FA-58381 / Loan amortization schedules / Open access
Schedule rows from a fixed payment: final principal clamp · case 01
The last schedule row drives the balance negative.
ROOT CAUSE
Principal applied is not limited to the remaining balance.
VERIFIED REPAIR
Apply at most the remaining balance as principal.
Unsuccessful approach: Capping the whole payment ignores the interest share and over-applies principal.
Case contract
x = {'principal', 'rate_bp', 'payment', 'max_months'}. For months 1..max_months while the balance is positive: interest = round_half_up(balance*bp/120000); if payment <= interest return {'error': 'negative_amortization', 'month': k}; principal paid = min(payment - interest, balance); append [k, interest, principal, balance after]. Return {'rows', 'balloon': remaining principal}.
Why this case matters
Amortization engines drive borrower statements, payoff quotes and investor remittances; a misplaced rounding step, boundary or ordering rule compounds across hundreds of periods.
1 / The failure
Exit 1"""Failure Map reference implementation. Python standard library only."""
import json
import math
from fractions import Fraction
N = 1
observations = []
def solve(x):
def rnd(n, d):
q, r = divmod(n, d)
return q + (1 if 2 * r >= d else 0)
bal = x['principal']
rows = []
for k in range(1, x['max_months'] + 1):
if bal == 0:
break
interest = rnd(bal * x['rate_bp'], 120000)
pay = x['payment']
if pay <= interest:
return {'error': 'negative_amortization', 'month': k}
princ = pay - interest
bal -= princ
rows.append([k, interest, princ, bal])
return {'rows': rows, 'balloon': bal}
def check(label, actual, expected):
observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[['regression: final principal clamp', {'principal': 100000, 'rate_bp': 2400, 'payment': 20007, 'max_months': 12}, {'rows': [[1, 2000, 18007, 81993], [2, 1640, 18367, 63626], [3, 1273, 18734, 44892], [4, 898, 19109, 25783], [5, 516, 19491, 6292], [6, 126, 6292, 0]], 'balloon': 0}], ['control 1', {'principal': 250000, 'rate_bp': 1999, 'payment': 5000, 'max_months': 24}, {'rows': [[1, 4165, 835, 249165], [2, 4151, 849, 248316], [3, 4137, 863, 247453], [4, 4122, 878, 246575], [5, 4108, 892, 245683], [6, 4093, 907, 244776], [7, 4078, 922, 243854], [8, 4062, 938, 242916], [9, 4047, 953, 241963], [10, 4031, 969, 240994], [11, 4015, 985, 240009], [12, 3998, 1002, 239007], [13, 3981, 1019, 237988], [14, 3964, 1036, 236952], [15, 3947, 1053, 235899], [16, 3930, 1070, 234829], [17, 3912, 1088, 233741], [18, 3894, 1106, 232635], [19, 3875, 1125, 231510], [20, 3857, 1143, 230367], [21, 3838, 1162, 229205], [22, 3818, 1182, 228023], [23, 3798, 1202, 226821], [24, 3778, 1222, 225599]], 'balloon': 225599}], ['control 2', {'principal': 250000, 'rate_bp': 0, 'payment': 500, 'max_months': 1}, {'rows': [[1, 0, 500, 249500]], 'balloon': 249500}], ['control 3', {'principal': 250000, 'rate_bp': 1999, 'payment': 500, 'max_months': 24}, {'error': 'negative_amortization', 'month': 1}], ['control 4', {'principal': 100000, 'rate_bp': 1999, 'payment': 1000, 'max_months': 0}, {'rows': [], 'balloon': 100000}], ['control 5', {'principal': 250000, 'rate_bp': 1200, 'payment': 5000, 'max_months': 24}, {'rows': [[1, 2500, 2500, 247500], [2, 2475, 2525, 244975], [3, 2450, 2550, 242425], [4, 2424, 2576, 239849], [5, 2398, 2602, 237247], [6, 2372, 2628, 234619], [7, 2346, 2654, 231965], [8, 2320, 2680, 229285], [9, 2293, 2707, 226578], [10, 2266, 2734, 223844], [11, 2238, 2762, 221082], [12, 2211, 2789, 218293], [13, 2183, 2817, 215476], [14, 2155, 2845, 212631], [15, 2126, 2874, 209757], [16, 2098, 2902, 206855], [17, 2069, 2931, 203924], [18, 2039, 2961, 200963], [19, 2010, 2990, 197973], [20, 1980, 3020, 194953], [21, 1950, 3050, 191903], [22, 1919, 3081, 188822], [23, 1888, 3112, 185710], [24, 1857, 3143, 182567]], 'balloon': 182567}], ['control 6', {'principal': 1000, 'rate_bp': 600, 'payment': 83, 'max_months': 6}, {'rows': [[1, 5, 78, 922], [2, 5, 78, 844], [3, 4, 79, 765], [4, 4, 79, 686], [5, 3, 80, 606], [6, 3, 80, 526]], 'balloon': 526}]], [['regression: final principal clamp', {'principal': 50000, 'rate_bp': 0, 'payment': 16666, 'max_months': 24}, {'rows': [[1, 0, 16666, 33334], [2, 0, 16666, 16668], [3, 0, 16666, 2], [4, 0, 2, 0]], 'balloon': 0}], ['regression: final principal clamp, partial-repair probe', {'principal': 100000, 'rate_bp': 600, 'payment': 20007, 'max_months': 1}, {'rows': [[1, 500, 19507, 80493]], 'balloon': 80493}], ['control 1', {'principal': 12345, 'rate_bp': 600, 'payment': 500, 'max_months': 24}, {'rows': [[1, 62, 438, 11907], [2, 60, 440, 11467], [3, 57, 443, 11024], [4, 55, 