FA-59906 / Inventory cost layering / Open access

Moving average perpetual costing: half-cent rounding · case 01

Averages that land exactly on half a cent are truncated, drifting unit cost down over many receipts.

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

ROOT CAUSE

The average uses floor division without the half-unit offset.

VERIFIED REPAIR

Round half up: (2*total + units) // (2*units).

Unsuccessful approach: Using Python round() applies banker rounding and still rounds some half-cent averages down.

Case contract

Input {onhand, avg (cents, integer), events}. On receipt the average becomes round-half-up((onhand*avg + qty*cost)/(onhand+qty)) to whole cents; an issue is costed at qty*avg with the current average and never changes it; an issue exceeding on-hand returns "short". When on-hand reaches zero the average is kept as the last value (not reset). Return {cogs, onhand, avg}.

Why this case matters

Inventory valuation and cost-of-goods decisions depend on this rule.

1 / The failure

Exit 1

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

N = 1
observations = []
def solve(x):
    onhand = x['onhand']
    avg = x['avg']
    cogs = []
    for ev in x['events']:
        if ev[0] == 'recv':
            q, c = ev[1], ev[2]
            total = onhand * avg + q * c
            units = onhand + q
            avg = total // units
            onhand = units
        else:
            q = ev[1]
            if q > onhand:
                cogs.append('short')
                continue
            cogs.append(q * avg)
            onhand -= q
    return {'cogs': cogs, 'onhand': onhand, 'avg': avg}
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[['receipt reprices', {'onhand': 10, 'avg': 100, 'events': [['recv', 10, 131], ['issue', 5]]}, {'cogs': [580], 'onhand': 15, 'avg': 116}], ['uneven rounding', {'onhand': 3, 'avg': 10, 'events': [['recv', 4, 12], ['issue', 2], ['issue', 1]]}, {'cogs': [22, 11], 'onhand': 4, 'avg': 11}], ['zero then receipt', {'onhand': 2, 'avg': 50, 'events': [['issue', 2], ['recv', 3, 71], ['issue', 1]]}, {'cogs': [100, 71], 'onhand': 2, 'avg': 71}], ['short issue', {'onhand': 2, 'avg': 50, 'events': [['issue', 4]]}, {'cogs': ['short'], 'onhand': 2, 'avg': 50}], ['many receipts', {'onhand': 0, 'avg': 0, 'events': [['recv', 1, 10], ['recv', 2, 13], ['recv', 1, 20], ['issue', 3]]}, {'cogs': [42], 'onhand': 1, 'avg': 14}], ['half cent', {'onhand': 1, 'avg': 1, 'events': [['recv', 1, 4], ['issue', 1]]}, {'cogs': [3], 'onhand': 1, 'avg': 3}], ['issue all', {'onhand': 4, 'avg': 25, 'events': [['recv', 4, 26], ['issue', 8]]}, {'cogs': [208], 'onhand': 0, 'avg': 26}], ['exact half', {'onhand': 1, 'avg': 2, 