{"abstract":"Products between nonmatching coordinates contaminate each row.","category":"Linear algebra","checks":4,"contract":"Integer matrix/vector entries, rectangular rows, compatible multiplication dimensions, and square matrices for determinant, trace, inverse, symmetry and characteristic-polynomial operations. Rational matrix outputs are reduced Fraction strings. Matrix vector product. Exact operational definition: [sum(x*y for x,y in zip(row,v)) for row in m]","evaluation_group":"model-99ae8bc92e70731a","failed_approach":"Row totals and vector totals are added instead of paired multiplication.","family":"xn-matrix-vector-product","id":"FA-6031","implementations":{"attempt":{"sha256":"8227d79b1584f55b798dffbbe68a096d2e512a447ae7c65280ea4b670ff0f808","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\nimport math\nimport calendar\nimport statistics\nimport itertools\nfrom fractions import Fraction\nfrom datetime import date, datetime, timedelta, timezone\nfrom decimal import Decimal, ROUND_HALF_UP, ROUND_DOWN, ROUND_CEILING, ROUND_FLOOR\n\nN = 1\nobservations = []\ndef solve(m, v):\n    return [sum(row)+sum(v) for row in m]\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('fixture 1: ([[1, 2], [3, 4]], [2, 1])', solve(*([[1, 2], [3, 4]], [2, 1])), [4, 10])\ncheck('fixture 2: ([[0, 0]], [1, 2])', solve(*([[0, 0]], [1, 2])), [0])\ncheck('fixture 3: ([[1, 0], [0, 1]], [3, 4])', solve(*([[1, 0], [0, 1]], [3, 4])), [3, 4])\ncheck('fixture 4: ([], [])', solve(*([], [])), [])\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":"d7a249c5b062d899abccd43a18b2570ec34969c3f493ad9437f46eb7d9acfeaf","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\nimport math\nimport calendar\nimport statistics\nimport itertools\nfrom fractions import Fraction\nfrom datetime import date, datetime, timedelta, timezone\nfrom decimal import Decimal, ROUND_HALF_UP, ROUND_DOWN, ROUND_CEILING, ROUND_FLOOR\n\nN = 1\nobservations = []\ndef solve(m, v):\n    return [sum(row)*sum(v) for row in m]\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('fixture 1: ([[1, 2], [3, 4]], [2, 1])', solve(*([[1, 2], [3, 4]], [2, 1])), [4, 10])\ncheck('fixture 2: ([[0, 0]], [1, 2])', solve(*([[0, 0]], [1, 2])), [0])\ncheck('fixture 3: ([[1, 0], [0, 1]], [3, 4])', solve(*([[1, 0], [0, 1]], [3, 4])), [3, 4])\ncheck('fixture 4: ([], [])', solve(*([], [])), [])\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":"ba18927a94abbed5ab512ab947e12c5fec0805a6048121caf9d9a06d94dcac9a","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\nimport math\nimport calendar\nimport statistics\nimport itertools\nfrom fractions import Fraction\nfrom datetime import date, datetime, timedelta, timezone\nfrom decimal import Decimal, ROUND_HALF_UP, ROUND_DOWN, ROUND_CEILING, ROUND_FLOOR\n\nN = 1\nobservations = []\ndef solve(m, v):\n    return [sum(x*y for x,y in zip(row,v)) for row in m]\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('fixture 1: ([[1, 2], [3, 4]], [2, 1])', solve(*([[1, 2], [3, 4]], [2, 1])), [4, 10])\ncheck('fixture 2: ([[0, 0]], [1, 2])', solve(*([[0, 0]], [1, 2])), [0])\ncheck('fixture 3: ([[1, 0], [0, 1]], [3, 4])', solve(*([[1, 0], [0, 1]], [3, 4])), [3, 4])\ncheck('fixture 4: ([], [])', solve(*([], [])), [])\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":" 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":"xn-matrix-vector-product","generated_at":"2026-09-29T14:37:56.799605+00:00","license":"CC0-1.0","python":"3.12.14","seed":1,"split":"open-access"},"relevance":"Small