445, 10579], [5, 53, 447, 10132], [6, 51, 449, 9683], [7, 48, 452, 9231], [8, 46, 454, 8777], [9, 44, 456, 8321], [10, 42, 458, 7863], [11, 39, 461, 7402], [12, 37, 463, 6939], [13, 35, 465, 6474], [14, 32, 468, 6006], [15, 30, 470, 5536], [16, 28, 472, 5064], [17, 25, 475, 4589], [18, 23, 477, 4112], [19, 21, 479, 3633], [20, 18, 482, 3151], [21, 16, 484, 2667], [22, 13, 487, 2180], [23, 11, 489, 1691], [24, 8, 492, 1199]], 'balloon': 1199}], ['control 2', {'principal': 100000, 'rate_bp': 0, 'payment': 20007, 'max_months': 3}, {'rows': [[1, 0, 20007, 79993], [2, 0, 20007, 59986], [3, 0, 20007, 39979]], 'balloon': 39979}], ['control 3', {'principal': 100000, 'rate_bp': 1200, 'payment': 5000, 'max_months': 6}, {'rows': [[1, 1000, 4000, 96000], [2, 960, 4040, 91960], [3, 920, 4080, 87880], [4, 879, 4121, 83759], [5, 838, 4162, 79597], [6, 796, 4204, 75393]], 'balloon': 75393}], ['control 4', {'principal': 1000, 'rate_bp': 0, 'payment': 1000, 'max_months': 0}, {'rows': [], 'balloon': 1000}], ['control 5', {'principal': 50000, 'rate_bp': 0, 'payment': 1000, 'max_months': 3}, {'rows': [[1, 0, 1000, 49000], [2, 0, 1000, 48000], [3, 0, 1000, 47000]], 'balloon': 47000}]], [['regression: final principal clamp', {'principal': 50000, 'rate_bp': 1200, 'payment': 5000, 'max_months': 24}, {'rows': [[1, 500, 4500, 45500], [2, 455, 4545, 40955], [3, 410, 4590, 36365], [4, 364, 4636, 31729], [5, 317, 4683, 27046], [6, 270, 4730, 22316], [7, 223, 4777, 17539], [8, 175, 4825, 12714], [9, 127, 4873, 7841], [10, 78, 4922, 2919], [11, 29, 2919, 0]], 'balloon': 0}], ['control 1', {'principal': 50000, 'rate_bp': 2400, 'payment': 5000, 'max_months': 3}, {'rows': [[1, 1000, 4000, 46000], [2, 920, 4080, 41920], [3, 838, 4162, 37758]], 'balloon': 37758}], ['control 2', {'principal': 12345, 'rate_bp': 0, 'payment': 4115, 'max_months': 24}, {'rows': [[1, 0, 4115, 8230], [2, 0, 4115, 4115], [3, 0, 4115, 0]], 'balloon': 0}], ['control 3', {'principal': 12345, 'rate_bp': 0, 'payment': 4115, 'max_months': 1}, {'rows': [[1, 0, 4115, 8230]], 'balloon': 8230}], ['control 4', {'principal': 250000, 'rate_bp': 600, 'payment': 20833, 'max_months': 1}, {'rows': [[1, 1250, 19583, 230417]], 'balloon': 230417}], ['control 5', {'principal': 1000, 'rate_bp': 2400, 'payment': 1050, 'max_months': 0}, {'rows': [], 'balloon': 1000}], ['control 6', {'principal': 250000, 'rate_bp': 1999, 'payment': 83333, 'max_months': 0}, {'rows': [], 'balloon': 250000}]], [['regression: final principal clamp', {'principal': 12345, 'rate_bp': 1200, 'payment': 5000, 'max_months': 3}, {'rows': [[1, 123, 4877, 7468], [2, 75, 4925, 2543], [3, 25, 2543, 0]], 'balloon': 0}], ['control 1', {'principal': 12345, 'rate_bp': 2400, 'payment': 500, 'max_months': 6}, {'rows': [[1, 247, 253, 12092], [2, 242, 258, 11834], [3, 237, 263, 11571], [4, 231, 269, 11302], [5, 226, 274, 11028], [6, 221, 279, 10749]], 'balloon': 10749}], ['control 2', {'principal': 250000, 'rate_bp': 600, 'payment': 500, 'max_months': 0}, {'rows': [], 'balloon': 250000}], ['control 3', {'principal': 50000, 'rate_bp': 600, 'payment': 1200, 'max_months': 24}, {'rows': [[1, 250, 950, 49050], [2, 245, 955, 48095], [3, 240, 960, 47135], [4, 236, 964, 46171], [5, 231, 969, 45202], [6, 226, 974, 44228], [7, 221, 979, 43249], [8, 216, 984, 42265], [9, 211, 989, 41276], [10, 206, 994, 40282], [11, 201, 999, 39283], [12, 196, 1004, 38279], [13, 191, 1009, 37270], [14, 186, 1014, 36256], [15, 181, 1019, 35237], [16, 176, 1024, 34213], [17, 171, 1029, 33184], [18, 166, 1034, 32150], [19, 161, 1039, 31111], [20, 156, 1044, 30067], [21, 150, 1050, 29017], [22, 145, 1055, 27962], [23, 140, 1060, 26902], [24, 135, 1065, 25837]], 'balloon': 25837}], ['control 4', {'principal': 50000, 'rate_bp': 1200, 'payment': 5000, 'max_months': 1}, {'rows': [[1, 500, 4500, 45500]], 'balloon': 45500}], ['control 5', {'principal': 250000, 'rate_bp': 1200, 'payment': 500, 'max_months': 6}, {'error': 'negative_amortization', 'month': 1}], ['control 6', {'principal': 1000, 'rate_bp': 0, 'payment': 1000, 'max_months': 1}, {'rows': [[1, 0, 1000, 0]], 'balloon': 0}]], [['regression: final principal clamp', {'principal': 1000, 'rate_bp': 2400, 'payment': 500, 'max_months': 3}, {'rows': [[1, 20, 480, 520], [2, 10, 490, 30], [3, 1, 30, 0]], 'balloon': 0}], ['control 1', {'principal': 12345, 'rate_bp': 2400, 'payment': 2476, 'max_months': 0}, {'rows': [], 'balloon': 12345}], ['control 2', {'principal': 250000, 'rate_bp': 2400, 'payment': 20833, 'max_months': 0}, {'rows': [], 'balloon': 250000}], ['control 3', {'principal': 50000, 'rate_bp': 600, 'payment': 1000, 'max_months': 0}, {'rows': [], 'balloon': 50000}], ['control 4', {'principal': 100000, 'rate_bp': 1200, 'payment': 1200, 'max_months': 1}, {'rows': [[1, 1000, 200, 99800]], 'balloon': 99800}], ['control 5', {'principal': 50000, 'rate_bp': 2400, 'payment': 4166, 'max_months': 0}, {'rows': [], 'balloon': 50000}], ['control 6', {'principal': 250000, 'rate_bp': 600, 'payment': 250050, 'max_months': 1}, {'rows': [[1, 1250, 248800, 1200]], 'balloon': 1200}]]]