'events': [['recv', 1, 3], ['issue', 2]]}, {'cogs': [6], 'onhand': 0, 'avg': 3}]], [['receipt reprices', {'onhand': 10, 'avg': 100, 'events': [['recv', 10, 132], ['issue', 5]]}, {'cogs': [580], 'onhand': 15, 'avg': 116}], ['uneven rounding', {'onhand': 3, 'avg': 10, 'events': [['recv', 4, 13], ['issue', 2], ['issue', 1]]}, {'cogs': [24, 12], 'onhand': 4, 'avg': 12}], ['zero then receipt', {'onhand': 2, 'avg': 50, 'events': [['issue', 2], ['recv', 3, 72], ['issue', 1]]}, {'cogs': [100, 72], 'onhand': 2, 'avg': 72}], ['short issue', {'onhand': 2, 'avg': 50, 'events': [['issue', 5]]}, {'cogs': ['short'], 'onhand': 2, 'avg': 50}], ['many receipts', {'onhand': 0, 'avg': 0, 'events': [['recv', 1, 10], ['recv', 2, 13], ['recv', 2, 20], ['issue', 3]]}, {'cogs': [45], 'onhand': 2, 'avg': 15}], ['half cent', {'onhand': 1, 'avg': 1, 'events': [['recv', 1, 6], ['issue', 1]]}, {'cogs': [4], 'onhand': 1, 'avg': 4}], ['issue all', {'onhand': 4, 'avg': 25, 'events': [['recv', 4, 26], ['issue', 8]]}, {'cogs': [208], 'onhand': 0, 'avg': 26}], ['exact half', {'onhand': 1, 'avg': 4, 'events': [['recv', 1, 5], ['issue', 2]]}, {'cogs': [10], 'onhand': 0, 'avg': 5}]], [['receipt reprices', {'onhand': 10, 'avg': 100, 'events': [['recv', 10, 133], ['issue', 5]]}, {'cogs': [585], 'onhand': 15, 'avg': 117}], ['uneven rounding', {'onhand': 3, 'avg': 10, 'events': [['recv', 4, 14], ['issue', 2], ['issue', 1]]}, {'cogs': [24, 12], 'onhand': 4, 'avg': 12}], ['zero then receipt', {'onhand': 2, 'avg': 50, 'events': [['issue', 2], ['recv', 3, 73], ['issue', 1]]}, {'cogs': [100, 73], 'onhand': 2, 'avg': 73}], ['short issue', {'onhand': 2, 'avg': 50, 'events': [['issue', 6]]}, {'cogs': ['short'], 'onhand': 2, 'avg': 50}], ['many receipts', {'onhand': 0, 'avg': 0, 'events': [['recv', 1, 10], ['recv', 2, 13], ['recv', 3, 20], ['issue', 3]]}, {'cogs': [48], 'onhand': 3, 'avg': 16}], ['half cent', {'onhand': 1, 'avg': 1, 'events': [['recv', 1, 8], ['issue', 1]]}, {'cogs': [5], 'onhand': 1, 'avg': 5}], ['issue all', {'onhand': 4, 'avg': 25, 'events': [['recv', 4, 26], ['issue', 8]]}, {'cogs': [208], 'onhand': 0, 'avg': 26}], ['exact half', {'onhand': 1, 'avg': 6, 'events': [['recv', 1, 7], ['issue', 2]]}, {'cogs': [14], 'onhand': 0, 'avg': 7}]], [['receipt reprices', {'onhand': 10, 'avg': 100, 'events': [['recv', 10, 134], ['issue', 5]]}, {'cogs': [585], 'onhand': 15, 'avg': 117}], ['uneven rounding', {'onhand': 3, 'avg': 10, 'events': [['recv', 4, 15], ['issue', 2], ['issue', 1]]}, {'cogs': [26, 13], 'onhand': 4, 'avg': 13}], ['zero then receipt', {'onhand': 2, 'avg': 50, 'events': [['issue', 2], ['recv', 3, 74], ['issue', 1]]}, {'cogs': [100, 74], 'onhand': 2, 'avg': 74}], ['short