exact fixtures expose this error without platform timing, external services, or probabilistic observations. Linear algebra results depend on the stated convention.","repair":"Apply the specified mathematical contract directly, preserving all terms and boundary cases: return [sum(x*y for x,y in zip(row,v)) for row in m]","root_cause":"Products between nonmatching coordinates contaminate each row.","sha256":"08505b48e5a9f8698cab03d31d6f4f2af089e2c487c2b28e6bfec87a220f0337","title":"Matrix vector product · case 01","variant":1,"variant_policy":"Five numbered records share a model and may reuse boundary fixtures.","verification":{"attempt":{"elapsed_ms":42.739,"exit_code":1,"observations":[{"actual":[6,10],"check":"fixture 1: ([[1, 2], [3, 4]], [2, 1])","expected":[4,10],"passed":false},{"actual":[3],"check":"fixture 2: ([[0, 0]], [1, 2])","expected":[0],"passed":false},{"actual":[8,8],"check":"fixture 3: ([[1, 0], [0, 1]], [3, 4])","expected":[3,4],"passed":false},{"actual":[],"check":"fixture 4: ([], [])","expected":[],"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"fixture 1: ([[1, 2], [3, 4]], [2, 1])\", \"actual\": [6, 10], \"expected\": [4, 10], \"passed\": false}, {\"check\": \"fixture 2: ([[0, 0]], [1, 2])\", \"actual\": [3], \"expected\": [0], \"passed\": false}, {\"check\": \"fixture 3: ([[1, 0], [0, 1]], [3, 4])\", \"actual\": [8, 8], \"expected\": [3, 4], \"passed\": false}, {\"check\": \"fixture 4: ([], [])\", \"actual\": [], \"expected\": [], \"passed\": true}], \"passed\": false}\n"},"broken":{"elapsed_ms":40.705,"exit_code":1,"observations":[{"actual":[9,21],"check":"fixture 1: ([[1, 2], [3, 4]], [2, 1])","expected":[4,10],"passed":false},{"actual":[0],"check":"fixture 2: ([[0, 0]], [1, 2])","expected":[0],"passed":true},{"actual":[7,7],"check":"fixture 3: ([[1, 0], [0, 1]], [3, 4])","expected":[3,4],"passed":false},{"actual":[],"check":"fixture 4: ([], [])","expected":[],"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"fixture 1: ([[1, 2], [3, 4]], [2, 1])\", \"actual\": [9, 21], \"expected\": [4, 10], \"passed\": false}, {\"check\": \"fixture 2: ([[0, 0]], [1, 2])\", \"actual\": [0], \"expected\": [0], \"passed\": true}, {\"check\": \"fixture 3: ([[1, 0], [0, 1]], [3, 4])\", \"actual\": [7, 7], \"expected\": [3, 4], \"passed\": false}, {\"check\": \"fixture 4: ([], [])\", \"actual\": [], \"expected\": [], \"passed\": true}], \"passed\": false}\n"},"fixed":{"elapsed_ms":47.585,"exit_code":0,"observations":[{"actual":[4,10],"check":"fixture 1: ([[1, 2], [3, 4]], [2, 1])","expected":[4,10],"passed":true},{"actual":[0],"check":"fixture 2: ([[0, 0]], [1, 2])","expected":[0],"passed":true},{"actual":[3,4],"check":"fixture 3: ([[1, 0], [0, 1]], [3, 4])","expected":[3,4],"passed":true},{"actual":[],"check":"fixture 4: ([], [])","expected":[],"passed":true}],"passed":true,"stderr":"","stdout":"{\"observations\": [{\"check\": \"fixture 1: ([[1, 2], [3, 4]], [2, 1])\", \"actual\": [4, 10], \"expected\": [4, 10], \"passed\": true}, {\"check\": \"fixture 2: ([[0, 0]], [1, 2])\", \"actual\": [0], \"expected\": [0], \"passed\": true}, {\"check\": \"fixture 3: ([[1, 0], [0, 1]], [3, 4])\", \"actual\": [3, 4], \"expected\": [3, 4], \"passed\": true}, {\"check\": \"fixture 4: ([], [])\", \"actual\": [], \"expected\": [], \"passed\": true}], \"passed\": true}\n"}},"verified":true,"visibility":"public"}