FA-83111 / Go territory scoring / Open access

Off-board diagonals count as opponent stones · case 01

Every corner eye is reported false.

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

ROOT CAUSE

Off-board diagonals are counted as bad and as on-board diagonals.

THE FAILURE

Off-board diagonals are counted as bad and as on-board diagonals.

Unsuccessful approach: Keeping the edge limit but still counting off-board diagonals as bad marks edge eyes false.

Case contract

Input [board, row, col]. A point is an eye candidate of colour X if it is empty and every on-board orthogonal neighbour is X. It is false if opponent stones occupy >= 2 diagonals in the centre, or >= 1 diagonal on the edge/corner. Return "eye-X", "false-X" or "none".

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):
    board, r, c = x
    n = len(board)
    m = len(board[0])
    if board[r][c] != '.':
        return 'none'
    orth = []
    for p, q in ((r - 1, c), (r + 1, c), (r, c - 1), (r, c + 1)):
        if 0 <= p < n and 0 <= q < m:
            orth.append(board[p][q])
    if not orth or orth.count(orth[0]) != len(orth) or orth[0] == '.':
        return 'none'
    col = orth[0]
    opp = 'W' if col == 'B' else 'B'
    bad = 0
    ondiag = 0
    for p, q in ((r - 1, c - 1), (r - 1, c + 1), (r + 1, c - 1), (r + 1, c + 1)):
        if not (0 <= p < n and 0 <= q < m) or board[p][q] == opp:
            bad += 1
        ondiag += 1
    limit = 2 if ondiag == 4 else 1
    if bad >= limit:
        return 'false-' + col
    return 'eye-' + col
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[[[['...', '...', '...'], 0, 1], 'none'], [[['...', '...', '...'], 0, 2], 'none'], [[['...', '...', '...'], 1, 0], 'none'], [[['...', '...', '...'], 1, 1], 'none'], [[['...', '...', '...'], 1, 2], 'none'], [[['.B.', 'B.B', '.B.'], 0, 0], 'eye-B'], [[['.B.', 'B.B', '.B.'], 0, 2], 'eye-B'], [[['.W.B.', 'W.WB.', '.WB..', 'WB...', 'B....'], 0, 0], 'eye-W']], [[[['.B.', 'B.B', '.B.'], 1, 1], 'eye-B'], [[['.B.', 'B.B', '.B.'], 2, 0], 'eye-B'], [[['.B.', 