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FA-94846 / Warehouse slotting and bin packing / Open access

ABC velocity: SKU that crosses 80% demoted · case 01

The SKU whose picks carry the cumulative share over 80% is classified B although the contract makes it A.

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

ROOT CAUSE

The A test uses the cumulative share including the SKU itself rather than the share of strictly faster SKUs.

THE FAILURE

The A test uses the cumulative share including the SKU itself rather than the share of strictly faster SKUs.

Unsuccessful approach: Making the prior comparison inclusive promotes a SKU whose prior share is exactly 80% into A.

Case contract

Input [[sku, weekly_picks]]. Rank by picks descending then sku ascending. SKUs with equal picks form a tie group whose cumulative prior share is the picks of strictly faster groups. picks 0 -> D (dead stock); prior share < 80% -> A; < 95% -> B; else C. Return [[sku, class]] in input order.

Why this case matters

Velocity classes drive which SKUs are slotted into forward pick areas.

1 / The failure

Exit 1
"""Failure Map reference implementation. Python standard library only."""
import json

N = 1
observations = []
def solve(skus):
    total = sum(p for _, p in skus)
    order = sorted(skus, key=lambda r: (-r[1], r[0]))
    cls = {}
    prior = 0
    i = 0
    while i < len(order):
        j = i
        while j < len(order) and order[j][1] == order[i][1]:
            j += 1
        for sku, picks in order[i:j]:
            if picks == 0:
                cls[sku] = 'D'
            elif (prior + picks) * 100 < 80 * total:
                cls[sku] = 'A'
            elif prior * 100 < 95 * total:
                cls[sku] = 'B'
            else:
                cls[sku] = 'C'
        prior += order[i][1] * (j - i)
        i = j
    return [[sku, cls[sku]] for sku, _ in skus]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[['crossing sku is A', [[['a', 70], ['b', 20], ['c', 10]]], [['a', 'A'], ['b', 'A'], ['c', 'B']]], ['exact 95 boundary', [[['p', 80], ['q', 15], ['r', 5]]], [['p', 'A'], ['q', 'B'], ['r', 'C']]], ['tie group straddles 80%', [[['x', 40], ['y', 40], ['z', 20]]], [['x', 'A'], ['y', 'A'], ['z', 'B']]], ['all zero', [[['a', 0], ['b', 0]]], [['a', 'D'], ['b', 'D']]], ['single sku', [[['solo', 3]]], [['solo', 'A']]], ['dead stock', [[['a', 5], ['b', 0]]], [['a', 'A'], ['b', 'D']]], ['generated mix 6', [[['S21', 10], ['S16', 