for label, args, expected in fixtures[N-1]:
try:
actual = solve(args)
except Exception as exc:
actual = 'raised ' + type(exc).__name__
check(label, actual, 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 |
|---|---|---|---|
| regression: final principal clamp | {'balloon': -141509, 'rows': [[1, 2000, 18007, 81993], [2, 1640, 18367, 63626], [3, 1273, 18734, 44892], [4, 898, 19109, 25783], [5, 516, 19491, 6292], [6, 126, 19881, -13589], [7, -272, 20279, -33868], [8, -677, 20684, -54552], [9, -1091, 21098, -75650], [10, -1513, 21520, -97170], [11, -1943, 21950, -119120], [12, -2382, 22389, -141509]]} | {'balloon': 0, 'rows': [[1, 2000, 18007, 81993], [2, 1640, 18367, 63626], [3, 1273, 18734, 44892], [4, 898, 19109, 25783], [5, 516, 19491, 6292], [6, 126, 6292, 0]]} | Failed |
| control 1 | {'balloon': 225599, 'rows': [[1, 4165, 835, 249165], [2, 4151, 849, 248316], [3, 4137, 863, 247453], [4, 4122, 878, 246575], [5, 4108, 892, 245683], [6, 4093, 907, 244776], [7, 4078, 922, 243854], [8, 4062, 938, 242916], [9, 4047, 953, 241963], [10, 4031, 969, 240994], [11, 4015, 985, 240009], [12, 3998, 1002, 239007], [13, 3981, 1019, 237988], [14, 3964, 1036, 236952], [15, 3947, 1053, 235899], [16, 3930, 1070, 234829], [17, 3912, 1088, 233741], [18, 3894, 1106, 232635], [19, 3875, 1125, 231510], [20, 3857, 1143, 230367], [21, 3838, 1162, 229205], [22, 3818, 1182, 228023], [23, 3798, 1202, 226821], [24, 3778, 1222, 225599]]} | {'balloon': 225599, 'rows': [[1, 4165, 835, 249165], [2, 4151, 849, 248316], [3, 4137, 863, 247453], [4, 4122, 878, 246575], [5, 4108, 892, 245683], [6, 4093, 907, 244776], [7, 4078, 922, 243854], [8, 4062, 938, 242916], [9, 4047, 953, 241963], [10, 4031, 969, 240994], [11, 4015, 985, 240009], [12, 3998, 1002, 239007], [13, 3981, 1019, 237988], [14, 3964, 1036, 236952], [15, 3947, 1053, 235899], [16, 3930, 1070, 234829], [17, 3912, 1088, 233741], [18, 3894, 1106, 232635], [19, 3875, 1125, 231510], [20, 3857, 1143, 230367], [21, 3838, 1162, 229205], [22, 3818, 1182, 228023], [23, 3798, 1202, 226821], [24, 3778, 1222, 225599]]} | Passed |
| control 2 | {'balloon': 249500, 'rows': [[1, 0, 500, 249500]]} | {'balloon': 249500, 'rows': [[1, 0, 500, 249500]]} | Passed |
| control 3 | {'error': 'negative_amortization', 'month': 1} | {'error': 'negative_amortization', 'month': 1} | Passed |
| control 4 | {'balloon': 100000, 'rows': []} | {'balloon': 100000, 'rows': []} | Passed |
| control 5 | {'balloon': 182567, 'rows': [[1, 2500, 2500, 247500], [2, 2475, 2525, 244975], [3, 2450, 2550, 242425], [4, 2424, 2576, 239849], [5, 2398, 2602, 237247], [6, 2372, 2628, 234619], [7, 2346, 2654, 231965], [8, 2320, 2680, 229285], [9, 2293, 2707, 226578], [10, 2266, 2734, 223844], [11, 2238, 2762, 221082], [12, 2211, 2789, 218293], [13, 2183, 2817, 215476], [14, 2155, 2845, 212631], [15, 2126, 2874, 209757], [16, 2098, 2902, 206855], [17, 2069, 2931, 203924], [18, 2039, 2961, 200963], [19, 2010, 2990, 197973], [20, 1980, 3020, 194953], [21, 1950, 3050, 191903], [22, 1919, 3081, 188822], [23, 1888, 3112, 185710], [24, 1857, 3143, 182567]]} | {'balloon': 182567, 'rows': [[1, 2500, 2500, 247500], [2, 2475, 2525, 244975], [3, 2450, 2550, 242425], [4, 2424, 2576, 239849], [5, 2398, 2602, 237247], [6, 2372, 2628, 234619], [7, 2346, 2654, 231965], [8, 2320, 2680, 229285], [9, 2293, 2707, 226578], [10, 2266, 2734, 223844], [11, 2238, 2762, 221082], [12, 2211, 2789, 218293], [13, 2183, 2817, 215476], [14, 2155, 2845, 212631], [15, 2126, 2874, 209757], [16, 2098, 2902, 206855], [17, 2069, 2931, 203924], [18, 2039, 2961, 200963], [19, 2010, 2990, 197973], [20, 1980, 3020, 194953], [21, 1950, 3050, 191903], [22, 1919, 3081, 188822], [23, 1888, 3112, 185710], [24, 1857, 3143, 182567]]} | Passed |
| control 6 | {'balloon': 526, 'rows': [[1, 5, 78, 922], [2, 5, 78, 844], [3, 4, 79, 765], [4, 4, 79, 686], [5, 3, 80, 606], [6, 3, 80, 526]]} | {'balloon': 526, 'rows': [[1, 5, 78, 922], [2, 5, 78, 844], [3, 4, 79, 765], [4, 4, 79, 686], [5, 3, 80, 606], [6, 3, 80, 526]]} | Passed |
SHA-256 / bb4d1ff7892e4810274d29b6009c5241390528d0c690aba25c671fc12e293794
2 / The unsuccessful fix
Exit 1"""Failure Map reference implementation. Python standard library only."""
