FAILURE MAP
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FA-83171 / Go territory scoring / Open access

One extra black point is worth one point of margin instead of two · case 01

The margin is half of the true difference between black and white areas.

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

ROOT CAUSE

The margin compares black with half of the board rather than with white area.

VERIFIED REPAIR

margin = 10*(2*black - total) - komi.

Unsuccessful approach: Halving komi keeps the doubling but compares against the wrong compensation.

Case contract

Input [size, black_area, komi_tenths] for a board with no dame. White area is size^2 - black_area. Return [margin_tenths, winner] where margin = 10*(black - white) - komi and winner is B, W or draw.

Why this case matters

Go servers and scoring tools compute this value automatically; a wrong answer changes a game result.

1 / The failure

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

N = 1
observations = []
def solve(x):
    size, black, komi = x
    total = size * size
    margin = 10 * black - 5 * total - komi
    if margin > 0:
        return [margin, 'B']
    if margin < 0:
        return [margin, 'W']
    return [0, 'draw']
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[[[9, 13, 65], [-615, 'W']], [[9, 3, 5], [-755, 'W']], [[9, 53, 75], [175, 'B']], [[9, 74, 0], [670, 'B']], [[9, 64, 0], [470, 'B']], [[9, 12, 65], [-635, 'W']], [[9, 27, 75], [-345, 'W']], [[9, 6, 0], [-690, 'W']]], [[[9, 80, 70], [720, 'B']], [[9, 3, 5], [-755, 'W']], [[9, 4, 0], [-730, 'W']], [[9, 69, 65], [505, 'B']], [[9, 35, 70], [-180, 'W']], [[9, 21, 75], [-465, 'W']], [[13, 30, 70], [-1160, 'W']], [[13, 163, 5], [1565, 'B']]], [[[9, 72, 5], [625, 'B']], [[13, 163, 5], [1565, 'B']], [[13, 111, 5], [525, 'B']], [[13, 13, 5], [-1435, 'W']], [[13, 7, 70], [-1620, 'W']], [[13, 46, 75], [-845, 'W']], [[13, 56, 75], [-645, 'W']], [[13, 167, 0], [1650, 'B']]], [[[9, 53, 75], [175, 'B']], [[13, 46, 75], [-845, 'W']], [[13, 130, 5], [905, 'B']], [[13, 39, 65], [-975, 'W']], [[13, 76, 65], [-235, 'W']], [[13, 132, 65], [885, 'B']], [[13, 27, 75], [-1225, 'W']], [[13, 107, 65], [385, 'B']]], [[[9, 12, 65], [-635, 'W']], [[13, 76, 65], [-235, 'W']], [[13, 137, 0], [1050, 'B']], [[13, 9, 65], [-1575, 'W']], [[13, 114, 65], [525, 'B']], [[19, 309, 0], [2570, 'B']], [[19, 303, 75], [2375, 'B']], [[19, 77, 5], [-2075, 'W']]]]
for i, (args, expected) in enumerate(fixtures[N-1]):
    check("black count case %d" % i, 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
black count case 0[-340, 'W'][-615, 'W']Failed
black count case 1[-380, 'W'][-755, 'W']Failed
black count case 2[50, 'B'][175, 'B']Failed
black count case 3[335, 'B'][670, 'B']Failed
black count case 4[235, 'B'][470, 'B']Failed
black count case 5[-350, 'W'][-635, 'W']Failed
black count case 6[-210, 'W'][-345, 'W']Failed
black count case 7[-345, 'W'][-690, 'W']Failed

