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FA-97456 / Knitting and sewing pattern grading / Open access

Pattern row locator: finishing offset · case 01

Finishing rows are numbered from the setup count upward.

Verified by executionVariant 1 · 8 checks per implementationDownload source bundle ↓JSON ↗

ROOT CAUSE

The finishing row uses the absolute row, not the offset after setup.

VERIFIED REPAIR

Count finishing rows from the end of the last repeat.

Unsuccessful approach: Subtracting one repeat fewer offsets the count by a whole repeat.

Case contract

Rows are 1-based. Rows 1..setup are ["setup", row]. The next length*repeats rows are ["repeat", repeat_number, row_in_repeat] (both 1-based). Later rows are ["finishing", k] counting from 1 after the last repeat. row < 1 -> "error: rows start at 1".

Why this case matters

Row counter apps must map an absolute row number onto setup, repeat and finishing sections.

1 / The failure

Exit 1
"""Failure Map reference implementation. Python standard library only."""
import json
import math
from fractions import Fraction
N = 1
observations = []
def solve(row, setup, length, repeats):
    if row < 1:
        return 'error: rows start at 1'
    if row <= setup:
        return ['setup', row]
    k = row - setup
    if k <= length * repeats:
        return ['repeat', (k - 1) // length + 1, (k - 1) % length + 1]
    return ['finishing', row - length * repeats]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[['last setup row', [4, 4, 8, 3], ['setup', 4]], ['first repeat row', [5, 4, 8, 3], ['repeat', 1, 1]],
  ['single setup row', [1, 1, 4, 2], ['setup', 1]],
  ['regression: finishing offset', [43, 1, 4, 1], ['finishing', 38]],
  ['repair check: finishing offset', [43, 2, 8, 3], ['finishing', 17]],
  ['generated control 1', [13, 6, 8, 2], ['repeat', 1, 7]],
  ['generated control 2', [30, 4, 4, 3], ['finishing', 14]],
  ['generated control 3', [51, 6, 4, 1], ['finishing', 41]]],
 [['first repeat row', [5, 4, 8, 3], ['repeat', 1, 1]], ['single setup row', [1, 1, 4, 2], ['setup', 1]],
  ['last row of repeat', [12, 4, 8, 3], ['repeat', 1, 8]],
  ['regression: finishing offset', [37, 1, 4, 5], ['finishing', 16]],
  ['repair check: finishing offset', [13, 0, 4, 1], ['finishing', 9]],
  ['generated control 1', [7, 0, 12, 2], ['repeat', 1, 7]],
  ['generated control 2', [48, 0, 8, 1], ['finishing', 40]],
  ['generated control 3', [33, 1, 4, 5], ['finishing', 12]]],
 [['single setup row', [1, 1, 4, 2], ['setup', 1]], ['last row of repeat', [12, 4, 8, 3], ['repeat', 1, 8]],
  ['first finishing row', [29, 4, 8, 3], ['finishing', 1]],
  ['regression: finishing offset', [35, 1, 8, 2], ['finishing', 18]],
  ['repair check: finishing offset', [4, 0, 1, 2], ['finishing', 2]],
  ['generated control 1', [21, 6, 6, 5], ['repeat', 3, 3]],
  ['generated control 2', [14, 2, 6, 5], ['repeat', 2, 6]],
  ['generated control 3', [6, 2, 1, 1], ['finishing', 3]]],
 [['last row of repeat', [12, 4, 8, 3], ['repeat', 1, 8]],
  ['first finishing row', [29, 4, 8, 3], ['finishing', 1]],
  ['row zero', [0, 2, 4, 2], 'error: rows start at 1'],
  ['regression: finishing offset', [47, 4, 8, 1], ['finishing', 35]],
  ['repair check: finishing offset', [56, 0, 4, 2], ['finishing', 48]],
  ['generated control 1', [44, 2, 6, 1], ['finishing', 36]],
  ['generated control 2', [41, 4, 12, 2], ['finishing', 13]],
  ['generated control 3', [52, 6, 1, 1], ['finishing', 45]]],
 [['first finishing row', [29, 4, 8, 3], ['finishing', 1]],
  ['row zero', [0, 2, 4, 2], 'error: rows start at 1'], ['last setup row', [4, 4, 8, 3], ['setup', 4]],
  ['regression: finishing offset', [34, 2, 4, 2], ['finishing', 24]],
  ['repair check: finishing offset', [47, 0, 1, 1], ['finishing', 46]],
  ['generated control 1', [47, 6, 1, 1], ['finishing', 40]],
  ['generated control 2', [5, 1, 8, 5], ['repeat', 1, 4]],
  ['generated control 3', [31, 2, 6, 3], ['finishing', 11]]]]
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
last setup row['setup', 4]['setup', 4]Passed
first repeat row['repeat', 1, 1]['repeat', 1, 1]Passed
single setup row['setup', 1]['setup', 1]Passed
regression: finishing offset['finishing', 39]['finishing', 38]Failed
repair check: finishing offset['finishing', 19]['finishing', 17]Failed
generated control 1['repeat', 1, 7]['repeat', 1, 7]Passed
generated control 2['finishing', 18]['finishing', 14]Failed
generated control 3['finishing', 47]['finishing', 41]Failed