import json
import math
from fractions import Fraction
N = 1
observations = []
def solve(x):
def rnd(n, d):
q, r = divmod(n, d)
return q + (1 if 2 * r >= d else 0)
bal = x['principal']
rows = []
for k in range(1, x['max_months'] + 1):
if bal == 0:
break
interest = rnd(bal * x['rate_bp'], 120000)
pay = x['payment']
if pay <= interest:
return {'error': 'negative_amortization', 'month': k}
princ = min(pay, bal)
bal -= princ
rows.append([k, interest, princ, bal])
return {'rows': rows, 'balloon': bal}
def check(label, actual, expected):
observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[['regression: final principal clamp', {'principal': 100000, 'rate_bp': 2400, 'payment': 20007, 'max_months': 12}, {'rows': [[1, 2000, 18007, 81993], [2, 1640, 18367, 63626], [3, 1273, 18734, 44892], [4, 898, 19109, 25783], [5, 516, 19491, 6292], [6, 126, 6292, 0]], 'balloon': 0}], ['control 1', {'principal': 250000, 'rate_bp': 1999, 'payment': 5000, 'max_months': 24}, {'rows': [[1, 4165, 835, 249165], [2, 4151, 849, 248316], [3, 4137, 863, 247453], [4, 4122, 878, 246575], [5, 4108, 892, 245683], [6, 4093, 907, 244776], [7, 4078, 922, 243854], [8, 4062, 938, 242916], [9, 4047, 953, 241963], [10, 4031, 969, 240994], [11, 4015, 985, 240009], [12, 3998, 1002, 239007], [13, 3981, 1019, 237988], [14, 3964, 1036, 236952], [15, 3947, 1053, 235899], [16, 3930, 1070, 234829], [17, 3912, 1088, 233741], [18, 3894, 1106, 232635], [19, 3875, 1125, 231510], [20, 3857, 1143, 230367], [21, 3838, 1162, 229205], [22, 3818, 1182, 228023], [23, 3798, 1202, 226821], [24, 3778, 1222, 225599]], 'balloon': 225599}], ['control 2', {'principal': 250000, 'rate_bp': 0, 'payment': 500, 'max_months': 1}, {'rows': [[1, 0, 500, 249500]], 'balloon': 249500}], ['control 3', {'principal': 250000, 'rate_bp': 1999, 'payment': 500, 'max_months': 24}, {'error': 'negative_amortization', 'month': 1}], ['control 4', {'principal': 100000, 'rate_bp': 1999, 'payment': 1000, 'max_months': 0}, {'rows': [], 'balloon': 100000}], ['control 5', {'principal': 250000, 'rate_bp': 1200, 'payment': 5000, 'max_months': 24}, {'rows': [[1, 2500, 2500, 247500], [2, 2475, 2525, 244975], [3, 2450, 2550, 242425], [4, 2424, 2576, 239849], [5, 2398, 2602, 237247], [6, 2372, 2628, 234619], [7, 2346, 2654, 231965], [8, 2320, 2680, 229285], [9, 2293, 2707, 226578], [10, 2266, 2734, 223844], [11, 2238, 2762, 221082], [12, 2211, 2789, 218293], [13, 2183, 2817, 215476], [14, 2155, 2845, 212631], [15, 2126, 2874, 209757], [16, 2098, 2902, 206855], [17, 2069, 2931, 203924], [18, 2039, 2961, 200963], [19, 2010, 2990, 197973], [20, 1980, 3020, 194953], [21, 1950, 3050, 191903], [22, 1919, 3081, 188822], [23, 1888, 3112, 185710], [24, 1857, 3143, 182567]], 'balloon': 182567}], ['control 6', {'principal': 1000, 'rate_bp': 600, 'payment': 83, 'max_months': 6}, {'rows': [[1, 5, 78, 922], [2, 5, 78, 844], [3, 4, 79, 765], [4, 4, 79, 686], [5, 3, 80, 606], [6, 3, 80, 526]], 'balloon': 526}]], [['regression: final principal clamp', {'principal': 50000, 'rate_bp': 0, 'payment': 16666, 'max_months': 24}, {'rows': [[1, 0, 16666, 33334], [2, 0, 16666, 16668], [3, 0, 16666, 2], [4, 0, 2, 0]], 'balloon': 0}], ['regression: final principal clamp, partial-repair probe', {'principal': 100000, 'rate_bp': 600, 'payment': 20007, 'max_months': 1}, {'rows': [[1, 500, 19507, 80493]], 'balloon': 80493}], ['control 1', {'principal': 12345, 'rate_bp': 600, 'payment': 500, 'max_months': 24}, {'rows': [[1, 62, 438, 11907], [2, 60, 440, 11467], [3, 57, 443, 11024], [4, 55, 445, 10579], [5, 53, 447, 10132], [6, 51, 449, 9683], [7, 48, 452, 9231], [8, 46, 454, 8777], [9, 44, 456, 8321], [10, 42, 458, 7863], [11, 39, 461, 7402], [12, 37, 463, 6939], [13, 35, 465, 6474], [14, 32, 468, 6006], [15, 30, 470, 5536], [16, 28, 472, 5064], [17, 25, 475, 4589], [18, 23, 477, 4112], [19, 21, 479, 3633], [20, 18, 482, 3151], [21, 16, 484, 2667], [22, 13, 487, 2180], [23, 11, 489, 1691], [24, 8, 492, 1199]], 'balloon': 1199}], ['control 2', {'principal': 100000, 'rate_bp': 0, 'payment': 20007, 'max_months': 3}, {'rows': [[1, 0, 20007, 79993], [2, 0, 20007, 59986], [3, 0, 20007, 39979]], 'balloon': 39979}], ['control 3', {'principal': 100000, 'rate_bp': 1200, 'payment': 5000, 'max_months': 6}, {'rows': [[1, 1000, 4000, 96000], [2, 960, 4040, 91960], [3, 920, 4080, 87880], [4, 879, 4121, 83759], [5, 838, 4162, 79597], [6, 796, 4204, 75393]], 'balloon': 75393}], ['control 4', {'principal': 1000, 'rate_bp': 0, 'payment': 1000, 'max_months': 0}, {'rows': [], 'balloon': 1000}], ['control 5', {'principal': 50000, 'rate_bp': 0, 'payment': 1000, 'max_months': 3}, {'rows': [[1, 0, 1000, 49000], [2, 0, 1000, 48000], [3, 0, 1000, 47000]], 'balloon': 47000}]], [['regression: final principal clamp', {'principal': 50000, 'rate_bp': 1200, 'payment': 5000, 'max_months': 24}, {'rows': [[1, 500, 4500, 45500], [2, 455, 4545, 40955], [3, 410, 4590, 36365], [4, 364, 4636, 31729], [5, 317, 4683, 27046], [6, 270, 4730, 22316], [7, 223, 4777, 17539], [8, 175, 4825, 12714], [9, 127, 4873, 7841], [10, 78, 4922, 2919], [11, 29, 2919, 0]], 'balloon': 0}], ['control 