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FA-83206 / Go territory scoring / Open access

The stronger player is given black · case 01

Handicap stones go to the stronger player.

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

ROOT CAUSE

The weaker comparison is inverted.

VERIFIED REPAIR

The player with the lower rank value takes black.

Unsuccessful approach: Comparing only the numeric part ignores whether ranks are kyu or dan.

Case contract

Input [rank_a, rank_b] as Nk (1..30) or Nd (1..9); 1k and 1d are one rank apart. Equal ranks -> [rank_a, 0, 65]; one rank apart -> [weaker, 0, 5]; otherwise [weaker, min(diff, 9), 5]. Invalid ranks -> "invalid". The first element is the player taking black.

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):
    def val(s):
        if len(s) < 2 or not s[:-1].isdigit():
            return None
        k = int(s[:-1])
        if s[-1] == 'k' and 1 <= k <= 30:
            return 1 - k
        if s[-1] == 'd' and 1 <= k <= 9:
            return k
        return None
    a, b = x
    va, vb = val(a), val(b)
    if va is None or vb is None:
        return 'invalid'
    diff = abs(va - vb)
    weaker = a if va > vb else b
    if diff == 0:
        return [a, 0, 65]
    if diff == 1:
        return [weaker, 0, 5]
    return [weaker, min(diff, 9), 5]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[[['30k', '3k'], ['30k', 9, 5]], [['20k', '2d'], ['20k', 9, 5]], [['20k', '5d'], ['20k', 9, 5]], [['20k', '9d'], ['20k', 9, 5]], [['20k', '3p'], 'invalid'], [['10k', '5k'], ['10k', 5, 5]], [['10k', 'k'], 'invalid'], [['1d', '6d'], ['1d', 5, 5]]], [[['20k', '1k'], ['20k', 9, 5]], [['10k', '6d'], ['10k', 9, 5]], [['5k', '1k'], ['5k', 4, 5]], [['5k', '0k'], 'invalid'], [['5k', 'k'], 'invalid'], [['3k', '2d'], ['3k', 4, 5]], [['3k', '3d'], ['3k', 5, 5]], [['5d', '3k'], ['3k', 7, 5]]], [[['20k', '5d'], ['20k', 9, 5]], [['3k', '9d'], ['3k', 9, 5]], [['3k', '0k'], 'invalid'], [['2k', '30k'], ['30k', 9, 5]], [['2k', '10k'], ['10k', 8, 5]], [['2k', '1d'], ['2k', 2, 5]], [['2k', '3d'], ['2k', 4, 5]], [['9d', '3d'], ['3d', 6, 5]]], [[['10k', '8k'], ['10k', 2, 5]], [['1k', '3k'], ['3k', 2, 5]], [['1k', '2k'], ['2k', 0, 5]], [['1k', '1k'], ['1k', 0, 65]], [['1k', '5d'], ['1k', 5, 5]], [['1k', '9d'], ['1k', 9, 5]], [['1k', '0k'], 'invalid'], [['6d', '3d'], ['3d', 3, 5]]], [[['3k', '2d'], ['3k', 4, 5]], [['3k', '5d'], ['3k', 7, 5]], [['1d', '20k'], ['20k', 9, 5]], [['1d', '2k'], ['2k', 2, 5]], [['1d', '8k'], ['8k', 8, 5]], [['1d', '6d'], ['1d', 5, 5]], [['1d', '4k'], ['4k', 4, 5]], [['2d', '20k'], ['20k', 9, 5]]]]
for i, (args, expected) in enumerate(fixtures[N-1]):
    check("handicap 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
handicap case 0['3k', 9, 5]['30k', 9, 5]Failed
handicap case 1['2d', 9, 5]['20k', 9, 5]Failed
handicap case 2['5d', 9, 5]['20k', 9, 5]Failed
handicap case 3['9d', 9, 5]['20k', 9, 5]Failed
handicap case 4invalidinvalidPassed
handicap case 5['5k', 5, 5]['10k', 5, 5]Failed
handicap case 6invalidinvalidPassed
handicap case 7['6d', 5, 5]['1d', 5, 5]Failed