SHA-256 / d2e0451b301e33503d091aa3bfb1c4e3cabb2d669c1617137b148b3ad0d5ea36

2 / The unsuccessful fix

Exit 1
"""Failure Map reference implementation. Python standard library only."""
import json
import math
from fractions import Fraction
N = 1
observations = []
def solve(row, setup, length, repeats):
    if row < 1:
        return 'error: rows start at 1'
    if row <= setup:
        return ['setup', row]
    k = row - setup
    if k <= length * repeats:
        return ['repeat', (k - 1) // length + 1, (k - 1) % length + 1]
    return ['finishing', k - length * (repeats - 1)]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[['last setup row', [4, 4, 8, 3], ['setup', 4]], ['first repeat row', [5, 4, 8, 3], ['repeat', 1, 1]],
  ['single setup row', [1, 1, 4, 2], ['setup', 1]],
  ['regression: finishing offset', [43, 1, 4, 1], ['finishing', 38]],
  ['repair check: finishing offset', [43, 2, 8, 3], ['finishing', 17]],
  ['generated control 1', [13, 6, 8, 2], ['repeat', 1, 7]],
  ['generated control 2', [30, 4, 4, 3], ['finishing', 14]],
  ['generated control 3', [51, 6, 4, 1], ['finishing', 41]]],
 [['first repeat row', [5, 4, 8, 3], ['repeat', 1, 1]], ['single setup row', [1, 1, 4, 2], ['setup', 1]],
  ['last row of repeat', [12, 4, 8, 3], ['repeat', 1, 8]],
  ['regression: finishing offset', [37, 1, 4, 5], ['finishing', 16]],
  ['repair check: finishing offset', [13, 0, 4, 1], ['finishing', 9]],
  ['generated control 1', [7, 0, 12, 2], ['repeat', 1, 7]],
  ['generated control 2', [48, 0, 8, 1], ['finishing', 40]],
  ['generated control 3', [33, 1, 4, 5], ['finishing', 12]]],
 [['single setup row', [1, 1, 4, 2], ['setup', 1]], ['last row of repeat', [12, 4, 8, 3], ['repeat', 1, 8]],
  ['first finishing row', [29, 4, 8, 3], ['finishing', 1]],
  ['regression: finishing offset', [35, 1, 8, 2], ['finishing', 18]],
  ['repair check: finishing offset', [4, 0, 1, 2], ['finishing', 2]],
  ['generated control 1', [21, 6, 6, 5], ['repeat', 3, 3]],
  ['generated control 2', [14, 2, 6, 5], ['repeat', 2, 6]],
  ['generated control 3', [6, 2, 1, 1], ['finishing', 3]]],
 [['last row of repeat', [12, 4, 8, 3], ['repeat', 1, 8]],
  ['first finishing row', [29, 4, 8, 3], ['finishing', 1]],
  ['row zero', [0, 2, 4, 2], 'error: rows start at 1'],
  ['regression: finishing offset', [47, 4, 8, 1], ['finishing', 35]],
  ['repair check: finishing offset', [56, 0, 4, 2], ['finishing', 48]],
  ['generated control 1', [44, 2, 6, 1], ['finishing', 36]],
  ['generated control 2', [41, 4, 12, 2], ['finishing', 13]],
  ['generated control 3', [52, 6, 1, 1], ['finishing', 45]]],
 [['first finishing row', [29, 4, 8, 3], ['finishing', 1]],
  ['row zero', [0, 2, 4, 2], 'error: rows start at 1'], ['last setup row', [4, 4, 8, 3], ['setup', 4]],
  ['regression: finishing offset', [34, 2, 4, 2], ['finishing', 24]],
  ['repair check: finishing offset', [47, 0, 1, 1], ['finishing', 46]],
  ['generated control 1', [47, 6, 1, 1], ['finishing', 40]],
  ['generated control 2', [5, 1, 8, 5], ['repeat', 1, 4]],
  ['generated control 3', [31, 2, 6, 3], ['finishing', 11]]]]
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
last setup row['setup', 4]['setup', 4]Passed
first repeat row['repeat', 1, 1]['repeat', 1, 1]Passed
single setup row['setup', 1]['setup', 1]Passed
regression: finishing offset['finishing', 42]['finishing', 38]Failed
repair check: finishing offset['finishing', 25]['finishing', 17]Failed
generated control 1['repeat', 1, 7]['repeat', 1, 7]Passed
generated control 2['finishing', 18]['finishing', 14]Failed
generated control 3['finishing', 45]['finishing', 41]Failed

