{"abstract":"Adaptive PCM encoder omits the reconstructed predictor.","category":"PCM sample encoding","checks":8,"contract":"Bounded fixed-step adaptive-nibble PCM encoder: greedy magnitude bits, a half-bin base, and predictor feedback from reconstructed rather than original amplitudes.","contract_signature":"samples, predictor, step","evaluation_group":"s3-pcm-pcm-adaptive-nibble-selection","failed_approach":"Reversing the residual changes the sign nibble.","family":"s3-pcm-pcm-adaptive-nibble-selection-difference-predictor","id":"FA-49741","implementations":{"attempt":{"sha256":"3ed9ff90e9ce8402cfd5742da9a43939d4ab9e653c4b47e0371b8d879e905347","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(samples, predictor, step):\n    out=[]\n    for sample in samples:\n        difference=predictor-sample\n        sign=8 if difference<0 else 0\n        magnitude=abs(difference)\n        code=0\n        restored=step//8\n        for bit,part in [(4,step),(2,step//2),(1,step//4)]:\n            if magnitude>=part:\n                code|=bit\n                magnitude-=part\n                restored+=part\n        predictor+=-restored if sign else restored\n        out.append(sign|code)\n    return [out,predictor]\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('oracle 1', solve(*([2, 6, -4, 10], 0, 8)), [[1, 1, 13, 7], 10])\ncheck('oracle 2', solve(*([10, 10, 10], 3, 12)), [[2, 0, 8], 10])\ncheck('oracle 3', solve(*([-5, -10, 0], 0, 8)), [[10, 10, 5], 1])\ncheck('oracle 4', solve(*([], 4, 8)), [[], 4])\ncheck('oracle 5', solve(*([0, 1, 2, 3], 0, 16)), [[0, 8, 0, 0], 4])\ncheck('oracle 6', solve(*([8, 16, 24], 0, 8)), [[4, 3, 4], 25])\ncheck('oracle 7', solve(*([6, -6, 6], 1, 4)), [[5, 15, 7], 6])\nif N == 1: check('variant packet 1', solve(*[[2, 6, -4, 10, 2, 6, -4, 10], 0, 8]), [[1, 1, 13, 7, 12, 2, 13, 7], 10])\nif N == 2: check('variant packet 2', solve(*[[2, 6, -4, 10, 2, 6, -4, 10, 2, 6, -4, 10], 0, 8]), [[1, 1, 13, 7, 12, 2, 13, 7, 12, 2, 13, 7], 10])\nif N == 3: check('variant packet 3', solve(*[[2, 6, -4, 10, 2, 6, -4, 10, 2, 6, -4, 10, 2, 6, -4, 10], 0, 8]), [[1, 1, 13, 7, 12, 2, 13, 7, 12, 2, 13, 7, 12, 2, 13, 7], 10])\nif N == 4: check('variant packet 4', solve(*[[2, 6, -4, 10, 2, 6, -4, 10, 2, 6, -4, 10, 2, 6, -4, 10, 2, 6, -4, 10], 0, 8]), [[1, 1, 13, 7, 12, 2, 13, 7, 12, 2, 13, 7, 12, 2, 13, 7, 12, 2, 13, 7], 10])\nif N == 5: check('variant packet 5', solve(*[[2, 6, -4, 10, 2, 6, -4, 10, 2, 6, -4, 10, 2, 6, -4, 10, 2, 6, -4, 10, 2, 6, -4, 10], 0, 8]), [[1, 1, 13, 7, 12, 2, 13, 7, 12, 2, 13, 7, 12, 2, 13, 7, 12, 2, 13, 7, 12, 2, 13, 7], 10])\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":"824eb9828dd009235e6fecbb270a73a349528578828a7d8cefb341ef990ead7f","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(samples, predictor, step):\n    out=[]\n    for sample in