{"abstract":"The exact lagrange interpolation value result violates the stated contract at basis accumulation.","category":"Numerics","checks":8,"contract":"Input [points,t] distinct integer abscissae and integer ordinates; exact rational interpolation value [p,q].","contract_signature":"x","evaluation_group":"s3-numerics-lagrange-interpolation-value","failed_approach":"The partial repair ans-term still violates the basis accumulation invariant.","family":"s3-numerics-lagrange-interpolation-value-basis-accumulation","id":"FA-14686","implementations":{"attempt":{"sha256":"c62af3766557174fd90c716b8b7f5ef974a2cb2395291075ab994d1a933bdad4","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\nimport math\nimport itertools\nfrom fractions import Fraction\nN = 1\nobservations = []\ndef solve(x):\n    points,t=x\n    ans=Fraction(0)\n    for i,(xi,yi) in enumerate(points):\n     term=Fraction(yi)\n     for j,(xj,yj) in enumerate(points):\n      if i==j:continue\n      den=xi-xj\n      if den==0:return None\n      term*=Fraction(t-xj,den)\n     ans=ans-term\n    return [ans.numerator,ans.denominator]\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\nfixtures = [[([[[-2, -2], [-1, -2], [0, -2]], -2], [-2, 1]), ([[[-2, -2], [-1, -2], [0, -2]], -3], [-2, 1]), ([[[0, 2], [2, 2]], 3], [2, 1]), ([[[-2, -2], [-1, -2], [0, -2]], -1], [-2, 1]), ([[[-2, -2], [-1, -2], [0, -2]], 0], [-2, 1]), ([[[-2, -2], [-1, -2], [0, -2]], 1], [-2, 1]), ([[[-2, -2], [-1, -2], [0, -2]], 2], [-2, 1]), ([[[-2, -2], [-1, -2], [0, -2]], 3], [-2, 1])], [([[[-2, -2], [-1, -2], [0, -2]], -1], [-2, 1]), ([[[-2, -2], [-1, -2], [0, -2]], 0], [-2, 1]), ([[[-2, -2], [-1, -2], [0, -2]], -3], [-2, 1]), ([[[0, 2], [2, 2]], 3], [2, 1]), ([[[-2, -2], [-1, -2], [0, 0]], 0], [0, 1]), ([[[-2, -2], [-1, -2], [0, 0]], 1], [4, 1]), ([[[-2, -2], [-1, -2], [0, 0]], 2], [10, 1]), ([[[-2, -2], [-1, -2], [0, 0]], 3], [18, 1])], [([[[-2, -2], [-1, -2], [0, -2]], 1], [-2, 1]), ([[[-2, -2], [-1, -2], [0, -2]], 3], [-2, 1]), ([[[-2, -2], [-1, -2], [0, -2]], -3], [-2, 1]), ([[[0, 2], [2, 2]], 3], [2, 1]), ([[[-2, -2], [-1, -2], [0, 2]], 3], [38, 1]), ([[[-2, -2], [-1, -1], [0, -2]], -3], [-5, 1]), ([[[-2, -2], [-1, -1], [0, -2]], -2], [-2, 1]), ([[[-2, -2], [-1, -1], [0, -2]], -1], [-1, 1])], [([[[-2, -2], [-1, -2], [0, -2]], 2], [-2, 1]), ([[[-2, -2], [-1, -2], [0, -1]], -1], [-2, 1]), ([[[-2, -2], [-1, -2], [0, -2]], -3], [-2, 1]), ([[[0, 2], [2, 2]], 3], [2, 1]), ([[[-2, -2], [-1, -1], [0, 0]], -1], [-1, 1]), ([[[-2, -2], [-1, -1], [0, 0]], 0], [0, 1]), ([[[-2, -2], [-1, -1], [0, 0]], 1], [1, 1]), ([[[-2, -2], [-1, -1], [0, 0]], 2], [2, 1])], [([[[-2, -2], [-1, -2], [0, -2]], 3], [-2, 1]), ([[[-2, -2], [-1, -2], [0, -1]], 2], [4, 1]), ([[[-2, -2], [-1, -2], [0, -2]], -3], [-2, 1]), ([[[0, 2], [2, 2]], 3], [2, 1]), ([[[-2, -2], [-1, -1], [0, 2]], 2], [14, 1]), ([[[-2, -2], [-1, -1], [0, 2]], 3], [23, 1]), ([[[-2, -2], [-1, 0], [0, -2]], -3], [-8, 1]), ([[[-2, -2], [-1, 0], [0, -2]], -2], [-2, 1])]]\nfor i, (args, expected) in enumerate(fixtures[N-1]):\n    check(\"explicit 