SHA-256 / d1c46e43bff09bb68d3bb62df8b20f79c32e1dc0aa21fa192c0cb125e2b0c157

3 / The verified repair

Exit 0
"""Failure Map reference implementation. Python standard library only."""
import json
import math
from fractions import Fraction
N = 1
observations = []
def solve(row, setup, length, repeats):
    if row < 1:
        return 'error: rows start at 1'
    if row <= setup:
        return ['setup', row]
    k = row - setup
    if k <= length * repeats:
        return ['repeat', (k - 1) // length + 1, (k - 1) % length + 1]
    return ['finishing', k - length * repeats]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[['last setup row', [4, 4, 8, 3], ['setup', 4]], ['first repeat row', [5, 4, 8, 3], ['repeat', 1, 1]],
  ['single setup row', [1, 1, 4, 2], ['setup', 1]],
  ['regression: finishing offset', [43, 1, 4, 1], ['finishing', 38]],
  ['repair check: finishing offset', [43, 2, 8, 3], ['finishing', 17]],
  ['generated control 1', [13, 6, 8, 2], ['repeat', 1, 7]],
  ['generated control 2', [30, 4, 4, 3], ['finishing', 14]],
  ['generated control 3', [51, 6, 4, 1], ['finishing', 41]]],
 [['first repeat row', [5, 4, 8, 3], ['repeat', 1, 1]], ['single setup row', [1, 1, 4, 2], ['setup', 1]],
  ['last row of repeat', [12, 4, 8, 3], ['repeat', 1, 8]],
  ['regression: finishing offset', [37, 1, 4, 5], ['finishing', 16]],
  ['repair check: finishing offset', [13, 0, 4, 1], ['finishing', 9]],
  ['generated control 1', [7, 0, 12, 2], ['repeat', 1, 7]],
  ['generated control 2', [48, 0, 8, 1], ['finishing', 40]],
  ['generated control 3', [33, 1, 4, 5], ['finishing', 12]]],
 [['single setup row', [1, 1, 4, 2], ['setup', 1]], ['last row of repeat', [12, 4, 8, 3], ['repeat', 1, 8]],
  ['first finishing row', [29, 4, 8, 3], ['finishing', 1]],
  ['regression: finishing offset', [35, 1, 8, 2], ['finishing', 18]],
  ['repair check: finishing offset', [4, 0, 1, 2], ['finishing', 2]],
  ['generated control 1', [21, 6, 6, 5], ['repeat', 3, 3]],
  ['generated control 2', [14, 2, 6, 5], ['repeat', 2, 6]],
  ['generated control 3', [6, 2, 1, 1], ['finishing', 3]]],
 [['last row of repeat', [12, 4, 8, 3], ['repeat', 1, 8]],
  ['first finishing row', [29, 4, 8, 3], ['finishing', 1]],
  ['row zero', [0, 2, 4, 2], 'error: rows start at 1'],
  ['regression: finishing offset', [47, 4, 8, 1], ['finishing', 35]],
  ['repair check: finishing offset', [56, 0, 4, 2], ['finishing', 48]],
  ['generated control 1', [44, 2, 6, 1], ['finishing', 36]],
  ['generated control 2', [41, 4, 12, 2], ['finishing', 13]],
  ['generated control 3', [52, 6, 1, 1], ['finishing', 45]]],
 [['first finishing row', [29, 4, 8, 3], ['finishing', 1]],
  ['row zero', [0, 2, 4, 2], 'error: rows start at 1'], ['last setup row', [4, 4, 8, 3], ['setup', 4]],
  ['regression: finishing offset', [34, 2, 4, 2], ['finishing', 24]],
  ['repair check: finishing offset', [47, 0, 1, 1], ['finishing', 46]],
  ['generated control 1', [47, 6, 1, 1], ['finishing', 40]],
  ['generated control 2', [5, 1, 8, 5], ['repeat', 1, 4]],
  ['generated control 3', [31, 2, 6, 3], ['finishing', 11]]]]
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
last setup row['setup', 4]['setup', 4]Passed
first repeat row['repeat', 1, 1]['repeat', 1, 1]Passed
single setup row['setup', 1]['setup', 1]Passed
regression: finishing offset['finishing', 38]['finishing', 38]Passed
repair check: finishing offset['finishing', 17]['finishing', 17]Passed
generated control 1['repeat', 1, 7]['repeat', 1, 7]Passed
generated control 2['finishing', 14]['finishing', 14]Passed
generated control 3['finishing', 41]['finishing', 41]Passed

SHA-256 / 60db1b4ab004b87cd373aaeaf11165f16968d0228b228a505534a823c49edbd0

Verification & scope

A deterministic toy contract stated in full here; it is a bounded teaching model, not an authoritative reference or standards 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 2026-09-29T14:52:32.376846+00:00.

Case digest / 6541bae02d26af154b6e97bb2d64a068aaf6ea437a7f91b7311df65dd4837247