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FA-84366 / Betting odds conversion / Open access

Negative moneyline profit computed from the wrong ratio · case 01

A -200 favourite is expanded as a 3.00 decimal price.

Verified by executionVariant 1 · 9 checks per implementationDownload source bundle ↓JSON ↗

ROOT CAUSE

The sign is ignored and the magnitude is always divided by 100.

THE FAILURE

The sign is ignored and the magnitude is always divided by 100.

Unsuccessful approach: Using 100 / (N + 100) mixes in the implied-probability formula and understates the profit.

Case contract

Expand an American moneyline ("+150", "150" or "-200"; magnitude at least 100, otherwise "invalid"). Profit per unit is N/100 for positive or unsigned lines and 100/N for negative lines. Return [decimal price with two decimals, reduced fractional profit "a/b", implied probability percent with one decimal], all computed exactly and rounded half up.

Why this case matters

Odds screens show American, decimal, fractional and implied-probability columns for one price.

1 / The failure

Exit 1
"""Failure Map reference implementation. Python standard library only."""
import json
from fractions import Fraction
import math
N = 1
observations = []
def solve(american):
    s = american.strip()
    neg = s.startswith('-')
    n = int(s.lstrip('+-'))
    if n < 100:
        return 'invalid'
    profit = Fraction(n, 100)
    dec = 1 + profit
    def fmt(x, places):
        q = 10 ** places
        v = math.floor(x * q + Fraction(1, 2))
        return '%d.%0*d' % (v // q, places, v % q)
    prob = Fraction(n, n + 100) * 100 if neg else Fraction(100, n + 100) * 100
    return [fmt(dec, 2), '%d/%d' % (profit.numerator, profit.denominator), fmt(prob, 1)]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
def run(args):
    try:
        return solve(*args)
    except Exception as exc:
        return 'raised ' + type(exc).__name__
cases = [[('control underdog', ('+150',), ['2.50', '3/2', '40.0']),
  ('control favourite', ('-200',), ['1.50', '1/2', '66.7']),
  ('boundary even money', ('+100',), ['2.00', '1/1', '50.0']),
  ('boundary unsigned line', ('250',), ['3.50', '5/2', '28.6']),
  ('boundary below minimum', ('+50',), 'invalid'),
  ('control half-up decimal', ('-800',), ['1.13', '1/8', '88.9']),
  ('regression: favourite profit', ('-105',), ['1.95', '20/21', '51.2']),
  ('variant scenario 1', ('162',), ['2.62', '81/50', '38.2']),
  ('variant scenario 2', ('-277',), ['1.36', '100/277', '73.5'])],
 [('control underdog', ('+150',), ['2.50', '3/2', '40.0']),
  ('control favourite', ('-200',), ['1.50', '1/2', '66.7']),
  ('boundary even money', ('+100',), ['2.00', '1/1', '50.0']),
  ('boundary unsigned line', ('250',), ['3.50', '5/2', '28.6']),
