FA-70631 / GIS polygon topology / Open access

Sliver polygon detection by thinness ratio: degenerate guard · case 01

Collapsed or fully-holed polygons get a negative or zero thinness and are reported as slivers.

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

ROOT CAUSE

The guard only checks the perimeter.

VERIFIED REPAIR

At the degenerate guard step restore `if area <= 0 or perim == 0:`, leaving the rest of the model unchanged.

Unsuccessful approach: Zero-area polygons still pass the guard and are reported as slivers with t = 0.

Case contract

Input [rings, threshold]: exterior then holes, closed rings in any orientation. Area = |exterior area| minus the sum of |hole areas|; perimeter = total length of all rings. If area <= 0 or perimeter == 0 return ["degenerate", 0.0]. Thinness t = 4*pi*area/perimeter**2; return ["sliver" if t < threshold else "ok", t rounded to 6 decimals].

Why this case matters

Overlay operations leave thin slivers along near-coincident boundaries; QA jobs flag them by compactness.

1 / The failure

Exit 1

"""Failure Map reference implementation. Python standard library only."""
import json
import math
N = 1
observations = []
def solve(x):
    rings, thresh = x
    def a2(r):
        return sum(p[0] * q[1] - q[0] * p[1] for p, q in zip(r, r[1:]))
    def per(r):
        return sum(math.hypot(q[0] - p[0], q[1] - p[1]) for p, q in zip(r, r[1:]))
    area = abs(a2(rings[0])) / 2 - sum(abs(a2(h)) / 2 for h in rings[1:])
    perim = sum(per(r) for r in rings)
    if perim == 0:
        return ['degenerate', 0.0]
    t = 4 * math.pi * area / perim ** 2
    return ['sliver' if t < thresh else 'ok', round(t, 6)]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[('control #0', [[[[0, 0], [10, 0], [10, 10], [0, 10], [0, 0]]], 0.3], ['ok', 0.785398]), ('control #1', [[[[0, 0], [100, 0], [100, 2], [0, 2], [0, 0]]], 0.3], ['sliver', 0.060392]), ('regression #2', [[[[0, 0], [20, 0], [20, 20], [0, 20], [0, 0]], [[1, 1], [1, 19], [19, 19], [19, 1], [1, 1]]], 0.3], ['sliver', 0.041337]), ('regression #3', [[[[0, 0], [0, 20], [20, 20], [20, 0], [0, 0]]], 0.3], ['ok', 0.785398]), ('regression #4', [[[[0, 0], [0, 20], [20, 20], [20, 0], [0, 0]], [[2, 2], [6, 2], [6, 6], [2, 6], [2, 2]]], 