{"abstract":"Shard values are placed by list position instead of declared offsets.","category":"Distributed training aggregation","checks":6,"contract":"Given [offset,value] pairs and output length, return dense list with None for unowned positions; duplicate offset last wins.","contract_signature":"pairs, length","evaluation_group":"w3-dta-owner-shard-index","failed_approach":"Sorting values alone ignores explicit offset gaps and ownership.","family":"w3-distributed-training-aggregation-owner-shard-index","id":"FA-99311","implementations":{"attempt":{"sha256":"5ce2772bad398206e32aa3b4e7d369734b84e2f1b2f3622880eeeb58b58f3ab0","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(pairs, length):\n    return [v for i,v in sorted(pairs,key=lambda x:x[1])][:length]\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('unordered ownership',solve([[2,'c'],[0,'a'],[1,'b']],3),['a','b','c'])\ncheck('gap preserved',solve([[2,'c'],[0,'a']],3),['a',None,'c'])\ncheck('empty',solve([],N),[None]*N)\ncheck('length zero',solve([[0,'x']],0),[])\ncheck('duplicate last wins',solve([[1,'old'],[1,'new']],2),[None,'new'])\ncheck('out of range ignored',solve([[-1,'x'],[0,'a']],1),['a'])\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":"d95bcdaf6d797702acca1e2c5083e1f29a58a424768249f52e15ef033383830f","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(pairs, length):\n    out=[None]*length\n    for i,(offset,v) in enumerate(pairs):\n        if i<length: out[i]=v\n    return out\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('unordered ownership',solve([[2,'c'],[0,'a'],[1,'b']],3),['a','b','c'])\ncheck('gap preserved',solve([[2,'c'],[0,'a']],3),['a',None,'c'])\ncheck('empty',solve([],N),[None]*N)\ncheck('length zero',solve([[0,'x']],0),[])\ncheck('duplicate last wins',solve([[1,'old'],[1,'new']],2),[None,'new'])\ncheck('out of range ignored',solve([[-1,'x'],[0,'a']],1),['a'])\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":"Inputs are already materialized Python values from a fixed toy collective; no transport, failure recovery, optimizer state, or real model behavior is represented. 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-distributed-training-aggregation-owner-shard-index","generated_at":"2026-09-30T16:48:22.633482+00:00","license":"CC0-1.0","python":"3.12.14","seed":1,"split":"open-access"},"relevance":"A toy distributed-training contract makes replica and shard contribution rules explicit without claiming framework compatibility or performance.","root_cause":"A worker can send disjoint ranges out of order.","sha256":"507f49886375420e56a21ac19634a77f9d6e3b7cca546016d49fdd517bcf36ab","title":"Shard values are placed by list position instead of declared offsets · 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":28.034,"exit_code":1,"observations":[{"actual":["a","b","c"],"check":"unordered ownership","expected":["a","b","c"],"passed":true},{"actual":["a","c"],"check":"gap preserved","expected":["a",null,"c"],"passed":false},{"actual":[],"check":"empty","expected":[null],"passed":false},{"actual":[],"check":"length zero","expected":[],"passed":true},{"actual":["new","old"],"check":"duplicate last wins","expected":[null,"new"],"passed":false},{"actual":["a"],"check":"out of range ignored","expected":["a"],"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"unordered ownership\", \"actual\": [\"a\", \"b\", \"c\"], \"expected\": [\"a\", \"b\", \"c\"], \"passed\": true}, {\"check\": \"gap preserved\", \"actual\": [\"a\", \"c\"], \"expected\": [\"a\", null, \"c\"], \"passed\": false}, {\"check\": \"empty\", \"actual\": [], \"expected\": [null], \"passed\": false}, {\"check\": \"length zero\", \"actual\": [], \"expected\": [], \"passed\": true}, {\"check\": \"duplicate last wins\", \"actual\": [\"new\", \"old\"], \"expected\": [null, \"new\"], \"passed\": false}, {\"check\": \"out of range ignored\", \"actual\": [\"a\"], \"expected\": [\"a\"], \"passed\": true}], \"passed\": false}\n"},"broken":{"elapsed_ms":27.53,"exit_code":1,"observations":[{"actual":["c","a","b"],"check":"unordered ownership","expected":["a","b","c"],"passed":false},{"actual":["c","a",null],"check":"gap preserved","expected":["a",null,"c"],"passed":false},{"actual":[null],"check":"empty","expected":[null],"passed":true},{"actual":[],"check":"length zero","expected":[],"passed":true},{"actual":["old","new"],"check":"duplicate last wins","expected":[null,"new"],"passed":false},{"actual":["x"],"check":"out of range ignored","expected":["a"],"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"unordered ownership\", \"actual\": [\"c\", \"a\", \"b\"], \"expected\": [\"a\", \"b\", \"c\"], \"passed\": false}, {\"check\": \"gap preserved\", \"actual\": [\"c\", \"a\", null], \"expected\": [\"a\", null, \"c\"], \"passed\": false}, {\"check\": \"empty\", \"actual\": [null], \"expected\": [null], \"passed\": true}, {\"check\": \"length zero\", \"actual\": [], \"expected\": [], \"passed\": true}, {\"check\": \"duplicate last wins\", \"actual\": [\"old\", \"new\"], \"expected\": [null, \"new\"], \"passed\": false}, {\"check\": \"out of range ignored\", \"actual\": [\"x\"], \"expected\": [\"a\"], \"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."}}