FAILURE MAP
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FA-92991 / EV charging session scheduling / Open access

Connector reservation conflict check: empty request window · case 01

A zero-length reservation is accepted and blocks a connector.

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

ROOT CAUSE

Only negative-length requests are treated as invalid.

THE FAILURE

Only negative-length requests are treated as invalid.

Unsuccessful approach: Rejecting requests shorter than the buffer refuses legitimate short sessions.

Case contract

Connectors are numbered 1..n_conn. existing holds [connector, start, end) reservations. req is [start, end, connector or None]. end <= start or an out-of-range connector returns 'invalid'. Two reservations on the same connector conflict unless separated by at least buffer minutes on both sides. Return the requested connector if free, or the lowest free connector when None was requested, else None.

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

N = 1
observations = []
def solve(existing, req, buffer, n_conn):
    s, e, want = req
    if e < s:
        return 'invalid'
    if want is not None and not 1 <= want <= n_conn:
        return 'invalid'
    conns = [want] if want is not None else list(range(1, n_conn + 1))
    for c in conns:
        clash = False
        for c2, s2, e2 in existing:
            if c2 == c and s < e2 + buffer and s2 < e + buffer:
                clash = True
                break
        if not clash:
            return c
    return None
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[['boundary: back-to-back with buffer', [[[1, 0, 30]], [40, 60, 1], 10, 1], 1],
  ['boundary: zero-length request', [[], [10, 10, None], 0, 2], 'invalid'],
  ['boundary: last connector requested', [[[1, 0, 30]], [0, 30, 3], 0, 3], 3],
  ['regression: empty request window',
   [[[1, 70, 116], [2, 43, 88], [1, 109, 153]], [45, 45, None], 0, 2], 'invalid'],
  ['regression: empty request window (partial repair)', [[], [159, 164, 1], 10, 3], 1],
  ['control 1', [[[2, 157, 203], [1, 191, 236]], [179, 224, None], 5, 2], None],
  ['control 2',
   [[[3, 190, 210], [4, 11, 28], [2, 54, 68], [4, 54, 104], [3, 134, 162]], [79, 139, 4], 5, 4],
   None]],
 [['boundary: back-to-back with buffer', [[[1, 0, 30]], [40, 60, 1], 10, 1], 1],
  ['boundary: zero-length request', [[], [10, 10, None], 0, 2], 'invalid'],
  ['boundary: last connector requested', [[[1, 0, 30]], [0, 30, 3], 0, 3], 3],
  ['regression: empty request window', [[[1, 191, 246], [2, 105, 128]], [128, 128, None], 15, 2],
   'invalid'],
  ['regression: empty request window (partial repair)', [[], [171, 171, None], 0, 1], 'invalid'],
  ['control 1',
