FAILURE MAP
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FA-87326 / Physics integrator stability / Open access

Monitor returns drift at the first exceedance before scanning for blowup · case 01

An exploding simulation is reported as mild drift.

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

ROOT CAUSE

The loop returns drift immediately on the first r>tol.

THE FAILURE

The loop returns drift immediately on the first r>tol.

Unsuccessful approach: Breaking out of the loop at the first drift also hides later blowups and truncates the maximum.

Case contract

solve(states, k, m, tol, blowup): states [[x,v],...] of a spring integrator; E=0.5 m v^2+0.5 k x^2. Relative drift r=|E-E0|/E0 (absolute when E0=0). Scan in order: first state with E>blowup*E0 (E0>0) returns ["blowup", index, its r]. Otherwise ["drift", first index with r>tol, max r] or ["ok", -1, max r].

Why this case matters

Game and robotics physics loops depend on integrator update order, step control and stabilization terms; a wrong decision point turns a stable simulation into drifting or exploding motion.

1 / The failure

Exit 1
"""Failure Map reference implementation. Python standard library only."""
import json
import math
N = 1
observations = []
def solve(states, k, m, tol, blowup):
    def en(s):
        return 0.5 * m * s[1] * s[1] + 0.5 * k * s[0] * s[0]
    e0 = en(states[0])
    scale = e0 if e0 > 0 else 1.0
    worst = 0.0
    first_drift = -1
    for i, s in enumerate(states):
        e = en(s)
        if e0 > 0 and e > blowup * e0:
            return ['blowup', i, round(abs(e - e0) / scale, 6)]
        r = abs(e - e0) / scale
        if r > worst:
            worst = r
        if r > tol and first_drift < 0:
            return ['drift', i, round(r, 6)]
    if first_drift >= 0:
        return ['drift', first_drift, round(worst, 6)]
    return ['ok', -1, round(worst, 6)]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[[[[[-0.783, -0.238], [-0.7094, -0.2142], [-0.6366, -0.1928], [-0.5724, -0.1735], [-0.5118, -0.1562], [-0.4515, -0.1405], [-0.4005, -0.1265], [-0.3653, -0.1138]], 0.542, 0.74, 0.01, 1.5], ['drift', 1, 0.781113]], [[[[-0.116, 0.802], [-0.0963, 0.7218], [-0.083, 0.6496], [-0.0736, 0.5847], [-0.0638, 0.5262]], 3.971, 2.001, 0.1, 1.5], ['drift', 1, 0.574622]], [[[[-0.727, -0.401], [-0.7918, -0.4411], [-0.8566, -0.4852], [-0.9532, -0.5337], [-1.0294, -0.5871], [-1.1522, -0.6458], [-1.2399, -0.7104]], 3.173, 0.604, 0.01, 3.0], ['drift', 1, 1.921313]], [[[[0.299, -0.699], [0.3106, -0.713], [0.3249, -0.7272], [0.332, -0.7418]], 1.57, 2.945, 0.01, 2.0], ['drift', 1, 0.135693]], [[[[0.865, 0.17], [0.8809, 0.17], [0.8942, 0.17], [0.8825, 0.17], [0.8875, 0.17]], 4.902, 1.518, 0.05, 2.0], ['drift', 2, 0.067843]], [[[[-0.138, 0.988], [-0.1281, 0.988], [-0.1264, 0.988]], 2.839, 1.096, 0.1, 3.0], ['ok', -1, 0.007747]], [[[[-0.5, -0.212], [-0.5001, -0.2162], [-0.5057, -0.2206], [-0.5073, -0.225], [-0.5207, -0.2295], [-0.5225, -0.2341]], 