samples:\n        difference=sample\n        sign=8 if difference<0 else 0\n        magnitude=abs(difference)\n        code=0\n        restored=step//8\n        for bit,part in [(4,step),(2,step//2),(1,step//4)]:\n            if magnitude>=part:\n                code|=bit\n                magnitude-=part\n                restored+=part\n        predictor+=-restored if sign else restored\n        out.append(sign|code)\n    return [out,predictor]\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('oracle 1', solve(*([2, 6, -4, 10], 0, 8)), [[1, 1, 13, 7], 10])\ncheck('oracle 2', solve(*([10, 10, 10], 3, 12)), [[2, 0, 8], 10])\ncheck('oracle 3', solve(*([-5, -10, 0], 0, 8)), [[10, 10, 5], 1])\ncheck('oracle 4', solve(*([], 4, 8)), [[], 4])\ncheck('oracle 5', solve(*([0, 1, 2, 3], 0, 16)), [[0, 8, 0, 0], 4])\ncheck('oracle 6', solve(*([8, 16, 24], 0, 8)), [[4, 3, 4], 25])\ncheck('oracle 7', solve(*([6, -6, 6], 1, 4)), [[5, 15, 7], 6])\nif N == 1: check('variant packet 1', solve(*[[2, 6, -4, 10, 2, 6, -4, 10], 0, 8]), [[1, 1, 13, 7, 12, 2, 13, 7], 10])\nif N == 2: check('variant packet 2', solve(*[[2, 6, -4, 10, 2, 6, -4, 10, 2, 6, -4, 10], 0, 8]), [[1, 1, 13, 7, 12, 2, 13, 7, 12, 2, 13, 7], 10])\nif N == 3: check('variant packet 3', solve(*[[2, 6, -4, 10, 2, 6, -4, 10, 2, 6, -4, 10, 2, 6, -4, 10], 0, 8]), [[1, 1, 13, 7, 12, 2, 13, 7, 12, 2, 13, 7, 12, 2, 13, 7], 10])\nif N == 4: check('variant packet 4', solve(*[[2, 6, -4, 10, 2, 6, -4, 10, 2, 6, -4, 10, 2, 6, -4, 10, 2, 6, -4, 10], 0, 8]), [[1, 1, 13, 7, 12, 2, 13, 7, 12, 2, 13, 7, 12, 2, 13, 7, 12, 2, 13, 7], 10])\nif N == 5: check('variant packet 5', solve(*[[2, 6, -4, 10, 2, 6, -4, 10, 2, 6, -4, 10, 2, 6, -4, 10, 2, 6, -4, 10, 2, 6, -4, 10], 0, 8]), [[1, 1, 13, 7, 12, 2, 13, 7, 12, 2, 13, 7, 12, 2, 13, 7, 12, 2, 13, 7, 12, 2, 13, 7], 10])\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-adaptive-nibble-selection-difference-predictor","generated_at":"2026-09-29T14:45:02.910943+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":"Adaptive PCM encoder omits the reconstructed predictor.","sha256":"c6122544c8efe7a3a9b5ea677002b82770fc2ecdc44bb20ac724bb3cc5db17fa","title":"Pcm adaptive nibble selection: difference predictor · 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":38.899,"exit_code":1,"observations":[{"actual":[[9,12,12,15],-36],"check":"oracle 1","expected":[[1,1,13,7],10],"passed":false},{"actual":[[10,12,15],-39],"check":"oracle 2","expected":[[2,0,8],10],"passed":false},{"actual":[[2,7,7],35],"check":"oracle 3","expected":[[10,10,5],1],"passed":false},{"actual":[[],4],"check":"oracle 4","expected":[[],4],"passed":true},{"actual":[[0,0,0,0],8],"check":"oracle 5","expected":[[0,8,0,0],4],"passed":false},{"actual":[[12,15,15],-39],"check":"oracle 6","expected":[[4,3,4],25],"passed":false},{"actual":[[13,2,15],-9],"check":"oracle 