{"abstract":"The reduction disagrees with its explicit aggregation oracle.","category":"Numerical aggregation","checks":8,"contract":"Return probability that two distinct uniformly chosen observation indices carry equal integer labels, as an exact Fraction string. Fewer than two observations returns None. Labels themselves are nominal; repeated indices are excluded.","evaluation_group":"s3-na-empirical-distinct-draw-collision","failed_approach":"Subtracting one self-pair per label fails to remove one per observation.","family":"s3-numerical-aggregation-empirical-distinct-draw-collision-self-pair-numerator","id":"FA-13341","implementations":{"attempt":{"sha256":"9a5cd71114095d59af32b779b91105b88eadd70214529453896916ab75bf634f","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\nfrom fractions import Fraction\nfrom collections import Counter, defaultdict\nimport math\nimport itertools\nN = 1\nobservations = []\ndef solve(xs):\n    counts=Counter(xs)\n    n=len(xs)\n    if n<2: return None\n    return str(Fraction(sum(max(0,v*v-1) for v in counts.values()),n*(n-1)))\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('regression 1', solve(*([1, 1, 2],)), '1/3')\ncheck('regression 2', solve(*([1, 2, 3],)), '0')\ncheck('regression 3', solve(*([],)), None)\ncheck('regression 4', solve(*([9],)), None)\ncheck('regression 5', solve(*([2, 2, 2, 2],)), '1')\ncheck('regression 6', solve(*([0, 0, 1, 1, 1, 2],)), '4/15')\ncheck('regression 7', solve(*([-1, -1, 0, 0],)), '1/3')\ncheck(\"variable collision multiplicity\",solve([0]*N+[1]),str(Fraction(N*(N-1),(N+1)*N)))\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":"d9559a0b36c7e001071a1837565d1a74c182842a7a3ff45b5cce2ed104979417","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\nfrom fractions import Fraction\nfrom collections import Counter, defaultdict\nimport math\nimport itertools\nN = 1\nobservations = []\ndef solve(xs):\n    counts=Counter(xs)\n    n=len(xs)\n    if n<2: return None\n    return str(Fraction(sum(v*v for v in counts.values()),n*(n-1)))\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('regression 1', solve(*([1, 1, 2],)), '1/3')\ncheck('regression 2', solve(*([1, 2, 3],)), '0')\ncheck('regression 3', solve(*([],)), None)\ncheck('regression 4', solve(*([9],)), None)\ncheck('regression 5', solve(*([2, 2, 2, 2],)), '1')\ncheck('regression 6', solve(*([0, 0, 1, 1, 1, 2],)), '4/15')\ncheck('regression 7', solve(*([-1, -1, 0, 0],)), '1/3')\ncheck(\"variable collision multiplicity\",solve([0]*N+[1]),str(Fraction(N*(N-1),(N+1)*N)))\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":"1a4fae3a590539025dd4b2a652d158dbbd99f79868cffa8a0ba14904108f78f5","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\nfrom fractions import Fraction\nfrom collections import Counter, defaultdict\nimport math\nimport itertools\nN = 1\nobservations = []\ndef solve(xs):\n    counts=Counter(xs)\n    n=len(xs)\n    if n<2: return None\n    return str(Fraction(sum(v*(v-1) for v in counts.values()),n*(n-1)))\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('regression 1', solve(*([1, 1, 2],)), '1/3')\ncheck('regression 2', solve(*([1, 2, 3],)), '0')\ncheck('regression 3', solve(*([],)), None)\ncheck('regression 4', solve(*([9],)), None)\ncheck('regression 5', solve(*([2, 2, 2, 2],)), '1')\ncheck('regression 6', solve(*([0, 0, 1, 1, 1, 2],)), '4/15')\ncheck('regression 7', solve(*([-1, -1, 0, 0],)), '1/3')\ncheck(\"variable collision multiplicity\",solve([0]*N+[1]),str(Fraction(N*(N-1),(N+1)*N)))\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":"Small offline integer/rational inputs only; no performance, statistical inference, or production-library conformance claim. 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-numerical-aggregation-empirical-distinct-draw-collision-self-pair-numerator","generated_at":"2026-09-29T14:39:06.051687+00:00","license":"CC0-1.0","python":"3.12.14","seed":1,"split":"open-access"},"relevance":"Exact bounded examples isolate a reduction defect without floating-point or external-service effects.","repair":"Preserve the empirical distinct draw collision contract at the identified reduction decision.","root_cause":"The collision numerator includes drawing an observation with itself.","sha256":"19215920582b8d5f9118e23933810d68fb2ad59cba50775c1c81d36e26de61e6","title":"Empirical distinct draw collision: The collision numerator includes drawing an observation with itself. · case 01","variant":1,"variant_policy":"Five