{"abstract":"Every matrix entry is summed rather than only the diagonal.","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 trace. Exact operational definition: sum(m[i][i] for i in range(len(m)))","contract_signature":"m","evaluation_group":"model-2800d164d6b3d446","failed_approach":"The antidiagonal is selected.","family":"xn-matrix-trace","id":"FA-6021","implementations":{"attempt":{"sha256":"daf3e94ececb3a719d1d0bdba5e84a88eaea434d299fe42e4cb31d5ce27e7d8b","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):\n    return sum(m[i][-i-1] for i in range(len(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]],)', solve(*([[1, 2], [3, 4]],)), 5)\ncheck('fixture 2: ([[1, 2, 3], [4, 5, 6], [7, 8, 10]],)', solve(*([[1, 2, 3], [4, 5, 6], [7, 8, 10]],)), 16)\ncheck('fixture 3: ([],)', solve(*([],)), 0)\ncheck('fixture 4: ([[7]],)', solve(*([[7]],)), 7)\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":"da7a1adbe23877dfb3f7f27a482992bd4ff1c05720e14c253c38519021064359","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):\n    return sum(map(sum,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]],)', solve(*([[1, 2], [3, 4]],)), 5)\ncheck('fixture 2: ([[1, 2, 3], [4, 5, 6], [7, 8, 10]],)', solve(*([[1, 2, 3], [4, 5, 6], [7, 8, 10]],)), 16)\ncheck('fixture 3: ([],)', solve(*([],)), 0)\ncheck('fixture 4: ([[7]],)', solve(*([[7]],)), 7)\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-trace","generated_at":"2026-09-29T14:37:56.487491+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.","root_cause":"Every matrix entry is summed rather than only the diagonal.","sha256":"c891d495682be8aa8c9e093b320b7c2aa2ec7103b443916e5f218e36742c29d5","title":"Matrix trace · 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":50.708,"exit_code":1,"observations":[{"actual":5,"check":"fixture 1: ([[1, 2], [3, 4]],)","expected":5,"passed":true},{"actual":15,"check":"fixture 2: ([[1, 2, 3], [4, 5, 6], [7, 8, 10]],)","expected":16,"passed":false},{"actual":0,"check":"fixture 3: ([],)","expected":0,"passed":true},{"actual":7,"check":"fixture 4: ([[7]],)","expected":7,"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"fixture 1: ([[1, 2], [3, 4]],)\", \"actual\": 5, \"expected\": 5, \"passed\": true}, {\"check\": \"fixture 2: ([[1, 2, 3], [4, 5, 6], [7, 8, 10]],)\", \"actual\": 15, \"expected\": 16, \"passed\": false}, {\"check\": \"fixture 3: ([],)\", \"actual\": 0, \"expected\": 0, \"passed\": true}, {\"check\": \"fixture 4: ([[7]],)\", \"actual\": 7, \"expected\": 7, \"passed\": true}], \"passed\": false}\n"},"broken":{"elapsed_ms":46.947,"exit_code":1,"observations":[{"actual":10,"check":"fixture 1: ([[1, 2], [3, 4]],)","expected":5,"passed":false},{"actual":46,"check":"fixture 2: ([[1, 2, 3], [4, 5, 6], [7, 8, 10]],)","expected":16,"passed":false},{"actual":0,"check":"fixture 3: ([],)","expected":0,"passed":true},{"actual":7,"check":"fixture 4: ([[7]],)","expected":7,"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"fixture 1: ([[1, 2], [3, 4]],)\", \"actual\": 10, \"expected\": 5, \"passed\": false}, {\"check\": \"fixture 2: ([[1, 2, 3], [4, 5, 6], [7, 8, 10]],)\", \"actual\": 46, \"expected\": 16, \"passed\": false}, {\"check\": \"fixture 3: ([],)\", \"actual\": 0, \"expected\": 0, \"passed\": true}, {\"check\": \"fixture 4: ([[7]],)\", \"actual\": 7, \"expected\": 7, \"passed\": true}], \"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."}}