FA-83061 / Go territory scoring / Open access

The equalising stone is credited to white · case 01

Black-last games give white an extra prisoner.

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

ROOT CAUSE

The final-pass correction increments white prisoners.

VERIFIED REPAIR

When black passed last, white hands black one stone.

Unsuccessful approach: Triggering the correction on a white final pass inverts when the stone is due.

Case contract

Input [terr_b, terr_w, prisoners_b, prisoners_w, passes, komi_tenths]; passes lists passing colours in order. Each pass gives one prisoner to the opponent; if the final pass was black, white hands one extra stone to black. Return [black_tenths, white_tenths, winner] with winner B, W or tie.

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):
    tb, tw, cb, cw, passes, komi = x
    pb = cb + passes.count('W')
    pw = cw + passes.count('B')
    if passes and passes[-1] == 'B':
        pw += 1
    sb = (tb + pb) * 10
    sw = (tw + pw) * 10 + komi
    if sb > sw:
        winner = 'B'
    elif sw > sb:
        winner = 'W'
    else:
        winner = 'tie'
    return [sb, sw, winner]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[[[11, 24, 5, 1, ['B'], 75], [170, 335, 'W']], [[12, 29, 2, 1, ['B'], 75], [150, 385, 'W']], [[9, 19, 1, 1, ['W'], 5], [110, 205, 'W']], [[19, 16, 2, 4, ['B'], 75], [220, 285, 'W']], [[28, 11, 4, 3, ['B', 'W', 'W', 'B'], 0], [350, 160, 'B']], [[5, 17, 2, 2, [], 5], [70, 195, 'W']], [[16, 18, 1, 5, ['B'], 5], [180, 245, 'W']], [[22, 11, 2, 4, ['B', 'B'], 75], [250, 245, 'B']]], [[[15, 19, 1, 0, ['W', 'B'], 70], [180, 270, 'W']], [[28, 11, 4, 3, ['B', 'W', 'W', 'B'], 0], [350, 160, 'B']], [[28, 12, 2, 1, ['B', 'W'], 75], [310, 215, 'B']], [[9, 10, 4, 5, ['W', 'W', 'B', 'W'], 70], [160, 230, 'W']], [[19, 26, 4, 1, ['W'], 0], [240, 270, 'W']], [[25, 8, 5, 0, ['W', 'W', 'W', 'B'], 70], [340, 160, 'B']], [[15, 27, 0, 4, ['B', 'W'], 