   [[[2, 130, 150], [3, 5, 36], [3, 174, 193], [2, 18, 78], [1, 61, 115], [4, 68, 95]],
    [171, 201, 2], 10, 4],
   2],
  ['control 2',
   [[[3, 116, 135], [1, 178, 208], [1, 83, 123], [1, 136, 157], [3, 111, 126], [1, 97, 137]],
    [217, 222, 2], 0, 3],
   2]],
 [['boundary: back-to-back with buffer', [[[1, 0, 30]], [40, 60, 1], 10, 1], 1],
  ['boundary: zero-length request', [[], [10, 10, None], 0, 2], 'invalid'],
  ['boundary: last connector requested', [[[1, 0, 30]], [0, 30, 3], 0, 3], 3],
  ['regression: empty request window',
   [[[1, 61, 98], [2, 89, 148], [1, 159, 190], [2, 124, 167], [1, 197, 219]], [29, 29, None], 15,
    2],
   'invalid'],
  ['regression: empty request window (partial repair)',
   [[[1, 125, 139], [4, 142, 161], [2, 3, 17]], [206, 211, None], 15, 4], 1],
  ['control 1', [[[3, 198, 211], [1, 147, 191], [4, 137, 178]], [148, 208, None], 10, 4], 2],
  ['control 2',
   [[[1, 75, 109], [1, 5, 46], [3, 128, 161], [3, 171, 198], [2, 190, 240], [1, 13, 36]],
    [58, 73, 1], 10, 3],
   None]],
 [['boundary: back-to-back with buffer', [[[1, 0, 30]], [40, 60, 1], 10, 1], 1],
  ['boundary: zero-length request', [[], [10, 10, None], 0, 2], 'invalid'],
  ['boundary: last connector requested', [[[1, 0, 30]], [0, 30, 3], 0, 3], 3],
  ['regression: empty request window',
   [[[1, 144, 201], [1, 99, 140], [1, 187, 246], [1, 92, 150], [1, 120, 150]], [55, 55, 1], 0, 2],
   'invalid'],
  ['regression: empty request window (partial repair)',
   [[[1, 1, 57], [2, 28, 64]], [70, 75, 2], 15, 2], None],
  ['control 1', [[[3, 69, 129], [1, 134, 154], [4, 142, 167]], [67, 72, 0], 15, 4], 'invalid'],
  ['control 2', [[[2, 188, 212]], [190, 180, 2], 15, 2], 'invalid']],
 [['boundary: back-to-back with buffer', [[[1, 0, 30]], [40, 60, 1], 10, 1], 1],
  ['boundary: zero-length request', [[], [10, 10, None], 0, 2], 'invalid'],
  ['boundary: last connector requested', [[[1, 0, 30]], [0, 30, 3], 0, 3], 3],
  ['regression: empty request window',
   [[[2, 141, 198], [2, 146, 161], [3, 91, 117], [2, 43, 82]], [0, 0, 1], 5, 4], 'invalid'],
  ['regression: empty request window (partial repair)', [[], [64, 69, None], 15, 4], 1],
  ['control 1', [[[4, 7, 51], [4, 60, 108], [1, 80, 129]], [8, 68, None], 0, 4], 1],
  ['control 2',
   [[[1, 169, 199], [1, 193, 217], [1, 118, 149], [1, 4, 58], [1, 125, 169], [1, 1, 52]],
    [156, 146, None], 10, 1],
   'invalid']]]
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: back-to-back with buffer11Passed
boundary: zero-length request1invalidFailed
boundary: last connector requested33Passed
regression: empty request window1invalidFailed
regression: empty request window (partial repair)11Passed
control 1NoneNonePassed
control 2NoneNonePassed