0.3], ['ok', 0.523599]), ('boundary #5', [[[[0, 0], [10, 0], [10, 10], [0, 10], [0, 0]]], 0.7853981633974483], ['ok', 0.785398]), ('boundary #6', [[[[0, 0], [10, 0], [20, 0], [0, 0]]], 0.3], ['degenerate', 0.0]), ('regression #7', [[[[0, 0], [10, 0], [10, 10], [0, 10], [0, 0]], [[0, 0], [0, 10], [10, 10], [10, 0], [0, 0]]], 0.3], ['degenerate', 0.0])], [('regression #3', [[[[0, 0], [0, 20], [20, 20], [20, 0], [0, 0]]], 0.3], ['ok', 0.785398]), ('regression #4', [[[[0, 0], [0, 20], [20, 20], [20, 0], [0, 0]], [[2, 2], [6, 2], [6, 6], [2, 6], [2, 2]]], 0.3], ['ok', 0.523599]), ('boundary #5', [[[[0, 0], [10, 0], [10, 10], [0, 10], [0, 0]]], 0.7853981633974483], ['ok', 0.785398]), ('boundary #6', [[[[0, 0], [10, 0], [20, 0], [0, 0]]], 0.3], ['degenerate', 0.0]), ('regression #7', [[[[0, 0], [10, 0], [10, 10], [0, 10], [0, 0]], [[0, 0], [0, 10], [10, 10], [10, 0], [0, 0]]], 0.3], ['degenerate', 0.0]), ('control #8', [[[[0, 0], [30, 0], [15, 26], [0, 0]]], 0.5], ['ok', 0.6046]), ('regression #9', [[[[0, 0], [30, 0], [30, 30], [0, 30], [0, 0]], [[5, 5], [5, 25], [25, 25], [25, 5], [5, 5]]], 0.2], ['sliver', 0.15708]), ('regression #10', [[[[0, 0], [30, 0], [30, 30], [0, 30], [0, 0]], [[5, 5], [5, 25], [10, 25], [10, 5], [5, 5]], [[15, 5], [15, 25], [25, 25], [25, 5], [15, 5]]], 0.2], ['sliver', 0.14253])], [('boundary #6', [[[[0, 0], [10, 0], [20, 0], [0, 0]]], 0.3], ['degenerate', 0.0]), ('regression #7', [[[[0, 0], [10, 0], [10, 10], [0, 10], [0, 0]], [[0, 0], [0, 10], [10, 10], [10, 0], [0, 0]]], 0.3], ['degenerate', 0.0]), ('control #8', [[[[0, 0], [30, 0], [15, 26], [0, 0]]], 0.5], ['ok', 0.6046]), ('regression #9', [[[[0, 0], [30, 0], [30, 30], [0, 30], [0, 0]], [[5, 5], [5, 25], [25, 25], [25, 5], [5, 5]]], 0.2], ['sliver', 0.15708]), ('regression #10', [[[[0, 0], [30, 0], [30, 30], [0, 30], [0, 0]], [[5, 5], [5, 25], [10, 25], [10, 5], [5, 5]], [[15, 5], [15, 25], [25, 25], [25, 5], [15, 5]]], 0.2], ['sliver', 0.14253]), ('control #11', [[[[0, 0], [40, 0], [40, 5], [0, 5], [0, 0]]], 0.5], ['sliver', 0.310281]), ('boundary #12', [[[[0, 0], [40, 0], [40, 10], [0, 10], [0, 0]]], 0.5], ['ok', 0.502655]), ('regression #13', [[[[0, 0], [12, 0], [12, 12], [0, 12], [0, 0]], [[1, 1], [1, 2], [11, 2], [11, 1], [1, 