1', {'principal': 50000, 'rate_bp': 2400, 'payment': 5000, 'max_months': 3}, {'rows': [[1, 1000, 4000, 46000], [2, 920, 4080, 41920], [3, 838, 4162, 37758]], 'balloon': 37758}], ['control 2', {'principal': 12345, 'rate_bp': 0, 'payment': 4115, 'max_months': 24}, {'rows': [[1, 0, 4115, 8230], [2, 0, 4115, 4115], [3, 0, 4115, 0]], 'balloon': 0}], ['control 3', {'principal': 12345, 'rate_bp': 0, 'payment': 4115, 'max_months': 1}, {'rows': [[1, 0, 4115, 8230]], 'balloon': 8230}], ['control 4', {'principal': 250000, 'rate_bp': 600, 'payment': 20833, 'max_months': 1}, {'rows': [[1, 1250, 19583, 230417]], 'balloon': 230417}], ['control 5', {'principal': 1000, 'rate_bp': 2400, 'payment': 1050, 'max_months': 0}, {'rows': [], 'balloon': 1000}], ['control 6', {'principal': 250000, 'rate_bp': 1999, 'payment': 83333, 'max_months': 0}, {'rows': [], 'balloon': 250000}]], [['regression: final principal clamp', {'principal': 12345, 'rate_bp': 1200, 'payment': 5000, 'max_months': 3}, {'rows': [[1, 123, 4877, 7468], [2, 75, 4925, 2543], [3, 25, 2543, 0]], 'balloon': 0}], ['control 1', {'principal': 12345, 'rate_bp': 2400, 'payment': 500, 'max_months': 6}, {'rows': [[1, 247, 253, 12092], [2, 242, 258, 11834], [3, 237, 263, 11571], [4, 231, 269, 11302], [5, 226, 274, 11028], [6, 221, 279, 10749]], 'balloon': 10749}], ['control 2', {'principal': 250000, 'rate_bp': 600, 'payment': 500, 'max_months': 0}, {'rows': [], 'balloon': 250000}], ['control 3', {'principal': 50000, 'rate_bp': 600, 'payment': 1200, 'max_months': 24}, {'rows': [[1, 250, 950, 49050], [2, 245, 955, 48095], [3, 240, 960, 47135], [4, 236, 964, 46171], [5, 231, 969, 45202], [6, 226, 974, 44228], [7, 221, 979, 43249], [8, 216, 984, 42265], [9, 211, 989, 41276], [10, 206, 994, 40282], [11, 201, 999, 39283], [12, 196, 1004, 38279], [13, 191, 1009, 37270], [14, 186, 1014, 36256], [15, 181, 1019, 35237], [16, 176, 1024, 34213], [17, 171, 1029, 33184], [18, 166, 1034, 32150], [19, 161, 1039, 31111], [20, 156, 1044, 30067], [21, 150, 1050, 29017], [22, 145, 1055, 27962], [23, 140, 1060, 26902], [24, 135, 1065, 25837]], 'balloon': 25837}], ['control 4', {'principal': 50000, 'rate_bp': 1200, 'payment': 5000, 'max_months': 1}, {'rows': [[1, 500, 4500, 45500]], 'balloon': 45500}], ['control 5', {'principal': 250000, 'rate_bp': 1200, 'payment': 500, 'max_months': 6}, {'error': 'negative_amortization', 'month': 1}], ['control 6', {'principal': 1000, 'rate_bp': 0, 'payment': 1000, 'max_months': 1}, {'rows': [[1, 0, 1000, 0]], 'balloon': 0}]], [['regression: final principal clamp', {'principal': 1000, 'rate_bp': 2400, 'payment': 500, 'max_months': 3}, {'rows': [[1, 20, 480, 520], [2, 10, 490, 30], [3, 1, 30, 0]], 'balloon': 0}], ['control 1', {'principal': 12345, 'rate_bp': 2400, 'payment': 2476, 'max_months': 0}, {'rows': [], 'balloon': 12345}], ['control 2', {'principal': 250000, 'rate_bp': 2400, 'payment': 20833, 'max_months': 0}, {'rows': [], 'balloon': 250000}], ['control 3', {'principal': 50000, 'rate_bp': 600, 'payment': 1000, 'max_months': 0}, {'rows': [], 'balloon': 50000}], ['control 4', {'principal': 100000, 'rate_bp': 1200, 'payment': 1200, 'max_months': 1}, {'rows': [[1, 1000, 200, 99800]], 'balloon': 99800}], ['control 5', {'principal': 50000, 'rate_bp': 2400, 'payment': 4166, 'max_months': 0}, {'rows': [], 'balloon': 50000}], ['control 6', {'principal': 250000, 'rate_bp': 600, 'payment': 250050, 'max_months': 1}, {'rows': [[1, 1250, 248800, 1200]], 'balloon': 1200}]]]
for label, args, expected in fixtures[N-1]:
try:
actual = solve(args)
except Exception as exc:
actual = 'raised ' + type(exc).__name__
check(label, actual, 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 |
|---|---|---|---|
| regression: final principal clamp | {'balloon': 0, 'rows': [[1, 2000, 20007, 79993], [2, 1600, 20007, 59986], [3, 1200, 20007, 39979], [4, 800, 20007, 19972], [5, 399, 19972, 0]]} | {'balloon': 0, 'rows': [[1, 2000, 18007, 81993], [2, 1640, 18367, 63626], [3, 1273, 18734, 44892], [4, 898, 19109, 25783], [5, 516, 19491, 6292], [6, 126, 6292, 0]]} | Failed |
| control 1 | {'balloon': 130000, 'rows': [[1, 4165, 5000, 245000], [2, 4081, 5000, 240000], [3, 3998, 5000, 235000], [4, 3915, 5000, 230000], [5, 3831, 5000, 225000], [6, 3748, 5000, 220000], [7, 3665, 5000, 215000], [8, 3582, 5000, 210000], [9, 3498, 5000, 205000], [10, 3415, 5000, 200000], [11, 3332, 5000, 195000], [12, 3248, 5000, 190000], [13, 3165, 5000, 185000], [14, 3082, 5000, 180000], [15, 2999, 5000, 175000], [16, 2915, 5000, 170000], [17, 2832, 5000, 165000], [18, 2749, 5000, 160000], [19, 2665, 5000, 155000], [20, 2582, 5000, 150000], [21, 2499, 5000, 145000], [22, 2415, 5000, 140000], [23, 2332, 5000, 135000], [24, 2249, 5000, 130000]]} | {'balloon': 225599, 'rows': [[1, 4165, 835, 249165], [2, 4151, 849, 248316], [3, 4137, 863, 247453], [4, 4122, 878, 246575], [5, 4108, 892, 245683], [6, 4093, 907, 244776], [7, 4078, 922, 243854], [8, 4062, 938, 242916], [9, 4047, 953, 241963], [10, 4031, 969, 240994], [11, 4015, 985, 240009], [12, 3998, 1002, 239007], [13, 3981, 1019, 237988], [14, 3964, 1036, 236952], [15, 3947, 1053, 235899], [16, 3930, 1070, 234829], [17, 3912, 1088, 233741], [18, 3894, 1106, 232635], [19, 3875, 1125, 231510], [20, 3857, 1143, 230367], [21, 3838, 1162, 229205], [22, 3818, 1182, 228023], [23, 3798, 1202, 226821], [24, 3778, 1222, 225599]]} | Failed |
