{"abstract":"exact multiples emit an empty trailing block.","category":"Dataset split isolation","checks":6,"contract":"For n items and positive width w, return [start,end) blocks covering each index once.","contract_signature":"n, width","evaluation_group":"ds-block-boundary","failed_approach":"Reducing each block end by one avoids the empty block but leaves uncovered indices.","family":"w3-dataset-split-isolation-block-boundary-ownership","id":"FA-97916","implementations":{"attempt":{"sha256":"04f73418868dd9be734f53e75864405ae027db38235fcf54a115ea7397e91bcb","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(n, width):\n    return [[s,min(n,s+width-1)] for s in range(0,n,width)]\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('tail block',solve(5,3),[[0,3],[3,5]])\ncheck('exact multiple',solve(6,3),[[0,3],[3,6]])\ncheck('singleton',solve(1,N),[[0,1]])\ncheck('empty sequence',solve(0,N),[])\ncheck('width one',solve(3,1),[[0,1],[1,2],[2,3]])\ncheck('shorter than width',solve(2,4),[[0,2]])\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":"e627eedf6c33896406c8ce6f11b0d6ac0f02ba6fadf56fa5e1cd42214871e6e2","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(n, width):\n    return [[s,min(n,s+width)] for s in range(0,n+1,width)]\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('tail block',solve(5,3),[[0,3],[3,5]])\ncheck('exact multiple',solve(6,3),[[0,3],[3,6]])\ncheck('singleton',solve(1,N),[[0,1]])\ncheck('empty sequence',solve(0,N),[])\ncheck('width one',solve(3,1),[[0,1],[1,2],[2,3]])\ncheck('shorter than width',solve(2,4),[[0,2]])\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 small in-memory records with self-contained contracts; no claim is made about production sampling quality. 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-dataset-split-isolation-block-boundary-ownership","generated_at":"2026-09-30T16:48:07.117292+00:00","license":"CC0-1.0","python":"3.12.14","seed":1,"split":"open-access"},"relevance":"This toy split allocator makes membership rules explicit for reproducible evaluation fixtures.","root_cause":"The range includes a start at n when n is exactly divisible by width, creating a zero-length block.","sha256":"321458e15848b1d857bcf6b77e0c28eb84b5d07858962a7e43f905f22487e1d8","title":"Dataset split: exact multiples emit an empty trailing block · 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":27.012,"exit_code":1,"observations":[{"actual":[[0,2],[3,5]],"check":"tail block","expected":[[0,3],[3,5]],"passed":false},{"actual":[[0,2],[3,5]],"check":"exact multiple","expected":[[0,3],[3,6]],"passed":false},{"actual":[[0,0]],"check":"singleton","expected":[[0,1]],"passed":false},{"actual":[],"check":"empty sequence","expected":[],"passed":true},{"actual":[[0,0],[1,1],[2,2]],"check":"width one","expected":[[0,1],[1,2],[2,3]],"passed":false},{"actual":[[0,2]],"check":"shorter than width","expected":[[0,2]],"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"tail block\", \"actual\": [[0, 2], [3, 5]], \"expected\": [[0, 3], [3, 5]], \"passed\": false}, {\"check\": \"exact multiple\", \"actual\": [[0, 2], [3, 5]], \"expected\": [[0, 3], [3, 6]], \"passed\": false}, {\"check\": \"singleton\", \"actual\": [[0, 0]], \"expected\": [[0, 1]], \"passed\": false}, {\"check\": \"empty sequence\", \"actual\": [], \"expected\": [], \"passed\": true}, {\"check\": \"width one\", \"actual\": [[0, 0], [1, 1], [2, 2]], \"expected\": [[0, 1], [1, 2], [2, 3]], \"passed\": false}, {\"check\": \"shorter than width\", \"actual\": [[0, 2]], \"expected\": [[0, 2]], \"passed\": true}], \"passed\": false}\n"},"broken":{"elapsed_ms":26.722,"exit_code":1,"observations":[{"actual":[[0,3],[3,5]],"check":"tail block","expected":[[0,3],[3,5]],"passed":true},{"actual":[[0,3],[3,6],[6,6]],"check":"exact multiple","expected":[[0,3],[3,6]],"passed":false},{"actual":[[0,1],[1,1]],"check":"singleton","expected":[[0,1]],"passed":false},{"actual":[[0,0]],"check":"empty sequence","expected":[],"passed":false},{"actual":[[0,1],[1,2],[2,3],[3,3]],"check":"width one","expected":[[0,1],[1,2],[2,3]],"passed":false},{"actual":[[0,2]],"check":"shorter than width","expected":[[0,2]],"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"tail block\", \"actual\": [[0, 3], [3, 5]], \"expected\": [[0, 3], [3, 5]], \"passed\": true}, {\"check\": \"exact multiple\", \"actual\": [[0, 3], [3, 6], [6, 6]], \"expected\": [[0, 3], [3, 6]], \"passed\": false}, {\"check\": \"singleton\", \"actual\": [[0, 1], [1, 1]], \"expected\": [[0, 1]], \"passed\": false}, {\"check\": \"empty sequence\", \"actual\": [[0, 0]], \"expected\": [], \"passed\": false}, {\"check\": \"width one\", \"actual\": [[0, 1], [1, 2], [2, 3], [3, 3]], \"expected\": [[0, 1], [1, 2], [2, 3]], \"passed\": false}, {\"check\": \"shorter than width\", \"actual\": [[0, 2]], \"expected\": [[0, 2]], \"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."}}