{"abstract":"Partial quantisation of late notes moves them one tick further than the requested strength.","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 to nearest moves notes too far whenever the fractional displacement exceeds one half.","family":"w2-midi-event-timing-grid-quantize-displacement-truncation","id":"FA-81546","implementations":{"attempt":{"sha256":"fb1354c58701b57e880e85aa895a9c88bf7c1a34ed2b2437edd7e98579b9e099","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        out.append(t + round(move / 100))\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]), ([[10, 110], 120, 50], [5, 115]), ([[10, 110], 120, 75], [3, 117]), ([[5, 115], 120, 0], [5, 115]), ([[5, 115], 120, 100], [0, 120]), ([[239, 241], 240, 50], [239, 241])], [([[10, 110], 120, 50], [5, 115]), ([[7, 113], 120, 33], [5, 115]), ([[5, 115], 120, 0], [5, 115]), ([[5, 115], 120, 100], [0, 120]), ([[5], 120, 101], None), ([[5], 0, 50], None), ([[1, 2, 3, 4], 3, 50], [1, 2, 3, 4]), ([[44, 76], 30, 90], [32, 88])], [([[5], 120, 101], None), ([[5], 0, 50], None), ([[5], 120, -1], None), ([[239, 241], 240, 50], [239, 241]), ([[45, 75], 30, 100], [60, 90]), ([[44, 76], 30, 90], [32, 88]), ([[1000, 1030], 120, 80], [968, 1070]), ([[125], 120, 99], [121])], [([[10, 110], 120, 75], [3, 117]), ([[7, 113], 120, 33], [5, 115]), ([[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]), ([[125], 120, 99], [121])], [([[0, 10, 50, 110, 120], 120, 100], [0, 0, 0, 120, 120]), ([[60, 180], 120, 100], [120, 240]), ([[10, 110], 120, 75], [3, 117]), ([[7, 113], 120, 33], [5, 115]), ([[239, 241], 240, 50], [239, 241]), ([[1, 2, 3, 4], 3, 50], [1, 2, 3, 4]), ([[44, 76], 30, 90], [32, 88]), ([[125], 120, 99], [121])]]\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":"4375eaeaa2e4ff439cdbaecbc0ee8249c7a69a5dc35e3d91bc6a368cae608f72","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        out.append(t + move // 100)\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]), ([[10, 110], 120, 50], [5, 115]), ([[10, 110], 120, 75], [3, 117]), ([[5, 115], 120, 0], [5, 115]), ([[5, 115], 120, 100], [0, 120]), ([[239, 241], 240, 50], [239, 241])], [([[10, 110], 120, 50], [5, 115]), ([[7, 113], 120, 33], [5, 115]), ([[5, 115], 120, 0], [5, 115]), ([[5, 115], 120, 100], [0, 120]), ([[5], 120, 101], None), ([[5], 0, 50], None), ([[1, 2, 3, 4], 3, 50], [1, 2, 3, 4]), ([[44, 76], 30, 90], [32, 88])], [([[5], 120, 101], None), ([[5], 0, 50], None), ([[5], 120, -1], None), ([[239, 241], 240, 50], [239, 241]), ([[45, 75], 30, 100], [60, 90]), ([[44, 76], 30, 90], [32, 88]), ([[1000, 1030], 120, 80], [968, 1070]), ([[125], 120, 99], [121])], [([[10, 110], 120, 75], [3, 117]), ([[7, 113], 120, 33], [5, 115]), ([[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]), ([[125], 120, 99], [121])], [([[0, 10, 50, 110, 120], 120, 100], [0, 0, 0, 120, 120]), ([[60, 180], 120, 100], [120, 240]), ([[10, 110], 120, 75], [3, 117]), ([[7, 113], 120, 33], [5, 115]), ([[239, 241], 240, 50], [239, 241]), ([[1, 2, 3, 4], 3, 50], [1, 2, 3, 4]), ([[44, 76], 30, 90], [32, 88]), ([[125], 120, 99], [121])]]\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":"36b09b5c2fe82d56615a967658f214c06fc3dc785752fa0ca313b0fa5beb71c5","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]), ([[10, 110], 120, 50], [5, 115]), ([[10, 110], 120, 75], [3, 117]), ([[5, 115], 120, 0], [5, 115]), ([[5, 115], 120, 100], [0, 120]), ([[239, 241], 240, 50], [239, 241])], [([[10, 110], 120, 50], [5, 115]), ([[7, 113], 120, 33], [5, 115]), ([[5, 115], 120, 0], [5, 115]), ([[5, 115], 120, 100], [0, 120]), ([[5], 120, 101], None), ([[5], 0, 50], None), ([[1, 2, 3, 4], 3, 50], [1, 2, 3, 4]), ([[44, 76], 30, 90], [32, 88])], [([[5], 120, 101], None), ([[5], 0, 50], None), ([[5], 120, -1], None), ([[239, 241], 240, 