SHA-256 / d5211472dc14e53904ca1f8d523fd135ba8eadaf78b31b1b91a1b3a610526398

2 / The unsuccessful fix

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

N = 1
observations = []
def solve(x):
    size, black, komi = x
    total = size * size
    margin = 20 * black - 10 * total - komi // 2
    if margin > 0:
        return [margin, 'B']
    if margin < 0:
        return [margin, 'W']
    return [0, 'draw']
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[[[9, 13, 65], [-615, 'W']], [[9, 3, 5], [-755, 'W']], [[9, 53, 75], [175, 'B']], [[9, 74, 0], [670, 'B']], [[9, 64, 0], [470, 'B']], [[9, 12, 65], [-635, 'W']], [[9, 27, 75], [-345, 'W']], [[9, 6, 0], [-690, 'W']]], [[[9, 80, 70], [720, 'B']], [[9, 3, 5], [-755, 'W']], [[9, 4, 0], [-730, 'W']], [[9, 69, 65], [505, 'B']], [[9, 35, 70], [-180, 'W']], [[9, 21, 75], [-465, 'W']], [[13, 30, 70], [-1160, 'W']], [[13, 163, 5], [1565, 'B']]], [[[9, 72, 5], [625, 'B']], [[13, 163, 5], [1565, 'B']], [[13, 111, 5], [525, 'B']], [[13, 13, 5], [-1435, 'W']], [[13, 7, 70], [-1620, 'W']], [[13, 46, 75], [-845, 'W']], [[13, 56, 75], [-645, 'W']], [[13, 167, 0], [1650, 'B']]], [[[9, 53, 75], [175, 'B']], [[13, 46, 75], [-845, 'W']], [[13, 130, 5], [905, 'B']], [[13, 39, 65], [-975, 'W']], [[13, 76, 65], [-235, 'W']], [[13, 132, 65], [885, 'B']], [[13, 27, 75], [-1225, 'W']], [[13, 107, 65], [385, 'B']]], [[[9, 12, 65], [-635, 'W']], [[13, 76, 65], [-235, 'W']], [[13, 137, 0], [1050, 'B']], [[13, 9, 65], [-1575, 'W']], [[13, 114, 65], [525, 'B']], [[19, 309, 0], [2570, 'B']], [[19, 303, 75], [2375, 'B']], [[19, 77, 5], [-2075, 'W']]]]
for i, (args, expected) in enumerate(fixtures[N-1]):
    check("black count case %d" % i, 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
black count case 0[-582, 'W'][-615, 'W']Failed
black count case 1[-752, 'W'][-755, 'W']Failed
black count case 2[213, 'B'][175, 'B']Failed
black count case 3[670, 'B'][670, 'B']Passed
black count case 4[470, 'B'][470, 'B']Passed
black count case 5[-602, 'W'][-635, 'W']Failed
black count case 6[-307, 'W'][-345, 'W']Failed
black count case 7[-690, 'W'][-690, 'W']Passed

SHA-256 / 1c087736b20a8fa5b9173c07469031c94a68ccdc4d35b9a88dba683fc7891d8e

3 / The verified repair

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

N = 1
observations = []
def solve(x):
    size, black, komi = x
    total = size * size
    margin = 20 * black - 10 * total - komi
    if margin > 0:
        return [margin, 'B']
    if margin < 0:
        return [margin, 'W']
    return [0, 'draw']
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[[[9, 13, 65], [-615, 'W']], [[9, 3, 5], [-755, 'W']], [[9, 53, 75], [175, 'B']], [[9, 74, 0], [670, 'B']], [[9, 64, 0], [470, 'B']], [[9, 12, 65], [-635, 'W']], [[9, 27, 75], [-345, 'W']], [[9, 6, 0], [-690, 'W']]], [[[9, 80, 70], [720, 'B']], [[9, 3, 5], [-755, 'W']], [[9, 4, 0], [-730, 'W']], [[9, 69, 65], [505, 'B']], [[9, 35, 70], [-180, 'W']], [[9, 21, 75], [-465, 'W']], [[13, 30, 70], [-1160, 'W']], [[13, 163, 5], [1565, 'B']]], [[[9, 72, 5], [625, 'B']], [[13, 163, 5], [1565, 'B']], [[13, 111, 5], [525, 'B']], [[13, 13, 5], [-1435, 'W']], [[13, 7, 70], [-1620, 'W']], [[13, 46, 75], [-845, 'W']], [[13, 56, 75], [-645, 'W']], [[13, 167, 0], [1650, 'B']]], [[[9, 53, 75], [175, 'B']], [[13, 46, 75], [-845, 'W']], [[13, 130, 5], [905, 'B']], [[13, 39, 65], [-975, 'W']], [[13, 76, 65], [-235, 'W']], [[13, 132, 65], [885, 'B']], [[13, 27, 75], [-1225, 'W']], [[13, 107, 65], [385, 'B']]], [[[9, 12, 65], [-635, 'W']], [[13, 76, 65], [-235, 'W']], [[13, 137, 0], [1050, 'B']], [[13, 9, 65], [-1575, 'W']], [[13, 114, 65], [525, 'B']], [[19, 309, 0], [2570, 'B']], [[19, 303, 75], [2375, 'B']], [[19, 77, 5], [-2075, 'W']]]]
for i, (args, expected) in enumerate(fixtures[N-1]):
    check("black count case %d" % i, 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
black count case 0[-615, 'W'][-615, 'W']Passed
black count case 1[-755, 'W'][-755, 'W']Passed
black count case 2[175, 'B'][175, 'B']Passed
black count case 3[670, 'B'][670, 'B']Passed
black count case 4[470, 'B'][470, 'B']Passed
black count case 5[-635, 'W'][-635, 'W']Passed
black count case 6[-345, 'W'][-345, 'W']Passed
black count case 7[-690, 'W'][-690, 'W']Passed

SHA-256 / 9bc062ab676c86736710969c61713d81c69e21d6da142f1b87749eb4bdeee5fe

Verification & scope

Small rectangular toy boards given as strings of B, W and dot; a bounded teaching model of one scoring or bookkeeping rule, not a complete rules engine or server implementation. 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 2026-09-29T14:50:19.189564+00:00.

Case digest / b4edfe08fb469ab9223dcbdb308da5aa49d8926a82ddaee42b9ac3c6a13a8b73