  ('boundary below minimum', ('+50',), 'invalid'),
  ('control half-up decimal', ('-800',), ['1.13', '1/8', '88.9']),
  ('regression: favourite profit', ('-474',), ['1.21', '50/237', '82.6']),
  ('variant scenario 1', ('+1140',), ['12.40', '57/5', '8.1']),
  ('variant scenario 2', ('+1195',), ['12.95', '239/20', '7.7'])],
 [('control underdog', ('+150',), ['2.50', '3/2', '40.0']),
  ('control favourite', ('-200',), ['1.50', '1/2', '66.7']),
  ('boundary even money', ('+100',), ['2.00', '1/1', '50.0']),
  ('boundary unsigned line', ('250',), ['3.50', '5/2', '28.6']),
  ('boundary below minimum', ('+50',), 'invalid'),
  ('control half-up decimal', ('-800',), ['1.13', '1/8', '88.9']),
  ('regression: favourite profit', ('-1020',), ['1.10', '5/51', '91.1']),
  ('variant scenario 1', ('110',), ['2.10', '11/10', '47.6']),
  ('variant scenario 2', ('-225',), ['1.44', '4/9', '69.2'])],
 [('control underdog', ('+150',), ['2.50', '3/2', '40.0']),
  ('control favourite', ('-200',), ['1.50', '1/2', '66.7']),
  ('boundary even money', ('+100',), ['2.00', '1/1', '50.0']),
  ('boundary unsigned line', ('250',), ['3.50', '5/2', '28.6']),
  ('boundary below minimum', ('+50',), 'invalid'),
  ('control half-up decimal', ('-800',), ['1.13', '1/8', '88.9']),
  ('regression: favourite profit', ('-397',), ['1.25', '100/397', '79.9']),
  ('variant scenario 1', ('+355',), ['4.55', '71/20', '22.0']),
  ('variant scenario 2', ('-179',), ['1.56', '100/179', '64.2'])],
 [('control underdog', ('+150',), ['2.50', '3/2', '40.0']),
  ('control favourite', ('-200',), ['1.50', '1/2', '66.7']),
  ('boundary even money', ('+100',), ['2.00', '1/1', '50.0']),
  ('boundary unsigned line', ('250',), ['3.50', '5/2', '28.6']),
  ('boundary below minimum', ('+50',), 'invalid'),
  ('control half-up decimal', ('-800',), ['1.13', '1/8', '88.9']),
  ('regression: favourite profit', ('-363',), ['1.28', '100/363', '78.4']),
  ('variant scenario 1', ('267',), ['3.67', '267/100', '27.2']),
  ('variant scenario 2', ('+486',), ['5.86', '243/50', '17.1'])]]
for label, args, expected in cases[N - 1]:
    check(label, run(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
control underdog['2.50', '3/2', '40.0']['2.50', '3/2', '40.0']Passed
control favourite['3.00', '2/1', '66.7']['1.50', '1/2', '66.7']Failed
boundary even money['2.00', '1/1', '50.0']['2.00', '1/1', '50.0']Passed
boundary unsigned line['3.50', '5/2', '28.6']['3.50', '5/2', '28.6']Passed
boundary below minimuminvalidinvalidPassed
control half-up decimal['9.00', '8/1', '88.9']['1.13', '1/8', '88.9']Failed
regression: favourite profit['2.05', '21/20', '51.2']['1.95', '20/21', '51.2']Failed
variant scenario 1['2.62', '81/50', '38.2']['2.62', '81/50', '38.2']Passed
variant scenario 2['3.77', '277/100', '73.5']['1.36', '100/277', '73.5']Failed

