FA-97901 / Dataset split isolation / Open access

Dataset split: equal event times follow input order instead of record ID order · case 01

equal event times follow input order instead of record ID order.

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

ROOT CAUSE

Sorting only by timestamp preserves the incoming order for equal-time records, so the tie rule is not based on ID.

THE FAILURE

Sorting only by timestamp preserves the incoming order for equal-time records, so the tie rule is not based on ID.

Unsuccessful approach: Comparing only the first character of each ID leaves same-prefix ties in input order.

Case contract

Rows [id,time] have unique string IDs; return IDs in chronological order, breaking time ties by full lexical ID.

Why this case matters

This toy split allocator makes membership rules explicit for reproducible evaluation fixtures.

1 / The failure

Exit 1

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

N = 1
observations = []
def solve(rows):
    return [i for i,t in sorted(rows,key=lambda r:r[1])]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('tie order',solve([['b',N],['a',N]]),['a','b'])
check('chronology',solve([['b',N+1],['a',N]]),['a','b'])
check('empty',solve([]),[])
check('singleton',solve([['x',N]]),['x'])
check('mixed ties',solve([['c',N+1],['b',N],['a',N]]),['a','b','c'])
check('same prefix ties',solve([['ay',N],['ax',N]]),['ax','ay'])
check('duplicate times',solve([['z',0],['a',0],['m',0]]),['a','m','z'])
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
tie order	`['b', 'a']`	`['a', 'b']`	Failed
chronology	`['a', 'b']`	`['a', 'b']`	Passed
empty	`[]`	`[]`	Passed
singleton	`['x']`	`['x']`	Passed
mixed ties	`['b', 'a', 'c']`	`['a', 'b', 'c']`	Failed
same prefix ties	`['ay', 'ax']`	`['ax', 'ay']`	Failed
duplicate times	`['z', 'a', 'm']`	`['a', 'm', 'z']`	Failed

SHA-256 / e65a5c58ed0a739587822bdae61dee20beaf7ab0d05b888a295090236f003dde

2 / The unsuccessful fix

Exit 1

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

N = 1
observations = []
def solve(rows):
    return [i for i,t in sorted(rows,key=lambda r:(r[1],r[0][0]))]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('tie order',solve([['b',N],['a',N]]),['a','b'])
check('chronology',solve([['b',N+1],['a',N]]),['a','b'])
check('empty',solve([]),[])
check('singleton',solve([['x',N]]),['x'])
check('mixed ties',solve([['c',N+1],['b',N],['a',N]]),['a','b','c'])
check('same prefix ties',solve([['ay',N],['ax',N]]),['ax','ay'])
check('duplicate times',solve([['z',0],['a',0],['m',0]]),['a','m','z'])
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
tie order	`['a', 'b']`	`['a', 'b']`	Passed
chronology	`['a', 'b']`	`['a', 'b']`	Passed
empty	`[]`	`[]`	Passed
singleton	`['x']`	`['x']`	Passed
mixed ties	`['a', 'b', 'c']`	`['a', 'b', 'c']`	Passed
same prefix ties	`['ay', 'ax']`	`['ax', 'ay']`	Failed
duplicate times	`['a', 'm', 'z']`	`['a', 'm', 'z']`	Passed

SHA-256 / 2a03c83bd89ef3d2a8e6943e840c2a7b3f64dc5ff712aae752542ca5ed5da080

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.

Member access is invitation-based. Sign in with your invited account to inspect the repair.

Verification & scope

Inputs are small in-memory records with self-contained contracts; no claim is made about production sampling quality. 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 2026-09-30T16:48:07.116958+00:00.

Case digest / 3ca9fa36c2bcd8cf116bd5f11722df939329bfffe2e064c97d9009fe5552ee5f