{"abstract":"Dividing predictor terms separately changes integer rounding.","category":"PCM sample encoding","checks":8,"contract":"Stipulated two-history adaptive PCM decoder with explicit integer predictor coefficients, floor divisor, signed residual nibble and fixed residual amplitude scale.","contract_signature":"codes, last, older, coefficients, divisor, delta","evaluation_group":"s3-pcm-pcm-two-tap-predictor","failed_approach":"Truncation does not match the declared floor predictor on negative sums.","family":"s3-pcm-pcm-two-tap-predictor-prediction-division","id":"FA-49796","implementations":{"attempt":{"sha256":"e12b181742a0889fbf45c93f0c7c9e1dfcd42266ef1a19e135190b9fd60502f1","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(codes, last, older, coefficients, divisor, delta):\n    out=[]\n    for code in codes:\n        predicted=int((last*coefficients[0]+older*coefficients[1])/divisor)\n        signed=code-16 if code&8 else code\n        sample=predicted+signed*delta\n        older,last=last,sample\n        out.append(sample)\n    return [out,last,older]\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('oracle 1', solve(*([1, 15, 8, 7], 3, 1, [3, -1], 2, 2)), [[6, 5, -12, -7], -7, -12])\ncheck('oracle 2', solve(*([1, 2, 3], 2, -3, [1, 1], 3, 1)), [[0, 2, 3], 3, 2])\ncheck('oracle 3', solve(*([0, 0], -2, 1, [1, 2], 3, 4)), [[0, -2], -2, 0])\ncheck('oracle 4', solve(*([], 5, 2, [2, -1], 1, 1)), [[], 5, 2])\ncheck('oracle 5', solve(*([8, 0, 7], 0, 0, [1, 0], 1, 3)), [[-24, -24, -3], -3, -24])\ncheck('oracle 6', solve(*([15, 15, 1], 4, 3, [2, -1], 2, 2)), [[0, -4, -2], -2, -4])\ncheck('oracle 7', solve(*([2, 0, 14], -3, -1, [3, 1], 4, 1)), [[-1, -2, -4], -4, -2])\nif N == 1: check('variant packet 1', solve(*[[1, 15, 8, 7, 1, 15, 8, 7], 3, 1, [3, -1], 2, 2]), [[6, 5, -12, -7, -3, -3, -19, -13], -13, -19])\nif N == 2: check('variant packet 2', solve(*[[1, 15, 8, 7, 1, 15, 8, 7, 1, 15, 8, 7], 3, 1, [3, -1], 2, 2]), [[6, 5, -12, -7, -3, -3, -19, -13, -8, -8, -24, -18], -18, -24])\nif N == 3: check('variant packet 3', solve(*[[1, 15, 8, 7, 1, 15, 8, 7, 1, 15, 8, 7, 1, 15, 8, 7], 3, 1, [3, -1], 2, 2]), [[6, 5, -12, -7, -3, -3, -19, -13, -8, -8, -24, -18, -13, -13, -29, -23], -23, -29])\nif N == 4: check('variant packet 4', solve(*[[1, 15, 8, 7, 1, 15, 8, 7, 1, 15, 8, 7, 1, 15, 8, 7, 1, 15, 8, 7], 3, 1, [3, -1], 2, 2]), [[6, 5, -12, -7, -3, -3, -19, -13, -8, -8, -24, -18, -13, -13, -29, -23, -18, -18, -34, -28], -28, -34])\nif N == 5: check('variant packet 5', solve(*[[1, 15, 8, 7, 1, 15, 8, 7, 1, 15, 8, 7, 1, 15, 8, 7, 1, 15, 8, 7, 1, 15, 8, 7], 3, 1, [3, -1], 2, 2]), [[6, 5, -12, -7, -3, -3, -19, -13, -8, -8, -24, -18, -13, -13, -29, -23, -18, -18, -34, -28, -23, -23, -39, -33], -33, -39])\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":"ce25bd065f058a7c4c4f4d40500300263b4c80d758145b4909534123ffcd5d7e","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(codes, last, older, coefficients, divisor, delta):\n    out=[]\n    for code in codes:\n        predicted=last*coefficients[0]//divisor+older*coefficients[1]//divisor\n        signed=code-16 if code&8 else code\n        sample=predicted+signed*delta\n        older,last=last,sample\n        out.append(sample)\n    