0], [160, 320, 'W']], [[27, 20, 5, 1, ['B'], 70], [330, 290, 'B']]], [[[15, 14, 3, 3, ['B', 'B', 'W', 'B'], 70], [200, 270, 'W']], [[9, 10, 4, 5, ['W', 'W', 'B', 'W'], 70], [160, 230, 'W']], [[23, 20, 1, 3, ['W', 'W'], 75], [260, 305, 'W']], [[9, 14, 1, 0, ['B', 'B', 'B', 'B'], 70], [110, 250, 'W']], [[27, 17, 0, 5, ['B'], 0], [280, 230, 'B']], [[18, 4, 0, 3, [], 5], [180, 75, 'B']], [[7, 19, 2, 1, ['W', 'B'], 70], [110, 280, 'W']], [[20, 13, 2, 0, ['B', 'B', 'W', 'W'], 70], [240, 220, 'B']]], [[[16, 18, 1, 5, ['B'], 5], [180, 245, 'W']], [[24, 3, 3, 2, ['W', 'W'], 0], [290, 50, 'B']], [[20, 18, 4, 4, ['B', 'W', 'B', 'B'], 75], [260, 325, 'W']], [[26, 10, 1, 0, ['W', 'W'], 5], [290, 105, 'B']], [[1, 17, 1, 2, ['B', 'W', 'W'], 5], [40, 205, 'W']], [[12, 11, 3, 5, ['W', 'B', 'B', 'B'], 70], [170, 260, 'W']], [[12, 19, 1, 1, ['B'], 5], [140, 215, 'W']], [[18, 1, 5, 2, [], 0], [230, 30, 'B']]], [[[25, 8, 5, 0, ['W', 'W', 'W', 'B'], 70], [340, 160, 'B']], [[20, 13, 2, 0, ['B', 'B', 'W', 'W'], 70], [240, 220, 'B']], [[25, 22, 0, 4, ['B', 'B', 'B'], 70], [260, 360, 'W']], [[29, 1, 0, 1, ['B', 'W'], 5], [300, 35, 'B']], [[23, 0, 0, 3, ['W', 'W'], 70], [250, 100, 'B']], [[28, 1, 0, 2, ['B'], 5], [290, 45, 'B']], [[24, 22, 2, 4, ['W', 'B'], 70], [280, 340, 'W']], [[0, 22, 1, 3, ['B'], 75], [20, 335, 'W']]]]
for i, (args, expected) in enumerate(fixtures[N-1]):
    check("pass stones 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
pass stones case 0	`[160, 345, 'W']`	`[170, 335, 'W']`	Failed
pass stones case 1	`[140, 395, 'W']`	`[150, 385, 'W']`	Failed
pass stones case 2	`[110, 205, 'W']`	`[110, 205, 'W']`	Passed
pass stones case 3	`[210, 295, 'W']`	`[220, 285, 'W']`	Failed
pass stones case 4	`[340, 170, 'B']`	`[350, 160, 'B']`	Failed
pass stones case 5	`[70, 195, 'W']`	`[70, 195, 'W']`	Passed
pass stones case 6	`[170, 255, 'W']`	`[180, 245, 'W']`	Failed
pass stones case 7	`[240, 255, 'W']`	`[250, 245, 'B']`	Failed