numbered records share a model and may reuse boundary fixtures.","verification":{"attempt":{"elapsed_ms":47.147,"exit_code":1,"observations":[{"actual":"1/2","check":"regression 1","expected":"1/3","passed":false},{"actual":"0","check":"regression 2","expected":"0","passed":true},{"actual":null,"check":"regression 3","expected":null,"passed":true},{"actual":null,"check":"regression 4","expected":null,"passed":true},{"actual":"5/4","check":"regression 5","expected":"1","passed":false},{"actual":"11/30","check":"regression 6","expected":"4/15","passed":false},{"actual":"1/2","check":"regression 7","expected":"1/3","passed":false},{"actual":"0","check":"variable collision multiplicity","expected":"0","passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"regression 1\", \"actual\": \"1/2\", \"expected\": \"1/3\", \"passed\": false}, {\"check\": \"regression 2\", \"actual\": \"0\", \"expected\": \"0\", \"passed\": true}, {\"check\": \"regression 3\", \"actual\": null, \"expected\": null, \"passed\": true}, {\"check\": \"regression 4\", \"actual\": null, \"expected\": null, \"passed\": true}, {\"check\": \"regression 5\", \"actual\": \"5/4\", \"expected\": \"1\", \"passed\": false}, {\"check\": \"regression 6\", \"actual\": \"11/30\", \"expected\": \"4/15\", \"passed\": false}, {\"check\": \"regression 7\", \"actual\": \"1/2\", \"expected\": \"1/3\", \"passed\": false}, {\"check\": \"variable collision multiplicity\", \"actual\": \"0\", \"expected\": \"0\", \"passed\": true}], \"passed\": false}\n"},"broken":{"elapsed_ms":46.673,"exit_code":1,"observations":[{"actual":"5/6","check":"regression 1","expected":"1/3","passed":false},{"actual":"1/2","check":"regression 2","expected":"0","passed":false},{"actual":null,"check":"regression 3","expected":null,"passed":true},{"actual":null,"check":"regression 4","expected":null,"passed":true},{"actual":"4/3","check":"regression 5","expected":"1","passed":false},{"actual":"7/15","check":"regression 6","expected":"4/15","passed":false},{"actual":"2/3","check":"regression 7","expected":"1/3","passed":false},{"actual":"1","check":"variable collision multiplicity","expected":"0","passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"regression 1\", \"actual\": \"5/6\", \"expected\": \"1/3\", \"passed\": false}, {\"check\": \"regression 2\", \"actual\": \"1/2\", \"expected\": \"0\", \"passed\": false}, {\"check\": \"regression 3\", \"actual\": null, \"expected\": null, \"passed\": true}, {\"check\": \"regression 4\", \"actual\": null, \"expected\": null, \"passed\": true}, {\"check\": \"regression 5\", \"actual\": \"4/3\", \"expected\": \"1\", \"passed\": false}, {\"check\": \"regression 6\", \"actual\": \"7/15\", \"expected\": \"4/15\", \"passed\": false}, {\"check\": \"regression 7\", \"actual\": \"2/3\", \"expected\": \"1/3\", \"passed\": false}, {\"check\": \"variable collision multiplicity\", \"actual\": \"1\", \"expected\": \"0\", \"passed\": false}], \"passed\": false}\n"},"fixed":{"elapsed_ms":43.918,"exit_code":0,"observations":[{"actual":"1/3","check":"regression 1","expected":"1/3","passed":true},{"actual":"0","check":"regression 2","expected":"0","passed":true},{"actual":null,"check":"regression 3","expected":null,"passed":true},{"actual":null,"check":"regression 4","expected":null,"passed":true},{"actual":"1","check":"regression 5","expected":"1","passed":true},{"actual":"4/15","check":"regression 6","expected":"4/15","passed":true},{"actual":"1/3","check":"regression 7","expected":"1/3","passed":true},{"actual":"0","check":"variable collision multiplicity","expected":"0","passed":true}],"passed":true,"stderr":"","stdout":"{\"observations\": [{\"check\": \"regression 1\", \"actual\": \"1/3\", \"expected\": \"1/3\", \"passed\": true}, {\"check\": \"regression 2\", \"actual\": \"0\", \"expected\": \"0\", \"passed\": true}, {\"check\": \"regression 3\", \"actual\": null, \"expected\": null, \"passed\": true}, {\"check\": \"regression 4\", \"actual\": null, \"expected\": null, \"passed\": true}, {\"check\": \"regression 5\", \"actual\": \"1\", \"expected\": \"1\", \"passed\": true}, {\"check\": \"regression 6\", \"actual\": \"4/15\", \"expected\": \"4/15\", \"passed\": true}, {\"check\": \"regression 7\", \"actual\": \"1/3\", \"expected\": \"1/3\", \"passed\": true}, {\"check\": \"variable collision multiplicity\", \"actual\": \"0\", \"expected\": \"0\", \"passed\": true}], \"passed\": true}\n"}},"verified":true,"visibility":"public"}