2.84, 2.401, 0.1, 2.0], ['drift', 5, 0.108825]], [[[[0.0, 0.0], [0.0023, 0.0], [0.008, 0.0], [0.0167, 0.0], [0.0239, 0.0]], 1.47, 2.583, 0.01, 2.0], ['ok', -1, 0.00042]]], [[[[[-0.642, -0.0], [-0.6185, -0.0], [-0.5905, -0.0], [-0.5692, -0.0]], 4.928, 1.024, 0.01, 3.0], ['drift', 1, 0.213933]], [[[[-0.821, -0.56], [-0.7394, -0.504], [-0.6518, -0.4536]], 1.819, 0.974, 0.05, 1.5], ['drift', 1, 0.36456]], [[[[0.881, -0.663], [0.8983, -0.663], [0.8938, -0.663], [0.8794, -0.663], [0.895, -0.663]], 1.391, 0.858, 0.05, 2.0], ['ok', -1, 0.029392]], [[[[-0.758, 0.799], [-0.7781, 0.815], [-0.7769, 0.8313], [-0.7869, 0.8479], [-0.7916, 0.8649], [-0.8053, 0.8822], [-0.8216, 0.8998]], 4.754, 2.008, 0.01, 1.5], ['drift', 1, 0.204677]], [[[[0.0, 0.0], [0.0066, 0.0], [0.0158, 0.0], [0.0191, 0.0], [0.0228, 0.0], [0.023, 0.0]], 1.146, 1.18, 0.1, 1.5], ['ok', -1, 0.000303]], [[[[0.05, 0.208], [0.0629, 0.2288], [0.0783, 0.2517], [0.0915, 0.2768], [0.1073, 0.3045], [0.1215, 0.335]], 0.567, 1.399, 0.05, 3.0], ['drift', 1, 1.669724]], [[[[0.388, 0.822], [0.3906, 0.7973], [0.3822, 0.7734], [0.382, 0.7502], [0.3761, 0.7277], [0.3717, 0.7059], [0.3586, 0.6847], [0.3536, 0.6642]], 1.849, 1.488, 0.05, 3.0], ['drift', 2, 0.308574]], [[[[-0.009, 0.479], [-0.0002, 0.479], [0.0045, 0.479], [0.0118, 0.479], [0.0156, 0.479]], 4.602, 1.292, 0.01, 2.0], ['ok', -1, 0.002517]]], [[[[[0.109, -0.125], [0.1286, -0.1375], [0.1452, -0.1513], [0.1681, -0.1664]], 2.292, 1.906, 0.1, 1.5], ['blowup', 2, 0.612872]], [[[[0.201, -0.117], [0.1866, -0.1053], [0.1651, -0.0948], [0.1587, -0.0853], [0.1496, -0.0768], [0.1401, -0.0691], [0.1356, -0.0622], [0.13, -0.056], [0.1226, -0.0504], [0.1122, -0.0453]], 2.394, 1.441, 0.05, 1.5], ['drift', 1, 0.715793]], [[[[0.009, 0.587], [0.0118, 0.5283], [0.0122, 0.4755], [0.0149, 0.4279], [0.0189, 0.3851], [0.0254, 0.3466]], 2.481, 2.002, 0.1, 1.5], ['drift', 1, 0.649139]], [[[[0.585, -0.43], [0.6088, -0.4386], [0.6199, -0.4474], [0.6363, -0.4563], [0.6676, -0.4654], [0.6834, -0.4748]], 3.589, 1.482, 0.01, 2.0], ['drift', 1, 0.338168]], [[[[0.563, -0.115], [0.5674, -0.115], [0.576, -0.115], [0.5797, -0.115], [0.5794, -0.115], [0.5764, -0.115], [0.5793, -0.115], [0.5693, -0.115], [0.5687, -0.115], [0.5645, -0.115]], 0.631, 2.836, 0.1, 2.0], ['ok', -1, 0.050698]], [[[[-0.864, -0.368], [-0.8698, -0.3754], [-0.8662, -0.3829], [-0.8745, -0.3905]], 1.369, 0.756, 0.05, 1.5], ['ok', -1, 0.033702]], [[[[0.058, -0.164], [0.0735, -0.1804], [0.0839, -0.1984], [0.101, -0.2183], [0.1181, -0.2401]], 2.553, 1.801, 0.1, 3.0], ['drift', 1, 1.44498]], [[[[0.955, 0.743], [0.9477, 0.743], [0.9408, 0.743], [0.9342, 0.743]], 2.622, 2.919, 0.05, 2.0], ['ok', -1, 0.02574]]], [[[[[0.0, 0.0], [0.0094, 0.0], [0.0161, 0.0], [0.025, 0.0], [0.0329, 0.0], [0.0397, 0.0], [0.0448, 0.0], [0.0471, 0.0]], 1.394, 2.588, 0.05, 3.0], ['ok', -1, 0.001546]], [[[[0.644, -0.025], [0.6559, -0.0255], [0.6763, -0.026], [0.689, -0.0265]], 