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FA-18016 / Time representation / Open access

Clock offset estimator uses interval radius or discards half tick · case 01

The decoded time state disagrees with the explicit regression oracle for offset.

Verified by executionVariant 1 · 11 checks per implementationDownload source bundle ↓JSON ↗

ROOT CAUSE

Clock offset estimator uses interval radius or discards half tick.

THE FAILURE

Clock offset estimator uses interval radius or discards half tick.

Unsuccessful approach: The partial correction still substitutes Fraction((offset_low + offset_high)//2) at the same fault site.

Case contract

Four timestamps are ordered by message path: client send c0, server receive s1, server send s2, client receive c3. Constant offset server-minus-client is estimated by symmetric path assumption. Preserve exact half-tick fractions; report network round trip, offset, projected server now, local send/receive server equivalents, one-way path estimate and delay bounds from nonnegative path delays.

Why this case matters

Clock transfer and timestamp consumers require preserved coordinate, phase, validity and elapsed-time semantics.

1 / The failure

Exit 1
"""Failure Map reference implementation. Python standard library only."""
import json
from fractions import Fraction
N = 1
observations = []
def solve(r):
    client_span = r['c3'] - r['c0']
    server_span = r['s2'] - r['s1']
    round_trip = client_span - server_span
    offset_low = r['s2'] - r['c3']
    offset_high = r['s1'] - r['c0']
    offset = Fraction(offset_high - offset_low,2)
    projected = r['now'] + offset
    one_way = Fraction(round_trip,2)
    valid = round_trip >= 0
    uncertainty = Fraction(offset_high - offset_low,2)
    return [valid,str(offset),str(projected),str(one_way),[offset_low,offset_high],str(uncertainty),str(r['c0']+offset),str(r['c3']+offset)]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('fixture 1', solve({'c0': 0, 's1': 7, 's2': 9, 'c3': 6, 'now': 10}), [True, '5', '15', '2', [3, 7], '2', '5', '11'])
check('fixture 2', solve({'c0': 10, 's1': 9, 's2': 12, 'c3': 18, 'now': 20}), [True, '-7/2', '33/2', '5/2', [-6, -1], '5/2', '13/2', '29/2'])
check('fixture 3', solve({'c0': 0, 's1': 5, 's2': 5, 'c3': 0, 'now': 2}), [True, '5', '7', '0', [5, 5], '0', '5', '5'])
check('fixture 4', solve({'c0': 10, 's1': 10, 's2': 20, 'c3': 15, 'now': 30}), [False, '5/2', '65/2', '-5/2', [5, 0], '-5/2', '25/2', '35/2'])
check('fixture 5', solve({'c0': 20, 's1': 10, 's2': 10, 'c3': 10, 'now': 30}), [False, '-5', '25', '-5', [0, -10], '-5', '15', '5'])