0], ['S28', 5], ['S06', 5], ['S04', 0], ['S08', 3]]], [['S21', 'A'], ['S16', 'D'], ['S28', 'A'], ['S06', 'A'], ['S04', 'D'], ['S08', 'B']]], ['generated mix 14', [[['S13', 60], ['S02', 8], ['S18', 5], ['S26', 5], ['S20', 5], ['S10', 5], ['S01', 10]]], [['S13', 'A'], ['S02', 'A'], ['S18', 'A'], ['S26', 'A'], ['S20', 'A'], ['S10', 'A'], ['S01', 'A']]]], [['generated mix 3', [[['S24', 20], ['S10', 2], ['S13', 20], ['S21', 40], ['S27', 3], ['S15', 60], ['S26', 5], ['S09', 40]]], [['S24', 'A'], ['S10', 'C'], ['S13', 'A'], ['S21', 'A'], ['S27', 'C'], ['S15', 'A'], ['S26', 'B'], ['S09', 'A']]], ['exact 95 boundary', [[['p', 80], ['q', 15], ['r', 5]]], [['p', 'A'], ['q', 'B'], ['r', 'C']]], ['all zero', [[['a', 0], ['b', 0]]], [['a', 'D'], ['b', 'D']]], ['single sku', [[['solo', 3]]], [['solo', 'A']]], ['crossing sku is A', [[['a', 70], ['b', 20], ['c', 10]]], [['a', 'A'], ['b', 'A'], ['c', 'B']]], ['dead stock', [[['a', 5], ['b', 0]]], [['a', 'A'], ['b', 'D']]], ['generated mix 10', [[['S07', 20], ['S27', 60], ['S28', 8]]], [['S07', 'A'], ['S27', 'A'], ['S28', 'B']]], ['generated mix 18', [[['S03', 10], ['S14', 10], ['S28', 0], ['S16', 20], ['S23', 60]]], [['S03', 'B'], ['S14', 'B'], ['S28', 'D'], ['S16', 'A'], ['S23', 'A']]]], [['generated mix 13', [[['S04', 10], ['S26', 40], ['S07', 3], ['S24', 2], ['S23', 40], ['S13', 2], ['S27', 0], ['S11', 5]]], [['S04', 'A'], ['S26', 'A'], ['S07', 'B'], ['S24', 'C'], ['S23', 'A'], ['S13', 'C'], ['S27', 'D'], ['S11', 'B']]], ['exact 95 boundary', [[['p', 80], ['q', 15], ['r', 5]]], [['p', 'A'], ['q', 'B'], ['r', 'C']]], ['empty', [[]], []], ['tie group straddles 80%', [[['x', 40], ['y', 40], ['z', 20]]], [['x', 'A'], ['y', 'A'], ['z', 'B']]], ['all zero', [[['a', 0], ['b', 0]]], [['a', 'D'], ['b', 'D']]], ['single sku', [[['solo', 3]]], [['solo', 'A']]], ['generated mix 21', [[['S23', 1], ['S07', 1], ['S04', 0], ['S22', 60], ['S03', 60], ['S21', 1]]], [['S23', 'C'], ['S07', 'C'], ['S04', 'D'], ['S22', 'A'], ['S03', 'A'], ['S21', 'C']]], ['generated mix 29', [[['S28', 5], ['S11', 60]]], [['S28', 'B'], ['S11', 'A']]]], [['generated mix 22', [[['S10', 40], ['S21', 20], ['S20', 2], ['S13', 10], ['S09', 1]]], [['S10', 'A'], ['S21', 'A'], ['S20', 'C'], ['S13', 'B'], ['S09', 'C']]], ['exact 95 boundary', [[['p', 80], ['q', 15], ['r', 5]]], [['p', 'A'], ['q', 'B'], ['r', 'C']]], ['dead stock', [[['a', 5], ['b', 0]]], [['a', 'A'], ['b', 'D']]], ['input order kept', [[['m', 1], ['k', 9], ['a', 