SHA-256 / bcea9c5271be40ca07423f8a2021f4188c06a1f9f3e3e87432176f2bf296623b

2 / The unsuccessful fix

Exit 1

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

N = 1
observations = []
def solve(x):
    tb, tw, cb, cw, passes, komi = x
    pb = cb + passes.count('W')
    pw = cw + passes.count('B')
    if passes and passes[-1] == 'W':
        pb += 1
    sb = (tb + pb) * 10
    sw = (tw + pw) * 10 + komi
    if sb > sw:
        winner = 'B'
    elif sw > sb:
        winner = 'W'
    else:
        winner = 'tie'
    return [sb, sw, winner]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[[[11, 24, 5, 1, ['B'], 75], [170, 335, 'W']], [[12, 29, 2, 1, ['B'], 75], [150, 385, 'W']], [[9, 19, 1, 1, ['W'], 5], [110, 205, 'W']], [[19, 16, 2, 4, ['B'], 75], [220, 285, 'W']], [[28, 11, 4, 3, ['B', 'W', 'W', 'B'], 0], [350, 160, 'B']], [[5, 17, 2, 2, [], 5], [70, 195, 'W']], [[16, 18, 1, 5, ['B'], 5], [180, 245, 'W']], [[22, 11, 2, 4, ['B', 'B'], 75], [250, 245, 'B']]], [[[15, 19, 1, 0, ['W', 'B'], 70], [180, 270, 'W']], [[28, 11, 4, 3, ['B', 'W', 'W', 'B'], 0], [350, 160, 'B']], [[28, 12, 2, 1, ['B', 'W'], 75], [310, 215, 'B']], [[9, 10, 4, 5, ['W', 'W', 'B', 'W'], 70], [160, 230, 'W']], [[19, 26, 4, 1, ['W'], 0], [240, 270, 'W']], [[25, 8, 5, 0, ['W', 'W', 'W', 'B'], 70], [340, 160, 'B']], [[15, 27, 0, 4, ['B', 'W'], 0], [160, 320, 'W']], [[27, 20, 5, 1, ['B'], 70], [330, 290, 'B']]], [[[15, 14, 3, 3, ['B', 'B', 'W', 'B'], 70], [200, 270, 'W']], [[9, 10, 4, 5, ['W', 'W', 'B', 'W'], 70], [160, 230, 'W']], [[23, 20, 1, 3, ['W', 'W'], 75], [260, 305, 'W']], [[9, 14, 1, 0, ['B', 'B', 'B', 'B'], 70], [110, 250, 'W']], [[27, 17, 0, 5, ['B'], 0], [280, 230, 'B']], [[18, 4, 0, 3, [], 5], [180, 75, 'B']], [[7, 19, 2, 1, ['W', 'B'], 70], [110, 280, 'W']], [[20, 13, 2, 0, ['B', 'B', 'W', 'W'], 70], [240, 220, 'B']]], [[[16, 18, 1, 5, ['B'], 5], [180, 245, 'W']], [[24, 3, 3, 2, ['W', 'W'], 0], [290, 50, 'B']], [[20, 18, 4, 4, ['B', 'W', 'B', 'B'], 75], [260, 325, 'W']], [[26, 10, 1, 0, ['W', 'W'], 5], [290, 105, 'B']], [[1, 17, 1, 2, ['B', 'W', 'W'], 5], [40, 205, 'W']], [[12, 11, 3, 5, ['W', 'B', 'B', 'B'], 70], [170, 260, 'W']], [[12, 19, 1, 1, ['B'], 5], [140, 215, 'W']], [[18, 1, 5, 2, [], 0], [230, 30, 'B']]], [[[25, 8, 5, 0, ['W', 'W', 'W', 'B'], 70], [340, 160, 'B']], [[20, 13, 2, 0, ['B', 'B', 'W', 'W'], 70], [240, 220, 'B']], [[25, 22, 0, 4, ['B', 'B', 'B'], 70], [260, 360, 'W']], [[29, 1, 0, 1, ['B', 'W'], 5], [300, 35, 'B']], [[23, 0, 0, 3, ['W', 'W'], 70], [250, 100, 'B']], [[28, 1, 0, 2, ['B'], 5], [290, 45, 'B']], [[24, 22, 2, 4, ['W', 'B'], 70], [280, 340, 'W']], [[0, 22, 1, 3, ['B'], 75], [20, 335, 'W']]]]
for i, (args, expected) in enumerate(fixtures[N-1]):
    check("pass stones 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
pass stones case 0	`[160, 335, 'W']`	`[170, 335, 'W']`	Failed
pass stones case 1	`[140, 385, 'W']`	`[150, 385, 'W']`	Failed
pass stones case 2	`[120, 205, 'W']`	`[110, 205, 'W']`	Failed
pass stones case 3	`[210, 285, 'W']`	`[220, 285, 'W']`	Failed
pass stones case 4	`[340, 160, 'B']`	`[350, 160, 'B']`	Failed
pass stones case 5	`[70, 195, 'W']`	`[70, 195, 'W']`	Passed
pass stones case 6	`[170, 245, 'W']`	`[180, 245, 'W']`	Failed
pass stones case 7	`[240, 245, 'W']`	`[250, 245, 'B']`	Failed