SHA-256 / 8830d5fe2291a698bd6f410e5800095dbb301e676cc3c2d1d6cbbb897558bd1f

2 / The unsuccessful fix

Exit 1
"""Failure Map reference implementation. Python standard library only."""
import json
from fractions import Fraction
import math
N = 1
observations = []
def solve(american):
    s = american.strip()
    neg = s.startswith('-')
    n = int(s.lstrip('+-'))
    if n < 100:
        return 'invalid'
    profit = Fraction(100, n + 100) if neg else Fraction(n, 100)
    dec = 1 + profit
    def fmt(x, places):
        q = 10 ** places
        v = math.floor(x * q + Fraction(1, 2))
        return '%d.%0*d' % (v // q, places, v % q)
    prob = Fraction(n, n + 100) * 100 if neg else Fraction(100, n + 100) * 100
    return [fmt(dec, 2), '%d/%d' % (profit.numerator, profit.denominator), fmt(prob, 1)]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
def run(args):
    try:
        return solve(*args)
    except Exception as exc:
        return 'raised ' + type(exc).__name__
cases = [[('control underdog', ('+150',), ['2.50', '3/2', '40.0']),
  ('control favourite', ('-200',), ['1.50', '1/2', '66.7']),
  ('boundary even money', ('+100',), ['2.00', '1/1', '50.0']),
  ('boundary unsigned line', ('250',), ['3.50', '5/2', '28.6']),
  ('boundary below minimum', ('+50',), 'invalid'),
  ('control half-up decimal', ('-800',), ['1.13', '1/8', '88.9']),
  ('regression: favourite profit', ('-105',), ['1.95', '20/21', '51.2']),
  ('variant scenario 1', ('162',), ['2.62', '81/50', '38.2']),
  ('variant scenario 2', ('-277',), ['1.36', '100/277', '73.5'])],
 [('control underdog', ('+150',), ['2.50', '3/2', '40.0']),
  ('control favourite', ('-200',), ['1.50', '1/2', '66.7']),
  ('boundary even money', ('+100',), ['2.00', '1/1', '50.0']),
  ('boundary unsigned line', ('250',), ['3.50', '5/2', '28.6']),
  ('boundary below minimum', ('+50',), 'invalid'),
  ('control half-up decimal', ('-800',), ['1.13', '1/8', '88.9']),
  ('regression: favourite profit', ('-474',), ['1.21', '50/237', '82.6']),
  ('variant scenario 1', ('+1140',), ['12.40', '57/5', '8.1']),
  ('variant scenario 2', ('+1195',), ['12.95', '239/20', '7.7'])],
 [('control underdog', ('+150',), ['2.50', '3/2', '40.0']),
  ('control favourite', ('-200',), ['1.50', '1/2', '66.7']),
  ('boundary even money', ('+100',), ['2.00', '1/1', '50.0']),
  ('boundary unsigned line', ('250',), ['3.50', '5/2', '28.6']),
  ('boundary below minimum', ('+50',), 'invalid'),
  ('control half-up decimal', ('-800',), ['1.13', '1/8', '88.9']),
  ('regression: favourite profit', ('-1020',), ['1.10', '5/51', '91.1']),
  ('variant scenario 1', ('110',), ['2.10', '11/10', '47.6']),
  ('variant scenario 2', ('-225',), ['1.44', '4/9', '69.2'])],
 [('control underdog', ('+150',), ['2.50', '3/2', '40.0']),
  ('control favourite', ('-200',), ['1.50', '1/2', '66.7']),
  ('boundary even money', ('+100',), ['2.00', '1/1', '50.0']),
  ('boundary unsigned line', ('250',), ['3.50', '5/2', '28.6']),
  ('boundary below minimum', ('+50',), 'invalid'),
  ('control half-up decimal', ('-800',), ['1.13', '1/8', '88.9']),
  ('regression: favourite profit', ('-397',), ['1.25', '100/397', '79.9']),
  ('variant scenario 1', ('+355',), ['4.55', '71/20', '22.0']),
  ('variant scenario 2', ('-179',), ['1.56', '100/179', '64.2'])],
 [('control underdog', ('+150',), ['2.50', '3/2', '40.0']),
  ('control favourite', ('-200',), ['1.50', '1/2', '66.7']),
  ('boundary even money', ('+100',), ['2.00', '1/1', '50.0']),
  ('boundary unsigned line', ('250',), ['3.50', '5/2', '28.6']),
  ('boundary below minimum', ('+50',), 'invalid'),
  ('control half-up decimal', ('-800',), ['1.13', '1/8', '88.9']),
  ('regression: favourite profit', ('-363',), ['1.28', '100/363', '78.4']),
  ('variant scenario 1', ('267',), ['3.67', '267/100', '27.2']),
  ('variant scenario 2', ('+486',), ['5.86', '243/50', '17.1'])]]
for label, args, expected in cases[N - 1]:
    check(label, run(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
control underdog['2.50', '3/2', '40.0']['2.50', '3/2', '40.0']Passed
control favourite['1.33', '1/3', '66.7']['1.50', '1/2', '66.7']Failed
boundary even money['2.00', '1/1', '50.0']['2.00', '1/1', '50.0']Passed
boundary unsigned line['3.50', '5/2', '28.6']['3.50', '5/2', '28.6']Passed
boundary below minimuminvalidinvalidPassed
control half-up decimal['1.11', '1/9', '88.9']['1.13', '1/8', '88.9']Failed
regression: favourite profit['1.49', '20/41', '51.2']['1.95', '20/21', '51.2']Failed
variant scenario 1['2.62', '81/50', '38.2']['2.62', '81/50', '38.2']Passed
variant scenario 2['1.27', '100/377', '73.5']['1.36', '100/277', '73.5']Failed

SHA-256 / aa949d2b87d9badc85c83f40c1c086414bd5bea8c07824051ee4fa96c6234a8a

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This mechanism has 9 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.

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Verification & scope

Stipulated, bounded toy contract stated in the contract field; not a claim of conformance with any operator, exchange or regulator rule set. 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 2026-09-29T14:50:30.283778+00:00.

Case digest / cf94529f93081043bf7dc72ed071416dd0e4ed1153f5850349b143ed09359194