7","expected":[[5,15,7],6],"passed":false},{"actual":[[9,12,12,15,15,15,15,15],-96],"check":"variant packet 1","expected":[[1,1,13,7,12,2,13,7],10],"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"oracle 1\", \"actual\": [[9, 12, 12, 15], -36], \"expected\": [[1, 1, 13, 7], 10], \"passed\": false}, {\"check\": \"oracle 2\", \"actual\": [[10, 12, 15], -39], \"expected\": [[2, 0, 8], 10], \"passed\": false}, {\"check\": \"oracle 3\", \"actual\": [[2, 7, 7], 35], \"expected\": [[10, 10, 5], 1], \"passed\": false}, {\"check\": \"oracle 4\", \"actual\": [[], 4], \"expected\": [[], 4], \"passed\": true}, {\"check\": \"oracle 5\", \"actual\": [[0, 0, 0, 0], 8], \"expected\": [[0, 8, 0, 0], 4], \"passed\": false}, {\"check\": \"oracle 6\", \"actual\": [[12, 15, 15], -39], \"expected\": [[4, 3, 4], 25], \"passed\": false}, {\"check\": \"oracle 7\", \"actual\": [[13, 2, 15], -9], \"expected\": [[5, 15, 7], 6], \"passed\": false}, {\"check\": \"variant packet 1\", \"actual\": [[9, 12, 12, 15, 15, 15, 15, 15], -96], \"expected\": [[1, 1, 13, 7, 12, 2, 13, 7], 10], \"passed\": false}], \"passed\": false}\n"},"broken":{"elapsed_ms":38.259,"exit_code":1,"observations":[{"actual":[[1,3,10,5],16],"check":"oracle 1","expected":[[1,1,13,7],10],"passed":false},{"actual":[[3,3,3],33],"check":"oracle 2","expected":[[2,0,8],10],"passed":false},{"actual":[[10,13,0],-15],"check":"oracle 3","expected":[[10,10,5],1],"passed":false},{"actual":[[],4],"check":"oracle 4","expected":[[],4],"passed":true},{"actual":[[0,0,0,0],8],"check":"oracle 5","expected":[[0,8,0,0],4],"passed":false},{"actual":[[4,7,7],39],"check":"oracle 6","expected":[[4,3,4],25],"passed":false},{"actual":[[6,14,6],7],"check":"oracle 7","expected":[[5,15,7],6],"passed":false},{"actual":[[1,3,10,5,1,3,10,5],32],"check":"variant packet 1","expected":[[1,1,13,7,12,2,13,7],10],"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"oracle 1\", \"actual\": [[1, 3, 10, 5], 16], \"expected\": [[1, 1, 13, 7], 10], \"passed\": false}, {\"check\": \"oracle 2\", \"actual\": [[3, 3, 3], 33], \"expected\": [[2, 0, 8], 10], \"passed\": false}, {\"check\": \"oracle 3\", \"actual\": [[10, 13, 0], -15], \"expected\": [[10, 10, 5], 1], \"passed\": false}, {\"check\": \"oracle 4\", \"actual\": [[], 4], \"expected\": [[], 4], \"passed\": true}, {\"check\": \"oracle 5\", \"actual\": [[0, 0, 0, 0], 8], \"expected\": [[0, 8, 0, 0], 4], \"passed\": false}, {\"check\": \"oracle 6\", \"actual\": [[4, 7, 7], 39], \"expected\": [[4, 3, 4], 25], \"passed\": false}, {\"check\": \"oracle 7\", \"actual\": [[6, 14, 6], 7], \"expected\": [[5, 15, 7], 6], \"passed\": false}, {\"check\": \"variant packet 1\", \"actual\": [[1, 3, 10, 5, 1, 3, 10, 5], 32], \"expected\": [[1, 1, 13, 7, 12, 2, 13, 7], 10], \"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."}}