1.658, 2.588, 0.05, 3.0], ['drift', 2, 0.144585]], [[[[0.423, -0.046], [0.4239, -0.046], [0.4257, -0.046], [0.4288, -0.046], [0.4231, -0.046], [0.4219, -0.046], [0.4287, -0.046], [0.4355, -0.046]], 3.517, 0.566, 0.05, 3.0], ['drift', 7, 0.059861]], [[[[-0.83, -0.352], [-0.7456, -0.3168], [-0.6688, -0.2851], [-0.5968, -0.2566], [-0.5378, -0.2309], [-0.4811, -0.2079]], 1.595, 0.91, 0.05, 1.5], ['drift', 1, 0.662823]], [[[[0.699, -0.578], [0.707, -0.578], [0.7158, -0.578], [0.7171, -0.578]], 4.155, 2.539, 0.05, 1.5], ['ok', -1, 0.037]], [[[[-0.418, -0.23], [-0.4168, -0.2346], [-0.4241, -0.2393], [-0.4299, -0.2441], [-0.4457, -0.249], [-0.4569, -0.2539], [-0.4578, -0.259]], 2.552, 1.183, 0.05, 3.0], ['drift', 3, 0.207936]], [[[[0.935, 0.607], [0.9784, 0.6191], [0.9876, 0.6315], [0.9907, 0.6442]], 1.868, 0.979, 0.1, 2.0], ['drift', 2, 0.12335]], [[[[-0.322, -0.896], [-0.3112, -0.8691], [-0.3041, -0.843], [-0.2959, -0.8178], [-0.2873, -0.7932], [-0.277, -0.7694], [-0.2571, -0.7463], [-0.2386, -0.724], [-0.2285, -0.7022], [-0.2117, -0.6812]], 3.185, 1.656, 0.05, 3.0], ['drift', 1, 0.450995]]], [[[[[0.0, 0.0], [0.0076, 0.0], [0.0119, 0.0]], 3.375, 0.919, 0.1, 3.0], ['ok', -1, 0.000239]], [[[[-0.985, -0.74], [-0.8703, -0.666], [-0.7906, -0.5994], [-0.7156, -0.5395], [-0.648, -0.4855], [-0.589, -0.437], [-0.5247, -0.3933], [-0.4684, -0.3539], [-0.4164, -0.3185]], 2.627, 2.374, 0.05, 2.0], ['drift', 1, 0.819081]], [[[[-0.143, -0.952], [-0.1382, -0.952], [-0.1308, -0.952], [-0.1243, -0.952], [-0.1212, -0.952]], 2.712, 1.57, 0.01, 2.0], ['drift', 4, 0.010566]], [[[[0.355, -0.075], [0.3414, -0.0727], [0.3418, -0.0706], [0.3422, -0.0685], [0.3388, -0.0664]], 4.633, 0.948, 0.05, 1.5], ['drift', 1, 0.090335]], [[[[0.174, -0.48], [0.1771, -0.4896], [0.1863, -0.4994], [0.1987, -0.5094], [0.2011, -0.5196]], 1.179, 1.294, 0.01, 1.5], ['drift', 1, 0.189336]], [[[[0.996, -0.695], [0.9888, -0.695], [0.9931, -0.695], [0.9804, -0.695], [0.9865, -0.695], [1.0062, -0.695]], 3.899, 1.966, 0.05, 2.0], ['ok', -1, 0.024953]], [[[[-0.121, -0.819], [-0.1224, -0.8354], [-0.1203, -0.8521], [-0.1142, -0.8691], [-0.1142, -0.8865]], 4.298, 2.862, 0.01, 1.5], ['drift', 1, 0.162713]], [[[[0.304, 0.926], [0.2951, 0.8982], [0.2913, 0.8713], [0.2845, 0.8451], [0.273, 0.8198]], 4.318, 0.794, 0.01, 2.0], ['drift', 1, 0.207843]]]]
for i, (args, expected) in enumerate(fixtures[N-1]):
    check("case %d" % i, 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
case 0['drift', 1, 0.180374]['drift', 1, 0.781113]Failed
case 1['drift', 1, 0.194816]['drift', 1, 0.574622]Failed
case 2['drift', 1, 0.187514]['drift', 1, 1.921313]Failed
case 3['drift', 1, 0.043892]['drift', 1, 0.135693]Failed
case 4['drift', 2, 0.067843]['drift', 2, 0.067843]Passed
case 5['ok', -1, 0.007747]['ok', -1, 0.007747]Passed
case 6['drift', 5, 0.108825]['drift', 5, 0.108825]Passed
case 7['ok', -1, 0.00042]['ok', -1, 0.00042]Passed

