FA-92981 / EV charging session scheduling / Open access
Connector reservation conflict check: leading buffer · case 01
A new reservation may end right as the next one starts, leaving no turnover time.
ROOT CAUSE
The buffer is applied only after existing reservations, not before them.
VERIFIED REPAIR
Require e + buffer <= s2 for a request that precedes an existing reservation.
Unsuccessful approach: Adding the buffer to the existing start shrinks the protected window instead of extending it.
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:
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: leading buffer',
[[[3, 167, 214], [1, 185, 245], [1, 49, 98], [3, 101, 158], [2, 29, 77], [4, 51, 78]],
[11, 41, None], 10, 4],
3],
['regression: leading buffer (partial repair)',
[[[1, 75, 109], [1, 5, 46], [3, 128, 161], [3, 171, 198], [2, 190, 240], [1, 13, 36]],
[58, 73, 1], 10, 3],
None],
['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: leading buffer',
[[[3, 167, 214], [1, 185, 245], [1, 49, 98], [3, 101, 158], [2, 29, 77], [4, 51, 78]],
[11, 41, None], 10, 4],
3],
['regression: leading buffer (partial repair)',
[[[1, 75, 109], [1, 5, 46], [3, 128, 161], [3, 171, 198], [2, 190, 240], [1, 13, 36]],
[58, 73, 1], 10, 3],
None],
['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: leading buffer', [[[1, 136, 191], [1, 16, 74]], [120, 135, None], 15, 1], None],
['regression: leading buffer (partial repair)',
[[[1, 73, 113], [1, 68, 107], [1, 36, 89], [3, 200, 258], [1, 22, 79], [3, 72, 84]],
[4, 34, None], 15, 3],
2],
['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: leading buffer', [[[1, 136, 191], [1, 16, 74]], [120, 135, None], 15, 1], None],
['regression: leading buffer (partial repair)',
[[[1, 73, 113], [1, 68, 107], [1, 36, 89], [3, 200, 258], [1, 22, 79], [3, 72, 84]],
[4, 34, None], 15, 3],
2],
['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: leading buffer', [[[1, 136, 191], [1, 16, 74]], [120, 135, None], 15, 1], None],
['regression: leading buffer (partial repair)',
[[[1, 73, 113], [1, 68, 107], [1, 36, 89], [3, 200, 258], [1, 22, 79], [3, 72, 84]],
[4, 34, None], 15, 3],
2],
['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 fixture | Actual | Expected | Outcome |
|---|---|---|---|
| boundary: back-to-back with buffer | 1 | 1 | Passed |
| boundary: zero-length request | invalid | invalid | Passed |
| boundary: last connector requested | 3 | 3 | Passed |
| regression: leading buffer | 1 | 3 | Failed |
| regression: leading buffer (partial repair) | 1 | None | Failed |
| control 1 | None | None | Passed |
| control 2 | None | None | Passed |
SHA-256 / 941bff112ad5e236a1f7d3da7a13ea88a731b61e21f2ae0893bd310f5f27eb89
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:
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 + buffer < e:
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: leading buffer',
[[[3, 167, 214], [1, 185, 245], [1, 49, 98], [3, 101, 158], [2, 29, 77], [4, 51, 78]],
[11, 41, None], 10, 4],
3],
['regression: leading buffer (partial repair)',
[[[1, 75, 109], [1, 5, 46], [3, 128, 161], [3, 171, 198], [2, 190, 240], [1, 13, 36]],
[58, 73, 1], 10, 3],
None],
['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: leading buffer',
[[[3, 167, 214], [1, 185, 245], [1, 49, 98], [3, 101, 158], [2, 29, 77], [4, 51, 78]],
[11, 41, None], 10, 4],
3],
['regression: leading buffer (partial repair)',
[[[1, 75, 109], [1, 5, 46], [3, 128, 161], [3, 171, 198], [2, 190, 240], [1, 13, 36]],
[58, 73, 1], 10, 3],
None],
['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: leading buffer', [[[1, 136, 191], [1, 16, 74]], [120, 135, None], 15, 1], None],
