FA-97726 / Knitting and sewing pattern grading / Open access
Post-wash swatch gauge: even row rounding · case 01
The body ends on a right-side row.
ROOT CAUSE
Rows are rounded to any integer instead of the nearest even count.
THE FAILURE
Rows are rounded to any integer instead of the nearest even count.
Unsuccessful approach: Always rounding up to even adds rows.
Case contract
A swatch of sts x rows measured before and after washing. Use post-wash dimensions: cast on = half-up target_w*sts/w_post; rows = target_h*rows/h_post rounded to the nearest even number (ties up); width change % = (w_post/w_pre - 1)*100 half-up to 0.1. Return [cast_on, rows, width_change].
Why this case matters
Knitters block swatches because many fibres grow or shrink after washing.
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(sts, rows, w_pre, w_post, h_pre, h_post, target_w, target_h):
wpo = Fraction(w_post)
hpo = Fraction(h_post)
cast = math.floor(target_w * sts / wpo + Fraction(1, 2))
rr = target_h * rows / hpo
row_count = math.floor(rr + Fraction(1, 2))
change = (wpo / Fraction(w_pre) - 1) * 100
return [cast, row_count, math.floor(change * 10 + Fraction(1, 2)) / 10]
def check(label, actual, expected):
observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[['no change', [20, 28, '10', '10', '10', '10', 50, 45], [100, 126, 0.0]],
['growth', [22, 30, '10', '11', '10', '10.4', 50, 60], [100, 174, 10.0]],
['shrink', [24, 32, '10.5', '9.5', '10.2', '9', 40, 30], [101, 106, -9.5]],
['regression: even row rounding', [20, 30, '10', '10.5', '10.2', '10.4', 50, 30], [95, 86, 5.0]],
['repair check: even row rounding', [20, 40, '10', '11', '10', '9.5', 50, 60], [91, 252, 10.0]],
['generated control 1', [30, 28, '10', '10.8', '10.2', '10', 40, 30], [111, 84, 8.0]],
['generated control 2', [20, 28, '10', '11', '10', '9', 40, 45], [73, 140, 10.0]],
['generated control 3', [30, 28, '10.5', '10.5', '10', '10', 40, 60], [114, 168, 0.0]]],
[['growth', [22, 30, '10', '11', '10', '10.4', 50, 60], [100, 174, 10.0]],
['shrink', [24, 32, '10.5', '9.5', '10.2', '9', 40, 30], [101, 106, -9.5]],
['no change', [20, 28, '10', '10', '10', '10', 50, 45], [100, 126, 0.0]],
['regression: even row rounding', [30, 28, '10', '10.5', '10', '10.4', 55, 45], [157, 122, 5.0]],
['repair check: even row rounding', [30, 28, '10.5', '10.8', '10', '9.5', 50, 45], [139, 132, 2.9]],
['generated control 1', [20, 30, '10', '11', '10.2', '10.4', 55, 45], [100, 130, 10.0]],
['generated control 2', [22, 40, '10.5', '11', '10.2', '9', 50, 60], [100, 266, 4.8]],
['generated control 3', [20, 30, '10', '10.8', '10.2', '10', 55, 45], [102, 136, 8.0]]],
[['shrink', [24, 32, '10.5', '9.5', '10.2', '9', 40, 30], [101, 106, -9.5]],
['no change', [20, 28, '10', '10', '10', '10', 50, 45], [100, 126, 0.0]],
['growth', [22, 30, '10', '11', '10', '10.4', 50, 60], [100, 174, 10.0]],
['regression: even row rounding', [22, 32, '10', '10.5', '10', '9.5', 50, 30], [105, 102, 5.0]],
['repair check: even row rounding', [22, 30, '10', '10', '10', '9.5', 40, 30], [88, 94, 0.0]],
['generated control 1', [20, 40, '10.5', '10.8', '10', '10', 40, 60], [74, 240, 2.9]],
['generated control 2', [20, 32, '10', '10.8', '10.2', '9', 55, 45], [102, 160, 8.0]],
['generated control 3', [22, 28, '10', '9.5', '10', '10', 40, 60], [93, 168, -5.0]]],
[['no change', [20, 28, '10', '10', '10', '10', 50, 45], [100, 126, 0.0]],
['growth', [22, 30, '10', '11', '10', '10.4', 50, 60], [100, 174, 10.0]],