SHA-256 / b8e17bbfa1d07b45507e3c4a660ffdebd7d0ab8b7990935ed714f0d274c5db1e

2 / The unsuccessful fix

Exit 1
"""Failure Map reference implementation. Python standard library only."""
import json
import math
N = 1
observations = []
def solve(states, k, m, tol, blowup):
    def en(s):
        return 0.5 * m * s[1] * s[1] + 0.5 * k * s[0] * s[0]
    e0 = en(states[0])
    scale = e0 if e0 > 0 else 1.0
    worst = 0.0
    first_drift = -1
    for i, s in enumerate(states):
        e = en(s)
        if e0 > 0 and e > blowup * e0:
            return ['blowup', i, round(abs(e - e0) / scale, 6)]
        r = abs(e - e0) / scale
        if r > worst:
            worst = r
        if r > tol and first_drift < 0:
            first_drift = i
            break
    if first_drift >= 0:
        return ['drift', first_drift, round(worst, 6)]
    return ['ok', -1, round(worst, 6)]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[[[[[-0.783, -0.238], [-0.7094, -0.2142], [-0.6366, -0.1928], [-0.5724, -0.1735], [-0.5118, -0.1562], [-0.4515, -0.1405], [-0.4005, -0.1265], [-0.3653, -0.1138]], 0.542, 0.74, 0.01, 1.5], ['drift', 1, 0.781113]], [[[[-0.116, 0.802], [-0.0963, 0.7218], [-0.083, 0.6496], [-0.0736, 0.5847], [-0.0638, 0.5262]], 3.971, 2.001, 0.1, 1.5], ['drift', 1, 0.574622]], [[[[-0.727, -0.401], [-0.7918, -0.4411], [-0.8566, -0.4852], [-0.9532, -0.5337], [-1.0294, -0.5871], [-1.1522, -0.6458], [-1.2399, -0.7104]], 3.173, 0.604, 0.01, 3.0], ['drift', 1, 1.921313]], [[[[0.299, -0.699], [0.3106, -0.713], [0.3249, -0.7272], [0.332, -0.7418]], 1.57, 2.945, 0.01, 2.0], ['drift', 1, 0.135693]], [[[[0.865, 0.17], [0.8809, 0.17], [0.8942, 0.17], [0.8825, 0.17], [0.8875, 0.17]], 4.902, 1.518, 0.05, 2.0], ['drift', 2, 0.067843]], [[[[-0.138, 0.988], [-0.1281, 0.988], [-0.1264, 0.988]], 2.839, 1.096, 0.1, 3.0], ['ok', -1, 0.007747]], [[[[-0.5, -0.212], [-0.5001, -0.2162], [-0.5057, -0.2206], [-0.5073, -0.225], [-0.5207, -0.2295], [-0.5225, -0.2341]], 2.84, 2.401, 0.1, 2.0], ['drift', 5, 0.108825]], [[[[0.0, 0.0], [0.0023, 0.0], [0.008, 0.0], [0.0167, 0.0], [0.0239, 0.0]], 1.47, 2.583, 0.01, 2.0], ['ok', -1, 0.00042]]], [[[[[-0.642, -0.0], [-0.6185, -0.0], [-0.5905, -0.0], [-0.5692, -0.0]], 4.928, 1.024, 0.01, 3.0], ['drift', 1, 0.213933]], [[[[-0.821, -0.56], [-0.7394, -0.504], [-0.6518, -0.4536]], 1.819, 0.974, 0.05, 1.5], ['drift', 1, 0.36456]], [[[[0.881, -0.663], [0.8983, -0.663], [0.8938, -0.663], [0.8794, -0.663], [0.895, -0.663]], 1.391, 0.858, 0.05, 2.0], ['ok', -1, 0.029392]], [[[[-0.758, 0.799], [-0.7781, 0.815], [-0.7769, 0.8313], [-0.7869, 0.8479], [-0.7916, 0.8649], [-0.8053, 0.8822], [-0.8216, 0.8998]], 4.754, 2.008, 0.01, 1.5], ['drift', 1, 0.204677]], [[[[0.0, 0.0], [0.0066, 0.0], [0.0158, 0.0], [0.0191, 0.0], [0.0228, 0.0], [0.023, 