{"abstract":"A note just before the beat is dragged back almost a full grid step instead of forward to the beat.","category":"MIDI event timing","checks":8,"contract":"Input [ticks, grid, strength] with grid > 0 and strength 0..100 percent. Each tick moves toward its nearest grid line (exact halves go to the later line) by strength percent of the distance, with the displacement truncated toward zero. Invalid parameters return None.","evaluation_group":"w2-midi-event-timing-grid-quantize","failed_approach":"Rounding exact halves down pulls notes midway between lines backward, against the stipulated later-line rule.","family":"w2-midi-event-timing-grid-quantize-nearest-grid-line","id":"FA-81541","implementations":{"attempt":{"sha256":"f290e396a23acdf9bd3316455f2e41ba4ca9b1be018cc0c5ed12d0814de0bdd2","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(x):\n    if not isinstance(x, list) or len(x) != 3:\n        return None\n    ticks, grid, strength = x\n    if grid <= 0 or not 0 <= strength <= 100:\n        return None\n    out = []\n    for t in ticks:\n        target = (2 * t + grid - 1) // (2 * grid) * grid\n        move = (target - t) * strength\n        step = abs(move) // 100\n        out.append(t + step if move >= 0 else t - step)\n    return out\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\nfixtures = [[([[0, 10, 50, 110, 120], 120, 100], [0, 0, 0, 120, 120]), ([[60, 180], 120, 100], [120, 240]), ([[59, 61], 120, 100], [0, 120]), ([[5, 115], 120, 0], [5, 115]), ([[5], 120, 101], None), ([[5], 0, 50], None), ([[5], 120, -1], None), ([[45, 75], 30, 100], [60, 90])], [([[0, 10, 50, 110, 120], 120, 100], [0, 0, 0, 120, 120]), ([[60, 180], 120, 100], [120, 240]), ([[59, 61], 120, 100], [0, 120]), ([[10, 110], 120, 50], [5, 115]), ([[10, 110], 120, 75], [3, 117]), ([[5], 120, -1], None), ([[45, 75], 30, 100], [60, 90]), ([[125], 120, 99], [121])], [([[60, 180], 120, 100], [120, 240]), ([[59, 61], 120, 100], [0, 120]), ([[10, 110], 120, 50], [5, 115]), ([[10, 110], 120, 75], [3, 117]), ([[7, 113], 120, 33], [5, 115]), ([[5, 115], 120, 100], [0, 120]), ([[239, 241], 240, 50], [239, 241]), ([[45, 75], 30, 100], [60, 90])], [([[60, 180], 120, 100], [120, 240]), ([[10, 110], 120, 50], [5, 115]), ([[10, 110], 120, 75], [3, 117]), ([[7, 113], 120, 33], [5, 115]), ([[5, 115], 120, 100], [0, 120]), ([[239, 241], 240, 50], [239, 241]), ([[1, 2, 3, 4], 3, 50], [1, 2, 3, 4]), ([[45, 75], 30, 100], [60, 90])], [([[60, 180], 120, 100], [120, 240]), ([[10, 110], 120, 75], [3, 117]), ([[5, 115], 120, 100], [0, 120]), ([[239, 241], 240, 50], [239, 241]), ([[1, 2, 3, 4], 3, 50], [1, 2, 3, 4]), ([[45, 75], 30, 100], [60, 90]), ([[44, 76], 30, 90], [32, 88]), ([[1000, 1030], 120, 80], [968, 1070])]]\nfor i, (args, expected) in enumerate(fixtures[N-1]):\n    check(\"oracle %d\" % i, solve(args), expected)\nprint(json.dumps({\"observations\": observations, \"passed\": all(x[\"passed\"] for x in observations)}, ensure_ascii=False))\nraise SystemExit(0 if all(x[\"passed\"] for x in observations) else 1)\n"},"broken":{"sha256":"b1fb816d5f11c61fd68837a31394ea9390465f9a0809b87830511961a763e526","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(x):\n    if not isinstance(x, list) or len(x) != 3:\n        return None\n    ticks, grid, strength = x\n    if grid <= 0 or not 0 <= strength <= 100:\n        return None\n    out = []\n    for t in ticks:\n        target = t // grid * grid\n        move = (target - t) * strength\n        step = abs(move) // 100\n        out.append(t + step if move >= 0 else t - step)\n    return out\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\nfixtures = [[([[0, 10, 50, 110, 120], 120, 100], [0, 0, 0, 120, 120]), ([[60, 180], 120, 100], [120, 240]), ([[59, 61], 120, 100], [0, 120]), ([[5, 115], 120, 0], [5, 115]), ([[5], 120, 101], None), ([[5], 0, 50], None), ([[5], 120, -1], None), ([[45, 75], 30, 100], [60, 90])], [([[0, 10, 50, 110, 120], 120, 100], [0, 0, 0, 120, 120]), ([[60, 180], 120, 100], [120, 240]), ([[59, 61], 120, 100], [0, 120]), ([[10, 110], 120, 50], [5, 115]), ([[10, 110], 120, 75], [3, 117]), ([[5], 120, -1], None), ([[45, 75], 30, 100], [60, 90]), ([[125], 120, 99], [121])], [([[60, 180], 120, 100], [120, 240]), ([[59, 61], 120, 100], [0, 120]), ([[10, 110], 120, 50], [5, 115]), ([[10, 110], 120, 75], [3, 117]), ([[7, 113], 120, 33], [5, 115]), ([[5, 115], 120, 100], [0, 120]), ([[239, 241], 240, 50], [239, 241]), ([[45, 75], 30, 100], [60, 90])], [([[60, 180], 120, 100], [120, 240]), ([[10, 110], 120, 50], [5, 115]), ([[10, 110], 120, 75], [3, 117]), ([[7, 113], 120, 33], [5, 115]), ([[5, 115], 120, 100], [0, 120]), ([[239, 241], 240, 50], [239, 241]), ([[1, 2, 3, 4], 3, 50], [1, 2, 3, 4]), ([[45, 75], 30, 100], [60, 90])], [([[60, 180], 120, 100], [120, 240]), ([[10, 110], 120, 75], [3, 117]), ([[5, 115], 120, 100], [0, 120]), ([[239, 241], 240, 50], [239, 241]), ([[1, 2, 3, 4], 3, 50], [1, 2, 3, 4]), ([[45, 75], 30, 100], [60, 90]), ([[44, 76], 30, 90], [32, 88]), ([[1000, 1030], 120, 80], [968, 1070])]]\nfor i, (args, expected) in enumerate(fixtures[N-1]):\n    check(\"oracle %d\" % i, solve(args), expected)\nprint(json.dumps({\"observations\": observations, \"passed\": all(x[\"passed\"] for x in observations)}, ensure_ascii=False))\nraise SystemExit(0 if all(x[\"passed\"] for x in observations) else 1)\n"},"fixed":{"sha256":"f1cf38bca8c29a41bd96d025960cdda4cb29fc09cfa4bbc9258e86c52a9ce015","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(x):\n    if not isinstance(x, list) or len(x) != 3:\n        return None\n    ticks, grid, strength = x\n    if grid <= 0 or not 0 <= strength <= 100:\n        return None\n    out = []\n    for t in ticks:\n        target = (2 * t + grid) // (2 * grid) * grid\n        move = (target - t) * strength\n        step = abs(move) // 100\n        out.append(t + step if move >= 0 else t - step)\n    return out\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\nfixtures = [[([[0, 10, 50, 110, 120], 120, 100], [0, 0, 0, 120, 120]), ([[60, 180], 120, 100], [120, 240]), ([[59, 61], 120, 100], [0, 120]), ([[5, 115], 120, 0], [5, 115]), ([[5], 120, 101], None), ([[5], 0, 50], None), ([[5], 120, -1], None), ([[45, 75], 30, 100], [60, 90])], [([[0, 10, 50, 110, 120], 120, 100], [0, 0, 0, 120, 120]), ([[60, 180], 120, 100], [120, 240]), ([[59, 61], 120, 100], [0, 120]), ([[10, 110], 120, 50], [5, 115]), ([[10, 110], 120, 75], [3, 117]), ([[5], 120, -1], None), ([[45, 75], 30, 100], [60, 90]), ([[125], 120, 99], [121])], [([[60, 180], 120, 100], [120, 240]), ([[59, 