check('fixture 6', solve({'c0': 0, 's1': 1, 's2': 2, 'c3': 4, 'now': 5}), [True, '-1/2', '9/2', '3/2', [-2, 1], '3/2', '-1/2', '7/2'])
check('fixture 7', solve({'c0': -10, 's1': -5, 's2': -3, 'c3': -2, 'now': 0}), [True, '2', '2', '3', [-1, 5], '3', '-8', '0'])
check('fixture 8', solve({'c0': 100, 's1': 150, 's2': 170, 'c3': 140, 'now': 200}), [True, '40', '240', '10', [30, 50], '10', '140', '180'])
check('fixture 9', solve({'c0': 0, 's1': -5, 's2': -3, 'c3': 5, 'now': 10}), [True, '-13/2', '7/2', '3/2', [-8, -5], '3/2', '-13/2', '-3/2'])
check('fixture 10', solve({'c0': 2, 's1': 5, 's2': 5, 'c3': 8, 'now': 10}), [True, '0', '10', '3', [-3, 3], '3', '2', '8'])
variant = [({'c0': 0, 's1': 7, 's2': 9, 'c3': 6, 'now': 11}, [True, '5', '16', '2', [3, 7], '2', '5', '11']), ({'c0': 0, 's1': 7, 's2': 9, 'c3': 6, 'now': 12}, [True, '5', '17', '2', [3, 7], '2', '5', '11']), ({'c0': 0, 's1': 7, 's2': 9, 'c3': 6, 'now': 13}, [True, '5', '18', '2', [3, 7], '2', '5', '11']), ({'c0': 0, 's1': 7, 's2': 9, 'c3': 6, 'now': 14}, [True, '5', '19', '2', [3, 7], '2', '5', '11']), ({'c0': 0, 's1': 7, 's2': 9, 'c3': 6, 'now': 15}, [True, '5', '20', '2', [3, 7], '2', '5', '11'])]
check("variant capture", solve(variant[N-1][0]), variant[N-1][1])
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
fixture 1[True, '2', '12', '2', [3, 7], '2', '2', '8'][True, '5', '15', '2', [3, 7], '2', '5', '11']Failed
fixture 2[True, '5/2', '45/2', '5/2', [-6, -1], '5/2', '25/2', '41/2'][True, '-7/2', '33/2', '5/2', [-6, -1], '5/2', '13/2', '29/2']Failed
fixture 3[True, '0', '2', '0', [5, 5], '0', '0', '0'][True, '5', '7', '0', [5, 5], '0', '5', '5']Failed
fixture 4[False, '-5/2', '55/2', '-5/2', [5, 0], '-5/2', '15/2', '25/2'][False, '5/2', '65/2', '-5/2', [5, 0], '-5/2', '25/2', '35/2']Failed
fixture 5[False, '-5', '25', '-5', [0, -10], '-5', '15', '5'][False, '-5', '25', '-5', [0, -10], '-5', '15', '5']Passed
fixture 6[True, '3/2', '13/2', '3/2', [-2, 1], '3/2', '3/2', '11/2'][True, '-1/2', '9/2', '3/2', [-2, 1], '3/2', '-1/2', '7/2']Failed
fixture 7[True, '3', '3', '3', [-1, 5], '3', '-7', '1'][True, '2', '2', '3', [-1, 5], '3', '-8', '0']Failed
fixture 8[True, '10', '210', '10', [30, 50], '10', '110', '150'][True, '40', '240', '10', [30, 50], '10', '140', '180']Failed
fixture 9[True, '3/2', '23/2', '3/2', [-8, -5], '3/2', '3/2', '13/2'][True, '-13/2', '7/2', '3/2', [-8, -5], '3/2', '-13/2', '-3/2']Failed
fixture 10[True, '3', '13', '3', [-3, 3], '3', '5', '11'][True, '0', '10', '3', [-3, 3], '3', '2', '8']Failed
variant capture[True, '2', '13', '2', [3, 7], '2', '2', '8'][True, '5', '16', '2', [3, 7], '2', '5', '11']Failed