1]]], 0.6], ['sliver', 0.343652])], [('boundary #6', [[[[0, 0], [10, 0], [20, 0], [0, 0]]], 0.3], ['degenerate', 0.0]), ('regression #7', [[[[0, 0], [10, 0], [10, 10], [0, 10], [0, 0]], [[0, 0], [0, 10], [10, 10], [10, 0], [0, 0]]], 0.3], ['degenerate', 0.0]), ('control #11', [[[[0, 0], [40, 0], [40, 5], [0, 5], [0, 0]]], 0.5], ['sliver', 0.310281]), ('boundary #12', [[[[0, 0], [40, 0], [40, 10], [0, 10], [0, 0]]], 0.5], ['ok', 0.502655]), ('regression #13', [[[[0, 0], [12, 0], [12, 12], [0, 12], [0, 0]], [[1, 1], [1, 2], [11, 2], [11, 1], [1, 1]]], 0.6], ['sliver', 0.343652]), ('control #14', [[[[0, 0], [8, 1], [9, 9], [1, 8], [0, 0]]], 0.4], ['ok', 0.761232]), ('regression #15', [[[[0, 0], [1, 8], [9, 9], [8, 1], [0, 0]], [[3, 3], [5, 3], [5, 5], [3, 5], [3, 3]]], 0.4], ['ok', 0.457668]), ('regression #16', [[[[0, 0], [40, 0], [40, 10], [0, 10], [0, 0]]], 0.502], ['ok', 0.502655])], [('control #0', [[[[0, 0], [10, 0], [10, 10], [0, 10], [0, 0]]], 0.3], ['ok', 0.785398]), ('control #1', [[[[0, 0], [100, 0], [100, 2], [0, 2], [0, 0]]], 0.3], ['sliver', 0.060392]), ('boundary #6', [[[[0, 0], [10, 0], [20, 0], [0, 0]]], 0.3], ['degenerate', 0.0]), ('regression #7', [[[[0, 0], [10, 0], [10, 10], [0, 10], [0, 0]], [[0, 0], [0, 10], [10, 10], [10, 0], [0, 0]]], 0.3], ['degenerate', 0.0]), ('control #14', [[[[0, 0], [8, 1], [9, 9], [1, 8], [0, 0]]], 0.4], ['ok', 0.761232]), ('regression #15', [[[[0, 0], [1, 8], [9, 9], [8, 1], [0, 0]], [[3, 3], [5, 3], [5, 5], [3, 5], [3, 3]]], 0.4], ['ok', 0.457668]), ('regression #16', [[[[0, 0], [40, 0], [40, 10], [0, 10], [0, 0]]], 0.502], ['ok', 0.502655]), ('regression #17', [[[[0, 0], [30, 0], [30, 10], [0, 10], [0, 0]]], 0.587], ['ok', 0.589049])]]
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
control #0	`['ok', 0.785398]`	`['ok', 0.785398]`	Passed
control #1	`['sliver', 0.060392]`	`['sliver', 0.060392]`	Passed
regression #2	`['sliver', 0.041337]`	`['sliver', 0.041337]`	Passed
regression #3	`['ok', 0.785398]`	`['ok', 0.785398]`	Passed
regression #4	`['ok', 0.523599]`	`['ok', 0.523599]`	Passed
boundary #5	`['ok', 0.785398]`	`['ok', 0.785398]`	Passed
boundary #6	`['sliver', 0.0]`	`['degenerate', 0.0]`	Failed
regression #7	`['sliver', 0.0]`	`['degenerate', 0.0]`	Failed