SHA-256 / 1b0acf517d7967bfa7909beaed626e4dc1a7ecbf5164b3d2eb075a5b0ef8c6e7

2 / The unsuccessful fix

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

N = 1
observations = []
def solve(x):
    def val(s):
        if len(s) < 2 or not s[:-1].isdigit():
            return None
        k = int(s[:-1])
        if s[-1] == 'k' and 1 <= k <= 30:
            return 1 - k
        if s[-1] == 'd' and 1 <= k <= 9:
            return k
        return None
    a, b = x
    va, vb = val(a), val(b)
    if va is None or vb is None:
        return 'invalid'
    diff = abs(va - vb)
    weaker = a if int(a[:-1]) > int(b[:-1]) else b
    if diff == 0:
        return [a, 0, 65]
    if diff == 1:
        return [weaker, 0, 5]
    return [weaker, min(diff, 9), 5]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[[['30k', '3k'], ['30k', 9, 5]], [['20k', '2d'], ['20k', 9, 5]], [['20k', '5d'], ['20k', 9, 5]], [['20k', '9d'], ['20k', 9, 5]], [['20k', '3p'], 'invalid'], [['10k', '5k'], ['10k', 5, 5]], [['10k', 'k'], 'invalid'], [['1d', '6d'], ['1d', 5, 5]]], [[['20k', '1k'], ['20k', 9, 5]], [['10k', '6d'], ['10k', 9, 5]], [['5k', '1k'], ['5k', 4, 5]], [['5k', '0k'], 'invalid'], [['5k', 'k'], 'invalid'], [['3k', '2d'], ['3k', 4, 5]], [['3k', '3d'], ['3k', 5, 5]], [['5d', '3k'], ['3k', 7, 5]]], [[['20k', '5d'], ['20k', 9, 5]], [['3k', '9d'], ['3k', 9, 5]], [['3k', '0k'], 'invalid'], [['2k', '30k'], ['30k', 9, 5]], [['2k', '10k'], ['10k', 8, 5]], [['2k', '1d'], ['2k', 2, 5]], [['2k', '3d'], ['2k', 4, 5]], [['9d', '3d'], ['3d', 6, 5]]], [[['10k', '8k'], ['10k', 2, 5]], [['1k', '3k'], ['3k', 2, 5]], [['1k', '2k'], ['2k', 0, 5]], [['1k', '1k'], ['1k', 0, 65]], [['1k', '5d'], ['1k', 5, 5]], [['1k', '9d'], ['1k', 9, 5]], [['1k', '0k'], 'invalid'], [['6d', '3d'], ['3d', 3, 5]]], [[['3k', '2d'], ['3k', 4, 5]], [['3k', '5d'], ['3k', 7, 5]], [['1d', '20k'], ['20k', 9, 5]], [['1d', '2k'], ['2k', 2, 5]], [['1d', '8k'], ['8k', 8, 5]], [['1d', '6d'], ['1d', 5, 5]], [['1d', '4k'], ['4k', 4, 5]], [['2d', '20k'], ['20k', 9, 5]]]]
for i, (args, expected) in enumerate(fixtures[N-1]):
    check("handicap 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
handicap case 0['30k', 9, 5]['30k', 9, 5]Passed
handicap case 1['20k', 9, 5]['20k', 9, 5]Passed
handicap case 2['20k', 9, 5]['20k', 9, 5]Passed
handicap case 3['20k', 9, 5]['20k', 9, 5]Passed
handicap case 4invalidinvalidPassed
handicap case 5['10k', 5, 5]['10k', 5, 5]Passed
handicap case 6invalidinvalidPassed
handicap case 7['6d', 5, 5]['1d', 5, 5]Failed

