FA-17406 / Time representation / Open access

Fraction validator confuses the reserved endpoint · case 01

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

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

ROOT CAUSE

Fraction validator confuses the reserved endpoint.

THE FAILURE

Fraction validator confuses the reserved endpoint.

Unsuccessful approach: The partial correction still substitutes fraction < 999 at the same fault site.

Case contract

Decode four unsigned bytes: signed 16-bit big-endian seconds and unsigned 16-bit fractional microticks, 1000 per second. Fraction >=1000 is invalid. Return validity and, only for valid input, exact total microticks, signed decimal timestamp with three fractional digits, and whole-second coordinate after a one-microtick increment. Negative display uses magnitude decomposition.

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):
    word = r[0] * 256 + r[1]
    seconds = word - 65536 if word >= 32768 else word
    fraction = r[2] * 256 + r[3]
    valid = fraction <= 1000
    total = seconds * 1000 + fraction
    negative = total < 0
    magnitude = abs(total)
    whole = magnitude // 1000
    part = magnitude % 1000
    next_second = seconds + (fraction + 1) // 1000
    return [valid, total if valid else None, ('-' if negative else '') + str(whole) + '.' + str(part).zfill(3) if valid else None,next_second if valid else None]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('fixture 1', solve([0, 1, 0, 0]), [True, 1000, '1.000', 1])
check('fixture 2', solve([255, 255, 0, 1]), [True, -999, '-0.999', -1])
check('fixture 3', solve([128, 0, 3, 231]), [True, -32767001, '-32767.001', -32767])
check('fixture 4', solve([0, 0, 0, 0]), [True, 0, '0.000', 0])
check('fixture 5', solve([0, 0, 3, 232]), [False, None, None, None])
check('fixture 6', solve([255, 255, 3, 232]), [False, None, None, None])
check('fixture 7', solve([0, 2, 1, 3]), [True, 2259, '2.259', 2])
check('fixture 8', solve([127, 255, 3, 231]), [True, 32767999, '32767.999', 32768])
check('fixture 9', solve([255, 254, 0, 0]), [True, -2000, '-2.000', -2])
check('fixture 10', solve([0, 0, 3, 231]), [True, 999, '0.999', 1])
variant = [([0, 2, 0, 0], [True, 2000, '2.000', 2]), ([0, 3, 0, 0], [True, 3000, '3.000', 3]), ([0, 4, 0, 0], [True, 4000, '4.000', 4]), ([0, 5, 0, 0], [True, 5000, '5.000', 5]), ([0, 6, 0, 0], [True, 6000, '6.000', 6])]
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 fixture	Actual	Expected	Outcome
fixture 1	`[True, 1000, '1.000', 1]`	`[True, 1000, '1.000', 1]`	Passed
fixture 2	`[True, -999, '-0.999', -1]`	`[True, -999, '-0.999', -1]`	Passed
fixture 3	`[True, -32767001, '-32767.001', -32767]`	`[True, -32767001, '-32767.001', -32767]`	Passed
fixture 4	`[True, 0, '0.000', 0]`	`[True, 0, '0.000', 0]`	Passed
fixture 5	`[True, 1000, '1.000', 1]`	`[False, None, None, None]`	Failed
fixture 6	`[True, 0, '0.000', 0]`	`[False, None, None, None]`	Failed
fixture 7	`[True, 2259, '2.259', 2]`	`[True, 2259, '2.259', 2]`	Passed
fixture 8	`[True, 32767999, '32767.999', 32768]`	`[True, 32767999, '32767.999', 32768]`	Passed
fixture 9	`[True, -2000, '-2.000', -2]`	`[True, -2000, '-2.000', -2]`	Passed
fixture 10	`[True, 999, '0.999', 1]`	`[True, 999, '0.999', 1]`	Passed
variant capture	`[True, 2000, '2.000', 2]`	`[True, 2000, '2.000', 2]`	Passed

SHA-256 / 36a3f9bf2fc3a00904b39bc2486d35e174f7d7e21f6d8251b50f533f09b651c4

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):
    word = r[0] * 256 + r[1]
    seconds = word - 65536 if word >= 32768 else word
    fraction = r[2] * 256 + r[3]
    valid = fraction < 999
    total = seconds * 1000 + fraction
    negative = total < 0
    magnitude = abs(total)
    whole = magnitude // 1000
    part = magnitude % 1000
    next_second = seconds + (fraction + 1) // 1000
    return [valid, total if valid else None, ('-' if negative else '') + str(whole) + '.' + str(part).zfill(3) if valid else None,next_second if valid else None]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('fixture 1', solve([0, 1, 0, 0]), [True, 1000, '1.000', 1])
check('fixture 2', solve([255, 255, 0, 1]), [True, -999, '-0.999', -1])
check('fixture 3', solve([128, 0, 3, 231]), [True, -32767001, '-32767.001', -32767])
check('fixture 4', solve([0, 0, 0, 0]), [True, 0, '0.000', 0])
check('fixture 5', solve([0, 0, 3, 232]), [False, None, None, None])
check('fixture 6', solve([255, 255, 3, 232]), [False, None, None, None])
check('fixture 7', solve([0, 2, 1, 3]), [True, 2259, '2.259', 2])
check('fixture 8', solve([127, 255, 3, 231]), [True, 32767999, '32767.999', 32768])
check('fixture 9', solve([255, 254, 0, 0]), [True, -2000, '-2.000', -2])
check('fixture 10', solve([0, 0, 3, 231]), [True, 999, '0.999', 1])
variant = [([0, 2, 0, 0], [True, 2000, '2.000', 2]), ([0, 3, 0, 0], [True, 3000, '3.000', 3]), ([0, 4, 0, 0], [True, 4000, '4.000', 4]), ([0, 5, 0, 0], [True, 5000, '5.000', 5]), ([0, 6, 0, 0], [True, 6000, '6.000', 6])]
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 fixture	Actual	Expected	Outcome
fixture 1	`[True, 1000, '1.000', 1]`	`[True, 1000, '1.000', 1]`	Passed
fixture 2	`[True, -999, '-0.999', -1]`	`[True, -999, '-0.999', -1]`	Passed
fixture 3	`[False, None, None, None]`	`[True, -32767001, '-32767.001', -32767]`	Failed
fixture 4	`[True, 0, '0.000', 0]`	`[True, 0, '0.000', 0]`	Passed
fixture 5	`[False, None, None, None]`	`[False, None, None, None]`	Passed
fixture 6	`[False, None, None, None]`	`[False, None, None, None]`	Passed
fixture 7	`[True, 2259, '2.259', 2]`	`[True, 2259, '2.259', 2]`	Passed
fixture 8	`[False, None, None, None]`	`[True, 32767999, '32767.999', 32768]`	Failed
fixture 9	`[True, -2000, '-2.000', -2]`	`[True, -2000, '-2.000', -2]`	Passed
fixture 10	`[False, None, None, None]`	`[True, 999, '0.999', 1]`	Failed
variant capture	`[True, 2000, '2.000', 2]`	`[True, 2000, '2.000', 2]`	Passed

SHA-256 / 3d847a4586304a0d24ba1405cf93a6aa3053e729532d5a7be304b398ec127947

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 2026-09-29T14:39:46.512961+00:00.

Case digest / 6b4a754b548445ae7630731f3b3057696c3e0215bb404a94063be7a007972d7c