FAILURE MAP
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FA-93256 / EV charging session scheduling / Open access

Arrival charger matching: AC/DC classification boundary · case 01

22 kW AC points are skipped for vehicles without DC support.

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

ROOT CAUSE

The DC classification includes the 22 kW AC rating.

THE FAILURE

The DC classification includes the 22 kW AC rating.

Unsuccessful approach: Raising the boundary to 50 kW treats small DC units as AC and caps them by the onboard charger.

Case contract

chargers are [id, kw, free_at]; kw > 22 is DC (usable only if dc_ok, full kw), otherwise AC limited to the vehicle onboard max_ac. vehicle is [need_kwh, depart, max_ac, dc_ok]. Finish = max(now, free_at) + ceil(need*60/power) minutes. Among chargers finishing by depart pick the lowest power, then earliest finish, then id; otherwise the earliest finish (then id) with status 'late'. Return [id, finish, status] or None when no charger is usable.

Why this case matters

Depot, workplace and public EV chargers schedule sessions against prices, circuit limits and departure deadlines; a wrong decision silently strands a driver or overloads a feeder.

1 / The failure

Exit 1
"""Failure Map reference implementation. Python standard library only."""
import json
import math
N = 1
observations = []
def solve(chargers, vehicle, now):
    need, depart, max_ac, dc_ok = vehicle
    opts = []
    for cid, kw, free_at in chargers:
        if kw >= 22:
            if not dc_ok:
                continue
            pw = kw
        else:
            pw = min(kw, max_ac)
        start = max(now, free_at)
        finish = start + math.ceil(need * 60 / pw)
        opts.append([pw, finish, cid])
    if not opts:
        return None
    ok = [o for o in opts if o[1] <= depart]
    if ok:
        pw, finish, cid = min(ok)
        return [cid, finish, 'ok']
    pw, finish, cid = min(opts, key=lambda o: (o[1], o[2]))
    return [cid, finish, 'late']
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[['boundary: 22 kW AC charger', [[[1, 22, 0]], [11, 300, 11, False], 0], [1, 60, 'ok']],
  ['boundary: finish exactly at departure', [[[1, 7.4, 0]], [37, 300, 7.4, True], 0],
   [1, 300, 'ok']],
  ['boundary: only DC and no DC support', [[[1, 50, 0]], [10, 100, 11, False], 0], None],
  ['regression: AC/DC classification boundary',
   [[[1, 150, 10], [2, 22, 120], [3, 150, 30], [4, 3.7, 120]], [20, 111, 3.7, False], 6],
   [2, 445, 'late']],
  ['regression: AC/DC classification boundary (partial repair)',
   [[[1, 50, 0]], [45, 372, 7.4, False], 56], None],
  ['control 1', [[[1, 22, 60]], [5, 244, 11, False], 8], [1, 88, 'ok']],
  ['control 2', [[[1, 50, 0], [2, 50, 0]], [5, 160, 11, False], 39], None]],
 [['boundary: 22 kW AC charger', [[[1, 22, 0]], [11, 300, 11, False], 0], [1, 60, 'ok']],
  ['boundary: finish exactly at departure', [[[1, 7.4, 0]], [37, 300, 7.4, True], 0],
   [1, 300, 'ok']],
  ['boundary: only DC and no DC support', [[[1, 50, 0]], [10, 100, 11, False], 0], None],
  ['regression: AC/DC classification boundary', [[[1, 22, 120]], [20, 345, 3.7, True], 47],