issue', {'onhand': 2, 'avg': 50, 'events': [['issue', 7]]}, {'cogs': ['short'], 'onhand': 2, 'avg': 50}], ['many receipts', {'onhand': 0, 'avg': 0, 'events': [['recv', 1, 10], ['recv', 2, 13], ['recv', 4, 20], ['issue', 3]]}, {'cogs': [51], 'onhand': 4, 'avg': 17}], ['half cent', {'onhand': 1, 'avg': 1, 'events': [['recv', 1, 10], ['issue', 1]]}, {'cogs': [6], 'onhand': 1, 'avg': 6}], ['issue all', {'onhand': 4, 'avg': 25, 'events': [['recv', 4, 26], ['issue', 8]]}, {'cogs': [208], 'onhand': 0, 'avg': 26}], ['exact half', {'onhand': 1, 'avg': 8, 'events': [['recv', 1, 9], ['issue', 2]]}, {'cogs': [18], 'onhand': 0, 'avg': 9}]], [['receipt reprices', {'onhand': 10, 'avg': 100, 'events': [['recv', 10, 135], ['issue', 5]]}, {'cogs': [590], 'onhand': 15, 'avg': 118}], ['uneven rounding', {'onhand': 3, 'avg': 10, 'events': [['recv', 4, 16], ['issue', 2], ['issue', 1]]}, {'cogs': [26, 13], 'onhand': 4, 'avg': 13}], ['zero then receipt', {'onhand': 2, 'avg': 50, 'events': [['issue', 2], ['recv', 3, 75], ['issue', 1]]}, {'cogs': [100, 75], 'onhand': 2, 'avg': 75}], ['short issue', {'onhand': 2, 'avg': 50, 'events': [['issue', 8]]}, {'cogs': ['short'], 'onhand': 2, 'avg': 50}], ['many receipts', {'onhand': 0, 'avg': 0, 'events': [['recv', 1, 10], ['recv', 2, 13], ['recv', 5, 20], ['issue', 3]]}, {'cogs': [51], 'onhand': 5, 'avg': 17}], ['half cent', {'onhand': 1, 'avg': 1, 'events': [['recv', 1, 12], ['issue', 1]]}, {'cogs': [7], 'onhand': 1, 'avg': 7}], ['issue all', {'onhand': 4, 'avg': 25, 'events': [['recv', 4, 26], ['issue', 8]]}, {'cogs': [208], 'onhand': 0, 'avg': 26}], ['exact half', {'onhand': 1, 'avg': 10, 'events': [['recv', 1, 11], ['issue', 2]]}, {'cogs': [22], 'onhand': 0, 'avg': 11}]]]
for label, args, expected in fixtures[N-1]:
    check(label, 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
receipt reprices	`{'avg': 115, 'cogs': [575], 'onhand': 15}`	`{'avg': 116, 'cogs': [580], 'onhand': 15}`	Failed
uneven rounding	`{'avg': 11, 'cogs': [22, 11], 'onhand': 4}`	`{'avg': 11, 'cogs': [22, 11], 'onhand': 4}`	Passed
zero then receipt	`{'avg': 71, 'cogs': [100, 71], 'onhand': 2}`	`{'avg': 71, 'cogs': [100, 71], 'onhand': 2}`	Passed
short issue	`{'avg': 50, 'cogs': ['short'], 'onhand': 2}`	`{'avg': 50, 'cogs': ['short'], 'onhand': 2}`	Passed
many receipts	`{'avg': 14, 'cogs': [42], 'onhand': 1}`	`{'avg': 14, 'cogs': [42], 'onhand': 1}`	Passed
half cent	`{'avg': 2, 'cogs': [2], 'onhand': 1}`	`{'avg': 3, 'cogs': [3], 'onhand': 1}`	Failed
issue all	`{'avg': 25, 'cogs': [200], 'onhand': 0}`	`{'avg': 26, 'cogs': [208], 'onhand': 0}`	Failed
exact half	`{'avg': 2, 'cogs': [4], 'onhand': 0}`	`{'avg': 3, 'cogs': [6], 'onhand': 0}`	Failed