['shrink', [24, 32, '10.5', '9.5', '10.2', '9', 40, 30], [101, 106, -9.5]],
['regression: even row rounding', [30, 30, '10', '11', '10', '9.5', 40, 60], [109, 190, 10.0]],
['repair check: even row rounding', [22, 32, '10', '10.8', '10', '9.5', 40, 60], [81, 202, 8.0]],
['generated control 1', [24, 30, '10', '10', '10', '9', 55, 60], [132, 200, 0.0]],
['generated control 2', [24, 40, '10.5', '10.8', '10.2', '10', 50, 30], [111, 120, 2.9]],
['generated control 3', [30, 30, '10', '10.5', '10.2', '9', 40, 60], [114, 200, 5.0]]],
[['growth', [22, 30, '10', '11', '10', '10.4', 50, 60], [100, 174, 10.0]],
['shrink', [24, 32, '10.5', '9.5', '10.2', '9', 40, 30], [101, 106, -9.5]],
['no change', [20, 28, '10', '10', '10', '10', 50, 45], [100, 126, 0.0]],
['regression: even row rounding', [22, 30, '10', '10.8', '10', '10', 40, 45], [81, 136, 8.0]],
['repair check: even row rounding', [20, 40, '10.5', '10.5', '10.2', '9.5', 50, 30], [95, 126, 0.0]],
['generated control 1', [20, 30, '10', '11', '10', '10', 50, 60], [91, 180, 10.0]],
['generated control 2', [24, 30, '10', '10.8', '10', '9', 40, 45], [89, 150, 8.0]],
['generated control 3', [24, 30, '10.5', '10.5', '10.2', '10.4', 40, 60], [91, 174, 0.0]]]]
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 |
|---|---|---|---|
| no change | [100, 126, 0.0] | [100, 126, 0.0] | Passed |
| growth | [100, 173, 10.0] | [100, 174, 10.0] | Failed |
| shrink | [101, 107, -9.5] | [101, 106, -9.5] | Failed |
| regression: even row rounding | [95, 87, 5.0] | [95, 86, 5.0] | Failed |
| repair check: even row rounding | [91, 253, 10.0] | [91, 252, 10.0] | Failed |
| generated control 1 | [111, 84, 8.0] | [111, 84, 8.0] | Passed |
| generated control 2 | [73, 140, 10.0] | [73, 140, 10.0] | Passed |
| generated control 3 | [114, 168, 0.0] | [114, 168, 0.0] | Passed |
SHA-256 / f7e36c84dd511a04ee423b3b7441fad14bf7218de61218a285489d20bd0c18d2
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(sts, rows, w_pre, w_post, h_pre, h_post, target_w, target_h):
wpo = Fraction(w_post)
hpo = Fraction(h_post)
cast = math.floor(target_w * sts / wpo + Fraction(1, 2))
rr = target_h * rows / hpo
row_count = 2 * math.ceil(rr / 2)
change = (wpo / Fraction(w_pre) - 1) * 100
return [cast, row_count, math.floor(change * 10 + Fraction(1, 2)) / 10]
def check(label, actual, expected):
observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[['no change', [20, 28, '10', '10', '10', '10', 50, 45], [100, 126, 0.0]],
['growth', [22, 30, '10', '11', '10', '10.4', 50, 60], [100, 174, 10.0]],
['shrink', [24, 32, '10.5', '9.5', '10.2', '9', 40, 30], [101, 106, -9.5]],
['regression: even row rounding', [20, 30, '10', '10.5', '10.2', '10.4', 50, 30], [95, 86, 5.0]],
['repair check: even row rounding', [20, 40, '10', '11', '10', '9.5', 50, 60], [91, 252, 10.0]],
['generated control 1', [30, 28, '10', '10.8', '10.2', '10', 40, 30], [111, 84, 8.0]],
['generated control 2', [20, 28, '10', '11', '10', '9', 40, 45], [73, 140, 10.0]],
['generated control 3', [30, 28, '10.5', '10.5', '10', '10', 40, 60], [114, 168, 0.0]]],
[['growth', [22, 30, '10', '11', '10', '10.4', 50, 60], [100, 174, 10.0]],
['shrink', [24, 32, '10.5', '9.5', '10.2', '9', 40, 30], [101, 106, -9.5]],
['no change', [20, 28, '10', '10', '10', '10', 50, 45], [100, 126, 0.0]],
['regression: even row rounding', [30, 28, '10', '10.5', '10', '10.4', 55, 45], [157, 122, 5.0]],