| control 2 | {'balloon': 249500, 'rows': [[1, 0, 500, 249500]]} | {'balloon': 249500, 'rows': [[1, 0, 500, 249500]]} | Passed |
| control 3 | {'error': 'negative_amortization', 'month': 1} | {'error': 'negative_amortization', 'month': 1} | Passed |
| control 4 | {'balloon': 100000, 'rows': []} | {'balloon': 100000, 'rows': []} | Passed |
| control 5 | {'balloon': 130000, 'rows': [[1, 2500, 5000, 245000], [2, 2450, 5000, 240000], [3, 2400, 5000, 235000], [4, 2350, 5000, 230000], [5, 2300, 5000, 225000], [6, 2250, 5000, 220000], [7, 2200, 5000, 215000], [8, 2150, 5000, 210000], [9, 2100, 5000, 205000], [10, 2050, 5000, 200000], [11, 2000, 5000, 195000], [12, 1950, 5000, 190000], [13, 1900, 5000, 185000], [14, 1850, 5000, 180000], [15, 1800, 5000, 175000], [16, 1750, 5000, 170000], [17, 1700, 5000, 165000], [18, 1650, 5000, 160000], [19, 1600, 5000, 155000], [20, 1550, 5000, 150000], [21, 1500, 5000, 145000], [22, 1450, 5000, 140000], [23, 1400, 5000, 135000], [24, 1350, 5000, 130000]]} | {'balloon': 182567, 'rows': [[1, 2500, 2500, 247500], [2, 2475, 2525, 244975], [3, 2450, 2550, 242425], [4, 2424, 2576, 239849], [5, 2398, 2602, 237247], [6, 2372, 2628, 234619], [7, 2346, 2654, 231965], [8, 2320, 2680, 229285], [9, 2293, 2707, 226578], [10, 2266, 2734, 223844], [11, 2238, 2762, 221082], [12, 2211, 2789, 218293], [13, 2183, 2817, 215476], [14, 2155, 2845, 212631], [15, 2126, 2874, 209757], [16, 2098, 2902, 206855], [17, 2069, 2931, 203924], [18, 2039, 2961, 200963], [19, 2010, 2990, 197973], [20, 1980, 3020, 194953], [21, 1950, 3050, 191903], [22, 1919, 3081, 188822], [23, 1888, 3112, 185710], [24, 1857, 3143, 182567]]} | Failed |
| control 6 | {'balloon': 502, 'rows': [[1, 5, 83, 917], [2, 5, 83, 834], [3, 4, 83, 751], [4, 4, 83, 668], [5, 3, 83, 585], [6, 3, 83, 502]]} | {'balloon': 526, 'rows': [[1, 5, 78, 922], [2, 5, 78, 844], [3, 4, 79, 765], [4, 4, 79, 686], [5, 3, 80, 606], [6, 3, 80, 526]]} | Failed |
SHA-256 / 3289c3db19ae7845bf6997bd56a8ac1645d8cc0978bb9a31b265265c5a518171
3 / The verified repair
Exit 0"""Failure Map reference implementation. Python standard library only."""
import json
import math
from fractions import Fraction
N = 1
observations = []
def solve(x):
def rnd(n, d):
q, r = divmod(n, d)
return q + (1 if 2 * r >= d else 0)
bal = x['principal']
rows = []
for k in range(1, x['max_months'] + 1):
if bal == 0:
break
interest = rnd(bal * x['rate_bp'], 120000)
pay = x['payment']
if pay <= interest:
return {'error': 'negative_amortization', 'month': k}
princ = min(pay - interest, bal)
bal -= princ
rows.append([k, interest, princ, bal])
return {'rows': rows, 'balloon': bal}
def check(label, actual, expected):
observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[['regression: final principal clamp', {'principal': 100000, 'rate_bp': 2400, 'payment': 20007, 'max_months': 12}, {'rows': [[1, 2000, 18007, 81993], [2, 1640, 18367, 63626], [3, 1273, 18734, 44892], [4, 898, 19109, 25783], [5, 516, 19491, 6292], [6, 126, 6292, 0]], 'balloon': 0}], ['control 1', {'principal': 250000, 'rate_bp': 1999, 'payment': 5000, 'max_months': 24}, {'rows': [[1, 4165, 835, 249165], [2, 4151, 849, 248316], [3, 4137, 863, 247453], [4, 4122, 878, 246575], [5, 4108, 892, 245683], [6, 4093, 907, 244776], [7, 4078, 922, 243854], [8, 4062, 938, 242916], [9, 4047, 953, 241963], [10, 4031, 969, 240994], [11, 4015, 985, 240009], [12, 3998, 1002, 239007], [13, 3981, 1019, 237988], [14, 3964, 1036, 236952], [15, 3947, 1053, 235899], [16, 3930, 1070, 234829], [17, 3912, 1088, 233741], [18, 3894, 1106, 232635], [19, 3875, 1125, 231510], [20, 3857, 1143, 230367], [21, 3838, 1162, 229205], [22, 3818, 1182, 228023], [23, 3798, 1202, 226821], [24, 3778, 1222, 225599]], 'balloon': 225599}], ['control 2', {'principal': 250000, 'rate_bp': 0, 'payment': 500, 'max_months': 1}, {'rows': [[1, 0, 500, 249500]], 'balloon': 249500}], ['control 3', {'principal': 250000, 'rate_bp': 1999, 'payment': 500, 'max_months': 24}, {'error': 'negative_amortization', 'month': 1}], ['control 4', {'principal': 100000, 'rate_bp': 1999, 'payment': 1000, 'max_months': 0}, {'rows': [], 'balloon': 100000}], ['control 5', {'principal': 250000, 'rate_bp': 1200, 'payment': 5000, 'max_months': 24}, {'rows': [[1, 2500, 2500, 247500], [2, 2475, 2525, 244975], [3, 2450, 2550, 242425], [4, 2424, 2576, 239849], [5, 2398, 2602, 237247], [6, 2372, 2628, 234619], [7, 2346, 2654, 231965], [8, 2320, 2680, 229285], [9, 2293, 2707, 226578], [10, 2266, 2734, 223844], [11, 2238, 2762, 221082], [12, 2211, 2789, 218293], [13, 2183, 2817, 215476], [14, 2155, 2845, 212631], [15, 2126, 2874, 209757], [16, 2098, 2902, 206855], [17, 2069, 2931, 203924], [18, 2039, 2961, 200963], [19, 2010, 2990, 197973], [20, 1980, 3020, 194953], [21, 1950, 3050, 191903], [22, 1919, 3081, 188822], [23, 1888, 3112, 185710], [24, 1857, 3143, 