SHA-256 / 531f74747bd58b83b6cd78d3ef36f6b0484593ae8b80547a2f7818e1b1df073d

2 / The unsuccessful fix

Exit 1

"""Failure Map reference implementation. Python standard library only."""
import json
import math
N = 1
observations = []
def solve(x):
    rings, thresh = x
    def a2(r):
        return sum(p[0] * q[1] - q[0] * p[1] for p, q in zip(r, r[1:]))
    def per(r):
        return sum(math.hypot(q[0] - p[0], q[1] - p[1]) for p, q in zip(r, r[1:]))
    area = abs(a2(rings[0])) / 2 - sum(abs(a2(h)) / 2 for h in rings[1:])
    perim = sum(per(r) for r in rings)
    if area < 0 or perim == 0:
        return ['degenerate', 0.0]
    t = 4 * math.pi * area / perim ** 2
    return ['sliver' if t < thresh else 'ok', round(t, 6)]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[('control #0', [[[[0, 0], [10, 0], [10, 10], [0, 10], [0, 0]]], 0.3], ['ok', 0.785398]), ('control #1', [[[[0, 0], [100, 0], [100, 2], [0, 2], [0, 0]]], 0.3], ['sliver', 0.060392]), ('regression #2', [[[[0, 0], [20, 0], [20, 20], [0, 20], [0, 0]], [[1, 1], [1, 19], [19, 19], [19, 1], [1, 1]]], 0.3], ['sliver', 0.041337]), ('regression #3', [[[[0, 0], [0, 20], [20, 20], [20, 0], [0, 0]]], 0.3], ['ok', 0.785398]), ('regression #4', [[[[0, 0], [0, 20], [20, 20], [20, 0], [0, 0]], [[2, 2], [6, 2], [6, 6], [2, 6], [2, 2]]], 0.3], ['ok', 0.523599]), ('boundary #5', [[[[0, 0], [10, 0], [10, 10], [0, 10], [0, 0]]], 0.7853981633974483], ['ok', 0.785398]), ('boundary #6', [[[[0, 0], [10, 0], [20, 0], [0, 0]]], 0.3], ['degenerate', 0.0]), ('regression #7', [[[[0, 0], [10, 0], [10, 10], [0, 10], [0, 0]], [[0, 0], [0, 10], [10, 10], [10, 0], [0, 0]]], 0.3], ['degenerate', 0.0])], [('regression #3', [[[[0, 0], [0, 20], [20, 20], [20, 0], [0, 0]]], 0.3], ['ok', 0.785398]), ('regression #4', [[[[0, 0], [0, 20], [20, 20], [20, 0], [0, 0]], [[2, 2], [6, 2], [6, 6], [2, 6], [2, 2]]], 0.3], ['ok', 0.523599]), ('boundary #5', [[[[0, 0], [10, 0], [10, 10], [0, 10], [0, 0]]], 0.7853981633974483], ['ok', 0.785398]), ('boundary #6', [[[[0, 0], [10, 0], [20, 0], [0, 0]]], 0.3], ['degenerate', 0.0]), ('regression #7', [[[[0, 0], [10, 0], [10, 10], [0, 10], [0, 0]], [[0, 0], [0, 10], [10, 10], [10, 0], [0, 0]]], 0.3], ['degenerate', 0.0]), ('control #8', [[[[0, 0], [30, 0], [15, 26], [0, 0]]], 0.5], ['ok', 0.6046]), ('regression #9', [[[[0, 0], [30, 0], [30, 30], [0, 30], [0, 0]], [[5, 5], [5, 25], [25, 25], [25, 5], [5, 5]]], 0.2], ['sliver', 0.15708]), ('regression #10', [[[[0, 0], [30, 0], [30, 30], [0, 30], [0, 0]], [[5, 5], [5, 25], [10, 25], [10, 5], [5, 5]], [[15, 5], [15, 25], [25, 25], [25, 5], [15, 5]]], 0.2], ['sliver', 0.14253])], [('boundary #6', [[[[0, 0], [10, 0], [20, 0], [0, 0]]], 0.3], ['degenerate', 0.0]), ('regression #7', [[[[0, 0], [10, 0], [10, 10], [0, 10], [0, 0]], [[0, 0], [0, 10], [10, 10], [10, 0], [0, 0]]], 0.3], ['degenerate', 0.0]), ('control #8', [[[[0, 0], [30, 0], [15, 26], [0, 