SHA-256 / 18e13fa3a963c5378e6a9d2d7020e124e6f628daad52e2cdd500f804cefdce37

3 / The verified repair

Exit 0

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

N = 1
observations = []
def solve(x):
    tb, tw, cb, cw, passes, komi = x
    pb = cb + passes.count('W')
    pw = cw + passes.count('B')
    if passes and passes[-1] == 'B':
        pb += 1
    sb = (tb + pb) * 10
    sw = (tw + pw) * 10 + komi
    if sb > sw:
        winner = 'B'
    elif sw > sb:
        winner = 'W'
    else:
        winner = 'tie'
    return [sb, sw, winner]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[[[11, 24, 5, 1, ['B'], 75], [170, 335, 'W']], [[12, 29, 2, 1, ['B'], 75], [150, 385, 'W']], [[9, 19, 1, 1, ['W'], 5], [110, 205, 'W']], [[19, 16, 2, 4, ['B'], 75], [220, 285, 'W']], [[28, 11, 4, 3, ['B', 'W', 'W', 'B'], 0], [350, 160, 'B']], [[5, 17, 2, 2, [], 5], [70, 195, 'W']], [[16, 18, 1, 5, ['B'], 5], [180, 245, 'W']], [[22, 11, 2, 4, ['B', 'B'], 75], [250, 245, 'B']]], [[[15, 19, 1, 0, ['W', 'B'], 70], [180, 270, 'W']], [[28, 11, 4, 3, ['B', 'W', 'W', 'B'], 0], [350, 160, 'B']], [[28, 12, 2, 1, ['B', 'W'], 75], [310, 215, 'B']], [[9, 10, 4, 5, ['W', 'W', 'B', 'W'], 70], [160, 230, 'W']], [[19, 26, 4, 1, ['W'], 0], [240, 270, 'W']], [[25, 8, 5, 0, ['W', 'W', 'W', 'B'], 70], [340, 160, 'B']], [[15, 27, 0, 4, ['B', 'W'], 0], [160, 320, 'W']], [[27, 20, 5, 1, ['B'], 70], [330, 290, 'B']]], [[[15, 14, 3, 3, ['B', 'B', 'W', 'B'], 70], [200, 270, 'W']], [[9, 10, 4, 5, ['W', 'W', 'B', 'W'], 70], [160, 230, 'W']], [[23, 20, 1, 3, ['W', 'W'], 75], [260, 305, 'W']], [[9, 14, 1, 0, ['B', 'B', 'B', 'B'], 70], [110, 250, 'W']], [[27, 17, 0, 5, ['B'], 0], [280, 230, 'B']], [[18, 4, 0, 3, [], 5], [180, 75, 'B']], [[7, 19, 2, 1, ['W', 'B'], 70], [110, 280, 'W']], [[20, 13, 2, 0, ['B', 'B', 'W', 'W'], 70], [240, 220, 'B']]], [[[16, 18, 1, 5, ['B'], 5], [180, 245, 'W']], [[24, 3, 3, 2, ['W', 'W'], 0], [290, 50, 'B']], [[20, 18, 4, 4, ['B', 'W', 'B', 'B'], 75], [260, 325, 'W']], [[26, 10, 1, 0, ['W', 'W'], 5], [290, 105, 'B']], [[1, 17, 1, 2, ['B', 'W', 'W'], 5], [40, 205, 'W']], [[12, 11, 3, 5, ['W', 'B', 'B', 'B'], 70], [170, 260, 'W']], [[12, 19, 1, 1, ['B'], 5], [140, 215, 'W']], [[18, 1, 5, 2, [], 0], [230, 30, 'B']]], [[[25, 8, 5, 0, ['W', 'W', 'W', 'B'], 70], [340, 160, 'B']], [[20, 13, 2, 0, ['B', 'B', 'W', 'W'], 70], [240, 220, 'B']], [[25, 22, 0, 4, ['B', 'B', 'B'], 70], [260, 360, 'W']], [[29, 1, 0, 1, ['B', 'W'], 5], [300, 35, 'B']], [[23, 0, 0, 3, ['W', 'W'], 70], [250, 100, 'B']], [[28, 1, 0, 2, ['B'], 5], [290, 45, 'B']], [[24, 22, 2, 4, ['W', 'B'], 70], [280, 340, 'W']], [[0, 22, 1, 3, ['B'], 75], [20, 335, 'W']]]]
for i, (args, expected) in enumerate(fixtures[N-1]):
    check("pass stones 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
pass stones case 0	`[170, 335, 'W']`	`[170, 335, 'W']`	Passed
pass stones case 1	`[150, 385, 'W']`	`[150, 385, 'W']`	Passed
pass stones case 2	`[110, 205, 'W']`	`[110, 205, 'W']`	Passed
pass stones case 3	`[220, 285, 'W']`	`[220, 285, 'W']`	Passed
pass stones case 4	`[350, 160, 'B']`	`[350, 160, 'B']`	Passed
pass stones case 5	`[70, 195, 'W']`	`[70, 195, 'W']`	Passed
pass stones case 6	`[180, 245, 'W']`	`[180, 245, 'W']`	Passed
pass stones case 7	`[250, 245, 'B']`	`[250, 245, 'B']`	Passed

SHA-256 / 689bf512e98b8ebeb45e593bf0733c26f5c7255ada1a69a60a3734aa747f9bdd

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 2026-09-29T14:50:18.067760+00:00.

Case digest / 0561b158979bf5d3ca31277eac06d747c1bce556bf489f9789c912b1f41fc618