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":"5324bf6504ec90f6c1d6004a29d9003fde0a868216f8e25cb0468161e8210ae7","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\nimport math\nimport itertools\nfrom fractions import Fraction\nN = 1\nobservations = []\ndef solve(x):\n    points,t=x\n    ans=Fraction(0)\n    for i,(xi,yi) in enumerate(points):\n     term=Fraction(yi)\n     for j,(xj,yj) in enumerate(points):\n      if i==j:continue\n      den=xi-xj\n      if den==0:return None\n      term*=Fraction(t-xj,den)\n     ans=term\n    return [ans.numerator,ans.denominator]\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\nfixtures = [[([[[-2, -2], [-1, -2], [0, -2]], -2], [-2, 1]), ([[[-2, -2], [-1, -2], [0, -2]], -3], [-2, 1]), ([[[0, 2], [2, 2]], 3], [2, 1]), ([[[-2, -2], [-1, -2], [0, -2]], -1], [-2, 1]), ([[[-2, -2], [-1, -2], [0, -2]], 0], [-2, 1]), ([[[-2, -2], [-1, -2], [0, -2]], 1], [-2, 1]), ([[[-2, -2], [-1, -2], [0, -2]], 2], [-2, 1]), ([[[-2, -2], [-1, -2], [0, -2]], 3], [-2, 1])], [([[[-2, -2], [-1, -2], [0, -2]], -1], [-2, 1]), ([[[-2, -2], [-1, -2], [0, -2]], 0], [-2, 1]), ([[[-2, -2], [-1, -2], [0, -2]], -3], [-2, 1]), ([[[0, 2], [2, 2]], 3], [2, 1]), ([[[-2, -2], [-1, -2], [0, 0]], 0], [0, 1]), ([[[-2, -2], [-1, -2], [0, 0]], 1], [4, 1]), ([[[-2, -2], [-1, -2], [0, 0]], 2], [10, 1]), ([[[-2, -2], [-1, -2], [0, 0]], 3], [18, 1])], [([[[-2, -2], [-1, -2], [0, -2]], 1], [-2, 1]), ([[[-2, -2], [-1, -2], [0, -2]], 3], [-2, 1]), ([[[-2, -2], [-1, -2], [0, -2]], -3], [-2, 1]), ([[[0, 2], [2, 2]], 3], [2, 1]), ([[[-2, -2], [-1, -2], [0, 2]], 3], [38, 1]), ([[[-2, -2], [-1, -1], [0, -2]], -3], [-5, 1]), ([[[-2, -2], [-1, -1], [0, -2]], -2], [-2, 1]), ([[[-2, -2], [-1, -1], [0, -2]], -1], [-1, 1])], [([[[-2, -2], [-1, -2], [0, -2]], 2], [-2, 1]), ([[[-2, -2], [-1, -2], [0, -1]], -1], [-2, 1]), ([[[-2, -2], [-1, -2], [0, -2]], -3], [-2, 1]), ([[[0, 2], [2, 2]], 3], [2, 1]), ([[[-2, -2], [-1, -1], [0, 0]], -1], [-1, 1]), ([[[-2, -2], [-1, -1], [0, 0]], 0], [0, 1]), ([[[-2, -2], [-1, -1], [0, 0]], 1], [1, 1]), ([[[-2, -2], [-1, -1], [0, 0]], 2], [2, 1])], [([[[-2, -2], [-1, -2], [0, -2]], 3], [-2, 1]), ([[[-2, -2], [-1, -2], [0, -1]], 2], [4, 1]), ([[[-2, -2], [-1, -2], [0, -2]], -3], [-2, 1]), ([[[0, 2], [2, 2]], 3], [2, 1]), ([[[-2, -2], [-1, -1], [0, 2]], 2], [14, 1]), ([[[-2, -2], [-1, -1], [0, 2]], 3], [23, 1]), ([[[-2, -2], [-1, 0], [0, -2]], -3], [-8, 1]), ([[[-2, -2], [-1, 0], [0, -2]], -2], [-2, 1])]]\nfor i, (args, expected) in enumerate(fixtures[N-1]):\n    check(\"explicit 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. Inputs are restricted to the explicit contract; this is not a production algebra library. 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-numerics-lagrange-interpolation-value-basis-accumulation","generated_at":"2026-09-29T14:39:19.289380+00:00","license":"CC0-1.0","python":"3.12.14","seed":1,"split":"open-access"},"relevance":"Exact discrete arithmetic with observable algorithmic state; no floating point approximation is used.","root_cause":"The basis accumulation step uses term instead of ans+term.","sha256":"4d25584d60e7e945e034a1467b9ed592443484ebb52af94200e80a8df0a84f07","title":"Lagrange