['repair check: even row rounding', [30, 28, '10.5', '10.8', '10', '9.5', 50, 45], [139, 132, 2.9]],
['generated control 1', [20, 30, '10', '11', '10.2', '10.4', 55, 45], [100, 130, 10.0]],
['generated control 2', [22, 40, '10.5', '11', '10.2', '9', 50, 60], [100, 266, 4.8]],
['generated control 3', [20, 30, '10', '10.8', '10.2', '10', 55, 45], [102, 136, 8.0]]],
[['shrink', [24, 32, '10.5', '9.5', '10.2', '9', 40, 30], [101, 106, -9.5]],
['no change', [20, 28, '10', '10', '10', '10', 50, 45], [100, 126, 0.0]],
['growth', [22, 30, '10', '11', '10', '10.4', 50, 60], [100, 174, 10.0]],
['regression: even row rounding', [22, 32, '10', '10.5', '10', '9.5', 50, 30], [105, 102, 5.0]],
['repair check: even row rounding', [22, 30, '10', '10', '10', '9.5', 40, 30], [88, 94, 0.0]],
['generated control 1', [20, 40, '10.5', '10.8', '10', '10', 40, 60], [74, 240, 2.9]],
['generated control 2', [20, 32, '10', '10.8', '10.2', '9', 55, 45], [102, 160, 8.0]],
['generated control 3', [22, 28, '10', '9.5', '10', '10', 40, 60], [93, 168, -5.0]]],
[['no change', [20, 28, '10', '10', '10', '10', 50, 45], [100, 126, 0.0]],
['growth', [22, 30, '10', '11', '10', '10.4', 50, 60], [100, 174, 10.0]],
['shrink', [24, 32, '10.5', '9.5', '10.2', '9', 40, 30], [101, 106, -9.5]],
['regression: even row rounding', [30, 30, '10', '11', '10', '9.5', 40, 60], [109, 190, 10.0]],
['repair check: even row rounding', [22, 32, '10', '10.8', '10', '9.5', 40, 60], [81, 202, 8.0]],
['generated control 1', [24, 30, '10', '10', '10', '9', 55, 60], [132, 200, 0.0]],
['generated control 2', [24, 40, '10.5', '10.8', '10.2', '10', 50, 30], [111, 120, 2.9]],
['generated control 3', [30, 30, '10', '10.5', '10.2', '9', 40, 60], [114, 200, 5.0]]],
[['growth', [22, 30, '10', '11', '10', '10.4', 50, 60], [100, 174, 10.0]],
['shrink', [24, 32, '10.5', '9.5', '10.2', '9', 40, 30], [101, 106, -9.5]],
['no change', [20, 28, '10', '10', '10', '10', 50, 45], [100, 126, 0.0]],
['regression: even row rounding', [22, 30, '10', '10.8', '10', '10', 40, 45], [81, 136, 8.0]],
['repair check: even row rounding', [20, 40, '10.5', '10.5', '10.2', '9.5', 50, 30], [95, 126, 0.0]],
['generated control 1', [20, 30, '10', '11', '10', '10', 50, 60], [91, 180, 10.0]],
['generated control 2', [24, 30, '10', '10.8', '10', '9', 40, 45], [89, 150, 8.0]],
['generated control 3', [24, 30, '10.5', '10.5', '10.2', '10.4', 40, 60], [91, 174, 0.0]]]]
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 |
|---|---|---|---|
| no change | [100, 126, 0.0] | [100, 126, 0.0] | Passed |
| growth | [100, 174, 10.0] | [100, 174, 10.0] | Passed |
| shrink | [101, 108, -9.5] | [101, 106, -9.5] | Failed |
| regression: even row rounding | [95, 88, 5.0] | [95, 86, 5.0] | Failed |
| repair check: even row rounding | [91, 254, 10.0] | [91, 252, 10.0] | Failed |
| generated control 1 | [111, 84, 8.0] | [111, 84, 8.0] | Passed |
| generated control 2 | [73, 140, 10.0] | [73, 140, 10.0] | Passed |
| generated control 3 | [114, 168, 0.0] | [114, 168, 0.0] | Passed |
SHA-256 / 5f6a71852e2ee42569f84c180f3bd075f6121a2c12d79ef07f321281a26461e4
HELD IN THE MEMBER ARCHIVE
The verified repair and its recorded checks are member-only.
This mechanism has 8 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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Sign in to the archive ↗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 2026-09-29T14:52:35.043807+00:00.
Case digest / f074de62db0d5708299b58ac32aee817cdd8fbec5d5a1134ba16b4a338f97f20