182567]], 'balloon': 182567}], ['control 6', {'principal': 1000, 'rate_bp': 600, 'payment': 83, 'max_months': 6}, {'rows': [[1, 5, 78, 922], [2, 5, 78, 844], [3, 4, 79, 765], [4, 4, 79, 686], [5, 3, 80, 606], [6, 3, 80, 526]], 'balloon': 526}]], [['regression: final principal clamp', {'principal': 50000, 'rate_bp': 0, 'payment': 16666, 'max_months': 24}, {'rows': [[1, 0, 16666, 33334], [2, 0, 16666, 16668], [3, 0, 16666, 2], [4, 0, 2, 0]], 'balloon': 0}], ['regression: final principal clamp, partial-repair probe', {'principal': 100000, 'rate_bp': 600, 'payment': 20007, 'max_months': 1}, {'rows': [[1, 500, 19507, 80493]], 'balloon': 80493}], ['control 1', {'principal': 12345, 'rate_bp': 600, 'payment': 500, 'max_months': 24}, {'rows': [[1, 62, 438, 11907], [2, 60, 440, 11467], [3, 57, 443, 11024], [4, 55, 445, 10579], [5, 53, 447, 10132], [6, 51, 449, 9683], [7, 48, 452, 9231], [8, 46, 454, 8777], [9, 44, 456, 8321], [10, 42, 458, 7863], [11, 39, 461, 7402], [12, 37, 463, 6939], [13, 35, 465, 6474], [14, 32, 468, 6006], [15, 30, 470, 5536], [16, 28, 472, 5064], [17, 25, 475, 4589], [18, 23, 477, 4112], [19, 21, 479, 3633], [20, 18, 482, 3151], [21, 16, 484, 2667], [22, 13, 487, 2180], [23, 11, 489, 1691], [24, 8, 492, 1199]], 'balloon': 1199}], ['control 2', {'principal': 100000, 'rate_bp': 0, 'payment': 20007, 'max_months': 3}, {'rows': [[1, 0, 20007, 79993], [2, 0, 20007, 59986], [3, 0, 20007, 39979]], 'balloon': 39979}], ['control 3', {'principal': 100000, 'rate_bp': 1200, 'payment': 5000, 'max_months': 6}, {'rows': [[1, 1000, 4000, 96000], [2, 960, 4040, 91960], [3, 920, 4080, 87880], [4, 879, 4121, 83759], [5, 838, 4162, 79597], [6, 796, 4204, 75393]], 'balloon': 75393}], ['control 4', {'principal': 1000, 'rate_bp': 0, 'payment': 1000, 'max_months': 0}, {'rows': [], 'balloon': 1000}], ['control 5', {'principal': 50000, 'rate_bp': 0, 'payment': 1000, 'max_months': 3}, {'rows': [[1, 0, 1000, 49000], [2, 0, 1000, 48000], [3, 0, 1000, 47000]], 'balloon': 47000}]], [['regression: final principal clamp', {'principal': 50000, 'rate_bp': 1200, 'payment': 5000, 'max_months': 24}, {'rows': [[1, 500, 4500, 45500], [2, 455, 4545, 40955], [3, 410, 4590, 36365], [4, 364, 4636, 31729], [5, 317, 4683, 27046], [6, 270, 4730, 22316], [7, 223, 4777, 17539], [8, 175, 4825, 12714], [9, 127, 4873, 7841], [10, 78, 4922, 2919], [11, 29, 2919, 0]], 'balloon': 0}], ['control 1', {'principal': 50000, 'rate_bp': 2400, 'payment': 5000, 'max_months': 3}, {'rows': [[1, 1000, 4000, 46000], [2, 920, 4080, 41920], [3, 838, 4162, 37758]], 'balloon': 37758}], ['control 2', {'principal': 12345, 'rate_bp': 0, 'payment': 4115, 'max_months': 24}, {'rows': [[1, 0, 4115, 8230], [2, 0, 4115, 4115], [3, 0, 4115, 0]], 'balloon': 0}], ['control 3', {'principal': 12345, 'rate_bp': 0, 'payment': 4115, 'max_months': 1}, {'rows': [[1, 0, 4115, 8230]], 'balloon': 8230}], ['control 4', {'principal': 250000, 'rate_bp': 600, 'payment': 20833, 'max_months': 1}, {'rows': [[1, 1250, 19583, 230417]], 'balloon': 230417}], ['control 5', {'principal': 1000, 'rate_bp': 2400, 'payment': 1050, 'max_months': 0}, {'rows': [], 'balloon': 1000}], ['control 6', {'principal': 250000, 'rate_bp': 1999, 'payment': 83333, 'max_months': 0}, {'rows': [], 'balloon': 250000}]], [['regression: final principal clamp', {'principal': 12345, 'rate_bp': 1200, 'payment': 5000, 'max_months': 3}, {'rows': [[1, 123, 4877, 7468], [2, 75, 4925, 2543], [3, 25, 2543, 0]], 'balloon': 0}], ['control 1', {'principal': 12345, 'rate_bp': 2400, 'payment': 500, 'max_months': 6}, {'rows': [[1, 247, 253, 12092], [2, 242, 258, 11834], [3, 237, 263, 11571], [4, 231, 269, 11302], [5, 226, 274, 11028], [6, 221, 279, 10749]], 'balloon': 10749}], ['control 2', {'principal': 250000, 'rate_bp': 600, 'payment': 500, 'max_months': 0}, {'rows': [], 'balloon': 250000}], ['control 3', {'principal': 50000, 'rate_bp': 600, 'payment': 1200, 'max_months': 24}, {'rows': [[1, 250, 950, 49050], [2, 245, 955, 48095], [3, 240, 960, 47135], [4, 236, 964, 46171], [5, 231, 969, 45202], [6, 226, 974, 44228], [7, 221, 979, 43249], [8, 216, 984, 42265], [9, 211, 989, 41276], [10, 206, 994, 40282], [11, 201, 999, 39283], [12, 196, 1004, 38279], [13, 191, 1009, 37270], [14, 186, 1014, 36256], [15, 181, 1019, 35237], [16, 176, 1024, 34213], [17, 171, 1029, 33184], [18, 166, 1034, 32150], [19, 161, 1039, 31111], [20, 156, 1044, 30067], [21, 150, 1050, 29017], [22, 145, 1055, 27962], [23, 140, 1060, 26902], [24, 135, 1065, 25837]], 'balloon': 25837}], ['control 4', {'principal': 50000, 'rate_bp': 1200, 'payment': 5000, 'max_months': 1}, {'rows': [[1, 500, 4500, 45500]], 'balloon': 45500}], ['control 5', {'principal': 250000, 'rate_bp': 1200, 'payment': 500, 'max_months': 6}, {'error': 'negative_amortization', 'month': 1}], ['control 6', {'principal': 1000, 'rate_bp': 0, 'payment': 1000, 'max_months': 1}, {'rows': [[1, 0, 1000, 0]], 'balloon': 0}]], [['regression: final principal clamp', {'principal': 1000, 'rate_bp': 2400, 'payment': 500, 'max_months': 3}, {'rows': [[1, 20, 480, 520], [2, 10, 490, 30], [3, 1, 30, 0]], 'balloon': 0}], ['control 1', {'principal': 12345, 'rate_bp': 2400, 'payment': 2476, 'max_months': 0}, {'rows': [], 'balloon': 12345}], ['control 2', {'principal': 250000, 'rate_bp': 2400, 'payment': 20833, 'max_months': 0}, {'rows': [], 'balloon': 250000}], ['control 3', {'principal': 50000, 'rate_bp': 600, 'payment': 1000, 'max_months': 0}, {'rows': [], 'balloon': 50000}], ['control 4', {'principal': 100000, 'rate_bp': 1200, 'payment': 1200, 'max_months': 1}, {'rows': [[1, 1000, 200, 99800]], 'balloon': 99800}], ['control 5', {'principal': 50000, 'rate_bp': 2400, 'payment': 4166, 'max_months': 0}, {'rows': [], 'balloon': 50000}], ['control 6', {'principal': 250000, 'rate_bp': 600, 'payment': 250050, 'max_months': 1}, {'rows': [[1, 1250, 248800, 1200]], 'balloon': 1200}]]]
