False}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'DARK', 'alarm': True, 'degraded': True}), ('sampled regression 43', {'requested': 'R', 'lamps': {'R': {'main': False, 'aux': False}, 'Y1': {'main': False, 'aux': False}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': False, 'aux': False}}}, {'shown': 'DARK', 'alarm': True, 'degraded': True}), ('boundary: green on auxiliary filament', {'requested': 'G', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': False, 'aux': True}}}, {'shown': 'G', 'alarm': True, 'degraded': False}), ('boundary: red on auxiliary filament', {'requested': 'R', 'lamps': {'R': {'main': False, 'aux': True}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'R', 'alarm': True, 'degraded': False}), ('boundary: green lamp dead', {'requested': 'G', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': False, 'aux': False}}}, {'shown': 'YY', 'alarm': False, 'degraded': True}), ('control 1', {'requested': 'G', 'lamps': {'R': {'main': True, 'aux': False}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'G', 'alarm': False, 'degraded': False}), ('control 4', {'requested': 'G', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'G', 'alarm': False, 'degraded': False}), ('control 7', {'requested': 'R', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': True, 'aux': False}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'R', 'alarm': False, 'degraded': False})], [('regression: red lamp dead', {'requested': 'R', 'lamps': {'R': {'main': False, 'aux': False}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'DARK', 'alarm': True, 'degraded': True}), ('sampled regression 43', {'requested': 'R', 'lamps': {'R': {'main': False, 'aux': False}, 'Y1': {'main': False, 'aux': False}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': False, 'aux': False}}}, {'shown': 'DARK', 'alarm': True, 'degraded': True}), ('boundary: green lamp dead', {'requested': 'G', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': False, 'aux': False}}}, {'shown': 'YY', 'alarm': False, 'degraded': True}), ('boundary: lower yellow dead under double yellow', {'requested': 'YY', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': False, 'aux': False}, 'G': {'main': True, 'aux': True}}}, {'shown': 'Y', 'alarm': False, 'degraded': True}), ('boundary: upper yellow dead under double yellow', {'requested': 'YY', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': False, 'aux': False}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'R', 'alarm': False, 'degraded': True}), ('control 12', {'requested': 'YY', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': True, 'aux': False}, 'G': {'main': False, 'aux': True}}}, {'shown': 'YY', 'alarm': False, 'degraded': False}), ('control 15', {'requested': 'YY', 'lamps': {'R': {'main': True, 'aux': False}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': False, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'YY', 'alarm': True, 'degraded': False}), ('control 18', {'requested': 'Y', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': False, 'aux': True}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': False, 'aux': True}}}, {'shown': 'Y', 'alarm': True, 'degraded': False})], [('regression: red lamp dead', {'requested': 'R', 'lamps': {'R': {'main': False, 'aux': False}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'DARK', 'alarm': True, 'degraded': True}), ('sampled regression 70', {'requested': 'R', 'lamps': {'R': {'main': False, 'aux': False}, 'Y1': {'main': False, 'aux': True}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': True, 'aux': False}}}, {'shown': 'DARK', 'alarm': True, 'degraded': True}), ('boundary: upper yellow dead under double yellow', {'requested': 'YY', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': False, 'aux': False}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'R', 'alarm': False, 'degraded': True}), ('boundary: unused lamp on auxiliary', {'requested': 'Y', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': False, 'aux': True}}}, {'shown': 'Y', 'alarm': False, 'degraded': False}), ('boundary: second yellow on auxiliary', {'requested': 'YY', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': False, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'YY', 'alarm': True, 'degraded': False}), ('control 23', {'requested': 'Y', 'lamps': {'R': {'main': True, 'aux': False}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'Y', 'alarm': False, 'degraded': False}), ('control 26', {'requested': 'Y', 'lamps': {'R': {'main': True, 'aux': False}, 'Y1': {'main': True, 'aux': False}, 'Y2': {'main': True, 'aux': False}, 'G': {'main': True, 'aux': True}}}, {'shown': 'Y', 'alarm': False, 