SHA-256 / e685cd47ac62691fb17e58831fa705d0cf63e19d7e529893ff66f42d6d54cc17

2 / The unsuccessful fix

Exit 1

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

N = 1
observations = []
def solve(x):
    onhand = x['onhand']
    avg = x['avg']
    cogs = []
    for ev in x['events']:
        if ev[0] == 'recv':
            q, c = ev[1], ev[2]
            total = onhand * avg + q * c
            units = onhand + q
            avg = round(total / units)
            onhand = units
        else:
            q = ev[1]
            if q > onhand:
                cogs.append('short')
                continue
            cogs.append(q * avg)
            onhand -= q
    return {'cogs': cogs, 'onhand': onhand, 'avg': avg}
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[['receipt reprices', {'onhand': 10, 'avg': 100, 'events': [['recv', 10, 131], ['issue', 5]]}, {'cogs': [580], 'onhand': 15, 'avg': 116}], ['uneven rounding', {'onhand': 3, 'avg': 10, 'events': [['recv', 4, 12], ['issue', 2], ['issue', 1]]}, {'cogs': [22, 11], 'onhand': 4, 'avg': 11}], ['zero then receipt', {'onhand': 2, 'avg': 50, 'events': [['issue', 2], ['recv', 3, 71], ['issue', 1]]}, {'cogs': [100, 71], 'onhand': 2, 'avg': 71}], ['short issue', {'onhand': 2, 'avg': 50, 'events': [['issue', 4]]}, {'cogs': ['short'], 'onhand': 2, 'avg': 50}], ['many receipts', {'onhand': 0, 'avg': 0, 'events': [['recv', 1, 10], ['recv', 2, 13], ['recv', 1, 20], ['issue', 3]]}, {'cogs': [42], 'onhand': 1, 'avg': 14}], ['half cent', {'onhand': 1, 'avg': 1, 'events': [['recv', 1, 4], ['issue', 1]]}, {'cogs': [3], 'onhand': 1, 'avg': 3}], ['issue all', {'onhand': 4, 'avg': 25, 'events': [['recv', 4, 26], ['issue', 8]]}, {'cogs': [208], 'onhand': 0, 'avg': 26}], ['exact half', {'onhand': 1, 'avg': 2, 'events': [['recv', 1, 3], ['issue', 2]]}, {'cogs': [6], 'onhand': 0, 'avg': 3}]], [['receipt reprices', {'onhand': 10, 'avg': 100, 'events': [['recv', 10, 132], ['issue', 5]]}, {'cogs': [580], 'onhand': 15, 'avg': 116}], ['uneven rounding', {'onhand': 3, 'avg': 10, 'events': [['recv', 4, 13], ['issue', 2], ['issue', 1]]}, {'cogs': [24, 12], 'onhand': 4, 'avg': 12}], ['zero then receipt', {'onhand': 2, 'avg': 50, 'events': [['issue', 2], ['recv', 3, 72], ['issue', 1]]}, {'cogs': [100, 72], 'onhand': 2, 'avg': 72}], ['short issue', {'onhand': 2, 'avg': 50, 'events': [['issue', 5]]}, {'cogs': ['short'], 'onhand': 2, 'avg': 50}], ['many receipts', {'onhand': 0, 'avg': 0, 'events': [['recv', 1, 10], ['recv', 2, 13], ['recv', 2, 20], ['issue', 3]]}, {'cogs': [45], 'onhand': 2, 'avg': 15}], ['half cent', {'onhand': 1, 'avg': 1, 'events': [['recv', 1, 6], ['issue', 1]]}, {'cogs': [4], 'onhand': 1, 'avg': 4}], ['issue all', {'onhand': 4, 'avg': 25, 'events': [['recv', 4, 26], ['issue', 8]]}, {'cogs': [208], 'onhand': 0, 'avg': 26}], ['exact half', {'onhand': 1, 'avg': 4, 'events': [['recv', 1, 5], ['issue', 2]]}, {'cogs': [10], 'onhand': 0, 'avg': 5}]], [['receipt reprices', {'onhand': 10, 'avg': 100, 'events': [['recv', 10, 133], ['issue', 5]]}, {'cogs': [585], 'onhand': 15, 'avg': 117}], ['uneven rounding', {'onhand': 3, 'avg': 10, 'events': [['recv', 4, 14], ['issue', 2], ['issue', 1]]}, {'cogs': [24, 12], 'onhand': 4, 'avg': 12}], ['zero then receipt', {'onhand': 2, 'avg': 50, 'events': [['issue', 2], ['recv', 3, 73], ['issue', 1]]}, {'cogs': [100, 73], 'onhand': 2, 'avg': 73}], ['short issue', {'onhand': 2, 'avg': 50, 'events': [['issue', 6]]}, {'cogs': ['short'], 'onhand': 2, 'avg': 50}], ['many receipts', {'onhand': 0, 'avg': 0, 'events': [['recv', 1, 10], ['recv', 2, 