61], 120, 100], [0, 120]), ([[10, 110], 120, 50], [5, 115]), ([[10, 110], 120, 75], [3, 117]), ([[7, 113], 120, 33], [5, 115]), ([[5, 115], 120, 100], [0, 120]), ([[239, 241], 240, 50], [239, 241]), ([[45, 75], 30, 100], [60, 90])], [([[60, 180], 120, 100], [120, 240]), ([[10, 110], 120, 50], [5, 115]), ([[10, 110], 120, 75], [3, 117]), ([[7, 113], 120, 33], [5, 115]), ([[5, 115], 120, 100], [0, 120]), ([[239, 241], 240, 50], [239, 241]), ([[1, 2, 3, 4], 3, 50], [1, 2, 3, 4]), ([[45, 75], 30, 100], [60, 90])], [([[60, 180], 120, 100], [120, 240]), ([[10, 110], 120, 75], [3, 117]), ([[5, 115], 120, 100], [0, 120]), ([[239, 241], 240, 50], [239, 241]), ([[1, 2, 3, 4], 3, 50], [1, 2, 3, 4]), ([[45, 75], 30, 100], [60, 90]), ([[44, 76], 30, 90], [32, 88]), ([[1000, 1030], 120, 80], [968, 1070])]]\nfor i, (args, expected) in enumerate(fixtures[N-1]):\n    check(\"oracle %d\" % i, solve(args), expected)\nprint(json.dumps({\"observations\": observations, \"passed\": all(x[\"passed\"] for x in observations)}, ensure_ascii=False))\nraise SystemExit(0 if all(x[\"passed\"] for x in observations) else 1)\n"}},"limitations":"A deterministic bounded teaching model with a stipulated toy contract; it is not a complete Standard MIDI File or MIDI 1.0/2.0 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.","method":"Deterministic executable model with adversarial boundary fixtures.","provenance":{"created_by":"Failure Map","dependencies":"Python standard library","family":"w2-midi-event-timing-grid-quantize-nearest-grid-line","generated_at":"2026-09-29T14:50:03.848456+00:00","license":"CC0-1.0","python":"3.12.14","seed":1,"split":"open-access"},"relevance":"MIDI sequencers, file readers and synth drivers depend on exact event ordering and tick/time arithmetic.","repair":"Restore the nearest grid line step so that it reads `(2 * t + grid) // (2 * grid)`.","root_cause":"The target grid line is the floor of the position rather than the nearest line.","sha256":"db4ef79c80c8847716b7ac8fbb8b2591ab8af95470be1452c79a42b05efb853b","title":"Strength-weighted grid quantisation: notes always pulled back to the previous grid line · case 01","variant":1,"variant_policy":"Five numbered records share a model and may reuse boundary fixtures.","verification":{"attempt":{"elapsed_ms":40.695,"exit_code":1,"observations":[{"actual":[0,0,0,120,120],"check":"oracle 0","expected":[0,0,0,120,120],"passed":true},{"actual":[0,120],"check":"oracle 1","expected":[120,240],"passed":false},{"actual":[0,120],"check":"oracle 2","expected":[0,120],"passed":true},{"actual":[5,115],"check":"oracle 3","expected":[5,115],"passed":true},{"actual":null,"check":"oracle 4","expected":null,"passed":true},{"actual":null,"check":"oracle 5","expected":null,"passed":true},{"actual":null,"check":"oracle 6","expected":null,"passed":true},{"actual":[30,60],"check":"oracle 7","expected":[60,90],"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"oracle 0\", \"actual\": [0, 0, 0, 120, 120], \"expected\": [0, 0, 0, 120, 120], \"passed\": true}, {\"check\": \"oracle 1\", \"actual\": [0, 120], \"expected\": [120, 240], \"passed\": false}, {\"check\": \"oracle 2\", \"actual\": [0, 120], \"expected\": [0, 120], \"passed\": true}, {\"check\": \"oracle 3\", \"actual\": [5, 115], \"expected\": [5, 