0.0]], 1.146, 1.18, 0.1, 1.5], ['ok', -1, 0.000303]], [[[[0.05, 0.208], [0.0629, 0.2288], [0.0783, 0.2517], [0.0915, 0.2768], [0.1073, 0.3045], [0.1215, 0.335]], 0.567, 1.399, 0.05, 3.0], ['drift', 1, 1.669724]], [[[[0.388, 0.822], [0.3906, 0.7973], [0.3822, 0.7734], [0.382, 0.7502], [0.3761, 0.7277], [0.3717, 0.7059], [0.3586, 0.6847], [0.3536, 0.6642]], 1.849, 1.488, 0.05, 3.0], ['drift', 2, 0.308574]], [[[[-0.009, 0.479], [-0.0002, 0.479], [0.0045, 0.479], [0.0118, 0.479], [0.0156, 0.479]], 4.602, 1.292, 0.01, 2.0], ['ok', -1, 0.002517]]], [[[[[0.109, -0.125], [0.1286, -0.1375], [0.1452, -0.1513], [0.1681, -0.1664]], 2.292, 1.906, 0.1, 1.5], ['blowup', 2, 0.612872]], [[[[0.201, -0.117], [0.1866, -0.1053], [0.1651, -0.0948], [0.1587, -0.0853], [0.1496, -0.0768], [0.1401, -0.0691], [0.1356, -0.0622], [0.13, -0.056], [0.1226, -0.0504], [0.1122, -0.0453]], 2.394, 1.441, 0.05, 1.5], ['drift', 1, 0.715793]], [[[[0.009, 0.587], [0.0118, 0.5283], [0.0122, 0.4755], [0.0149, 0.4279], [0.0189, 0.3851], [0.0254, 0.3466]], 2.481, 2.002, 0.1, 1.5], ['drift', 1, 0.649139]], [[[[0.585, -0.43], [0.6088, -0.4386], [0.6199, -0.4474], [0.6363, -0.4563], [0.6676, -0.4654], [0.6834, -0.4748]], 3.589, 1.482, 0.01, 2.0], ['drift', 1, 0.338168]], [[[[0.563, -0.115], [0.5674, -0.115], [0.576, -0.115], [0.5797, -0.115], [0.5794, -0.115], [0.5764, -0.115], [0.5793, -0.115], [0.5693, -0.115], [0.5687, -0.115], [0.5645, -0.115]], 0.631, 2.836, 0.1, 2.0], ['ok', -1, 0.050698]], [[[[-0.864, -0.368], [-0.8698, -0.3754], [-0.8662, -0.3829], [-0.8745, -0.3905]], 1.369, 0.756, 0.05, 1.5], ['ok', -1, 0.033702]], [[[[0.058, -0.164], [0.0735, -0.1804], [0.0839, -0.1984], [0.101, -0.2183], [0.1181, -0.2401]], 2.553, 1.801, 0.1, 3.0], ['drift', 1, 1.44498]], [[[[0.955, 0.743], [0.9477, 0.743], [0.9408, 0.743], [0.9342, 0.743]], 2.622, 2.919, 0.05, 2.0], ['ok', -1, 0.02574]]], [[[[[0.0, 0.0], [0.0094, 0.0], [0.0161, 0.0], [0.025, 0.0], [0.0329, 0.0], [0.0397, 0.0], [0.0448, 0.0], [0.0471, 0.0]], 1.394, 2.588, 0.05, 3.0], ['ok', -1, 0.001546]], [[[[0.644, -0.025], [0.6559, -0.0255], [0.6763, -0.026], [0.689, -0.0265]], 1.658, 2.588, 0.05, 3.0], ['drift', 2, 0.144585]], [[[[0.423, -0.046], [0.4239, -0.046], [0.4257, -0.046], [0.4288, -0.046], [0.4231, -0.046], [0.4219, -0.046], [0.4287, -0.046], [0.4355, -0.046]], 3.517, 0.566, 0.05, 3.0], ['drift', 7, 0.059861]], [[[[-0.83, -0.352], [-0.7456, -0.3168], [-0.6688, -0.2851], [-0.5968, -0.2566], [-0.5378, -0.2309], [-0.4811, -0.2079]], 1.595, 0.91, 0.05, 1.5], ['drift', 1, 0.662823]], [[[[0.699, -0.578], [0.707, -0.578], [0.7158, -0.578], [0.7171, -0.578]], 4.155, 2.539, 0.05, 1.5], ['ok', -1, 0.037]], [[[[-0.418, -0.23], [-0.4168, -0.2346], [-0.4241, -0.2393], [-0.4299, -0.2441], [-0.4457, -0.249], [-0.4569, -0.2539], [-0.4578, -0.259]], 