'B.B', '.B.'], 2, 2], 'eye-B'], [[['.B.', 'B.B', '.B.'], 0, 1], 'none'], [[['B..W', 'B..W', 'B..W', 'B..W'], 0, 1], 'none'], [[['B..W', 'B..W', 'B..W', 'B..W'], 0, 2], 'none'], [[['B..W', 'B..W', 'B..W', 'B..W'], 1, 1], 'none'], [[['WBW', '..W', '.WW', '.W.'], 3, 2], 'eye-W']], [[[['B..W', 'B..W', 'B..W', 'B..W'], 1, 2], 'none'], [[['B..W', 'B..W', 'B..W', 'B..W'], 2, 1], 'none'], [[['B..W', 'B..W', 'B..W', 'B..W'], 2, 2], 'none'], [[['B..W', 'B..W', 'B..W', 'B..W'], 0, 0], 'none'], [[['.BW.', '.BW.', '.BW.', '.BW.'], 0, 0], 'none'], [[['.BW.', '.BW.', '.BW.', '.BW.'], 0, 3], 'none'], [[['.W.B.', 'W.WB.', '.WB..', 'WB...', 'B....'], 0, 0], 'eye-W'], [[['.W.', 'W.B', '...'], 0, 0], 'eye-W']], [[[['.BW.', '.BW.', '.BW.', '.BW.'], 1, 3], 'none'], [[['.BW.', '.BW.', '.BW.', '.BW.'], 2, 0], 'none'], [[['.BW.', '.BW.', '.BW.', '.BW.'], 2, 3], 'none'], [[['.BW.', '.BW.', '.BW.', '.BW.'], 0, 1], 'none'], [[['..B..', '..B..', 'BBBBB', 'WWWWW', '..W..'], 0, 0], 'none'], [[['..B..', '..B..', 'BBBBB', 'WWWWW', '..W..'], 0, 1], 'none'], [[['WB.B', 'B.B.', '.B..', 'B...'], 2, 0], 'eye-B'], [[['B.B', '.B.', '...'], 0, 1], 'eye-B']], [[[['..B..', '..B..', 'BBBBB', 'WWWWW', '..W..'], 0, 4], 'none'], [[['..B..', '..B..', 'BBBBB', 'WWWWW', '..W..'], 1, 0], 'none'], [[['..B..', '..B..', 'BBBBB', 'WWWWW', '..W..'], 1, 1], 'none'], [[['..B..', '..B..', 'BBBBB', 'WWWWW', '..W..'], 0, 2], 'none'], [[['B.B.W', '.B.W.', 'B.BW.', 'BBW.W', '..W..'], 0, 1], 'eye-B'], [[['B.B.W', '.B.W.', 'B.BW.', 'BBW.W', '..W..'], 0, 3], 'none'], [[['WW.', '.WW', 'B.B', 'WB.', '..W'], 0, 2], 'eye-W'], [[['W.W', '.W.', 'W.W'], 1, 2], 'eye-W']]]
for i, (args, expected) in enumerate(fixtures[N-1]):
    check("eye 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 fixture	Actual	Expected	Outcome
eye case 0	`none`	`none`	Passed
eye case 1	`none`	`none`	Passed
eye case 2	`none`	`none`	Passed
eye case 3	`none`	`none`	Passed
eye case 4	`none`	`none`	Passed
eye case 5	`false-B`	`eye-B`	Failed
eye case 6	`false-B`	`eye-B`	Failed
eye case 7	`false-W`	`eye-W`	Failed

