{"abstract":"All-gather output follows arrival order.","category":"Distributed training aggregation","checks":6,"contract":"Given rank-tagged payloads and world size, return payloads in rank order; missing ranks are omitted and duplicate rank uses last listed payload.","contract_signature":"items, world","evaluation_group":"w3-dta-allgather-rank-order","failed_approach":"Sorting by payload value is deterministic but loses rank ownership.","family":"w3-distributed-training-aggregation-allgather-rank-order","id":"FA-99261","implementations":{"attempt":{"sha256":"3518dedc690bcd44de1e6c0df5ce03a8726bc74fe7f5efaaae16bc1f19382854","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(items, world):\n    return [v for r,v in sorted(items,key=lambda x:x[1])]\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\nit=[(2,'c'),(0,'a'),(1,'b')]\ncheck('arrival shuffled',solve(it,3),['a','b','c'])\ncheck('missing rank',solve([(2,'c'),(0,'a')],3),['a','c'])\ncheck('empty gather',solve([],N),[])\ncheck('singleton',solve([(0,'x')],1),['x'])\ncheck('duplicate rank last wins',solve([(1,'old'),(1,'new'),(0,'a')],2),['a','new'])\ncheck('ignore out of world',solve([(0,'a'),(4,'x')],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":"19ba050de0bd5328321ede949266e0295119d64b159ab2db8769d90a808384fe","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(items, world):\n    return [x[1] for x in items]\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\nit=[(2,'c'),(0,'a'),(1,'b')]\ncheck('arrival shuffled',solve(it,3),['a','b','c'])\ncheck('missing rank',solve([(2,'c'),(0,'a')],3),['a','c'])\ncheck('empty gather',solve([],N),[])\ncheck('singleton',solve([(0,'x')],1),['x'])\ncheck('duplicate rank last wins',solve([(1,'old'),(1,'new'),(0,'a')],2),['a','new'])\ncheck('ignore out of world',solve([(0,'a'),(4,'x')],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-allgather-rank-order","generated_at":"2026-09-30T16:48:22.178632+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":"Asynchronous arrival order differs from the logical rank order expected by consumers.","sha256":"7aa54db62b09850d78a60af3d527fa198c61e3dfa3bb3cbbd8583a6044be8eaa","title":"All-gather output follows arrival order · 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":30.391,"exit_code":1,"observations":[{"actual":["a","b","c"],"check":"arrival shuffled","expected":["a","b","c"],"passed":true},{"actual":["a","c"],"check":"missing rank","expected":["a","c"],"passed":true},{"actual":[],"check":"empty gather","expected":[],"passed":true},{"actual":["x"],"check":"singleton","expected":["x"],"passed":true},{"actual":["a","new","old"],"check":"duplicate rank last wins","expected":["a","new"],"passed":false},{"actual":["a","x"],"check":"ignore out of world","expected":["a"],"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"arrival shuffled\", \"actual\": [\"a\", \"b\", \"c\"], \"expected\": [\"a\", \"b\", \"c\"], \"passed\": true}, {\"check\": \"missing rank\", \"actual\": [\"a\", \"c\"], \"expected\": [\"a\", \"c\"], \"passed\": true}, {\"check\": \"empty gather\", \"actual\": [], \"expected\": [], \"passed\": true}, {\"check\": \"singleton\", \"actual\": [\"x\"], \"expected\": [\"x\"], \"passed\": true}, {\"check\": \"duplicate rank last wins\", \"actual\": [\"a\", \"new\", \"old\"], \"expected\": [\"a\", \"new\"], \"passed\": false}, {\"check\": \"ignore out of world\", \"actual\": [\"a\", \"x\"], \"expected\": [\"a\"], \"passed\": false}], \"passed\": false}\n"},"broken":{"elapsed_ms":30.143,"exit_code":1,"observations":[{"actual":["c","a","b"],"check":"arrival shuffled","expected":["a","b","c"],"passed":false},{"actual":["c","a"],"check":"missing rank","expected":["a","c"],"passed":false},{"actual":[],"check":"empty gather","expected":[],"passed":true},{"actual":["x"],"check":"singleton","expected":["x"],"passed":true},{"actual":["old","new","a"],"check":"duplicate rank last wins","expected":["a","new"],"passed":false},{"actual":["a","x"],"check":"ignore out of world","expected":["a"],"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"arrival shuffled\", \"actual\": [\"c\", \"a\", \"b\"], \"expected\": [\"a\", \"b\", \"c\"], \"passed\": false}, {\"check\": \"missing rank\", \"actual\": [\"c\", \"a\"], \"expected\": [\"a\", \"c\"], \"passed\": false}, {\"check\": \"empty gather\", \"actual\": [], \"expected\": [], \"passed\": true}, {\"check\": \"singleton\", \"actual\": [\"x\"], \"expected\": [\"x\"], \"passed\": true}, {\"check\": \"duplicate rank last wins\", \"actual\": [\"old\", \"new\", \"a\"], \"expected\": [\"a\", \"new\"], \"passed\": false}, {\"check\": \"ignore out of world\", \"actual\": [\"a\", \"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."}}