115], \"passed\": true}, {\"check\": \"oracle 4\", \"actual\": null, \"expected\": null, \"passed\": true}, {\"check\": \"oracle 5\", \"actual\": null, \"expected\": null, \"passed\": true}, {\"check\": \"oracle 6\", \"actual\": null, \"expected\": null, \"passed\": true}, {\"check\": \"oracle 7\", \"actual\": [30, 60], \"expected\": [60, 90], \"passed\": false}], \"passed\": false}\n"},"broken":{"elapsed_ms":39.458,"exit_code":1,"observations":[{"actual":[0,0,0,0,120],"check":"oracle 0","expected":[0,0,0,120,120],"passed":false},{"actual":[0,120],"check":"oracle 1","expected":[120,240],"passed":false},{"actual":[0,0],"check":"oracle 2","expected":[0,120],"passed":false},{"actual":[5,115],"check":"oracle 3","expected":[5,115],"passed":true},{"actual":null,"check":"oracle 4","expected":null,"passed":true},{"actual":null,"check":"oracle 5","expected":null,"passed":true},{"actual":null,"check":"oracle 6","expected":null,"passed":true},{"actual":[30,60],"check":"oracle 7","expected":[60,90],"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"oracle 0\", \"actual\": [0, 0, 0, 0, 120], \"expected\": [0, 0, 0, 120, 120], \"passed\": false}, {\"check\": \"oracle 1\", \"actual\": [0, 120], \"expected\": [120, 240], \"passed\": false}, {\"check\": \"oracle 2\", \"actual\": [0, 0], \"expected\": [0, 120], \"passed\": false}, {\"check\": \"oracle 3\", \"actual\": [5, 115], \"expected\": [5, 115], \"passed\": true}, {\"check\": \"oracle 4\", \"actual\": null, \"expected\": null, \"passed\": true}, {\"check\": \"oracle 5\", \"actual\": null, \"expected\": null, \"passed\": true}, {\"check\": \"oracle 6\", \"actual\": null, \"expected\": null, \"passed\": true}, {\"check\": \"oracle 7\", \"actual\": [30, 60], \"expected\": [60, 90], \"passed\": false}], \"passed\": false}\n"},"fixed":{"elapsed_ms":40.173,"exit_code":0,"observations":[{"actual":[0,0,0,120,120],"check":"oracle 0","expected":[0,0,0,120,120],"passed":true},{"actual":[120,240],"check":"oracle 1","expected":[120,240],"passed":true},{"actual":[0,120],"check":"oracle 2","expected":[0,120],"passed":true},{"actual":[5,115],"check":"oracle 3","expected":[5,115],"passed":true},{"actual":null,"check":"oracle 4","expected":null,"passed":true},{"actual":null,"check":"oracle 5","expected":null,"passed":true},{"actual":null,"check":"oracle 6","expected":null,"passed":true},{"actual":[60,90],"check":"oracle 7","expected":[60,90],"passed":true}],"passed":true,"stderr":"","stdout":"{\"observations\": [{\"check\": \"oracle 0\", \"actual\": [0, 0, 0, 120, 120], \"expected\": [0, 0, 0, 120, 120], \"passed\": true}, {\"check\": \"oracle 1\", \"actual\": [120, 240], \"expected\": [120, 240], \"passed\": true}, {\"check\": \"oracle 2\", \"actual\": [0, 120], \"expected\": [0, 120], \"passed\": true}, {\"check\": \"oracle 3\", \"actual\": [5, 115], \"expected\": [5, 115], \"passed\": true}, {\"check\": \"oracle 4\", \"actual\": null, \"expected\": null, \"passed\": true}, {\"check\": \"oracle 5\", \"actual\": null, \"expected\": null, \"passed\": true}, {\"check\": \"oracle 6\", \"actual\": null, \"expected\": null, \"passed\": true}, {\"check\": \"oracle 7\", \"actual\": [60, 90], \"expected\": [60, 90], \"passed\": true}], \"passed\": true}\n"}},"verified":true,"visibility":"public"}