SHA-256 / 3df501a1b86e45a947e50a63b8e029d6f7b653ef4e113646b2cfe9804c328005

2 / The unsuccessful fix

Exit 1

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

N = 1
observations = []
def solve(x):
    board, r, c = x
    n = len(board)
    m = len(board[0])
    if board[r][c] != '.':
        return 'none'
    orth = []
    for p, q in ((r - 1, c), (r + 1, c), (r, c - 1), (r, c + 1)):
        if 0 <= p < n and 0 <= q < m:
            orth.append(board[p][q])
    if not orth or orth.count(orth[0]) != len(orth) or orth[0] == '.':
        return 'none'
    col = orth[0]
    opp = 'W' if col == 'B' else 'B'
    bad = 0
    ondiag = 0
    for p, q in ((r - 1, c - 1), (r - 1, c + 1), (r + 1, c - 1), (r + 1, c + 1)):
        if not (0 <= p < n and 0 <= q < m):
            bad += 1
        else:
            ondiag += 1
            if board[p][q] == opp:
                bad += 1
    limit = 2 if ondiag == 4 else 1
    if bad >= limit:
        return 'false-' + col
    return 'eye-' + col
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[[[['...', '...', '...'], 0, 1], 'none'], [[['...', '...', '...'], 0, 2], 'none'], [[['...', '...', '...'], 1, 0], 'none'], [[['...', '...', '...'], 1, 1], 'none'], [[['...', '...', '...'], 1, 2], 'none'], [[['.B.', 'B.B', '.B.'], 0, 0], 'eye-B'], [[['.B.', 'B.B', '.B.'], 0, 2], 'eye-B'], [[['.W.B.', 'W.WB.', '.WB..', 'WB...', 'B....'], 0, 0], 'eye-W']], [[[['.B.', 'B.B', '.B.'], 1, 1], 'eye-B'], [[['.B.', 'B.B', '.B.'], 2, 0], 'eye-B'], [[['.B.', 'B.B', '.B.'], 2, 2], 'eye-B'], [[['.B.', 'B.B', '.B.'], 0, 1], 'none'], [[['B..W', 'B..W', 'B..W', 'B..W'], 0, 1], 'none'], [[['B..W', 'B..W', 'B..W', 'B..W'], 0, 2], 'none'], [[['B..W', 'B..W', 'B..W', 'B..W'], 1, 1], 'none'], [[['WBW', '..W', '.WW', '.W.'], 3, 2], 'eye-W']], [[[['B..W', 'B..W', 'B..W', 'B..W'], 1, 2], 'none'], [[['B..W', 'B..W', 'B..W', 'B..W'], 2, 1], 'none'], [[['B..W', 'B..W', 'B..W', 'B..W'], 2, 2], 'none'], [[['B..W', 'B..W', 'B..W', 'B..W'], 0, 0], 'none'], [[['.BW.', '.BW.', '.BW.', '.BW.'], 0, 0], 'none'], [[['.BW.', '.BW.', '.BW.', '.BW.'], 0, 3], 'none'], [[['.W.B.', 'W.WB.', '.WB..', 'WB...', 'B....'], 0, 0], 'eye-W'], [[['.W.', 'W.B', '...'], 0, 0], 'eye-W']], [[[['.BW.', '.BW.', '.BW.', '.BW.'], 1, 3], 'none'], [[['.BW.', '.BW.', '.BW.', '.BW.'], 2, 0], 'none'], [[['.BW.', '.BW.', '.BW.', '.BW.'], 2, 3], 'none'], [[['.BW.', '.BW.', '.BW.', '.BW.'], 0, 1], 'none'], [[['..B..', '..B..', 'BBBBB', 'WWWWW', '..W..'], 0, 0], 'none'], [[['..B..', '..B..', 'BBBBB', 'WWWWW', '..W..'], 0, 1], 'none'], [[['WB.B', 'B.B.', '.B..', 'B...'], 2, 0], 'eye-B'], [[['B.B', '.B.', '...'], 0, 1], 'eye-B']], [[[['..B..', '..B..', 'BBBBB', 'WWWWW', '..W..'], 0, 4], 'none'], [[['..B..', '..B..', 'BBBBB', 'WWWWW', '..W..'], 1, 0], 'none'], [[['..B..', '..B..', 'BBBBB', 'WWWWW', '..W..'], 1, 1], 'none'], [[['..B..', '..B..', 'BBBBB', 'WWWWW', '..W..'], 0, 2], 'none'], [[['B.B.W', '.B.W.', 'B.BW.', 'BBW.W', '..W..'], 0, 1], 'eye-B'], [[['B.B.W', '.B.W.', 'B.BW.', 'BBW.W', '..W..'], 0, 3], 'none'], [[['WW.', '.WW', 'B.B', 'WB.', '..W'], 0, 2], 'eye-W'], [[['W.W', '.W.', 'W.W'], 1, 2], 'eye-W']]]
for i, (args, expected) in enumerate(fixtures[N-1]):
    check("eye 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 fixture	Actual	Expected	Outcome
eye case 0	`none`	`none`	Passed
eye case 1	`none`	`none`	Passed
eye case 2	`none`	`none`	Passed
eye case 3	`none`	`none`	Passed
eye case 4	`none`	`none`	Passed
eye case 5	`false-B`	`eye-B`	Failed
eye case 6	`false-B`	`eye-B`	Failed
eye case 7	`false-W`	`eye-W`	Failed

SHA-256 / 55aea66011fc8e1db0a79d814b775fb1f4250177c15057df671c4136e206ece1

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

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 2026-09-29T14:50:18.700387+00:00.

Case digest / d5e5d39c3f01e6ab76d7bd6ac828b8f791ec17c63cf8f30580c172133160b943