13], ['recv', 3, 20], ['issue', 3]]}, {'cogs': [48], 'onhand': 3, 'avg': 16}], ['half cent', {'onhand': 1, 'avg': 1, 'events': [['recv', 1, 8], ['issue', 1]]}, {'cogs': [5], 'onhand': 1, 'avg': 5}], ['issue all', {'onhand': 4, 'avg': 25, 'events': [['recv', 4, 26], ['issue', 8]]}, {'cogs': [208], 'onhand': 0, 'avg': 26}], ['exact half', {'onhand': 1, 'avg': 6, 'events': [['recv', 1, 7], ['issue', 2]]}, {'cogs': [14], 'onhand': 0, 'avg': 7}]], [['receipt reprices', {'onhand': 10, 'avg': 100, 'events': [['recv', 10, 134], ['issue', 5]]}, {'cogs': [585], 'onhand': 15, 'avg': 117}], ['uneven rounding', {'onhand': 3, 'avg': 10, 'events': [['recv', 4, 15], ['issue', 2], ['issue', 1]]}, {'cogs': [26, 13], 'onhand': 4, 'avg': 13}], ['zero then receipt', {'onhand': 2, 'avg': 50, 'events': [['issue', 2], ['recv', 3, 74], ['issue', 1]]}, {'cogs': [100, 74], 'onhand': 2, 'avg': 74}], ['short issue', {'onhand': 2, 'avg': 50, 'events': [['issue', 7]]}, {'cogs': ['short'], 'onhand': 2, 'avg': 50}], ['many receipts', {'onhand': 0, 'avg': 0, 'events': [['recv', 1, 10], ['recv', 2, 13], ['recv', 4, 20], ['issue', 3]]}, {'cogs': [51], 'onhand': 4, 'avg': 17}], ['half cent', {'onhand': 1, 'avg': 1, 'events': [['recv', 1, 10], ['issue', 1]]}, {'cogs': [6], 'onhand': 1, 'avg': 6}], ['issue all', {'onhand': 4, 'avg': 25, 'events': [['recv', 4, 26], ['issue', 8]]}, {'cogs': [208], 'onhand': 0, 'avg': 26}], ['exact half', {'onhand': 1, 'avg': 8, 'events': [['recv', 1, 9], ['issue', 2]]}, {'cogs': [18], 'onhand': 0, 'avg': 9}]], [['receipt reprices', {'onhand': 10, 'avg': 100, 'events': [['recv', 10, 135], ['issue', 5]]}, {'cogs': [590], 'onhand': 15, 'avg': 118}], ['uneven rounding', {'onhand': 3, 'avg': 10, 'events': [['recv', 4, 16], ['issue', 2], ['issue', 1]]}, {'cogs': [26, 13], 'onhand': 4, 'avg': 13}], ['zero then receipt', {'onhand': 2, 'avg': 50, 'events': [['issue', 2], ['recv', 3, 75], ['issue', 1]]}, {'cogs': [100, 75], 'onhand': 2, 'avg': 75}], ['short issue', {'onhand': 2, 'avg': 50, 'events': [['issue', 8]]}, {'cogs': ['short'], 'onhand': 2, 'avg': 50}], ['many receipts', {'onhand': 0, 'avg': 0, 'events': [['recv', 1, 10], ['recv', 2, 13], ['recv', 5, 20], ['issue', 3]]}, {'cogs': [51], 'onhand': 5, 'avg': 17}], ['half cent', {'onhand': 1, 'avg': 1, 'events': [['recv', 1, 12], ['issue', 1]]}, {'cogs': [7], 'onhand': 1, 'avg': 7}], ['issue all', {'onhand': 4, 'avg': 25, 'events': [['recv', 4, 26], ['issue', 8]]}, {'cogs': [208], 'onhand': 0, 'avg': 26}], ['exact half', {'onhand': 1, 'avg': 10, 'events': [['recv', 1, 11], ['issue', 2]]}, {'cogs': [22], 'onhand': 0, 'avg': 11}]]]
for label, args, expected in fixtures[N-1]:
    check(label, 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
receipt reprices	`{'avg': 116, 'cogs': [580], 'onhand': 15}`	`{'avg': 116, 'cogs': [580], 'onhand': 15}`	Passed
uneven rounding	`{'avg': 11, 'cogs': [22, 11], 'onhand': 4}`	`{'avg': 11, 'cogs': [22, 11], 'onhand': 4}`	Passed
zero then receipt	`{'avg': 71, 'cogs': [100, 71], 'onhand': 2}`	`{'avg': 71, 'cogs': [100, 71], 'onhand': 2}`	Passed
short issue	`{'avg': 50, 'cogs': ['short'], 'onhand': 2}`	`{'avg': 50, 'cogs': ['short'], 'onhand': 2}`	Passed
many receipts	`{'avg': 14, 'cogs': [42], 'onhand': 1}`	`{'avg': 14, 'cogs': [42], 'onhand': 1}`	Passed
half cent	`{'avg': 2, 'cogs': [2], 'onhand': 1}`	`{'avg': 3, 'cogs': [3], 'onhand': 1}`	Failed
issue all	`{'avg': 26, 'cogs': [208], 'onhand': 0}`	`{'avg': 26, 'cogs': [208], 'onhand': 0}`	Passed
exact half	`{'avg': 2, 'cogs': [4], 'onhand': 0}`	`{'avg': 3, 'cogs': [6], 'onhand': 0}`	Failed