   [1, 445, 'late']],
  ['regression: AC/DC classification boundary (partial repair)',
   [[[1, 150, 0], [2, 7.4, 120], [3, 50, 0]], [20, 67, 11, True], 8], [3, 32, 'ok']],
  ['control 1', [[[1, 50, 0]], [45, 63, 7.4, True], 12], [1, 66, 'late']],
  ['control 2',
   [[[1, 7.4, 60], [2, 7.4, 10], [3, 22, 10], [4, 11, 120], [5, 50, 120]], [45, 353, 7.4, True],
    45],
   [5, 174, 'ok']]],
 [['boundary: 22 kW AC charger', [[[1, 22, 0]], [11, 300, 11, False], 0], [1, 60, 'ok']],
  ['boundary: finish exactly at departure', [[[1, 7.4, 0]], [37, 300, 7.4, True], 0],
   [1, 300, 'ok']],
  ['boundary: only DC and no DC support', [[[1, 50, 0]], [10, 100, 11, False], 0], None],
  ['regression: AC/DC classification boundary',
   [[[1, 22, 10], [2, 3.7, 30]], [5, 408, 3.7, False], 55], [1, 137, 'ok']],
  ['regression: AC/DC classification boundary (partial repair)',
   [[[1, 50, 10]], [10, 99, 3.7, True], 41], [1, 53, 'ok']],
  ['control 1', [[[1, 7.4, 10], [2, 7.4, 0]], [45, 88, 7.4, True], 40], [1, 405, 'late']],
  ['control 2', [[[1, 3.7, 10], [2, 3.7, 120], [3, 11, 10], [4, 50, 0]], [5, 42, 7.4, True], 27],
   [4, 33, 'ok']]],
 [['boundary: 22 kW AC charger', [[[1, 22, 0]], [11, 300, 11, False], 0], [1, 60, 'ok']],
  ['boundary: finish exactly at departure', [[[1, 7.4, 0]], [37, 300, 7.4, True], 0],
   [1, 300, 'ok']],
  ['boundary: only DC and no DC support', [[[1, 50, 0]], [10, 100, 11, False], 0], None],
  ['regression: AC/DC classification boundary',
   [[[1, 50, 0], [2, 7.4, 0], [3, 7.4, 120], [4, 22, 10]], [45, 278, 3.7, True], 26],
   [1, 80, 'ok']],
  ['regression: AC/DC classification boundary (partial repair)',
   [[[1, 50, 60], [2, 50, 60]], [45, 130, 7.4, True], 48], [1, 114, 'ok']],
  ['control 1', [[[1, 7.4, 60]], [30, 240, 3.7, True], 21], [1, 547, 'late']],
  ['control 2', [[[1, 3.7, 60], [2, 3.7, 120], [3, 150, 30], [4, 150, 0]], [45, 67, 11, False], 57],
   [1, 790, 'late']]],
 [['boundary: 22 kW AC charger', [[[1, 22, 0]], [11, 300, 11, False], 0], [1, 60, 'ok']],
  ['boundary: finish exactly at departure', [[[1, 7.4, 0]], [37, 300, 7.4, True], 0],
   [1, 300, 'ok']],
  ['boundary: only DC and no DC support', [[[1, 50, 0]], [10, 100, 11, False], 0], None],
  ['regression: AC/DC classification boundary',
   [[[1, 22, 0], [2, 3.7, 10], [3, 50, 30]], [20, 64, 3.7, False], 19], [1, 344, 'late']],
  ['regression: AC/DC classification boundary (partial repair)',
   [[[1, 50, 0], [2, 50, 30]], [10, 89, 7.4, True], 45], [1, 57, 'ok']],
  ['control 1', [[[1, 50, 60], [2, 50, 60]], [45, 130, 7.4, True], 48], [1, 114, 'ok']],
  ['control 2', [[[1, 150, 0], [2, 7.4, 10]], [10, 89, 3.7, True], 57], [1, 61, 'ok']]]]
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
boundary: 22 kW AC chargerNone[1, 60, 'ok']Failed
boundary: finish exactly at departure[1, 300, 'ok'][1, 300, 'ok']Passed
boundary: only DC and no DC supportNoneNonePassed
regression: AC/DC classification boundary[4, 445, 'late'][2, 445, 'late']Failed
regression: AC/DC classification boundary (partial repair)NoneNonePassed
control 1None[1, 88, 'ok']Failed
control 2NoneNonePassed

