{"abstract":"only adjacent candidates are paired.","category":"Preference pair construction","checks":6,"contract":"Candidates are [id,score]. Return every unordered pair [higher_id,lower_id] once; tied scores are skipped. Order follows input index pairs.","contract_signature":"candidates","evaluation_group":"preference-pairwise-combinations","failed_approach":"Extending the traversal to skip one candidate finds distant pairs but omits adjacent comparisons.","family":"w3-preference-pair-construction-pairwise-combinations","id":"FA-100086","implementations":{"attempt":{"sha256":"c74636e4aaa404da24912836eeaffd11c3756b715187f82f7100adac07d5ccf1","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(candidates):\n    return [[a[0],b[0]] if a[1]>b[1] else [b[0],a[0]] for i,a in enumerate(candidates) for b in candidates[i+2:] if a[1]!=b[1]]\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\na='a'+str(N); b='b'+str(N); c='c'+str(N)\ncheck('nonadjacent pair',solve([[a,3],[b,1],[c,2]]),[[a,b],[a,c],[c,b]])\ncheck('two candidates',solve([[a,1],[b,0]]),[[a,b]])\ncheck('tie skipped',solve([[a,1],[b,1]]),[])\ncheck('singleton',solve([[a,1]]),[])\ncheck('empty',solve([]),[])\ncheck('all descending',solve([[a,3],[b,2],[c,1]]),[[a,b],[a,c],[b,c]])\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":"838d5f37d90131c0028f8d18c67c3195740e424c0b4f87c31740741a1f84898f","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(candidates):\n    return [[candidates[i][0],candidates[i+1][0]] for i in range(len(candidates)-1) if candidates[i][1]>candidates[i+1][1]]\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\na='a'+str(N); b='b'+str(N); c='c'+str(N)\ncheck('nonadjacent pair',solve([[a,3],[b,1],[c,2]]),[[a,b],[a,c],[c,b]])\ncheck('two candidates',solve([[a,1],[b,0]]),[[a,b]])\ncheck('tie skipped',solve([[a,1],[b,1]]),[])\ncheck('singleton',solve([[a,1]]),[])\ncheck('empty',solve([]),[])\ncheck('all descending',solve([[a,3],[b,2],[c,1]]),[[a,b],[a,c],[b,c]])\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 explicit toy record contracts; they do not claim compatibility with a trainer or improved model behavior. 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-preference-pair-construction-pairwise-combinations","generated_at":"2026-09-30T16:48:31.716660+00:00","license":"CC0-1.0","python":"3.12.14","seed":1,"split":"open-access"},"relevance":"A small deterministic preference-data transform makes pair semantics inspectable without a training framework.","root_cause":"Adjacent list traversal omits valid preference comparisons between non-neighbor candidates.","sha256":"143e7852d13194b0ed62bda22d6f12b04c50b0aeb568b71e48c63c692f498f1c","title":"Preference pairs: only adjacent candidates are paired · case 01","variant":1,"variant_policy":"The fixture code references N, supplied as 1 through 5. Fixed boundary checks may repeat. These records share one mechanism and must remain together in evaluation splits.","verified":true,"visibility":"public","verification":{"attempt":{"elapsed_ms":29.389,"exit_code":1,"observations":[{"actual":[["a1","c1"]],"check":"nonadjacent pair","expected":[["a1","b1"],["a1","c1"],["c1","b1"]],"passed":false},{"actual":[],"check":"two candidates","expected":[["a1","b1"]],"passed":false},{"actual":[],"check":"tie skipped","expected":[],"passed":true},{"actual":[],"check":"singleton","expected":[],"passed":true},{"actual":[],"check":"empty","expected":[],"passed":true},{"actual":[["a1","c1"]],"check":"all descending","expected":[["a1","b1"],["a1","c1"],["b1","c1"]],"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"nonadjacent pair\", \"actual\": [[\"a1\", \"c1\"]], \"expected\": [[\"a1\", \"b1\"], [\"a1\", \"c1\"], [\"c1\", \"b1\"]], \"passed\": false}, {\"check\": \"two candidates\", \"actual\": [], \"expected\": [[\"a1\", \"b1\"]], \"passed\": false}, {\"check\": \"tie skipped\", \"actual\": [], \"expected\": [], \"passed\": true}, {\"check\": \"singleton\", \"actual\": [], \"expected\": [], \"passed\": true}, {\"check\": \"empty\", \"actual\": [], \"expected\": [], \"passed\": true}, {\"check\": \"all descending\", \"actual\": [[\"a1\", \"c1\"]], \"expected\": [[\"a1\", \"b1\"], [\"a1\", \"c1\"], [\"b1\", \"c1\"]], \"passed\": false}], \"passed\": false}\n"},"broken":{"elapsed_ms":27.932,"exit_code":1,"observations":[{"actual":[["a1","b1"]],"check":"nonadjacent pair","expected":[["a1","b1"],["a1","c1"],["c1","b1"]],"passed":false},{"actual":[["a1","b1"]],"check":"two candidates","expected":[["a1","b1"]],"passed":true},{"actual":[],"check":"tie skipped","expected":[],"passed":true},{"actual":[],"check":"singleton","expected":[],"passed":true},{"actual":[],"check":"empty","expected":[],"passed":true},{"actual":[["a1","b1"],["b1","c1"]],"check":"all descending","expected":[["a1","b1"],["a1","c1"],["b1","c1"]],"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"nonadjacent pair\", \"actual\": [[\"a1\", \"b1\"]], \"expected\": [[\"a1\", \"b1\"], [\"a1\", \"c1\"], [\"c1\", \"b1\"]], \"passed\": false}, {\"check\": \"two candidates\", \"actual\": [[\"a1\", \"b1\"]], \"expected\": [[\"a1\", \"b1\"]], \"passed\": true}, {\"check\": \"tie skipped\", \"actual\": [], \"expected\": [], \"passed\": true}, {\"check\": \"singleton\", \"actual\": [], \"expected\": [], \"passed\": true}, {\"check\": \"empty\", \"actual\": [], \"expected\": [], \"passed\": true}, {\"check\": \"all descending\", \"actual\": [[\"a1\", \"b1\"], [\"b1\", \"c1\"]], \"expected\": [[\"a1\", \"b1\"], [\"a1\", \"c1\"], [\"b1\", \"c1\"]], \"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."}}