return [out,last,older]\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('oracle 1', solve(*([1, 15, 8, 7], 3, 1, [3, -1], 2, 2)), [[6, 5, -12, -7], -7, -12])\ncheck('oracle 2', solve(*([1, 2, 3], 2, -3, [1, 1], 3, 1)), [[0, 2, 3], 3, 2])\ncheck('oracle 3', solve(*([0, 0], -2, 1, [1, 2], 3, 4)), [[0, -2], -2, 0])\ncheck('oracle 4', solve(*([], 5, 2, [2, -1], 1, 1)), [[], 5, 2])\ncheck('oracle 5', solve(*([8, 0, 7], 0, 0, [1, 0], 1, 3)), [[-24, -24, -3], -3, -24])\ncheck('oracle 6', solve(*([15, 15, 1], 4, 3, [2, -1], 2, 2)), [[0, -4, -2], -2, -4])\ncheck('oracle 7', solve(*([2, 0, 14], -3, -1, [3, 1], 4, 1)), [[-1, -2, -4], -4, -2])\nif N == 1: check('variant packet 1', solve(*[[1, 15, 8, 7, 1, 15, 8, 7], 3, 1, [3, -1], 2, 2]), [[6, 5, -12, -7, -3, -3, -19, -13], -13, -19])\nif N == 2: check('variant packet 2', solve(*[[1, 15, 8, 7, 1, 15, 8, 7, 1, 15, 8, 7], 3, 1, [3, -1], 2, 2]), [[6, 5, -12, -7, -3, -3, -19, -13, -8, -8, -24, -18], -18, -24])\nif N == 3: check('variant packet 3', solve(*[[1, 15, 8, 7, 1, 15, 8, 7, 1, 15, 8, 7, 1, 15, 8, 7], 3, 1, [3, -1], 2, 2]), [[6, 5, -12, -7, -3, -3, -19, -13, -8, -8, -24, -18, -13, -13, -29, -23], -23, -29])\nif N == 4: check('variant packet 4', solve(*[[1, 15, 8, 7, 1, 15, 8, 7, 1, 15, 8, 7, 1, 15, 8, 7, 1, 15, 8, 7], 3, 1, [3, -1], 2, 2]), [[6, 5, -12, -7, -3, -3, -19, -13, -8, -8, -24, -18, -13, -13, -29, -23, -18, -18, -34, -28], -28, -34])\nif N == 5: check('variant packet 5', solve(*[[1, 15, 8, 7, 1, 15, 8, 7, 1, 15, 8, 7, 1, 15, 8, 7, 1, 15, 8, 7, 1, 15, 8, 7], 3, 1, [3, -1], 2, 2]), [[6, 5, -12, -7, -3, -3, -19, -13, -8, -8, -24, -18, -13, -13, -29, -23, -18, -18, -34, -28, -23, -23, -39, -33], -33, -39])\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":"Stipulated finite model; no claim of hardware timing or full file-format conformance. 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":"s3-pcm-pcm-two-tap-predictor-prediction-division","generated_at":"2026-09-29T14:45:03.457660+00:00","license":"CC0-1.0","python":"3.12.14","seed":1,"split":"open-access"},"relevance":"Offline PCM interchange uses these exact bounded packet and sample representation decisions.","root_cause":"Dividing predictor terms separately changes integer rounding.","sha256":"23a278f92d053167175bc152dd4d80d4fbb7eaffb3f3a204ed65005abe4b9f45","title":"Pcm two tap predictor: prediction division · case 01","variant":1,"variant_policy":"Five numbered records share a model and may reuse boundary fixtures.","verified":true,"visibility":"public","verification":{"attempt":{"elapsed_ms":39.138,"exit_code":1,"observations":[{"actual":[[6,5,-12,-6],-6,-12],"check":"oracle 1","expected":[[6,5,-12,-7],-7,-12],"passed":false},{"actual":[[1,3,4],4,3],"check":"oracle 2","expected":[[0,2,3],3,2],"passed":false},{"actual":[[0,-1],-1,0],"check":"oracle 3","expected":[[0,-2],-2,0],"passed":false},{"actual":[[],5,2],"check":"oracle 4","expected":[[],5,2],"passed":true},{"actual":[[-24,-24,-3],-3,-24],"check":"oracle 5","expected":[[-24,-24,-3],-3,-24],"passed":true},{"actual":[[0,-4,-2],-2,-4],"check":"oracle 6","expected":[[0,-4,-2],-2,-4],"passed":true},{"actual":[[0,0,-2],-2,0],"check":"oracle 7","expected":[[-1,-2,-4],-4,-2],"passed":false},{"actual":[[6,5,-12,-6,-1,-1,-17,-11],-11,-17],"check":"variant