{"abstract":"arrival order changes reconstructed shard order.","category":"Checkpoint tensor mapping","checks":6,"contract":"Shards are [index, values]; concatenate values in ascending index order. Indices are unique.","contract_signature":"shards","evaluation_group":"w3-checkpoint-tensor-mapping-shard-concat","failed_approach":"Sorting by payload length does not recover shard identity.","family":"w3-checkpoint-tensor-mapping-shard-concat","id":"FA-99156","implementations":{"attempt":{"sha256":"cfd9e51bd76f44418cfa9cd341a8b87ee99d7ad30369a9c161d1bcfc3d9e672a","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(shards):\n    return sum((v for i,v in sorted(shards, key=lambda x: len(x[1]))), [])\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('reverse', solve(*([[1, [3]], [0, [0]]],)), [0, 3])\ncheck('three', solve(*([[2, [2]], [0, [0]], [1, [1]]],)), [0, 1, 2])\ncheck('single', solve(*([[0, [3]]],)), [3])\ncheck('empty', solve(*([],)), [])\ncheck('unequal', solve(*([[1, [8, 9]], [0, [6]]],)), [6, 8, 9])\ncheck('zero value', solve(*([[1, [0]], [0, [3]]],)), [3, 0])\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":"592d7f12c7688282a03c94d2fba7d61b7469e57ac320f089e3309c31639c40ea","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(shards):\n    return sum((v for i,v in shards), [])\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('reverse', solve(*([[1, [3]], [0, [0]]],)), [0, 3])\ncheck('three', solve(*([[2, [2]], [0, [0]], [1, [1]]],)), [0, 1, 2])\ncheck('single', solve(*([[0, [3]]],)), [3])\ncheck('empty', solve(*([],)), [])\ncheck('unequal', solve(*([[1, [8, 9]], [0, [6]]],)), [6, 8, 9])\ncheck('zero value', solve(*([[1, [0]], [0, [3]]],)), [3, 0])\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 decoded Python values; this toy contract makes no claim about a framework, file format, or production checkpoint. 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-checkpoint-tensor-mapping-shard-concat","generated_at":"2026-09-30T16:48:20.799687+00:00","license":"CC0-1.0","python":"3.12.14","seed":1,"split":"open-access"},"relevance":"A bounded offline model of checkpoint tensor bookkeeping in a training workflow.","root_cause":"Arrival order is mistaken for the declared shard order.","sha256":"054ac08ca9a060347944a8d4a70269461e5b793040027d0a3579cf5ce666653d","title":"Checkpoint mapping: arrival order changes reconstructed shard order · 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":26.9,"exit_code":1,"observations":[{"actual":[3,0],"check":"reverse","expected":[0,3],"passed":false},{"actual":[2,0,1],"check":"three","expected":[0,1,2],"passed":false},{"actual":[3],"check":"single","expected":[3],"passed":true},{"actual":[],"check":"empty","expected":[],"passed":true},{"actual":[6,8,9],"check":"unequal","expected":[6,8,9],"passed":true},{"actual":[0,3],"check":"zero value","expected":[3,0],"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"reverse\", \"actual\": [3, 0], \"expected\": [0, 3], \"passed\": false}, {\"check\": \"three\", \"actual\": [2, 0, 1], \"expected\": [0, 1, 2], \"passed\": false}, {\"check\": \"single\", \"actual\": [3], \"expected\": [3], \"passed\": true}, {\"check\": \"empty\", \"actual\": [], \"expected\": [], \"passed\": true}, {\"check\": \"unequal\", \"actual\": [6, 8, 9], \"expected\": [6, 8, 9], \"passed\": true}, {\"check\": \"zero value\", \"actual\": [0, 3], \"expected\": [3, 0], \"passed\": false}], \"passed\": false}\n"},"broken":{"elapsed_ms":28.251,"exit_code":1,"observations":[{"actual":[3,0],"check":"reverse","expected":[0,3],"passed":false},{"actual":[2,0,1],"check":"three","expected":[0,1,2],"passed":false},{"actual":[3],"check":"single","expected":[3],"passed":true},{"actual":[],"check":"empty","expected":[],"passed":true},{"actual":[8,9,6],"check":"unequal","expected":[6,8,9],"passed":false},{"actual":[0,3],"check":"zero value","expected":[3,0],"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"reverse\", \"actual\": [3, 0], \"expected\": [0, 3], \"passed\": false}, {\"check\": \"three\", \"actual\": [2, 0, 1], \"expected\": [0, 1, 2], \"passed\": false}, {\"check\": \"single\", \"actual\": [3], \"expected\": [3], \"passed\": true}, {\"check\": \"empty\", \"actual\": [], \"expected\": [], \"passed\": true}, {\"check\": \"unequal\", \"actual\": [8, 9, 6], \"expected\": [6, 8, 9], \"passed\": false}, {\"check\": \"zero value\", \"actual\": [0, 3], \"expected\": [3, 0], \"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."}}