90]]], [['m', 'C'], ['k', 'B'], ['a', 'A']]], ['empty', [[]], []], ['tie group straddles 80%', [[['x', 40], ['y', 40], ['z', 20]]], [['x', 'A'], ['y', 'A'], ['z', 'B']]], ['generated mix 32', [[['S07', 2], ['S02', 1], ['S17', 8], ['S24', 40], ['S05', 8], ['S11', 8], ['S28', 10]]], [['S07', 'C'], ['S02', 'C'], ['S17', 'A'], ['S24', 'A'], ['S05', 'A'], ['S11', 'A'], ['S28', 'A']]], ['generated mix 40', [[['S28', 20], ['S12', 0], ['S02', 2], ['S21', 10], ['S16', 40], ['S17', 60], ['S11', 5], ['S13', 2]]], [['S28', 'A'], ['S12', 'D'], ['S02', 'C'], ['S21', 'B'], ['S16', 'A'], ['S17', 'A'], ['S11', 'B'], ['S13', 'C']]]], [['generated mix 35', [[['S06', 2], ['S27', 8], ['S15', 2]]], [['S06', 'A'], ['S27', 'A'], ['S15', 'A']]], ['exact 95 boundary', [[['p', 80], ['q', 15], ['r', 5]]], [['p', 'A'], ['q', 'B'], ['r', 'C']]], ['single sku', [[['solo', 3]]], [['solo', 'A']]], ['crossing sku is A', [[['a', 70], ['b', 20], ['c', 10]]], [['a', 'A'], ['b', 'A'], ['c', 'B']]], ['dead stock', [[['a', 5], ['b', 0]]], [['a', 'A'], ['b', 'D']]], ['input order kept', [[['m', 1], ['k', 9], ['a', 90]]], [['m', 'C'], ['k', 'B'], ['a', 'A']]], ['generated mix 43', [[['S18', 60], ['S28', 60], ['S01', 3], ['S15', 5]]], [['S18', 'A'], ['S28', 'A'], ['S01', 'C'], ['S15', 'B']]], ['generated mix 51', [[['S24', 3], ['S13', 5], ['S29', 60], ['S16', 0], ['S22', 2], ['S05', 8], ['S14', 5], ['S04', 40]]], [['S24', 'C'], ['S13', 'B'], ['S29', 'A'], ['S16', 'D'], ['S22', 'C'], ['S05', 'B'], ['S14', 'B'], ['S04', 'A']]]]]
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 fixtureActualExpectedOutcome
crossing sku is A[['a', 'A'], ['b', 'B'], ['c', 'B']][['a', 'A'], ['b', 'A'], ['c', 'B']]Failed
exact 95 boundary[['p', 'B'], ['q', 'B'], ['r', 'C']][['p', 'A'], ['q', 'B'], ['r', 'C']]Failed
tie group straddles 80%[['x', 'A'], ['y', 'A'], ['z', 'B']][['x', 'A'], ['y', 'A'], ['z', 'B']]Passed
all zero[['a', 'D'], ['b', 'D']][['a', 'D'], ['b', 'D']]Passed
single sku[['solo', 'B']][['solo', 'A']]Failed
dead stock[['a', 'B'], ['b', 'D']][['a', 'A'], ['b', 'D']]Failed
generated mix 6[['S21', 'A'], ['S16', 'D'], ['S28', 'A'], ['S06', 'A'], ['S04', 'D'], ['S08', 'B']][['S21', 'A'], ['S16', 'D'], ['S28', 'A'], ['S06', 'A'], ['S04', 'D'], ['S08', 'B']]Passed
generated mix 14[['S13', 'A'], ['S02', 'A'], ['S18', 'B'], ['S26', 'B'], ['S20', 'B'], ['S10', 'B'], ['S01', 'A']][['S13', 'A'], ['S02', 'A'], ['S18', 'A'], ['S26', 'A'], ['S20', 'A'], ['S10', 'A'], ['S01', 'A']]Failed