packet 1","expected":[[6,5,-12,-7,-3,-3,-19,-13],-13,-19],"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"oracle 1\", \"actual\": [[6, 5, -12, -6], -6, -12], \"expected\": [[6, 5, -12, -7], -7, -12], \"passed\": false}, {\"check\": \"oracle 2\", \"actual\": [[1, 3, 4], 4, 3], \"expected\": [[0, 2, 3], 3, 2], \"passed\": false}, {\"check\": \"oracle 3\", \"actual\": [[0, -1], -1, 0], \"expected\": [[0, -2], -2, 0], \"passed\": false}, {\"check\": \"oracle 4\", \"actual\": [[], 5, 2], \"expected\": [[], 5, 2], \"passed\": true}, {\"check\": \"oracle 5\", \"actual\": [[-24, -24, -3], -3, -24], \"expected\": [[-24, -24, -3], -3, -24], \"passed\": true}, {\"check\": \"oracle 6\", \"actual\": [[0, -4, -2], -2, -4], \"expected\": [[0, -4, -2], -2, -4], \"passed\": true}, {\"check\": \"oracle 7\", \"actual\": [[0, 0, -2], -2, 0], \"expected\": [[-1, -2, -4], -4, -2], \"passed\": false}, {\"check\": \"variant packet 1\", \"actual\": [[6, 5, -12, -6, -1, -1, -17, -11], -11, -17], \"expected\": [[6, 5, -12, -7, -3, -3, -19, -13], -13, -19], \"passed\": false}], \"passed\": false}\n"},"broken":{"elapsed_ms":40.036,"exit_code":1,"observations":[{"actual":[[5,3,-15,-11],-11,-15],"check":"oracle 1","expected":[[6,5,-12,-7],-7,-12],"passed":false},{"actual":[[0,2,3],3,2],"check":"oracle 2","expected":[[0,2,3],3,2],"passed":true},{"actual":[[-1,-3],-3,-1],"check":"oracle 3","expected":[[0,-2],-2,0],"passed":false},{"actual":[[],5,2],"check":"oracle 4","expected":[[],5,2],"passed":true},{"actual":[[-24,-24,-3],-3,-24],"check":"oracle 5","expected":[[-24,-24,-3],-3,-24],"passed":true},{"actual":[[0,-4,-2],-2,-4],"check":"oracle 6","expected":[[0,-4,-2],-2,-4],"passed":true},{"actual":[[-2,-3,-6],-6,-3],"check":"oracle 7","expected":[[-1,-2,-4],-4,-2],"passed":false},{"actual":[[5,3,-15,-11,-8,-9,-26,-21],-21,-26],"check":"variant packet 1","expected":[[6,5,-12,-7,-3,-3,-19,-13],-13,-19],"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"oracle 1\", \"actual\": [[5, 3, -15, -11], -11, -15], \"expected\": [[6, 5, -12, -7], -7, -12], \"passed\": false}, {\"check\": \"oracle 2\", \"actual\": [[0, 2, 3], 3, 2], \"expected\": [[0, 2, 3], 3, 2], \"passed\": true}, {\"check\": \"oracle 3\", \"actual\": [[-1, -3], -3, -1], \"expected\": [[0, -2], -2, 0], \"passed\": false}, {\"check\": \"oracle 4\", \"actual\": [[], 5, 2], \"expected\": [[], 5, 2], \"passed\": true}, {\"check\": \"oracle 5\", \"actual\": [[-24, -24, -3], -3, -24], \"expected\": [[-24, -24, -3], -3, -24], \"passed\": true}, {\"check\": \"oracle 6\", \"actual\": [[0, -4, -2], -2, -4], \"expected\": [[0, -4, -2], -2, -4], \"passed\": true}, {\"check\": \"oracle 7\", \"actual\": [[-2, -3, -6], -6, -3], \"expected\": [[-1, -2, -4], -4, -2], \"passed\": false}, {\"check\": \"variant packet 1\", \"actual\": [[5, 3, -15, -11, -8, -9, -26, -21], -21, -26], \"expected\": [[6, 5, -12, -7, -3, -3, -19, -13], -13, -19], \"passed\": false}], \"passed\": false}\n"}},"member_only":{"stages":["fixed"],"fields":["implementations.fixed","verification.fixed","harness","repair"],"note":"The verified repair, its recorded checks, the repair description, and the scoring harness are available to members."}}