SHA-256 / 1e89ab417de4b6a666160c9b0cbbb00cbfa3bcf045573f79debcc805eb7560ae

2 / The unsuccessful fix

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

N = 1
observations = []
def solve(existing, req, buffer, n_conn):
    s, e, want = req
    if e - s < buffer:
        return 'invalid'
    if want is not None and not 1 <= want <= n_conn:
        return 'invalid'
    conns = [want] if want is not None else list(range(1, n_conn + 1))
    for c in conns:
        clash = False
        for c2, s2, e2 in existing:
            if c2 == c and s < e2 + buffer and s2 < e + buffer:
                clash = True
                break
        if not clash:
            return c
    return None
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[['boundary: back-to-back with buffer', [[[1, 0, 30]], [40, 60, 1], 10, 1], 1],
  ['boundary: zero-length request', [[], [10, 10, None], 0, 2], 'invalid'],
  ['boundary: last connector requested', [[[1, 0, 30]], [0, 30, 3], 0, 3], 3],
  ['regression: empty request window',
   [[[1, 70, 116], [2, 43, 88], [1, 109, 153]], [45, 45, None], 0, 2], 'invalid'],
  ['regression: empty request window (partial repair)', [[], [159, 164, 1], 10, 3], 1],
  ['control 1', [[[2, 157, 203], [1, 191, 236]], [179, 224, None], 5, 2], None],
  ['control 2',
   [[[3, 190, 210], [4, 11, 28], [2, 54, 68], [4, 54, 104], [3, 134, 162]], [79, 139, 4], 5, 4],
   None]],
 [['boundary: back-to-back with buffer', [[[1, 0, 30]], [40, 60, 1], 10, 1], 1],
  ['boundary: zero-length request', [[], [10, 10, None], 0, 2], 'invalid'],
  ['boundary: last connector requested', [[[1, 0, 30]], [0, 30, 3], 0, 3], 3],
  ['regression: empty request window', [[[1, 191, 246], [2, 105, 128]], [128, 128, None], 15, 2],
   'invalid'],
  ['regression: empty request window (partial repair)', [[], [171, 171, None], 0, 1], 'invalid'],
  ['control 1',
   [[[2, 130, 150], [3, 5, 36], [3, 174, 193], [2, 18, 78], [1, 61, 115], [4, 68, 95]],
    [171, 201, 2], 10, 4],
   2],
  ['control 2',
   [[[3, 116, 135], [1, 178, 208], [1, 83, 123], [1, 136, 157], [3, 111, 126], [1, 97, 137]],
    [217, 222, 2], 0, 3],
   2]],
 [['boundary: back-to-back with buffer', [[[1, 0, 30]], [40, 60, 1], 10, 1], 1],
  ['boundary: zero-length request', [[], [10, 10, None], 0, 2], 'invalid'],
  ['boundary: last connector requested', [[[1, 0, 30]], [0, 30, 3], 0, 3], 3],
  ['regression: empty request window',
   [[[1, 61, 98], [2, 89, 148], [1, 159, 190], [2, 124, 167], [1, 197, 219]], [29, 29, None], 15,
    2],
   'invalid'],
  ['regression: empty request window (partial repair)',
   [[[1, 125, 139], [4, 142, 161], [2, 3, 17]], [206, 211, None], 15, 4], 1],
  ['control 1', [[[3, 198, 211], [1, 147, 191], [4, 137, 178]], [148, 208, None], 10, 4], 2],
  ['control 2',
   [[[1, 75, 109], [1, 5, 46], [3, 128, 161], [3, 171, 198], [2, 190, 240], [1, 13, 36]],
    [58, 73, 1], 10, 3],
   None]],
 [['boundary: back-to-back with buffer', [[[1, 0, 30]], [40, 60, 1], 10, 1], 1],
  ['boundary: zero-length request', [[], [10, 10, None], 0, 2], 'invalid'],
  ['boundary: last connector requested', [[[1, 0, 30]], [0, 30, 3], 0, 3], 3],
  ['regression: empty request window',
   [[[1, 144, 201], [1, 99, 140], [1, 187, 246], [1, 92, 150], [1, 120, 150]], [55, 55, 1], 0, 2],
   'invalid'],
  ['regression: empty request window (partial repair)',
   [[[1, 1, 57], [2, 28, 64]], [70, 75, 2], 15, 2], None],
  ['control 1', [[[3, 69, 129], [1, 134, 154], [4, 142, 167]], [67, 72, 0], 15, 4], 'invalid'],
  ['control 2', [[[2, 188, 212]], [190, 180, 2], 15, 2], 'invalid']],
 [['boundary: back-to-back with buffer', [[[1, 0, 30]], [40, 60, 1], 10, 1], 1],
  ['boundary: zero-length request', [[], [10, 10, None], 0, 2], 'invalid'],
  ['boundary: last connector requested', [[[1, 0, 30]], [0, 30, 3], 0, 3], 3],
  ['regression: empty request window',
   [[[2, 141, 198], [2, 146, 161], [3, 91, 117], [2, 43, 82]], [0, 0, 1], 5, 4], 'invalid'],
  ['regression: empty request window (partial repair)', [[], [64, 69, None], 15, 4], 1],
  ['control 1', [[[4, 7, 51], [4, 60, 108], [1, 80, 129]], [8, 68, None], 0, 4], 1],
  ['control 2',
   [[[1, 169, 199], [1, 193, 217], [1, 118, 149], [1, 4, 58], [1, 125, 169], [1, 1, 52]],
    [156, 146, None], 10, 1],
   'invalid']]]
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: back-to-back with buffer11Passed
boundary: zero-length request1invalidFailed
boundary: last connector requested33Passed
regression: empty request window1invalidFailed
regression: empty request window (partial repair)invalid1Failed
control 1NoneNonePassed
control 2NoneNonePassed

SHA-256 / 35c92125d24b445861d2e0e0a71e0674a5687fa56141a2d51042514e8646950f

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 2026-09-29T14:51:51.031483+00:00.

Case digest / 8e7d5e5884e80cf1dd92ec8f54000a1d059c0f33445fa7134e6a310ec1455eb4