SHA-256 / 7aae3b45fade01d3d1f3ed9636e5cf27c9f3f08492c6f480d74276e1420cf68d

3 / The verified repair

Exit 0

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

N = 1
observations = []
def solve(x):
    onhand = x['onhand']
    avg = x['avg']
    cogs = []
    for ev in x['events']:
        if ev[0] == 'recv':
            q, c = ev[1], ev[2]
            total = onhand * avg + q * c
            units = onhand + q
            avg = (2 * total + units) // (2 * units)
            onhand = units
        else:
            q = ev[1]
            if q > onhand:
                cogs.append('short')
                continue
            cogs.append(q * avg)
            onhand -= q
    return {'cogs': cogs, 'onhand': onhand, 'avg': avg}
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[['receipt reprices', {'onhand': 10, 'avg': 100, 'events': [['recv', 10, 131], ['issue', 5]]}, {'cogs': [580], 'onhand': 15, 'avg': 116}], ['uneven rounding', {'onhand': 3, 'avg': 10, 'events': [['recv', 4, 12], ['issue', 2], ['issue', 1]]}, {'cogs': [22, 11], 'onhand': 4, 'avg': 11}], ['zero then receipt', {'onhand': 2, 'avg': 50, 'events': [['issue', 2], ['recv', 3, 71], ['issue', 1]]}, {'cogs': [100, 71], 'onhand': 2, 'avg': 71}], ['short issue', {'onhand': 2, 'avg': 50, 'events': [['issue', 4]]}, {'cogs': ['short'], 'onhand': 2, 'avg': 50}], ['many receipts', {'onhand': 0, 'avg': 0, 'events': [['recv', 1, 10], ['recv', 2, 13], ['recv', 1, 20], ['issue', 3]]}, {'cogs': [42], 'onhand': 1, 'avg': 14}], ['half cent', {'onhand': 1, 'avg': 1, 'events': [['recv', 1, 4], ['issue', 1]]}, {'cogs': [3], 'onhand': 1, 'avg': 3}], ['issue all', {'onhand': 4, 'avg': 25, 'events': [['recv', 4, 26], ['issue', 8]]}, {'cogs': [208], 'onhand': 0, 'avg': 26}], ['exact half', {'onhand': 1, 'avg': 2, 'events': [['recv', 1, 3], ['issue', 2]]}, {'cogs': [6], 'onhand': 0, 'avg': 3}]], [['receipt reprices', {'onhand': 10, 'avg': 100, 'events': [['recv', 10, 132], ['issue', 5]]}, {'cogs': [580], 'onhand': 15, 'avg': 116}], ['uneven rounding', {'onhand': 3, 'avg': 10, 'events': [['recv', 4, 13], ['issue', 2], ['issue', 1]]}, {'cogs': [24, 12], 'onhand': 4, 'avg': 12}], ['zero then receipt', {'onhand': 2, 'avg': 50, 'events': [['issue', 2], ['recv', 3, 72], ['issue', 1]]}, {'cogs': [100, 72], 'onhand': 2, 'avg': 72}], ['short issue', {'onhand': 2, 'avg': 50, 'events': [['issue', 5]]}, {'cogs': ['short'], 'onhand': 2, 'avg': 50}], ['many receipts', {'onhand': 0, 'avg': 0, 'events': [['recv', 1, 10], ['recv', 2, 