0]]], 0.5], ['ok', 0.6046]), ('regression #9', [[[[0, 0], [30, 0], [30, 30], [0, 30], [0, 0]], [[5, 5], [5, 25], [25, 25], [25, 5], [5, 5]]], 0.2], ['sliver', 0.15708]), ('regression #10', [[[[0, 0], [30, 0], [30, 30], [0, 30], [0, 0]], [[5, 5], [5, 25], [10, 25], [10, 5], [5, 5]], [[15, 5], [15, 25], [25, 25], [25, 5], [15, 5]]], 0.2], ['sliver', 0.14253]), ('control #11', [[[[0, 0], [40, 0], [40, 5], [0, 5], [0, 0]]], 0.5], ['sliver', 0.310281]), ('boundary #12', [[[[0, 0], [40, 0], [40, 10], [0, 10], [0, 0]]], 0.5], ['ok', 0.502655]), ('regression #13', [[[[0, 0], [12, 0], [12, 12], [0, 12], [0, 0]], [[1, 1], [1, 2], [11, 2], [11, 1], [1, 1]]], 0.6], ['sliver', 0.343652])], [('boundary #6', [[[[0, 0], [10, 0], [20, 0], [0, 0]]], 0.3], ['degenerate', 0.0]), ('regression #7', [[[[0, 0], [10, 0], [10, 10], [0, 10], [0, 0]], [[0, 0], [0, 10], [10, 10], [10, 0], [0, 0]]], 0.3], ['degenerate', 0.0]), ('control #11', [[[[0, 0], [40, 0], [40, 5], [0, 5], [0, 0]]], 0.5], ['sliver', 0.310281]), ('boundary #12', [[[[0, 0], [40, 0], [40, 10], [0, 10], [0, 0]]], 0.5], ['ok', 0.502655]), ('regression #13', [[[[0, 0], [12, 0], [12, 12], [0, 12], [0, 0]], [[1, 1], [1, 2], [11, 2], [11, 1], [1, 1]]], 0.6], ['sliver', 0.343652]), ('control #14', [[[[0, 0], [8, 1], [9, 9], [1, 8], [0, 0]]], 0.4], ['ok', 0.761232]), ('regression #15', [[[[0, 0], [1, 8], [9, 9], [8, 1], [0, 0]], [[3, 3], [5, 3], [5, 5], [3, 5], [3, 3]]], 0.4], ['ok', 0.457668]), ('regression #16', [[[[0, 0], [40, 0], [40, 10], [0, 10], [0, 0]]], 0.502], ['ok', 0.502655])], [('control #0', [[[[0, 0], [10, 0], [10, 10], [0, 10], [0, 0]]], 0.3], ['ok', 0.785398]), ('control #1', [[[[0, 0], [100, 0], [100, 2], [0, 2], [0, 0]]], 0.3], ['sliver', 0.060392]), ('boundary #6', [[[[0, 0], [10, 0], [20, 0], [0, 0]]], 0.3], ['degenerate', 0.0]), ('regression #7', [[[[0, 0], [10, 0], [10, 10], [0, 10], [0, 0]], [[0, 0], [0, 10], [10, 10], [10, 0], [0, 0]]], 0.3], ['degenerate', 0.0]), ('control #14', [[[[0, 0], [8, 1], [9, 9], [1, 8], [0, 0]]], 0.4], ['ok', 0.761232]), ('regression #15', [[[[0, 0], [1, 8], [9, 9], [8, 1], [0, 0]], [[3, 3], [5, 3], [5, 5], [3, 5], [3, 3]]], 0.4], ['ok', 0.457668]), ('regression #16', [[[[0, 0], [40, 0], [40, 10], [0, 10], [0, 0]]], 0.502], ['ok', 0.502655]), ('regression #17', [[[[0, 0], [30, 0], [30, 10], [0, 10], [0, 0]]], 0.587], ['ok', 0.589049])]]
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
control #0	`['ok', 0.785398]`	`['ok', 0.785398]`	Passed
control #1	`['sliver', 0.060392]`	`['sliver', 0.060392]`	Passed
regression #2	`['sliver', 0.041337]`	`['sliver', 0.041337]`	Passed
regression #3	`['ok', 0.785398]`	`['ok', 0.785398]`	Passed
regression #4	`['ok', 0.523599]`	`['ok', 0.523599]`	Passed
boundary #5	`['ok', 0.785398]`	`['ok', 0.785398]`	Passed
boundary #6	`['sliver', 0.0]`	`['degenerate', 0.0]`	Failed
regression #7	`['sliver', 0.0]`	`['degenerate', 0.0]`	Failed

