{"abstract":"Eta cutoff compares log probability to a probability threshold.","category":"Token sampling filters","checks":7,"contract":"Keep candidates with probability at least max(eta, sqrt(eta)*exp(-H)), where H is entropy; omit zero-mass tokens.","contract_signature":"probabilities, eta","evaluation_group":"w3-tsf-eta-cutoff-logprob","failed_approach":"The attempted repair uses only the absolute eta floor and omits the entropy-dependent cutoff term.","family":"w3-token-sampling-filters-eta-cutoff-logprob","id":"FA-98421","implementations":{"attempt":{"sha256":"49bf05f1edb23e2dee4b25f904837d871a50a72c8ba17f434d8771ebde41680b","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\nimport math\nN = 1\nobservations = []\ndef solve(probabilities, eta):\n    import math\n    H=-sum(p*math.log(p) for p in probabilities.values() if p>0)\n    threshold=eta\n    return sorted(t for t,p in probabilities.items() if p>=threshold and p>0)\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('eta floor',solve({'a':.7,'b':.2,'c':.1},.15),['a','b'])\ncheck('equality retained',solve({'a':.5,'b':.5},.5),['a','b'])\ncheck('empty',solve({},.2),[])\ncheck('zero mass ignored',solve({'a':1.0,'z':0.0},.2),['a'])\ncheck('one candidate',solve({'a':1.0},.9),['a'])\ncheck('uniform candidates',solve({'a':.25,'b':.25,'c':.25,'d':.25},.01),['a','b','c','d'])\ncheck('entropy cutoff active',solve({'a':.8,'b':.15,'c':.05},.01),['a','b'])\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":"9ddf6066a113593e03ce111b10922e760d8cc9a526e359bc3af35318cce2cf57","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\nimport math\nN = 1\nobservations = []\ndef solve(probabilities, eta):\n    import math\n    H=-sum(p*math.log(p) for p in probabilities.values() if p>0)\n    threshold=max(eta,math.sqrt(eta)*math.exp(-H))\n    return sorted(t for t,p in probabilities.items() if p>0 and math.log(p)>=threshold)\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('eta floor',solve({'a':.7,'b':.2,'c':.1},.15),['a','b'])\ncheck('equality retained',solve({'a':.5,'b':.5},.5),['a','b'])\ncheck('empty',solve({},.2),[])\ncheck('zero mass ignored',solve({'a':1.0,'z':0.0},.2),['a'])\ncheck('one candidate',solve({'a':1.0},.9),['a'])\ncheck('uniform candidates',solve({'a':.25,'b':.25,'c':.25,'d':.25},.01),['a','b','c','d'])\ncheck('entropy cutoff active',solve({'a':.8,'b':.15,'c':.05},.01),['a','b'])\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":"These are toy finite-vocabulary contracts with supplied scores, histories, and draws; they do not claim production model quality or compatibility. 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":"w3-token-sampling-filters-eta-cutoff-logprob","generated_at":"2026-09-30T16:48:12.803713+00:00","license":"CC0-1.0","python":"3.12.14","seed":1,"split":"open-access"},"relevance":"A finite, deterministic token-selection contract isolates one decoding operation from model inference and runtime behavior.","root_cause":"Candidate log probability is compared directly with the positive probability cutoff.","sha256":"4ab3cdfe6f5d4f3a9edf8ef7b5c977a5f75623ed85b82c19e91b7cc5d2c4d6a3","title":"Token sampling: Eta cutoff compares log probability to a probability threshold · case 01","variant":1,"variant_policy":"The same explicitly authored fixtures repeat across all five numbered records; runtime N is unused. These records share one mechanism and must remain together in evaluation splits.","verified":true,"visibility":"public","verification":{"attempt":{"elapsed_ms":27.649,"exit_code":1,"observations":[{"actual":["a","b"],"check":"eta floor","expected":["a","b"],"passed":true},{"actual":["a","b"],"check":"equality retained","expected":["a","b"],"passed":true},{"actual":[],"check":"empty","expected":[],"passed":true},{"actual":["a"],"check":"zero mass ignored","expected":["a"],"passed":true},{"actual":["a"],"check":"one candidate","expected":["a"],"passed":true},{"actual":["a","b","c","d"],"check":"uniform candidates","expected":["a","b","c","d"],"passed":true},{"actual":["a","b","c"],"check":"entropy cutoff active","expected":["a","b"],"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"eta floor\", \"actual\": [\"a\", \"b\"], \"expected\": [\"a\", \"b\"], \"passed\": true}, {\"check\": \"equality retained\", \"actual\": [\"a\", \"b\"], \"expected\": [\"a\", \"b\"], \"passed\": true}, {\"check\": \"empty\", \"actual\": [], \"expected\": [], \"passed\": true}, {\"check\": \"zero mass ignored\", \"actual\": [\"a\"], \"expected\": [\"a\"], \"passed\": true}, {\"check\": \"one candidate\", \"actual\": [\"a\"], \"expected\": [\"a\"], \"passed\": true}, {\"check\": \"uniform candidates\", \"actual\": [\"a\", \"b\", \"c\", \"d\"], \"expected\": [\"a\", \"b\", \"c\", \"d\"], \"passed\": true}, {\"check\": \"entropy cutoff active\", \"actual\": [\"a\", \"b\", \"c\"], \"expected\": [\"a\", \"b\"], \"passed\": false}], \"passed\": false}\n"},"broken":{"elapsed_ms":26.412,"exit_code":1,"observations":[{"actual":[],"check":"eta floor","expected":["a","b"],"passed":false},{"actual":[],"check":"equality retained","expected":["a","b"],"passed":false},{"actual":[],"check":"empty","expected":[],"passed":true},{"actual":[],"check":"zero mass ignored","expected":["a"],"passed":false},{"actual":[],"check":"one candidate","expected":["a"],"passed":false},{"actual":[],"check":"uniform candidates","expected":["a","b","c","d"],"passed":false},{"actual":[],"check":"entropy cutoff active","expected":["a","b"],"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"eta floor\", \"actual\": [], \"expected\": [\"a\", \"b\"], \"passed\": false}, {\"check\": \"equality retained\", \"actual\": [], \"expected\": [\"a\", \"b\"], \"passed\": false}, {\"check\": \"empty\", \"actual\": [], \"expected\": [], \"passed\": true}, {\"check\": \"zero mass ignored\", \"actual\": [], \"expected\": [\"a\"], \"passed\": false}, {\"check\": \"one candidate\", \"actual\": [], \"expected\": [\"a\"], \"passed\": false}, {\"check\": \"uniform candidates\", \"actual\": [], \"expected\": [\"a\", \"b\", \"c\", \"d\"], \"passed\": false}, {\"check\": \"entropy cutoff active\", \"actual\": [], \"expected\": [\"a\", \"b\"], \"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."}}