{"abstract":"Negative midpoint rounding is asymmetric.","category":"Model quantization arithmetic","checks":6,"contract":"Round each signed scalar to nearest integer with ties to even; values may be positive or negative. Inputs follow this explicit integer toy contract; ties use Python round-to-even where rounding is required.","contract_signature":"values","evaluation_group":"quant-rounding","failed_approach":"The attempted code adds a positive half before truncating, which shifts negative midpoints toward zero.","family":"w3-model-quantization-arithmetic-negative-midpoint","id":"FA-98666","implementations":{"attempt":{"sha256":"d63375e772ccbc5f4a11a619e3c4f69832abfacd9e85446dec4c7068ec353875","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(values):\n    return [int(x+0.5) for x in values]\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('negative odd tie',solve([-2.5]),[-2])\ncheck('negative even tie',solve([-3.5]),[-4])\ncheck('positive tie',solve([2.5]),[2])\ncheck('empty',solve([]),[])\ncheck('negative near tie',solve([-2.4]),[-2])\ncheck('negative below',solve([-2.6]),[-3])\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":"29661310fed926104e7829ae26f44852f1cbaa065edc7ec69d808d347718ae35","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(values):\n    return [int(x) for x in values]\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('negative odd tie',solve([-2.5]),[-2])\ncheck('negative even tie',solve([-3.5]),[-4])\ncheck('positive tie',solve([2.5]),[2])\ncheck('empty',solve([]),[])\ncheck('negative near tie',solve([-2.4]),[-2])\ncheck('negative below',solve([-2.6]),[-3])\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":"Toy scalar/list arithmetic only; it does not model a production quantizer, hardware instruction, or accuracy/performance gain. 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-model-quantization-arithmetic-negative-midpoint","generated_at":"2026-09-30T16:48:15.404403+00:00","license":"CC0-1.0","python":"3.12.14","seed":1,"split":"open-access"},"relevance":"This deterministic model isolates one quantization arithmetic contract from tensor storage and runtime kernels.","root_cause":"Round each signed scalar to nearest integer with ties to even; values may be positive or negative.","sha256":"ebb796e7f218a0c4b3617cbff8ec5427a8dbd26449836e9d29899d30ec08437a","title":"Quantization: Negative midpoint rounding is asymmetric · 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":29.593,"exit_code":1,"observations":[{"actual":[-2],"check":"negative odd tie","expected":[-2],"passed":true},{"actual":[-3],"check":"negative even tie","expected":[-4],"passed":false},{"actual":[3],"check":"positive tie","expected":[2],"passed":false},{"actual":[],"check":"empty","expected":[],"passed":true},{"actual":[-1],"check":"negative near tie","expected":[-2],"passed":false},{"actual":[-2],"check":"negative below","expected":[-3],"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"negative odd tie\", \"actual\": [-2], \"expected\": [-2], \"passed\": true}, {\"check\": \"negative even tie\", \"actual\": [-3], \"expected\": [-4], \"passed\": false}, {\"check\": \"positive tie\", \"actual\": [3], \"expected\": [2], \"passed\": false}, {\"check\": \"empty\", \"actual\": [], \"expected\": [], \"passed\": true}, {\"check\": \"negative near tie\", \"actual\": [-1], \"expected\": [-2], \"passed\": false}, {\"check\": \"negative below\", \"actual\": [-2], \"expected\": [-3], \"passed\": false}], \"passed\": false}\n"},"broken":{"elapsed_ms":26.994,"exit_code":1,"observations":[{"actual":[-2],"check":"negative odd tie","expected":[-2],"passed":true},{"actual":[-3],"check":"negative even tie","expected":[-4],"passed":false},{"actual":[2],"check":"positive tie","expected":[2],"passed":true},{"actual":[],"check":"empty","expected":[],"passed":true},{"actual":[-2],"check":"negative near tie","expected":[-2],"passed":true},{"actual":[-2],"check":"negative below","expected":[-3],"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"negative odd tie\", \"actual\": [-2], \"expected\": [-2], \"passed\": true}, {\"check\": \"negative even tie\", \"actual\": [-3], \"expected\": [-4], \"passed\": false}, {\"check\": \"positive tie\", \"actual\": [2], \"expected\": [2], \"passed\": true}, {\"check\": \"empty\", \"actual\": [], \"expected\": [], \"passed\": true}, {\"check\": \"negative near tie\", \"actual\": [-2], \"expected\": [-2], \"passed\": true}, {\"check\": \"negative below\", \"actual\": [-2], \"expected\": [-3], \"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."}}