SHA-256 / 6c28757430b077e26d0a7e1b0bac6546b27d5623d386d67531f12ff9289fd9b2

3 / The verified repair

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

N = 1
observations = []
def solve(x):
    def val(s):
        if len(s) < 2 or not s[:-1].isdigit():
            return None
        k = int(s[:-1])
        if s[-1] == 'k' and 1 <= k <= 30:
            return 1 - k
        if s[-1] == 'd' and 1 <= k <= 9:
            return k
        return None
    a, b = x
    va, vb = val(a), val(b)
    if va is None or vb is None:
        return 'invalid'
    diff = abs(va - vb)
    weaker = a if va < vb else b
    if diff == 0:
        return [a, 0, 65]
    if diff == 1:
        return [weaker, 0, 5]
    return [weaker, min(diff, 9), 5]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[[['30k', '3k'], ['30k', 9, 5]], [['20k', '2d'], ['20k', 9, 5]], [['20k', '5d'], ['20k', 9, 5]], [['20k', '9d'], ['20k', 9, 5]], [['20k', '3p'], 'invalid'], [['10k', '5k'], ['10k', 5, 5]], [['10k', 'k'], 'invalid'], [['1d', '6d'], ['1d', 5, 5]]], [[['20k', '1k'], ['20k', 9, 5]], [['10k', '6d'], ['10k', 9, 5]], [['5k', '1k'], ['5k', 4, 5]], [['5k', '0k'], 'invalid'], [['5k', 'k'], 'invalid'], [['3k', '2d'], ['3k', 4, 5]], [['3k', '3d'], ['3k', 5, 5]], [['5d', '3k'], ['3k', 7, 5]]], [[['20k', '5d'], ['20k', 9, 5]], [['3k', '9d'], ['3k', 9, 5]], [['3k', '0k'], 'invalid'], [['2k', '30k'], ['30k', 9, 5]], [['2k', '10k'], ['10k', 8, 5]], [['2k', '1d'], ['2k', 2, 5]], [['2k', '3d'], ['2k', 4, 5]], [['9d', '3d'], ['3d', 6, 5]]], [[['10k', '8k'], ['10k', 2, 5]], [['1k', '3k'], ['3k', 2, 5]], [['1k', '2k'], ['2k', 0, 5]], [['1k', '1k'], ['1k', 0, 65]], [['1k', '5d'], ['1k', 5, 5]], [['1k', '9d'], ['1k', 9, 5]], [['1k', '0k'], 'invalid'], [['6d', '3d'], ['3d', 3, 5]]], [[['3k', '2d'], ['3k', 4, 5]], [['3k', '5d'], ['3k', 7, 5]], [['1d', '20k'], ['20k', 9, 5]], [['1d', '2k'], ['2k', 2, 5]], [['1d', '8k'], ['8k', 8, 5]], [['1d', '6d'], ['1d', 5, 5]], [['1d', '4k'], ['4k', 4, 5]], [['2d', '20k'], ['20k', 9, 5]]]]
for i, (args, expected) in enumerate(fixtures[N-1]):
    check("handicap 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
handicap case 0['30k', 9, 5]['30k', 9, 5]Passed
handicap case 1['20k', 9, 5]['20k', 9, 5]Passed
handicap case 2['20k', 9, 5]['20k', 9, 5]Passed
handicap case 3['20k', 9, 5]['20k', 9, 5]Passed
handicap case 4invalidinvalidPassed
handicap case 5['10k', 5, 5]['10k', 5, 5]Passed
handicap case 6invalidinvalidPassed
handicap case 7['1d', 5, 5]['1d', 5, 5]Passed

SHA-256 / ffa99cbe8a15d77411bc83b017d04433a7e871f24294dd78e96a1464e402dfdc

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 2026-09-29T14:50:19.414059+00:00.

Case digest / 97e35124c3bfa066803368ec73828724167fb8b5a57777a6d28597425923315e