'degraded': False}), ('control 29', {'requested': 'R', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'R', 'alarm': False, 'degraded': False})], [('regression: red lamp dead', {'requested': 'R', 'lamps': {'R': {'main': False, 'aux': False}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'DARK', 'alarm': True, 'degraded': True}), ('sampled regression 43', {'requested': 'R', 'lamps': {'R': {'main': False, 'aux': False}, 'Y1': {'main': False, 'aux': False}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': False, 'aux': False}}}, {'shown': 'DARK', 'alarm': True, 'degraded': True}), ('boundary: unused lamp on auxiliary', {'requested': 'Y', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': False, 'aux': True}}}, {'shown': 'Y', 'alarm': False, 'degraded': False}), ('boundary: second yellow on auxiliary', {'requested': 'YY', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': False, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'YY', 'alarm': True, 'degraded': False}), ('boundary: all yellows dead', {'requested': 'YY', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': False, 'aux': False}, 'Y2': {'main': False, 'aux': False}, 'G': {'main': True, 'aux': True}}}, {'shown': 'R', 'alarm': False, 'degraded': True}), ('control 34', {'requested': 'R', 'lamps': {'R': {'main': False, 'aux': True}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': True, 'aux': False}, 'G': {'main': True, 'aux': True}}}, {'shown': 'R', 'alarm': True, 'degraded': False}), ('control 37', {'requested': 'R', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': False, 'aux': False}, 'Y2': {'main': False, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'R', 'alarm': False, 'degraded': False}), ('control 40', {'requested': 'YY', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': False, 'aux': False}}}, {'shown': 'YY', 'alarm': False, 'degraded': False})], [('regression: red lamp dead', {'requested': 'R', 'lamps': {'R': {'main': False, 'aux': False}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'DARK', 'alarm': True, 'degraded': True}), ('sampled regression 43', {'requested': 'R', 'lamps': {'R': {'main': False, 'aux': False}, 'Y1': {'main': False, 'aux': False}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': False, 'aux': False}}}, {'shown': 'DARK', 'alarm': True, 'degraded': True}), ('boundary: all yellows dead', {'requested': 'YY', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': False, 'aux': False}, 'Y2': {'main': False, 'aux': False}, 'G': {'main': True, 'aux': True}}}, {'shown': 'R', 'alarm': False, 'degraded': True}), ('boundary: green on auxiliary filament', {'requested': 'G', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': False, 'aux': True}}}, {'shown': 'G', 'alarm': True, 'degraded': False}), ('boundary: red on auxiliary filament', {'requested': 'R', 'lamps': {'R': {'main': False, 'aux': True}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'R', 'alarm': True, 'degraded': False}), ('control 45', {'requested': 'G', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': True, 'aux': False}, 'G': {'main': True, 'aux': False}}}, {'shown': 'G', 'alarm': False, 'degraded': False}), ('control 48', {'requested': 'G', 'lamps': {'R': {'main': False, 'aux': False}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': False, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'G', 'alarm': False, 'degraded': False}), ('control 51', {'requested': 'YY', 'lamps': {'R': {'main': False, 'aux': True}, 'Y1': {'main': True, 'aux': False}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'YY', 'alarm': False, 'degraded': False})]]
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: red lamp dead{'alarm': False, 'degraded': True, 'shown': 'DARK'}{'alarm': True, 'degraded': True, 'shown': 'DARK'}Failed
sampled regression 43{'alarm': False, 'degraded': True, 'shown': 'DARK'}{'alarm': True, 'degraded': True, 'shown': 'DARK'}Failed
boundary: green on auxiliary filament{'alarm': True, 'degraded': False, 'shown': 'G'}{'alarm': True, 'degraded': False, 'shown': 'G'}Passed
boundary: red on auxiliary filament{'alarm': True, 'degraded': False, 'shown': 'R'}{'alarm': True, 'degraded': False, 'shown': 'R'}Passed
boundary: green lamp dead{'alarm': False, 'degraded': True, 'shown': 'YY'}{'alarm': False, 'degraded': True, 'shown': 'YY'}Passed
control 1{'alarm': False, 'degraded': False, 'shown': 'G'}{'alarm': False, 'degraded': False, 'shown': 'G'}Passed
control 4{'alarm': False, 'degraded': False, 'shown': 'G'}{'alarm': False, 'degraded': False, 'shown': 'G'}Passed
control 7{'alarm': False, 'degraded': False, 'shown': 'R'}{'alarm': False, 'degraded': False, 'shown': 'R'}Passed

