{"abstract":"Sequential divisor allocation reuses initial priorities.","category":"Voting rule computation","checks":6,"contract":"Allocate nonnegative seats sequentially by highest exact votes/(awarded+1), resolving equal priorities by earlier index. Votes are nonnegative with positive total.","contract_signature":"votes, seats","evaluation_group":"model-24c3e26e1cab2a1e","failed_approach":"Using an odd divisor progression silently switches to a different allocation rule.","family":"z-voting_rules-divisor-update","id":"FA-12771","implementations":{"attempt":{"sha256":"df080fed9f1ab55ebedad1b380c16cf8b3f9fef076107fc56434b05846880d8e","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\nfrom fractions import Fraction\nN = 1\nobservations = []\ndef solve(votes, seats):\n    out=[0]*len(votes)\n    for _ in range(seats):\n        i=max(range(len(votes)),key=lambda i:Fraction(votes[i],2*out[i]+1))\n        out[i]+=1\n    return out\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('update seat priority', solve([5*N,2*N],2), [2,0])\ncheck('minority eventually receives seat', solve([5*N,2*N],3), [2,1])\ncheck('equal priorities stable', solve([N,N],3), [2,1])\ncheck('zero seats', solve([N,N],0), [0,0])\ncheck('zero votes', solve([0,N],3), [0,3])\ncheck('single group', solve([N],4), [4])\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":"3cc944b0068cca6d7c1a61233d90f4bfc41f0d0e115732c43530f86024b2290e","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\nfrom fractions import Fraction\nN = 1\nobservations = []\ndef solve(votes, seats):\n    out=[0]*len(votes)\n    out[max(range(len(votes)),key=lambda i:votes[i])]=seats\n    return out\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('update seat priority', solve([5*N,2*N],2), [2,0])\ncheck('minority eventually receives seat', solve([5*N,2*N],3), [2,1])\ncheck('equal priorities stable', solve([N,N],3), [2,1])\ncheck('zero seats', solve([N,N],0), [0,0])\ncheck('zero votes', solve([0,N],3), [0,3])\ncheck('single group', solve([N],4), [4])\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":"Abstract counting rules only; excludes jurisdictional law, ballot authentication and election operations. 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":"z-voting_rules-divisor-update","generated_at":"2026-09-29T14:39:00.079913+00:00","license":"CC0-1.0","python":"3.12.14","seed":1,"split":"open-access"},"relevance":"A deterministic toy ballot model makes the stated counting convention executable.","root_cause":"All seat priorities are frozen at the initial vote totals.","sha256":"4e43691edc0eb53591ff259cf760ca2e08d588da9611800b0766ed6f3ad25471","title":"Sequential divisor allocation reuses initial priorities · 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":44.796,"exit_code":1,"observations":[{"actual":[1,1],"check":"update seat priority","expected":[2,0],"passed":false},{"actual":[2,1],"check":"minority eventually receives seat","expected":[2,1],"passed":true},{"actual":[2,1],"check":"equal priorities stable","expected":[2,1],"passed":true},{"actual":[0,0],"check":"zero seats","expected":[0,0],"passed":true},{"actual":[0,3],"check":"zero votes","expected":[0,3],"passed":true},{"actual":[4],"check":"single group","expected":[4],"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"update seat priority\", \"actual\": [1, 1], \"expected\": [2, 0], \"passed\": false}, {\"check\": \"minority eventually receives seat\", \"actual\": [2, 1], \"expected\": [2, 1], \"passed\": true}, {\"check\": \"equal priorities stable\", \"actual\": [2, 1], \"expected\": [2, 1], \"passed\": true}, {\"check\": \"zero seats\", \"actual\": [0, 0], \"expected\": [0, 0], \"passed\": true}, {\"check\": \"zero votes\", \"actual\": [0, 3], \"expected\": [0, 3], \"passed\": true}, {\"check\": \"single group\", \"actual\": [4], \"expected\": [4], \"passed\": true}], \"passed\": false}\n"},"broken":{"elapsed_ms":45.86,"exit_code":1,"observations":[{"actual":[2,0],"check":"update seat priority","expected":[2,0],"passed":true},{"actual":[3,0],"check":"minority eventually receives seat","expected":[2,1],"passed":false},{"actual":[3,0],"check":"equal priorities stable","expected":[2,1],"passed":false},{"actual":[0,0],"check":"zero seats","expected":[0,0],"passed":true},{"actual":[0,3],"check":"zero votes","expected":[0,3],"passed":true},{"actual":[4],"check":"single group","expected":[4],"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"update seat priority\", \"actual\": [2, 0], \"expected\": [2, 0], \"passed\": true}, {\"check\": \"minority eventually receives seat\", \"actual\": [3, 0], \"expected\": [2, 1], \"passed\": false}, {\"check\": \"equal priorities stable\", \"actual\": [3, 0], \"expected\": [2, 1], \"passed\": false}, {\"check\": \"zero seats\", \"actual\": [0, 0], \"expected\": [0, 0], \"passed\": true}, {\"check\": \"zero votes\", \"actual\": [0, 3], \"expected\": [0, 3], \"passed\": true}, {\"check\": \"single group\", \"actual\": [4], \"expected\": [4], \"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."}}