SHA-256 / 3641b6d7122b42879cfa8261265216bb8ec1ff0f291edd1bf88548fe523aded3

3 / The verified repair

Exit 0

"""Failure Map reference implementation. Python standard library only."""
import json
import math
N = 1
observations = []
def solve(x):
    rings, thresh = x
    def a2(r):
        return sum(p[0] * q[1] - q[0] * p[1] for p, q in zip(r, r[1:]))
    def per(r):
        return sum(math.hypot(q[0] - p[0], q[1] - p[1]) for p, q in zip(r, r[1:]))
    area = abs(a2(rings[0])) / 2 - sum(abs(a2(h)) / 2 for h in rings[1:])
    perim = sum(per(r) for r in rings)
    if area <= 0 or perim == 0:
        return ['degenerate', 0.0]
    t = 4 * math.pi * area / perim ** 2
    return ['sliver' if t < thresh else 'ok', round(t, 6)]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[('control #0', [[[[0, 0], [10, 0], [10, 10], [0, 10], [0, 0]]], 0.3], ['ok', 0.785398]), ('control #1', [[[[0, 0], [100, 0], [100, 2], [0, 2], [0, 0]]], 0.3], ['sliver', 0.060392]), ('regression #2', [[[[0, 0], [20, 0], [20, 20], [0, 20], [0, 0]], [[1, 1], [1, 19], [19, 19], [19, 1], [1, 1]]], 0.3], ['sliver', 0.041337]), ('regression #3', [[[[0, 0], [0, 20], [20, 20], [20, 0], [0, 0]]], 0.3], ['ok', 0.785398]), ('regression #4', [[[[0, 0], [0, 20], [20, 20], [20, 0], [0, 0]], [[2, 2], [6, 2], [6, 6], [2, 6], [2, 2]]], 0.3], ['ok', 0.523599]), ('boundary #5', [[[[0, 0], [10, 0], [10, 10], [0, 10], [0, 0]]], 0.7853981633974483], ['ok', 0.785398]), ('boundary #6', [[[[0, 0], [10, 0], [20, 0], [0, 0]]], 0.3], ['degenerate', 0.0]), ('regression #7', [[[[0, 0], [10, 0], [10, 10], [0, 10], [0, 0]], [[0, 0], [0, 10], [10, 10], [10, 0], [0, 0]]], 0.3], ['degenerate', 0.0])], [('regression #3', [[[[0, 0], [0, 20], [20, 20], [20, 0], [0, 0]]], 0.3], ['ok', 0.785398]), ('regression #4', [[[[0, 0], [0, 20], [20, 20], [20, 0], [0, 0]], [[2, 2], [6, 2], [6, 6], [2, 6], [2, 2]]], 0.3], ['ok', 0.523599]), ('boundary #5', [[[[0, 0], [10, 0], [10, 10], [0, 10], [0, 0]]], 0.7853981633974483], ['ok', 0.785398]), ('boundary #6', [[[[0, 0], [10, 0], [20, 0], [0, 0]]], 0.3], ['degenerate', 0.0]), ('regression #7', [[[[0, 0], [10, 0], [10, 10], [0, 10], [0, 0]], [[0, 0], [0, 10], [10, 10], [10, 0], [0, 0]]], 0.3], ['degenerate', 0.0]), ('control #8', [[[[0, 0], [30, 0], [15, 26], [0, 0]]], 0.5], ['ok', 0.6046]), ('regression #9', [[[[0, 0], [30, 0], [30, 30], [0, 30], [0, 0]], [[5, 5], [5, 25], [25, 25], [25, 5], [5, 5]]], 0.2], ['sliver', 0.15708]), ('regression #10', [[[[0, 0], [30, 0], [30, 30], [0, 30], [0, 0]], [[5, 5], [5, 25], [10, 25], [10, 5], [5, 5]], [[15, 5], [15, 25], [25, 25], [25, 5], [15, 5]]], 0.2], ['sliver', 0.14253])], [('boundary #6', [[[[0, 0], [10, 0], [20, 0], [0, 0]]], 0.3], ['degenerate', 0.0]), ('regression #7', [[[[0, 0], [10, 0], [10, 10], [0, 10], [0, 0]], [[0, 0], [0, 10], [10, 10], [10, 0], [0, 0]]], 0.3], ['degenerate', 0.0]), ('control #8', [[[[0, 0], [30, 0], [15, 26], [0, 0]]], 0.5], ['ok', 0.6046]), ('regression #9', [[[[0, 0], [30, 0], [30, 30], [0, 30], [0, 0]], [[5, 5], [5, 25], [25, 25], [25, 5], [5, 5]]], 0.2], ['sliver', 0.15708]), ('regression #10', [[[[0, 0], [30, 0], [30, 