SHA-256 / 92c1c9ba34a0754636bb717bbf98a6f54c0571fb5bdab7a6b31082e71efd0af3

2 / The unsuccessful fix

Exit 1
"""Failure Map reference implementation. Python standard library only."""
import json

N = 1
observations = []
def solve(skus):
    total = sum(p for _, p in skus)
    order = sorted(skus, key=lambda r: (-r[1], r[0]))
    cls = {}
    prior = 0
    i = 0
    while i < len(order):
        j = i
        while j < len(order) and order[j][1] == order[i][1]:
            j += 1
        for sku, picks in order[i:j]:
            if picks == 0:
                cls[sku] = 'D'
            elif prior * 100 <= 80 * total:
                cls[sku] = 'A'
            elif prior * 100 < 95 * total:
                cls[sku] = 'B'
            else:
                cls[sku] = 'C'
        prior += order[i][1] * (j - i)
        i = j
    return [[sku, cls[sku]] for sku, _ in skus]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[['crossing sku is A', [[['a', 70], ['b', 20], ['c', 10]]], [['a', 'A'], ['b', 'A'], ['c', 'B']]], ['exact 95 boundary', [[['p', 80], ['q', 15], ['r', 5]]], [['p', 'A'], ['q', 'B'], ['r', 'C']]], ['tie group straddles 80%', [[['x', 40], ['y', 40], ['z', 20]]], [['x', 'A'], ['y', 'A'], ['z', 'B']]], ['all zero', [[['a', 0], ['b', 0]]], [['a', 'D'], ['b', 'D']]], ['single sku', [[['solo', 3]]], [['solo', 'A']]], ['dead stock', [[['a', 5], ['b', 0]]], [['a', 'A'], ['b', 'D']]], ['generated mix 6', [[['S21', 10], ['S16', 0], ['S28', 5], ['S06', 5], ['S04', 0], ['S08', 3]]], [['S21', 'A'], ['S16', 'D'], ['S28', 'A'], ['S06', 'A'], ['S04', 'D'], ['S08', 'B']]], ['generated mix 14', [[['S13', 60], ['S02', 8], ['S18', 5], ['S26', 5], ['S20', 5], ['S10', 5], ['S01', 10]]], [['S13', 'A'], ['S02', 'A'], ['S18', 'A'], ['S26', 'A'], ['S20', 'A'], ['S10', 'A'], ['S01', 'A']]]], [['generated mix 3', [[['S24', 20], ['S10', 2], ['S13', 20], ['S21', 40], ['S27', 3], ['S15', 60], ['S26', 5], ['S09', 40]]], [['S24', 'A'], ['S10', 'C'], ['S13', 'A'], ['S21', 'A'], ['S27', 'C'], ['S15', 'A'], ['S26', 'B'], ['S09', 'A']]], ['exact 95 boundary', [[['p', 80], ['q', 15], ['r', 5]]], [['p', 'A'], ['q', 'B'], ['r', 'C']]], ['all zero', [[['a', 0], ['b', 0]]], [['a', 'D'], ['b', 'D']]], ['single sku', [[['solo', 3]]], [['solo', 'A']]], ['crossing sku is A', [[['a', 70], ['b', 20], ['c', 10]]], [['a', 'A'], ['b', 'A'], ['c', 'B']]], ['dead stock', [[['a', 5], ['b', 0]]], [['a', 'A'], ['b', 'D']]], ['generated mix 10', [[['S07', 20], ['S27', 60], ['S28', 8]]], [['S07', 'A'], ['S27', 'A'], ['S28', 'B']]], ['generated mix 18', [[['S03', 10], ['S14', 10], ['S28', 0], ['S16', 20], ['S23', 60]]], [['S03', 'B'], ['S14', 'B'], ['S28', 'D'], ['S16', 'A'], ['S23', 'A']]]], [['generated mix 13', [[['S04', 10], ['S26', 40], ['S07', 3], ['S24', 2], ['S23', 40], ['S13', 2], ['S27', 0], ['S11', 5]]], [['S04', 'A'], ['S26', 'A'], ['S07', 'B'], ['S24', 'C'], ['S23', 'A'], ['S13', 'C'], ['S27', 'D'], ['S11', 'B']]], ['exact 95 boundary', [[['p', 80], ['q', 15], ['r', 5]]], [['p', 'A'], ['q', 'B'], ['r', 'C']]], ['empty', [[]], []], ['tie group straddles 80%', [[['x', 40], ['y', 40], ['z', 20]]], [['x', 'A'], ['y', 'A'], ['z', 'B']]], ['all zero', [[['a', 0], ['b', 0]]], [['a', 'D'], ['b', 'D']]], ['single sku', [[['solo', 3]]], [['solo', 'A']]], ['generated mix 21', [[['S23', 1], ['S07', 1], ['S04', 0], ['S22', 60], ['S03', 60], ['S21', 1]]], [['S23', 'C'], ['S07', 'C'], ['S04', 'D'], ['S22', 'A'], ['S03', 'A'], ['S21', 'C']]], ['generated mix 29', [[['S28', 5], ['S11', 60]]], [['S28', 'B'], ['S11', 'A']]]], [['generated mix 22', [[['S10', 40], ['S21', 20], ['S20', 2], ['S13', 