13], ['recv', 2, 20], ['issue', 3]]}, {'cogs': [45], 'onhand': 2, 'avg': 15}], ['half cent', {'onhand': 1, 'avg': 1, 'events': [['recv', 1, 6], ['issue', 1]]}, {'cogs': [4], 'onhand': 1, 'avg': 4}], ['issue all', {'onhand': 4, 'avg': 25, 'events': [['recv', 4, 26], ['issue', 8]]}, {'cogs': [208], 'onhand': 0, 'avg': 26}], ['exact half', {'onhand': 1, 'avg': 4, 'events': [['recv', 1, 5], ['issue', 2]]}, {'cogs': [10], 'onhand': 0, 'avg': 5}]], [['receipt reprices', {'onhand': 10, 'avg': 100, 'events': [['recv', 10, 133], ['issue', 5]]}, {'cogs': [585], 'onhand': 15, 'avg': 117}], ['uneven rounding', {'onhand': 3, 'avg': 10, 'events': [['recv', 4, 14], ['issue', 2], ['issue', 1]]}, {'cogs': [24, 12], 'onhand': 4, 'avg': 12}], ['zero then receipt', {'onhand': 2, 'avg': 50, 'events': [['issue', 2], ['recv', 3, 73], ['issue', 1]]}, {'cogs': [100, 73], 'onhand': 2, 'avg': 73}], ['short issue', {'onhand': 2, 'avg': 50, 'events': [['issue', 6]]}, {'cogs': ['short'], 'onhand': 2, 'avg': 50}], ['many receipts', {'onhand': 0, 'avg': 0, 'events': [['recv', 1, 10], ['recv', 2, 13], ['recv', 3, 20], ['issue', 3]]}, {'cogs': [48], 'onhand': 3, 'avg': 16}], ['half cent', {'onhand': 1, 'avg': 1, 'events': [['recv', 1, 8], ['issue', 1]]}, {'cogs': [5], 'onhand': 1, 'avg': 5}], ['issue all', {'onhand': 4, 'avg': 25, 'events': [['recv', 4, 26], ['issue', 8]]}, {'cogs': [208], 'onhand': 0, 'avg': 26}], ['exact half', {'onhand': 1, 'avg': 6, 'events': [['recv', 1, 7], ['issue', 2]]}, {'cogs': [14], 'onhand': 0, 'avg': 7}]], [['receipt reprices', {'onhand': 10, 'avg': 100, 'events': [['recv', 10, 134], ['issue', 5]]}, {'cogs': [585], 'onhand': 15, 'avg': 117}], ['uneven rounding', {'onhand': 3, 'avg': 10, 'events': [['recv', 4, 15], ['issue', 2], ['issue', 1]]}, {'cogs': [26, 13], 'onhand': 4, 'avg': 13}], ['zero then receipt', {'onhand': 2, 'avg': 50, 'events': [['issue', 2], ['recv', 3, 74], ['issue', 1]]}, {'cogs': [100, 74], 'onhand': 2, 'avg': 74}], ['short issue', {'onhand': 2, 'avg': 50, 'events': [['issue', 7]]}, {'cogs': ['short'], 'onhand': 2, 'avg': 50}], ['many receipts', {'onhand': 0, 'avg': 0, 'events': [['recv', 1, 10], ['recv', 2, 13], ['recv', 4, 20], ['issue', 3]]}, {'cogs': [51], 'onhand': 4, 'avg': 17}], ['half cent', {'onhand': 1, 'avg': 1, 'events': [['recv', 1, 10], ['issue', 1]]}, {'cogs': [6], 'onhand': 1, 'avg': 6}], ['issue all', {'onhand': 4, 'avg': 25, 'events': [['recv', 4, 26], ['issue', 8]]}, {'cogs': [208], 'onhand': 0, 'avg': 26}], ['exact half', {'onhand': 