['regression: leading buffer (partial repair)',
[[[1, 73, 113], [1, 68, 107], [1, 36, 89], [3, 200, 258], [1, 22, 79], [3, 72, 84]],
[4, 34, None], 15, 3],
2],
['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: leading buffer', [[[1, 136, 191], [1, 16, 74]], [120, 135, None], 15, 1], None],
['regression: leading buffer (partial repair)',
[[[1, 73, 113], [1, 68, 107], [1, 36, 89], [3, 200, 258], [1, 22, 79], [3, 72, 84]],
[4, 34, None], 15, 3],
2],
['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: leading buffer', [[[1, 136, 191], [1, 16, 74]], [120, 135, None], 15, 1], None],
['regression: leading buffer (partial repair)',
[[[1, 73, 113], [1, 68, 107], [1, 36, 89], [3, 200, 258], [1, 22, 79], [3, 72, 84]],
[4, 34, None], 15, 3],
2],
['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 fixture | Actual | Expected | Outcome |
|---|---|---|---|
| boundary: back-to-back with buffer | 1 | 1 | Passed |
| boundary: zero-length request | invalid | invalid | Passed |
| boundary: last connector requested | 3 | 3 | Passed |
| regression: leading buffer | 1 | 3 | Failed |
| regression: leading buffer (partial repair) | 1 | None | Failed |
| control 1 | None | None | Passed |
| control 2 | None | None | Passed |
SHA-256 / cb83f26a2ecb654f8994bb9ee12082f83efc84d59113c91e7ff003c4aed565b6
3 / The verified repair
Exit 0"""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: leading buffer',
[[[3, 167, 214], [1, 185, 245], [1, 49, 98], [3, 101, 158], [2, 29, 77], [4, 51, 78]],
[11, 41, None], 10, 4],
3],
['regression: leading buffer (partial repair)',
[[[1, 75, 109], [1, 5, 46], [3, 128, 161], [3, 171, 198], [2, 190, 240], [1, 13, 36]],
[58, 73, 1], 10, 3],
None],
['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: leading buffer',
[[[3, 167, 214], [1, 185, 245], [1, 49, 98], [3, 101, 158], [2, 29, 77], [4, 51, 78]],
[11, 41, None], 10, 4],
3],
['regression: leading buffer (partial repair)',
[[[1, 75, 109], [1, 5, 46], [3, 128, 161], [3, 171, 198], [2, 190, 240], [1, 13, 36]],
[58, 73, 1], 10, 3],
None],
['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: leading buffer', [[[1, 136, 191], [1, 16, 74]], [120, 135, None], 15, 1], None],
['regression: leading buffer (partial repair)',
[[[1, 73, 113], [1, 68, 107], [1, 36, 89], [3, 200, 258], [1, 22, 79], [3, 72, 84]],
[4, 34, None], 15, 3],
2],
['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: leading buffer', [[[1, 136, 191], [1, 16, 74]], [120, 135, None], 15, 1], None],
['regression: leading buffer (partial repair)',
[[[1, 73, 113], [1, 68, 107], [1, 36, 89], [3, 200, 258], [1, 22, 79], [3, 72, 84]],
[4, 34, None], 15, 3],
2],
['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: leading buffer', [[[1, 136, 191], [1, 16, 74]], [120, 135, None], 15, 1], None],
['regression: leading buffer (partial repair)',
[[[1, 73, 113], [1, 68, 107], [1, 36, 89], [3, 200, 258], [1, 22, 79], [3, 72, 84]],
[4, 34, None], 15, 3],
2],
['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 fixture | Actual | Expected | Outcome |
|---|---|---|---|
| boundary: back-to-back with buffer | 1 | 1 | Passed |
| boundary: zero-length request | invalid | invalid | Passed |
| boundary: last connector requested | 3 | 3 | Passed |
| regression: leading buffer | 3 | 3 | Passed |
| regression: leading buffer (partial repair) | None | None | Passed |
| control 1 | None | None | Passed |
| control 2 | None | None | Passed |
SHA-256 / d2c3f2efd65f014e5aaca2f313826e81764073b9f05f0773d9d3549eb0e9d27c
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 2026-09-29T14:51:51.030220+00:00.
Case digest / 0c225e987c3fde490a3e042758013a3d4f6cb05d896586c9a72e6a352a0e9212