SHA-256 / e0091c88e1438bcf820f421bf26c9fd6e9220f6d3afe6550585536b414159078

3 / The verified repair

Exit 0
"""Failure Map reference implementation. Python standard library only."""
import json

N = 1
observations = []
def solve(x):
    lamps = x['lamps']
    need = {'G': ['G'], 'YY': ['Y1', 'Y2'], 'Y': ['Y1'], 'R': ['R']}
    order = ['G', 'YY', 'Y', 'R']
    def lit(l):
        return lamps[l]['main'] or lamps[l]['aux']
    shown = 'DARK'
    for asp in order[order.index(x['requested']):]:
        if all(lit(l) for l in need[asp]):
            shown = asp
            break
    alarm = shown == 'DARK' or any(not lamps[l]['main'] for l in need[shown])
    return {'shown': shown, 'alarm': alarm, 'degraded': shown != x['requested']}
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[('regression: red lamp dead', {'requested': 'R', 'lamps': {'R': {'main': False, 'aux': False}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'DARK', 'alarm': True, 'degraded': True}), ('sampled regression 43', {'requested': 'R', 'lamps': {'R': {'main': False, 'aux': False}, 'Y1': {'main': False, 'aux': False}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': False, 'aux': False}}}, {'shown': 'DARK', 'alarm': True, 'degraded': True}), ('boundary: green on auxiliary filament', {'requested': 'G', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': False, 'aux': True}}}, {'shown': 'G', 'alarm': True, 'degraded': False}), ('boundary: red on auxiliary filament', {'requested': 'R', 'lamps': {'R': {'main': False, 'aux': True}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'R', 'alarm': True, 'degraded': False}), ('boundary: green lamp dead', {'requested': 'G', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': False, 'aux': False}}}, {'shown': 'YY', 'alarm': False, 'degraded': True}), ('control 1', {'requested': 'G', 'lamps': {'R': {'main': True, 'aux': False}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'G', 'alarm': False, 'degraded': False}), ('control 4', {'requested': 'G', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'G', 'alarm': False, 'degraded': False}), ('control 7', {'requested': 'R', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': True, 'aux': False}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'R', 'alarm': False, 'degraded': False})], [('regression: red lamp dead', {'requested': 'R', 'lamps': {'R': {'main': False, 'aux': False}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'DARK', 'alarm': True, 'degraded': True}), ('sampled regression 43', {'requested': 'R', 'lamps': {'R': {'main': False, 'aux': False}, 'Y1': {'main': False, 'aux': False}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': False, 'aux': False}}}, {'shown': 'DARK', 'alarm': True, 'degraded': True}), ('boundary: green lamp dead', {'requested': 'G', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': False, 'aux': False}}}, {'shown': 'YY', 'alarm': False, 'degraded': True}), ('boundary: lower yellow dead under double yellow', {'requested': 'YY', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': False, 'aux': False}, 'G': {'main': True, 'aux': True}}}, {'shown': 'Y', 'alarm': False, 'degraded': True}), ('boundary: upper yellow dead under double yellow', {'requested': 'YY', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': False, 'aux': False}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'R', 'alarm': False, 'degraded': True}), ('control 12', {'requested': 'YY', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': True, 'aux': False}, 'G': {'main': False, 'aux': True}}}, {'shown': 'YY', 'alarm': False, 'degraded': False}), ('control 15', {'requested': 'YY', 'lamps': {'R': {'main': True, 'aux': False}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': False, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'YY', 'alarm': True, 'degraded': False}), ('control 18', {'requested': 'Y', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': False, 'aux': True}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': False, 'aux': True}}}, {'shown': 'Y', 'alarm': True, 'degraded': False})], [('regression: red lamp dead', {'requested': 'R', 'lamps': {'R': {'main': False, 'aux': False}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'DARK', 'alarm': True, 'degraded': True}), ('sampled regression 70', {'requested': 'R', 'lamps': {'R': {'main': False, 'aux': False}, 'Y1': {'main': False, 'aux': True}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': True, 'aux': False}}}, {'shown': 'DARK', 'alarm': True, 'degraded': True}), ('boundary: upper yellow dead under double yellow', {'requested': 'YY', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': False, 'aux': False}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'R', 'alarm': False, 'degraded': True}), ('boundary: unused lamp on auxiliary', {'requested': 'Y', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': False, 'aux': True}}}, {'shown': 'Y', 'alarm': False, 'degraded': False}), ('boundary: second yellow on auxiliary', {'requested': 'YY', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': False, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'YY', 'alarm': True, 'degraded': False}), ('control 23', {'requested': 'Y', 'lamps': {'R': {'main': True, 