1, 'avg': 8, 'events': [['recv', 1, 9], ['issue', 2]]}, {'cogs': [18], 'onhand': 0, 'avg': 9}]], [['receipt reprices', {'onhand': 10, 'avg': 100, 'events': [['recv', 10, 135], ['issue', 5]]}, {'cogs': [590], 'onhand': 15, 'avg': 118}], ['uneven rounding', {'onhand': 3, 'avg': 10, 'events': [['recv', 4, 16], ['issue', 2], ['issue', 1]]}, {'cogs': [26, 13], 'onhand': 4, 'avg': 13}], ['zero then receipt', {'onhand': 2, 'avg': 50, 'events': [['issue', 2], ['recv', 3, 75], ['issue', 1]]}, {'cogs': [100, 75], 'onhand': 2, 'avg': 75}], ['short issue', {'onhand': 2, 'avg': 50, 'events': [['issue', 8]]}, {'cogs': ['short'], 'onhand': 2, 'avg': 50}], ['many receipts', {'onhand': 0, 'avg': 0, 'events': [['recv', 1, 10], ['recv', 2, 13], ['recv', 5, 20], ['issue', 3]]}, {'cogs': [51], 'onhand': 5, 'avg': 17}], ['half cent', {'onhand': 1, 'avg': 1, 'events': [['recv', 1, 12], ['issue', 1]]}, {'cogs': [7], 'onhand': 1, 'avg': 7}], ['issue all', {'onhand': 4, 'avg': 25, 'events': [['recv', 4, 26], ['issue', 8]]}, {'cogs': [208], 'onhand': 0, 'avg': 26}], ['exact half', {'onhand': 1, 'avg': 10, 'events': [['recv', 1, 11], ['issue', 2]]}, {'cogs': [22], 'onhand': 0, 'avg': 11}]]]
for label, args, expected in fixtures[N-1]:
    check(label, 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
receipt reprices	`{'avg': 116, 'cogs': [580], 'onhand': 15}`	`{'avg': 116, 'cogs': [580], 'onhand': 15}`	Passed
uneven rounding	`{'avg': 11, 'cogs': [22, 11], 'onhand': 4}`	`{'avg': 11, 'cogs': [22, 11], 'onhand': 4}`	Passed
zero then receipt	`{'avg': 71, 'cogs': [100, 71], 'onhand': 2}`	`{'avg': 71, 'cogs': [100, 71], 'onhand': 2}`	Passed
short issue	`{'avg': 50, 'cogs': ['short'], 'onhand': 2}`	`{'avg': 50, 'cogs': ['short'], 'onhand': 2}`	Passed
many receipts	`{'avg': 14, 'cogs': [42], 'onhand': 1}`	`{'avg': 14, 'cogs': [42], 'onhand': 1}`	Passed
half cent	`{'avg': 3, 'cogs': [3], 'onhand': 1}`	`{'avg': 3, 'cogs': [3], 'onhand': 1}`	Passed
issue all	`{'avg': 26, 'cogs': [208], 'onhand': 0}`	`{'avg': 26, 'cogs': [208], 'onhand': 0}`	Passed
exact half	`{'avg': 3, 'cogs': [6], 'onhand': 0}`	`{'avg': 3, 'cogs': [6], 'onhand': 0}`	Passed

SHA-256 / 67e6cb8e5387bd25d5df753d0f7806504655d24ccaf5bc5c2c2deaea7a239147

Verification & scope

Stipulated bounded teaching model with explicit toy rules; not an accounting-standard 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 2026-09-29T14:46:40.728930+00:00.

Case digest / 06c7ad3670109e4e69935c93f08e268466bc5e8bea0d5f58a56820cde673e46e