for label, args, expected in fixtures[N-1]:
try:
actual = solve(args)
except Exception as exc:
actual = 'raised ' + type(exc).__name__
check(label, actual, 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 |
|---|---|---|---|
| regression: final principal clamp | {'balloon': 0, 'rows': [[1, 2000, 18007, 81993], [2, 1640, 18367, 63626], [3, 1273, 18734, 44892], [4, 898, 19109, 25783], [5, 516, 19491, 6292], [6, 126, 6292, 0]]} | {'balloon': 0, 'rows': [[1, 2000, 18007, 81993], [2, 1640, 18367, 63626], [3, 1273, 18734, 44892], [4, 898, 19109, 25783], [5, 516, 19491, 6292], [6, 126, 6292, 0]]} | Passed |
| control 1 | {'balloon': 225599, 'rows': [[1, 4165, 835, 249165], [2, 4151, 849, 248316], [3, 4137, 863, 247453], [4, 4122, 878, 246575], [5, 4108, 892, 245683], [6, 4093, 907, 244776], [7, 4078, 922, 243854], [8, 4062, 938, 242916], [9, 4047, 953, 241963], [10, 4031, 969, 240994], [11, 4015, 985, 240009], [12, 3998, 1002, 239007], [13, 3981, 1019, 237988], [14, 3964, 1036, 236952], [15, 3947, 1053, 235899], [16, 3930, 1070, 234829], [17, 3912, 1088, 233741], [18, 3894, 1106, 232635], [19, 3875, 1125, 231510], [20, 3857, 1143, 230367], [21, 3838, 1162, 229205], [22, 3818, 1182, 228023], [23, 3798, 1202, 226821], [24, 3778, 1222, 225599]]} | {'balloon': 225599, 'rows': [[1, 4165, 835, 249165], [2, 4151, 849, 248316], [3, 4137, 863, 247453], [4, 4122, 878, 246575], [5, 4108, 892, 245683], [6, 4093, 907, 244776], [7, 4078, 922, 243854], [8, 4062, 938, 242916], [9, 4047, 953, 241963], [10, 4031, 969, 240994], [11, 4015, 985, 240009], [12, 3998, 1002, 239007], [13, 3981, 1019, 237988], [14, 3964, 1036, 236952], [15, 3947, 1053, 235899], [16, 3930, 1070, 234829], [17, 3912, 1088, 233741], [18, 3894, 1106, 232635], [19, 3875, 1125, 231510], [20, 3857, 1143, 230367], [21, 3838, 1162, 229205], [22, 3818, 1182, 228023], [23, 3798, 1202, 226821], [24, 3778, 1222, 225599]]} | Passed |
| control 2 | {'balloon': 249500, 'rows': [[1, 0, 500, 249500]]} | {'balloon': 249500, 'rows': [[1, 0, 500, 249500]]} | Passed |
| control 3 | {'error': 'negative_amortization', 'month': 1} | {'error': 'negative_amortization', 'month': 1} | Passed |
| control 4 | {'balloon': 100000, 'rows': []} | {'balloon': 100000, 'rows': []} | Passed |
| control 5 | {'balloon': 182567, 'rows': [[1, 2500, 2500, 247500], [2, 2475, 2525, 244975], [3, 2450, 2550, 242425], [4, 2424, 2576, 239849], [5, 2398, 2602, 237247], [6, 2372, 2628, 234619], [7, 2346, 2654, 231965], [8, 2320, 2680, 229285], [9, 2293, 2707, 226578], [10, 2266, 2734, 223844], [11, 2238, 2762, 221082], [12, 2211, 2789, 218293], [13, 2183, 2817, 215476], [14, 2155, 2845, 212631], [15, 2126, 2874, 209757], [16, 2098, 2902, 206855], [17, 2069, 2931, 203924], [18, 2039, 2961, 200963], [19, 2010, 2990, 197973], [20, 1980, 3020, 194953], [21, 1950, 3050, 191903], [22, 1919, 3081, 188822], [23, 1888, 3112, 185710], [24, 1857, 3143, 182567]]} | {'balloon': 182567, 'rows': [[1, 2500, 2500, 247500], [2, 2475, 2525, 244975], [3, 2450, 2550, 242425], [4, 2424, 2576, 239849], [5, 2398, 2602, 237247], [6, 2372, 2628, 234619], [7, 2346, 2654, 231965], [8, 2320, 2680, 229285], [9, 2293, 2707, 226578], [10, 2266, 2734, 223844], [11, 2238, 2762, 221082], [12, 2211, 2789, 218293], [13, 2183, 2817, 215476], [14, 2155, 2845, 212631], [15, 2126, 2874, 209757], [16, 2098, 2902, 206855], [17, 2069, 2931, 203924], [18, 2039, 2961, 200963], [19, 2010, 2990, 197973], [20, 1980, 3020, 194953], [21, 1950, 3050, 191903], [22, 1919, 3081, 188822], [23, 1888, 3112, 185710], [24, 1857, 3143, 182567]]} | Passed |
| control 6 | {'balloon': 526, 'rows': [[1, 5, 78, 922], [2, 5, 78, 844], [3, 4, 79, 765], [4, 4, 79, 686], [5, 3, 80, 606], [6, 3, 80, 526]]} | {'balloon': 526, 'rows': [[1, 5, 78, 922], [2, 5, 78, 844], [3, 4, 79, 765], [4, 4, 79, 686], [5, 3, 80, 606], [6, 3, 80, 526]]} | Passed |
SHA-256 / 3081d67ac9fbff1f37503b9232088182cc4720a994b25aaf73e6369d4e45a358
Verification & scope
A deterministic bounded teaching model with stipulated toy lending rules stated in the contract; money is integer cents and rates are basis points; it makes no claim of conformance to any regulation, servicing standard or product. 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 2026-09-29T14:46:26.123313+00:00.
Case digest / aca61c90772bb1eb3d636f3132d757e7215e91f45507e0c65c1d8540bb50ea88