2.552, 1.183, 0.05, 3.0], ['drift', 3, 0.207936]], [[[[0.935, 0.607], [0.9784, 0.6191], [0.9876, 0.6315], [0.9907, 0.6442]], 1.868, 0.979, 0.1, 2.0], ['drift', 2, 0.12335]], [[[[-0.322, -0.896], [-0.3112, -0.8691], [-0.3041, -0.843], [-0.2959, -0.8178], [-0.2873, -0.7932], [-0.277, -0.7694], [-0.2571, -0.7463], [-0.2386, -0.724], [-0.2285, -0.7022], [-0.2117, -0.6812]], 3.185, 1.656, 0.05, 3.0], ['drift', 1, 0.450995]]], [[[[[0.0, 0.0], [0.0076, 0.0], [0.0119, 0.0]], 3.375, 0.919, 0.1, 3.0], ['ok', -1, 0.000239]], [[[[-0.985, -0.74], [-0.8703, -0.666], [-0.7906, -0.5994], [-0.7156, -0.5395], [-0.648, -0.4855], [-0.589, -0.437], [-0.5247, -0.3933], [-0.4684, -0.3539], [-0.4164, -0.3185]], 2.627, 2.374, 0.05, 2.0], ['drift', 1, 0.819081]], [[[[-0.143, -0.952], [-0.1382, -0.952], [-0.1308, -0.952], [-0.1243, -0.952], [-0.1212, -0.952]], 2.712, 1.57, 0.01, 2.0], ['drift', 4, 0.010566]], [[[[0.355, -0.075], [0.3414, -0.0727], [0.3418, -0.0706], [0.3422, -0.0685], [0.3388, -0.0664]], 4.633, 0.948, 0.05, 1.5], ['drift', 1, 0.090335]], [[[[0.174, -0.48], [0.1771, -0.4896], [0.1863, -0.4994], [0.1987, -0.5094], [0.2011, -0.5196]], 1.179, 1.294, 0.01, 1.5], ['drift', 1, 0.189336]], [[[[0.996, -0.695], [0.9888, -0.695], [0.9931, -0.695], [0.9804, -0.695], [0.9865, -0.695], [1.0062, -0.695]], 3.899, 1.966, 0.05, 2.0], ['ok', -1, 0.024953]], [[[[-0.121, -0.819], [-0.1224, -0.8354], [-0.1203, -0.8521], [-0.1142, -0.8691], [-0.1142, -0.8865]], 4.298, 2.862, 0.01, 1.5], ['drift', 1, 0.162713]], [[[[0.304, 0.926], [0.2951, 0.8982], [0.2913, 0.8713], [0.2845, 0.8451], [0.273, 0.8198]], 4.318, 0.794, 0.01, 2.0], ['drift', 1, 0.207843]]]]
for i, (args, expected) in enumerate(fixtures[N-1]):
    check("case %d" % i, 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
case 0['drift', 1, 0.180374]['drift', 1, 0.781113]Failed
case 1['drift', 1, 0.194816]['drift', 1, 0.574622]Failed
case 2['drift', 1, 0.187514]['drift', 1, 1.921313]Failed
case 3['drift', 1, 0.043892]['drift', 1, 0.135693]Failed
case 4['drift', 2, 0.067843]['drift', 2, 0.067843]Passed
case 5['ok', -1, 0.007747]['ok', -1, 0.007747]Passed
case 6['drift', 5, 0.108825]['drift', 5, 0.108825]Passed
case 7['ok', -1, 0.00042]['ok', -1, 0.00042]Passed

SHA-256 / c6546b1b7cc8d7b9f363dd322a4b08392a53632ed444fed4372865d3d2fb590b

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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Verification & scope

A deterministic bounded teaching model with stipulated toy conventions and rounded float output; not a production physics engine or a proof of numerical stability. 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 2026-09-29T14:50:57.759713+00:00.

Case digest / db6b64b29832d39af69572a27e41b36e4a21b426314386d58c724deeef2ff3bc