10], ['S09', 1]]], [['S10', 'A'], ['S21', 'A'], ['S20', 'C'], ['S13', 'B'], ['S09', 'C']]], ['exact 95 boundary', [[['p', 80], ['q', 15], ['r', 5]]], [['p', 'A'], ['q', 'B'], ['r', 'C']]], ['dead stock', [[['a', 5], ['b', 0]]], [['a', 'A'], ['b', 'D']]], ['input order kept', [[['m', 1], ['k', 9], ['a', 90]]], [['m', 'C'], ['k', 'B'], ['a', 'A']]], ['empty', [[]], []], ['tie group straddles 80%', [[['x', 40], ['y', 40], ['z', 20]]], [['x', 'A'], ['y', 'A'], ['z', 'B']]], ['generated mix 32', [[['S07', 2], ['S02', 1], ['S17', 8], ['S24', 40], ['S05', 8], ['S11', 8], ['S28', 10]]], [['S07', 'C'], ['S02', 'C'], ['S17', 'A'], ['S24', 'A'], ['S05', 'A'], ['S11', 'A'], ['S28', 'A']]], ['generated mix 40', [[['S28', 20], ['S12', 0], ['S02', 2], ['S21', 10], ['S16', 40], ['S17', 60], ['S11', 5], ['S13', 2]]], [['S28', 'A'], ['S12', 'D'], ['S02', 'C'], ['S21', 'B'], ['S16', 'A'], ['S17', 'A'], ['S11', 'B'], ['S13', 'C']]]], [['generated mix 35', [[['S06', 2], ['S27', 8], ['S15', 2]]], [['S06', 'A'], ['S27', 'A'], ['S15', 'A']]], ['exact 95 boundary', [[['p', 80], ['q', 15], ['r', 5]]], [['p', 'A'], ['q', 'B'], ['r', 'C']]], ['single sku', [[['solo', 3]]], [['solo', 'A']]], ['crossing sku is A', [[['a', 70], ['b', 20], ['c', 10]]], [['a', 'A'], ['b', 'A'], ['c', 'B']]], ['dead stock', [[['a', 5], ['b', 0]]], [['a', 'A'], ['b', 'D']]], ['input order kept', [[['m', 1], ['k', 9], ['a', 90]]], [['m', 'C'], ['k', 'B'], ['a', 'A']]], ['generated mix 43', [[['S18', 60], ['S28', 60], ['S01', 3], ['S15', 5]]], [['S18', 'A'], ['S28', 'A'], ['S01', 'C'], ['S15', 'B']]], ['generated mix 51', [[['S24', 3], ['S13', 5], ['S29', 60], ['S16', 0], ['S22', 2], ['S05', 8], ['S14', 5], ['S04', 40]]], [['S24', 'C'], ['S13', 'B'], ['S29', 'A'], ['S16', 'D'], ['S22', 'C'], ['S05', 'B'], ['S14', 'B'], ['S04', 'A']]]]]
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 fixtureActualExpectedOutcome
crossing sku is A[['a', 'A'], ['b', 'A'], ['c', 'B']][['a', 'A'], ['b', 'A'], ['c', 'B']]Passed
exact 95 boundary[['p', 'A'], ['q', 'A'], ['r', 'C']][['p', 'A'], ['q', 'B'], ['r', 'C']]Failed
tie group straddles 80%[['x', 'A'], ['y', 'A'], ['z', 'A']][['x', 'A'], ['y', 'A'], ['z', 'B']]Failed
all zero[['a', 'D'], ['b', 'D']][['a', 'D'], ['b', 'D']]Passed
single sku[['solo', 'A']][['solo', 'A']]Passed
dead stock[['a', 'A'], ['b', 'D']][['a', 'A'], ['b', 'D']]Passed
generated mix 6[['S21', 'A'], ['S16', 'D'], ['S28', 'A'], ['S06', 'A'], ['S04', 'D'], ['S08', 'B']][['S21', 'A'], ['S16', 'D'], ['S28', 'A'], ['S06', 'A'], ['S04', 'D'], ['S08', 'B']]Passed
generated mix 14[['S13', 'A'], ['S02', 'A'], ['S18', 'A'], ['S26', 'A'], ['S20', 'A'], ['S10', 'A'], ['S01', 'A']][['S13', 'A'], ['S02', 'A'], ['S18', 'A'], ['S26', 'A'], ['S20', 'A'], ['S10', 'A'], ['S01', 'A']]Passed

SHA-256 / 286bc10d87642398ca7e2015b91da7a5c85b089dbacd7bf6db9e0242b3bc8412

HELD IN THE MEMBER ARCHIVE

The verified repair and its recorded checks are member-only.

This mechanism has 8 recorded checks per implementation. The open-access tier publishes the failure and the unsuccessful fix; the repaired source that passes every check, and the observations that prove it, are available to members.

Every case sharing this mechanism uses the same contract and the same repair, so this one record is held back for all of them.

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Verification & scope

Stipulated toy ABC policy with fixed 80/95 bands; not a vendor WMS 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 2026-09-29T14:52:08.162963+00:00.

Case digest / d5d7b6680126b79ea6c277b4d491c3aca1dc21791c41fd425195d49b17dc0485