SHA-256 / f95da59592194178fabe7df1cd295d17ade534a04f8fe2f7dfbbbac703305e07

2 / The unsuccessful fix

Exit 1
"""Failure Map reference implementation. Python standard library only."""
import json
import math
N = 1
observations = []
def solve(chargers, vehicle, now):
    need, depart, max_ac, dc_ok = vehicle
    opts = []
    for cid, kw, free_at in chargers:
        if kw > 50:
            if not dc_ok:
                continue
            pw = kw
        else:
            pw = min(kw, max_ac)
        start = max(now, free_at)
        finish = start + math.ceil(need * 60 / pw)
        opts.append([pw, finish, cid])
    if not opts:
        return None
    ok = [o for o in opts if o[1] <= depart]
    if ok:
        pw, finish, cid = min(ok)
        return [cid, finish, 'ok']
    pw, finish, cid = min(opts, key=lambda o: (o[1], o[2]))
    return [cid, finish, 'late']
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[['boundary: 22 kW AC charger', [[[1, 22, 0]], [11, 300, 11, False], 0], [1, 60, 'ok']],
  ['boundary: finish exactly at departure', [[[1, 7.4, 0]], [37, 300, 7.4, True], 0],
   [1, 300, 'ok']],
  ['boundary: only DC and no DC support', [[[1, 50, 0]], [10, 100, 11, False], 0], None],
  ['regression: AC/DC classification boundary',
   [[[1, 150, 10], [2, 22, 120], [3, 150, 30], [4, 3.7, 120]], [20, 111, 3.7, False], 6],
   [2, 445, 'late']],
  ['regression: AC/DC classification boundary (partial repair)',
   [[[1, 50, 0]], [45, 372, 7.4, False], 56], None],
  ['control 1', [[[1, 22, 60]], [5, 244, 11, False], 8], [1, 88, 'ok']],
  ['control 2', [[[1, 50, 0], [2, 50, 0]], [5, 160, 11, False], 39], None]],
 [['boundary: 22 kW AC charger', [[[1, 22, 0]], [11, 300, 11, False], 0], [1, 60, 'ok']],
  ['boundary: finish exactly at departure', [[[1, 7.4, 0]], [37, 300, 7.4, True], 0],
   [1, 300, 'ok']],
  ['boundary: only DC and no DC support', [[[1, 50, 0]], [10, 100, 11, False], 0], None],
  ['regression: AC/DC classification boundary', [[[1, 22, 120]], [20, 345, 3.7, True], 47],
   [1, 445, 'late']],
  ['regression: AC/DC classification boundary (partial repair)',
   [[[1, 150, 0], [2, 7.4, 120], [3, 50, 0]], [20, 67, 11, True], 8], [3, 32, 'ok']],
  ['control 1', [[[1, 50, 0]], [45, 63, 7.4, True], 12], [1, 66, 'late']],
  ['control 2',
   [[[1, 7.4, 60], [2, 7.4, 10], [3, 22, 10], [4, 11, 120], [5, 50, 120]], [45, 353, 7.4, True],
    45],
   [5, 174, 'ok']]],
 [['boundary: 22 kW AC charger', [[[1, 22, 0]], [11, 300, 11, False], 0], [1, 60, 'ok']],
  ['boundary: finish exactly at departure', [[[1, 7.4, 0]], [37, 300, 7.4, True], 0],
   [1, 300, 'ok']],
  ['boundary: only DC and no DC support', [[[1, 50, 0]], [10, 100, 11, False], 0], None],
  ['regression: AC/DC classification boundary',
   [[[1, 22, 10], [2, 3.7, 30]], [5, 408, 3.7, False], 55], [1, 137, 'ok']],
  ['regression: AC/DC classification boundary (partial repair)',
   [[[1, 50, 10]], [10, 99, 3.7, True], 41], [1, 53, 'ok']],
  ['control 1', [[[1, 7.4, 10], [2, 7.4, 0]], [45, 88, 7.4, True], 40], [1, 405, 'late']],
  ['control 2', [[[1, 3.7, 10], [2, 3.7, 120], [3, 11, 10], [4, 50, 0]], [5, 42, 7.4, True], 27],
   [4, 33, 'ok']]],
 [['boundary: 22 kW AC charger', [[[1, 22, 0]], [11, 300, 11, False], 0], [1, 60, 'ok']],
  ['boundary: finish exactly at departure', [[[1, 7.4, 0]], [37, 300, 7.4, True], 0],
   [1, 300, 'ok']],
  ['boundary: only DC and no DC support', [[[1, 50, 0]], [10, 100, 11, False], 0], None],
  ['regression: AC/DC classification boundary',
   [[[1, 50, 0], [2, 7.4, 0], [3, 7.4, 120], [4, 22, 10]], [45, 278, 3.7, True], 26],
   [1, 80, 'ok']],
  ['regression: AC/DC classification boundary (partial repair)',
   [[[1, 50, 60], [2, 50, 60]], [45, 130, 7.4, True], 48], [1, 114, 'ok']],
  ['control 1', [[[1, 7.4, 60]], [30, 240, 3.7, True], 21], [1, 547, 'late']],
  ['control 2', [[[1, 3.7, 60], [2, 3.7, 120], [3, 150, 30], [4, 150, 0]], [45, 67, 11, False], 57],
   [1, 790, 'late']]],
 [['boundary: 22 kW AC charger', [[[1, 22, 0]], [11, 300, 11, False], 0], [1, 60, 'ok']],
  ['boundary: finish exactly at departure', [[[1, 7.4, 0]], [37, 300, 7.4, True], 0],
   [1, 300, 'ok']],
  ['boundary: only DC and no DC support', [[[1, 50, 0]], [10, 100, 11, False], 0], None],
  ['regression: AC/DC classification boundary',
   [[[1, 22, 0], [2, 3.7, 10], [3, 50, 30]], [20, 64, 3.7, False], 19], [1, 344, 'late']],
  ['regression: AC/DC classification boundary (partial repair)',
   [[[1, 50, 0], [2, 50, 30]], [10, 89, 7.4, True], 45], [1, 57, 'ok']],
  ['control 1', [[[1, 50, 60], [2, 50, 60]], [45, 130, 7.4, True], 48], [1, 114, 'ok']],
  ['control 2', [[[1, 150, 0], [2, 7.4, 10]], [10, 89, 3.7, True], 57], [1, 61, 'ok']]]]
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
boundary: 22 kW AC charger[1, 60, 'ok'][1, 60, 'ok']Passed
boundary: finish exactly at departure[1, 300, 'ok'][1, 300, 'ok']Passed
boundary: only DC and no DC support[1, 55, 'ok']NoneFailed
regression: AC/DC classification boundary[2, 445, 'late'][2, 445, 'late']Passed
regression: AC/DC classification boundary (partial repair)[1, 421, 'late']NoneFailed
control 1[1, 88, 'ok'][1, 88, 'ok']Passed
control 2[1, 67, 'ok']NoneFailed

SHA-256 / 8118b932c772a1934a5bca3f632028e0c18421d9ef64975b88eef5547ce30afb

HELD IN THE MEMBER ARCHIVE

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

This mechanism has 7 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

Deterministic stipulated toy contract for teaching; no claim of conformance with any standard, vendor protocol or production controller. 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 2026-09-29T14:51:53.604399+00:00.

Case digest / f6a2f248b2c83724fa9a5c305cc99ade2ee3152d33b207683d73690aca6db124