interpolation value: basis accumulation · 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":43.898,"exit_code":1,"observations":[{"actual":[2,1],"check":"explicit oracle 0","expected":[-2,1],"passed":false},{"actual":[2,1],"check":"explicit oracle 1","expected":[-2,1],"passed":false},{"actual":[-2,1],"check":"explicit oracle 2","expected":[2,1],"passed":false},{"actual":[2,1],"check":"explicit oracle 3","expected":[-2,1],"passed":false},{"actual":[2,1],"check":"explicit oracle 4","expected":[-2,1],"passed":false},{"actual":[2,1],"check":"explicit oracle 5","expected":[-2,1],"passed":false},{"actual":[2,1],"check":"explicit oracle 6","expected":[-2,1],"passed":false},{"actual":[2,1],"check":"explicit oracle 7","expected":[-2,1],"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"explicit oracle 0\", \"actual\": [2, 1], \"expected\": [-2, 1], \"passed\": false}, {\"check\": \"explicit oracle 1\", \"actual\": [2, 1], \"expected\": [-2, 1], \"passed\": false}, {\"check\": \"explicit oracle 2\", \"actual\": [-2, 1], \"expected\": [2, 1], \"passed\": false}, {\"check\": \"explicit oracle 3\", \"actual\": [2, 1], \"expected\": [-2, 1], \"passed\": false}, {\"check\": \"explicit oracle 4\", \"actual\": [2, 1], \"expected\": [-2, 1], \"passed\": false}, {\"check\": \"explicit oracle 5\", \"actual\": [2, 1], \"expected\": [-2, 1], \"passed\": false}, {\"check\": \"explicit oracle 6\", \"actual\": [2, 1], \"expected\": [-2, 1], \"passed\": false}, {\"check\": \"explicit oracle 7\", \"actual\": [2, 1], \"expected\": [-2, 1], \"passed\": false}], \"passed\": false}\n"},"broken":{"elapsed_ms":41.936,"exit_code":1,"observations":[{"actual":[0,1],"check":"explicit oracle 0","expected":[-2,1],"passed":false},{"actual":[-2,1],"check":"explicit oracle 1","expected":[-2,1],"passed":true},{"actual":[3,1],"check":"explicit oracle 2","expected":[2,1],"passed":false},{"actual":[0,1],"check":"explicit oracle 3","expected":[-2,1],"passed":false},{"actual":[-2,1],"check":"explicit oracle 4","expected":[-2,1],"passed":true},{"actual":[-6,1],"check":"explicit oracle 5","expected":[-2,1],"passed":false},{"actual":[-12,1],"check":"explicit oracle 6","expected":[-2,1],"passed":false},{"actual":[-20,1],"check":"explicit oracle 7","expected":[-2,1],"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"explicit oracle 0\", \"actual\": [0, 1], \"expected\": [-2, 1], \"passed\": false}, {\"check\": \"explicit oracle 1\", \"actual\": [-2, 1], \"expected\": [-2, 1], \"passed\": true}, {\"check\": \"explicit oracle 2\", \"actual\": [3, 1], \"expected\": [2, 1], \"passed\": false}, {\"check\": \"explicit oracle 3\", \"actual\": [0, 1], \"expected\": [-2, 1], \"passed\": false}, {\"check\": \"explicit oracle 4\", \"actual\": [-2, 1], \"expected\": [-2, 1], \"passed\": true}, {\"check\": \"explicit oracle 5\", \"actual\": [-6, 1], \"expected\": [-2, 1], \"passed\": false}, {\"check\": \"explicit oracle 6\", \"actual\": [-12, 1], \"expected\": [-2, 1], \"passed\": false}, {\"check\": \"explicit oracle 7\", \"actual\": [-20, 1], \"expected\": [-2, 1], \"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."}}