30], [0, 30], [0, 0]], [[5, 5], [5, 25], [10, 25], [10, 5], [5, 5]], [[15, 5], [15, 25], [25, 25], [25, 5], [15, 5]]], 0.2], ['sliver', 0.14253]), ('control #11', [[[[0, 0], [40, 0], [40, 5], [0, 5], [0, 0]]], 0.5], ['sliver', 0.310281]), ('boundary #12', [[[[0, 0], [40, 0], [40, 10], [0, 10], [0, 0]]], 0.5], ['ok', 0.502655]), ('regression #13', [[[[0, 0], [12, 0], [12, 12], [0, 12], [0, 0]], [[1, 1], [1, 2], [11, 2], [11, 1], [1, 1]]], 0.6], ['sliver', 0.343652])], [('boundary #6', [[[[0, 0], [10, 0], [20, 0], [0, 0]]], 0.3], ['degenerate', 0.0]), ('regression #7', [[[[0, 0], [10, 0], [10, 10], [0, 10], [0, 0]], [[0, 0], [0, 10], [10, 10], [10, 0], [0, 0]]], 0.3], ['degenerate', 0.0]), ('control #11', [[[[0, 0], [40, 0], [40, 5], [0, 5], [0, 0]]], 0.5], ['sliver', 0.310281]), ('boundary #12', [[[[0, 0], [40, 0], [40, 10], [0, 10], [0, 0]]], 0.5], ['ok', 0.502655]), ('regression #13', [[[[0, 0], [12, 0], [12, 12], [0, 12], [0, 0]], [[1, 1], [1, 2], [11, 2], [11, 1], [1, 1]]], 0.6], ['sliver', 0.343652]), ('control #14', [[[[0, 0], [8, 1], [9, 9], [1, 8], [0, 0]]], 0.4], ['ok', 0.761232]), ('regression #15', [[[[0, 0], [1, 8], [9, 9], [8, 1], [0, 0]], [[3, 3], [5, 3], [5, 5], [3, 5], [3, 3]]], 0.4], ['ok', 0.457668]), ('regression #16', [[[[0, 0], [40, 0], [40, 10], [0, 10], [0, 0]]], 0.502], ['ok', 0.502655])], [('control #0', [[[[0, 0], [10, 0], [10, 10], [0, 10], [0, 0]]], 0.3], ['ok', 0.785398]), ('control #1', [[[[0, 0], [100, 0], [100, 2], [0, 2], [0, 0]]], 0.3], ['sliver', 0.060392]), ('boundary #6', [[[[0, 0], [10, 0], [20, 0], [0, 0]]], 0.3], ['degenerate', 0.0]), ('regression #7', [[[[0, 0], [10, 0], [10, 10], [0, 10], [0, 0]], [[0, 0], [0, 10], [10, 10], [10, 0], [0, 0]]], 0.3], ['degenerate', 0.0]), ('control #14', [[[[0, 0], [8, 1], [9, 9], [1, 8], [0, 0]]], 0.4], ['ok', 0.761232]), ('regression #15', [[[[0, 0], [1, 8], [9, 9], [8, 1], [0, 0]], [[3, 3], [5, 3], [5, 5], [3, 5], [3, 3]]], 0.4], ['ok', 0.457668]), ('regression #16', [[[[0, 0], [40, 0], [40, 10], [0, 10], [0, 0]]], 0.502], ['ok', 0.502655]), ('regression #17', [[[[0, 0], [30, 0], [30, 10], [0, 10], [0, 0]]], 0.587], ['ok', 0.589049])]]
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
control #0	`['ok', 0.785398]`	`['ok', 0.785398]`	Passed
control #1	`['sliver', 0.060392]`	`['sliver', 0.060392]`	Passed
regression #2	`['sliver', 0.041337]`	`['sliver', 0.041337]`	Passed
regression #3	`['ok', 0.785398]`	`['ok', 0.785398]`	Passed
regression #4	`['ok', 0.523599]`	`['ok', 0.523599]`	Passed
boundary #5	`['ok', 0.785398]`	`['ok', 0.785398]`	Passed
boundary #6	`['degenerate', 0.0]`	`['degenerate', 0.0]`	Passed
regression #7	`['degenerate', 0.0]`	`['degenerate', 0.0]`	Passed

SHA-256 / 016c41f2a4bf1d5a6a034523b45476379832e2fe4f5d8a85e8daca168ad9c479

Verification & scope

Stipulated deterministic toy contract on a bounded input domain; results are rounded as stated and no conformance with any published standard or library is claimed. 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 2026-09-29T14:48:22.485890+00:00.

Case digest / 660f5b69c2ae56c3eae8b4a1bc9cf436fae1a2a2d13b4d8f48a33f649c981ce7