{"abstract":"Round-robin packing consumes one source unevenly.","category":"Sequence batch packing","checks":6,"contract":"Interleave source token lists one token per source per pass, skipping exhausted sources, until all are empty.","contract_signature":"streams","evaluation_group":"w3-seqpack-round-robin-v1","failed_approach":"The attempted bound skips the last token in every stream.","family":"w3-sequence-batch-packing-round-robin-interleave","id":"FA-98106","implementations":{"attempt":{"sha256":"626940ed990ab96bb98fd97b368ece32a80fd48bb637ba5daf4523159d9843e6","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(streams):\n    return [stream[i] for i in range(max(map(len,streams),default=0)) for stream in streams if len(stream)>i+1]\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\na=[N,10*N]; b=[2*N]\ncheck('alternating', solve([a,b]), [N,2*N,10*N])\ncheck('empty sources', solve([[],[]]), [])\ncheck('single source', solve([[N]]), [N])\ncheck('uneven tails', solve([[1,2,3],[4]]), [1,4,2,3])\ncheck('three sources', solve([[1],[2,3],[4]]), [1,2,4,3])\ncheck('no sources', solve([]), [])\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":"95bfddee02d9e1a931c9d5aa3dd4d0044379598ab2f6c3b822d960a7842ad0b8","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(streams):\n    return [x for stream in streams for x in stream]\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\na=[N,10*N]; b=[2*N]\ncheck('alternating', solve([a,b]), [N,2*N,10*N])\ncheck('empty sources', solve([[],[]]), [])\ncheck('single source', solve([[N]]), [N])\ncheck('uneven tails', solve([[1,2,3],[4]]), [1,4,2,3])\ncheck('three sources', solve([[1],[2,3],[4]]), [1,2,4,3])\ncheck('no sources', solve([]), [])\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 short integer-token lists under the stated toy contract; results do not claim compatibility with a specific training framework. 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-sequence-batch-packing-round-robin-interleave","generated_at":"2026-09-30T16:48:09.321964+00:00","license":"CC0-1.0","python":"3.12.14","seed":1,"split":"open-access"},"relevance":"This deterministic toy packing rule models a common boundary in preparing bounded training sequences.","root_cause":"Flattening drains one stream completely before visiting the next.","sha256":"6608f30c0d9bba5afdb291281c30da9dfff4793ace742868a36674b2c49e85f7","title":"Round-robin packing consumes one source unevenly · 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":28.328,"exit_code":1,"observations":[{"actual":[1],"check":"alternating","expected":[1,2,10],"passed":false},{"actual":[],"check":"empty sources","expected":[],"passed":true},{"actual":[],"check":"single source","expected":[1],"passed":false},{"actual":[1,2],"check":"uneven tails","expected":[1,4,2,3],"passed":false},{"actual":[2],"check":"three sources","expected":[1,2,4,3],"passed":false},{"actual":[],"check":"no sources","expected":[],"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"alternating\", \"actual\": [1], \"expected\": [1, 2, 10], \"passed\": false}, {\"check\": \"empty sources\", \"actual\": [], \"expected\": [], \"passed\": true}, {\"check\": \"single source\", \"actual\": [], \"expected\": [1], \"passed\": false}, {\"check\": \"uneven tails\", \"actual\": [1, 2], \"expected\": [1, 4, 2, 3], \"passed\": false}, {\"check\": \"three sources\", \"actual\": [2], \"expected\": [1, 2, 4, 3], \"passed\": false}, {\"check\": \"no sources\", \"actual\": [], \"expected\": [], \"passed\": true}], \"passed\": false}\n"},"broken":{"elapsed_ms":26.654,"exit_code":1,"observations":[{"actual":[1,10,2],"check":"alternating","expected":[1,2,10],"passed":false},{"actual":[],"check":"empty sources","expected":[],"passed":true},{"actual":[1],"check":"single source","expected":[1],"passed":true},{"actual":[1,2,3,4],"check":"uneven tails","expected":[1,4,2,3],"passed":false},{"actual":[1,2,3,4],"check":"three sources","expected":[1,2,4,3],"passed":false},{"actual":[],"check":"no sources","expected":[],"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"alternating\", \"actual\": [1, 10, 2], \"expected\": [1, 2, 10], \"passed\": false}, {\"check\": \"empty sources\", \"actual\": [], \"expected\": [], \"passed\": true}, {\"check\": \"single source\", \"actual\": [1], \"expected\": [1], \"passed\": true}, {\"check\": \"uneven tails\", \"actual\": [1, 2, 3, 4], \"expected\": [1, 4, 2, 3], \"passed\": false}, {\"check\": \"three sources\", \"actual\": [1, 2, 3, 4], \"expected\": [1, 2, 4, 3], \"passed\": false}, {\"check\": \"no sources\", \"actual\": [], \"expected\": [], \"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."}}