SHA-256 / d1bd52ffc1ec169db22eb871e3bb2d375f783126936e2050a669b626a9a5f276

2 / The unsuccessful fix

Exit 1
"""Failure Map reference implementation. Python standard library only."""
import json
from fractions import Fraction
N = 1
observations = []
def solve(r):
    client_span = r['c3'] - r['c0']
    server_span = r['s2'] - r['s1']
    round_trip = client_span - server_span
    offset_low = r['s2'] - r['c3']
    offset_high = r['s1'] - r['c0']
    offset = Fraction((offset_low + offset_high)//2)
    projected = r['now'] + offset
    one_way = Fraction(round_trip,2)
    valid = round_trip >= 0
    uncertainty = Fraction(offset_high - offset_low,2)
    return [valid,str(offset),str(projected),str(one_way),[offset_low,offset_high],str(uncertainty),str(r['c0']+offset),str(r['c3']+offset)]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('fixture 1', solve({'c0': 0, 's1': 7, 's2': 9, 'c3': 6, 'now': 10}), [True, '5', '15', '2', [3, 7], '2', '5', '11'])
check('fixture 2', solve({'c0': 10, 's1': 9, 's2': 12, 'c3': 18, 'now': 20}), [True, '-7/2', '33/2', '5/2', [-6, -1], '5/2', '13/2', '29/2'])
check('fixture 3', solve({'c0': 0, 's1': 5, 's2': 5, 'c3': 0, 'now': 2}), [True, '5', '7', '0', [5, 5], '0', '5', '5'])
check('fixture 4', solve({'c0': 10, 's1': 10, 's2': 20, 'c3': 15, 'now': 30}), [False, '5/2', '65/2', '-5/2', [5, 0], '-5/2', '25/2', '35/2'])
check('fixture 5', solve({'c0': 20, 's1': 10, 's2': 10, 'c3': 10, 'now': 30}), [False, '-5', '25', '-5', [0, -10], '-5', '15', '5'])
check('fixture 6', solve({'c0': 0, 's1': 1, 's2': 2, 'c3': 4, 'now': 5}), [True, '-1/2', '9/2', '3/2', [-2, 1], '3/2', '-1/2', '7/2'])
check('fixture 7', solve({'c0': -10, 's1': -5, 's2': -3, 'c3': -2, 'now': 0}), [True, '2', '2', '3', [-1, 5], '3', '-8', '0'])
check('fixture 8', solve({'c0': 100, 's1': 150, 's2': 170, 'c3': 140, 'now': 200}), [True, '40', '240', '10', [30, 50], '10', '140', '180'])
check('fixture 9', solve({'c0': 0, 's1': -5, 's2': -3, 'c3': 5, 'now': 10}), [True, '-13/2', '7/2', '3/2', [-8, -5], '3/2', '-13/2', '-3/2'])
check('fixture 10', solve({'c0': 2, 's1': 5, 's2': 5, 'c3': 8, 'now': 10}), [True, '0', '10', '3', [-3, 3], '3', '2', '8'])
variant = [({'c0': 0, 's1': 7, 's2': 9, 'c3': 6, 'now': 11}, [True, '5', '16', '2', [3, 7], '2', '5', '11']), ({'c0': 0, 's1': 7, 's2': 9, 'c3': 6, 'now': 12}, [True, '5', '17', '2', [3, 7], '2', '5', '11']), ({'c0': 0, 's1': 7, 's2': 9, 'c3': 6, 'now': 13}, [True, '5', '18', '2', [3, 7], '2', '5', '11']), ({'c0': 0, 's1': 7, 's2': 9, 'c3': 6, 'now': 14}, [True, '5', '19', '2', [3, 7], '2', '5', '11']), ({'c0': 0, 's1': 7, 's2': 9, 'c3': 6, 'now': 15}, [True, '5', '20', '2', [3, 7], '2', '5', '11'])]
check("variant capture", solve(variant[N-1][0]), variant[N-1][1])
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
fixture 1[True, '5', '15', '2', [3, 7], '2', '5', '11'][True, '5', '15', '2', [3, 7], '2', '5', '11']Passed
fixture 2[True, '-4', '16', '5/2', [-6, -1], '5/2', '6', '14'][True, '-7/2', '33/2', '5/2', [-6, -1], '5/2', '13/2', '29/2']Failed
fixture 3[True, '5', '7', '0', [5, 5], '0', '5', '5'][True, '5', '7', '0', [5, 5], '0', '5', '5']Passed
fixture 4[False, '2', '32', '-5/2', [5, 0], '-5/2', '12', '17'][False, '5/2', '65/2', '-5/2', [5, 0], '-5/2', '25/2', '35/2']Failed
fixture 5[False, '-5', '25', '-5', [0, -10], '-5', '15', '5'][False, '-5', '25', '-5', [0, -10], '-5', '15', '5']Passed
fixture 6[True, '-1', '4', '3/2', [-2, 1], '3/2', '-1', '3'][True, '-1/2', '9/2', '3/2', [-2, 1], '3/2', '-1/2', '7/2']Failed
fixture 7[True, '2', '2', '3', [-1, 5], '3', '-8', '0'][True, '2', '2', '3', [-1, 5], '3', '-8', '0']Passed
fixture 8[True, '40', '240', '10', [30, 50], '10', '140', '180'][True, '40', '240', '10', [30, 50], '10', '140', '180']Passed
fixture 9[True, '-7', '3', '3/2', [-8, -5], '3/2', '-7', '-2'][True, '-13/2', '7/2', '3/2', [-8, -5], '3/2', '-13/2', '-3/2']Failed
fixture 10[True, '0', '10', '3', [-3, 3], '3', '2', '8'][True, '0', '10', '3', [-3, 3], '3', '2', '8']Passed
variant capture[True, '5', '16', '2', [3, 7], '2', '5', '11'][True, '5', '16', '2', [3, 7], '2', '5', '11']Passed

SHA-256 / e2e868151530e1201124a9301d8a704184820b49e29ee527ece610eea46a8d65

HELD IN THE MEMBER ARCHIVE

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

This mechanism has 11 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 integer reference model with stipulated units and policies; not a complete clock, wire standard or platform 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 2026-09-29T14:39:53.385599+00:00.

Case digest / 5bc977a6e14ce28ad4a4e73b7dd180f0146165a9915054ea3e02a99aba9d517b