50], [239, 241]), ([[45, 75], 30, 100], [60, 90]), ([[44, 76], 30, 90], [32, 88]), ([[1000, 1030], 120, 80], [968, 1070]), ([[125], 120, 99], [121])], [([[10, 110], 120, 75], [3, 117]), ([[7, 113], 120, 33], [5, 115]), ([[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]), ([[125], 120, 99], [121])], [([[0, 10, 50, 110, 120], 120, 100], [0, 0, 0, 120, 120]), ([[60, 180], 120, 100], [120, 240]), ([[10, 110], 120, 75], [3, 117]), ([[7, 113], 120, 33], [5, 115]), ([[239, 241], 240, 50], [239, 241]), ([[1, 2, 3, 4], 3, 50], [1, 2, 3, 4]), ([[44, 76], 30, 90], [32, 88]), ([[125], 120, 99], [121])]]\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-displacement-truncation","generated_at":"2026-09-29T14:50:03.849859+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 displacement truncation step so that it reads `step = abs(move) // 100\n    out.append(t + step if move >= 0 else t - step)`.","root_cause":"Floor division of a negative displacement rounds toward minus infinity instead of truncating toward zero.","sha256":"eee0695260bafa123a3536ae45dcba40049ddddbe5de011ef76c912dfa609a86","title":"Strength-weighted grid quantisation: backward moves rounded away from zero · case 01","variant":1,"variant_policy":"Five numbered records share a model and may reuse boundary fixtures.","verification":{"attempt":{"elapsed_ms":40.358,"exit_code":1,"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":[2,118],"check":"oracle 4","expected":[3,117],"passed":false},{"actual":[5,115],"check":"oracle 5","expected":[5,115],"passed":true},{"actual":[0,120],"check":"oracle 6","expected":[0,120],"passed":true},{"actual":[239,241],"check":"oracle 7","expected":[239,241],"passed":true}],"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\": [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\": [2, 118], \"expected\": [3, 117], \"passed\": false}, {\"check\": \"oracle 5\", \"actual\": [5, 115], \"expected\": [5, 115], \"passed\": true}, {\"check\": \"oracle 6\", \"actual\": [0, 120], \"expected\": [0, 120], \"passed\": true}, {\"check\": \"oracle 7\", \"actual\": [239, 241], \"expected\": [239, 241], \"passed\": true}], \"passed\": false}\n"},"broken":{"elapsed_ms":39.331,"exit_code":1,"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":[2,117],"check":"oracle 4","expected":[3,117],"passed":false},{"actual":[5,115],"check":"oracle 5","expected":[5,115],"passed":true},{"actual":[0,120],"check":"oracle 6","expected":[0,120],"passed":true},{"actual":[239,240],"check":"oracle 7","expected":[239,241],"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\": [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\": [2, 117], \"expected\": [3, 117], \"passed\": false}, {\"check\": \"oracle 5\", \"actual\": [5, 115], \"expected\": [5, 115], \"passed\": true}, {\"check\": \"oracle 6\", \"actual\": [0, 120], \"expected\": [0, 120], \"passed\": true}, {\"check\": \"oracle 7\", \"actual\": [239, 240], \"expected\": [239, 241], \"passed\": false}], \"passed\": false}\n"},"fixed":{"elapsed_ms":41.481,"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":[3,117],"check":"oracle 4","expected":[3,117],"passed":true},{"actual":[5,115],"check":"oracle 5","expected":[5,115],"passed":true},{"actual":[0,120],"check":"oracle 6","expected":[0,120],"passed":true},{"actual":[239,241],"check":"oracle 7","expected":[239,241],"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\": [3, 117], \"expected\": [3, 117], \"passed\": true}, {\"check\": \"oracle 5\", \"actual\": [5, 115], \"expected\": [5, 115], \"passed\": true}, {\"check\": \"oracle 6\", \"actual\": [0, 120], \"expected\": [0, 120], \"passed\": true}, {\"check\": \"oracle 7\", \"actual\": [239, 241], \"expected\": [239, 241], \"passed\": true}], \"passed\": true}\n"}},"verified":true,"visibility":"public"}