FA-59901 / Inventory cost layering / Open access

Moving average perpetual costing: average denominator · case 01

After a receipt the new average is far too high because the pooled cost is divided by the receipt quantity only.

Verified by executionVariant 1 · 7 checks per implementationDownload source bundle ↓JSON ↗

ROOT CAUSE

The weighted average divides the pooled value by the received units instead of total units on hand after receipt.

VERIFIED REPAIR

Divide pooled value by (on-hand + received) units.

Unsuccessful approach: Dividing by the pre-receipt on-hand units breaks when stock was empty and still misweights otherwise.

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 = (2 * total + q) // (2 * q)
            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}]], [['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}]], [['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}]], [['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}]], [['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}]]]
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': 231, 'cogs': [1155], 'onhand': 15}`	`{'avg': 116, 'cogs': [580], 'onhand': 15}`	Failed
uneven rounding	`{'avg': 20, 'cogs': [40, 20], 'onhand': 4}`	`{'avg': 11, 'cogs': [22, 11], 'onhand': 4}`	Failed
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': 74, 'cogs': [222], 'onhand': 1}`	`{'avg': 14, 'cogs': [42], 'onhand': 1}`	Failed
half cent	`{'avg': 5, 'cogs': [5], 'onhand': 1}`	`{'avg': 3, 'cogs': [3], 'onhand': 1}`	Failed
issue all	`{'avg': 51, 'cogs': [408], 'onhand': 0}`	`{'avg': 26, 'cogs': [208], 'onhand': 0}`	Failed

SHA-256 / 8074976509c29ed31738282d8b94aac7c659fd67fb8f9c6033390004164a490d

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 = (2 * total + max(onhand, 1)) // (2 * max(onhand, 1))
            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}]], [['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}]], [['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}]], [['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}]], [['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}]]]
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': 231, 'cogs': [1155], 'onhand': 15}`	`{'avg': 116, 'cogs': [580], 'onhand': 15}`	Failed
uneven rounding	`{'avg': 26, 'cogs': [52, 26], 'onhand': 4}`	`{'avg': 11, 'cogs': [22, 11], 'onhand': 4}`	Failed
zero then receipt	`{'avg': 213, 'cogs': [100, 213], 'onhand': 2}`	`{'avg': 71, 'cogs': [100, 71], 'onhand': 2}`	Failed
short issue	`{'avg': 50, 'cogs': ['short'], 'onhand': 2}`	`{'avg': 50, 'cogs': ['short'], 'onhand': 2}`	Passed
many receipts	`{'avg': 43, 'cogs': [129], 'onhand': 1}`	`{'avg': 14, 'cogs': [42], 'onhand': 1}`	Failed
half cent	`{'avg': 5, 'cogs': [5], 'onhand': 1}`	`{'avg': 3, 'cogs': [3], 'onhand': 1}`	Failed
issue all	`{'avg': 51, 'cogs': [408], 'onhand': 0}`	`{'avg': 26, 'cogs': [208], 'onhand': 0}`	Failed

SHA-256 / 692621b25c8aea27771c25c16f249852cde613d5377f9a4bcebcb45e213d2150

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}]], [['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}]], [['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}]], [['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}]], [['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}]]]
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

SHA-256 / 5d4a931234748314056837c197ef866c2920d3ed74598c622f949d8064f651ab

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 2026-09-29T14:46:40.670158+00:00.

Case digest / edb220533bb5f8875a3eb8c5321ef886ec38f7877d7bf6e06d945035e9851fda