FA-83221 / Go territory scoring / Open access

Out-of-range kyu ranks are accepted · case 01

0k and 31k produce handicaps.

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

ROOT CAUSE

The kyu branch accepts any number.

THE FAILURE

The kyu branch accepts any number.

Unsuccessful approach: Adding only the lower bound still accepts 31k and above.

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':
            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', '0k'], 'invalid'], [['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'], [['2d', '31k'], 'invalid']], [[['10k', '8k'], ['10k', 2, 5]], [['10k', '6d'], ['10k', 9, 5]], [['5k', '1k'], ['5k', 4, 5]], [['5k', '0k'], 'invalid'], [['5k', 'k'], 'invalid'], [['3k', '2d'], ['3k', 4, 5]], [['1k', '0k'], 'invalid'], [['4k', '31k'], 'invalid']], [[['3k', '5d'], ['3k', 7, 5]], [['3k', '9d'], ['3k', 9, 5]], [['3k', '0k'], 'invalid'], [['2k', '30k'], ['30k', 9, 5]], [['2k', '10k'], ['10k', 8, 5]], [['2k', '1d'], ['2k', 2, 5]], [['5d', '0k'], 'invalid'], [['31k', '2d'], 'invalid']], [[['2k', '4k'], ['4k', 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]], [['0k', '3d'], 'invalid'], [['31k', '2k'], 'invalid']], [[['1k', '8k'], ['8k', 7, 5]], [['1d', '30k'], ['30k', 9, 5]], [['1d', '20k'], ['20k', 9, 5]], [['1d', '2k'], ['2k', 2, 5]], [['1d', '8k'], ['8k', 8, 5]], [['1d', '6d'], ['1d', 5, 5]], [['31k', '10k'], 'invalid'], [['31k', '3k'], 'invalid']]]
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 fixture	Actual	Expected	Outcome
handicap case 0	`['30k', 9, 5]`	`invalid`	Failed
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 4	`invalid`	`invalid`	Passed
handicap case 5	`['10k', 5, 5]`	`['10k', 5, 5]`	Passed
handicap case 6	`invalid`	`invalid`	Passed
handicap case 7	`['31k', 9, 5]`	`invalid`	Failed

SHA-256 / cd21c68a6b074e1374eb8e99d91be96e4772551991ec4e20bcb83563c405bc55

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:
            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', '0k'], 'invalid'], [['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'], [['2d', '31k'], 'invalid']], [[['10k', '8k'], ['10k', 2, 5]], [['10k', '6d'], ['10k', 9, 5]], [['5k', '1k'], ['5k', 4, 5]], [['5k', '0k'], 'invalid'], [['5k', 'k'], 'invalid'], [['3k', '2d'], ['3k', 4, 5]], [['1k', '0k'], 'invalid'], [['4k', '31k'], 'invalid']], [[['3k', '5d'], ['3k', 7, 5]], [['3k', '9d'], ['3k', 9, 5]], [['3k', '0k'], 'invalid'], [['2k', '30k'], ['30k', 9, 5]], [['2k', '10k'], ['10k', 8, 5]], [['2k', '1d'], ['2k', 2, 5]], [['5d', '0k'], 'invalid'], [['31k', '2d'], 'invalid']], [[['2k', '4k'], ['4k', 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]], [['0k', '3d'], 'invalid'], [['31k', '2k'], 'invalid']], [[['1k', '8k'], ['8k', 7, 5]], [['1d', '30k'], ['30k', 9, 5]], [['1d', '20k'], ['20k', 9, 5]], [['1d', '2k'], ['2k', 2, 5]], [['1d', '8k'], ['8k', 8, 5]], [['1d', '6d'], ['1d', 5, 5]], [['31k', '10k'], 'invalid'], [['31k', '3k'], 'invalid']]]
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 fixture	Actual	Expected	Outcome
handicap case 0	`invalid`	`invalid`	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 4	`invalid`	`invalid`	Passed
handicap case 5	`['10k', 5, 5]`	`['10k', 5, 5]`	Passed
handicap case 6	`invalid`	`invalid`	Passed
handicap case 7	`['31k', 9, 5]`	`invalid`	Failed

SHA-256 / d6a9400ee57741c41fe5b568ca969de257cdd844386d34ee27013f7c33914613

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 2026-09-29T14:50:19.455889+00:00.

Case digest / 8fe124478191e60e015d5b6bf85fa48f2fd11bda443126272c2f2c34afd661c1