'aux': False}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'Y', 'alarm': False, 'degraded': False}), ('control 26', {'requested': 'Y', 'lamps': {'R': {'main': True, 'aux': False}, 'Y1': {'main': True, 'aux': False}, 'Y2': {'main': True, 'aux': False}, 'G': {'main': True, 'aux': True}}}, {'shown': 'Y', 'alarm': False, 'degraded': False}), ('control 29', {'requested': 'R', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'R', 'alarm': False, 'degraded': False})], [('regression: red lamp dead', {'requested': 'R', 'lamps': {'R': {'main': False, 'aux': False}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'DARK', 'alarm': True, 'degraded': True}), ('sampled regression 43', {'requested': 'R', 'lamps': {'R': {'main': False, 'aux': False}, 'Y1': {'main': False, 'aux': False}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': False, 'aux': False}}}, {'shown': 'DARK', 'alarm': True, 'degraded': True}), ('boundary: unused lamp on auxiliary', {'requested': 'Y', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': False, 'aux': True}}}, {'shown': 'Y', 'alarm': False, 'degraded': False}), ('boundary: second yellow on auxiliary', {'requested': 'YY', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': False, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'YY', 'alarm': True, 'degraded': False}), ('boundary: all yellows dead', {'requested': 'YY', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': False, 'aux': False}, 'Y2': {'main': False, 'aux': False}, 'G': {'main': True, 'aux': True}}}, {'shown': 'R', 'alarm': False, 'degraded': True}), ('control 34', {'requested': 'R', 'lamps': {'R': {'main': False, 'aux': True}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': True, 'aux': False}, 'G': {'main': True, 'aux': True}}}, {'shown': 'R', 'alarm': True, 'degraded': False}), ('control 37', {'requested': 'R', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': False, 'aux': False}, 'Y2': {'main': False, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'R', 'alarm': False, 'degraded': False}), ('control 40', {'requested': 'YY', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': False, 'aux': False}}}, {'shown': 'YY', 'alarm': False, 'degraded': False})], [('regression: red lamp dead', {'requested': 'R', 'lamps': {'R': {'main': False, 'aux': False}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'DARK', 'alarm': True, 'degraded': True}), ('sampled regression 43', {'requested': 'R', 'lamps': {'R': {'main': False, 'aux': False}, 'Y1': {'main': False, 'aux': False}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': False, 'aux': False}}}, {'shown': 'DARK', 'alarm': True, 'degraded': True}), ('boundary: all yellows dead', {'requested': 'YY', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': False, 'aux': False}, 'Y2': {'main': False, 'aux': False}, 'G': {'main': True, 'aux': True}}}, {'shown': 'R', 'alarm': False, 'degraded': True}), ('boundary: green on auxiliary filament', {'requested': 'G', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': False, 'aux': True}}}, {'shown': 'G', 'alarm': True, 'degraded': False}), ('boundary: red on auxiliary filament', {'requested': 'R', 'lamps': {'R': {'main': False, 'aux': True}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'R', 'alarm': True, 'degraded': False}), ('control 45', {'requested': 'G', 'lamps': {'R': {'main': True, 'aux': True}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': True, 'aux': False}, 'G': {'main': True, 'aux': False}}}, {'shown': 'G', 'alarm': False, 'degraded': False}), ('control 48', {'requested': 'G', 'lamps': {'R': {'main': False, 'aux': False}, 'Y1': {'main': True, 'aux': True}, 'Y2': {'main': False, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'G', 'alarm': False, 'degraded': False}), ('control 51', {'requested': 'YY', 'lamps': {'R': {'main': False, 'aux': True}, 'Y1': {'main': True, 'aux': False}, 'Y2': {'main': True, 'aux': True}, 'G': {'main': True, 'aux': True}}}, {'shown': 'YY', 'alarm': False, 'degraded': False})]]
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: red lamp dead{'alarm': True, 'degraded': True, 'shown': 'DARK'}{'alarm': True, 'degraded': True, 'shown': 'DARK'}Passed
sampled regression 43{'alarm': True, 'degraded': True, 'shown': 'DARK'}{'alarm': True, 'degraded': True, 'shown': 'DARK'}Passed
boundary: green on auxiliary filament{'alarm': True, 'degraded': False, 'shown': 'G'}{'alarm': True, 'degraded': False, 'shown': 'G'}Passed
boundary: red on auxiliary filament{'alarm': True, 'degraded': False, 'shown': 'R'}{'alarm': True, 'degraded': False, 'shown': 'R'}Passed
boundary: green lamp dead{'alarm': False, 'degraded': True, 'shown': 'YY'}{'alarm': False, 'degraded': True, 'shown': 'YY'}Passed
control 1{'alarm': False, 'degraded': False, 'shown': 'G'}{'alarm': False, 'degraded': False, 'shown': 'G'}Passed
control 4{'alarm': False, 'degraded': False, 'shown': 'G'}{'alarm': False, 'degraded': False, 'shown': 'G'}Passed
control 7{'alarm': False, 'degraded': False, 'shown': 'R'}{'alarm': False, 'degraded': False, 'shown': 'R'}Passed

SHA-256 / 99aedc0d7cfc64f67a42c9f8d764a5d190f335c26e75f955e1ffaf1e795dc4e8

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 2026-09-29T14:47:50.456282+00:00.

Case digest / 99affcf0579047fa499df104dae4785b8677b6937bc2ecfbea4d023a5329ae1c