{"abstract":"Adding both channels retains their overlap during exclusive compositing.","category":"Raster compositing","checks":4,"contract":"Source and destination are premultiplied channel values with corresponding normalized alphas. Return Porter-Duff XOR channel.","evaluation_group":"xg-xor-disjoint-coverage","failed_approach":"Each color is attenuated by its own alpha instead of opposite-layer coverage.","family":"xg-xor-disjoint-coverage","id":"FA-10571","implementations":{"attempt":{"sha256":"65770c43c173c31b53fd5319a228f59636a86989c77fc7c0026e3e3398859a05","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\nimport math\nN = 1\nobservations = []\ndef solve(source, sa, destination, da):\n    return source*(1-sa)+destination*(1-da)\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('fixture 1', solve(*(0.5, 0.5, 0.25, 0.25)), 0.5)\ncheck('fixture 2', solve(*(1, 1, 1, 1)), 0)\ncheck('fixture 3', solve(*(0.25, 0.25, 0, 0)), 0.25)\ncheck('fixture 4', solve(*(0, 0, 0.5, 0.5)), 0.5)\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":"ce8bb15488d4d1379bdf737911ab1b2a4f4ca986a12c0ddaec5bb8e73cd633dc","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\nimport math\nN = 1\nobservations = []\ndef solve(source, sa, destination, da):\n    return source+destination\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('fixture 1', solve(*(0.5, 0.5, 0.25, 0.25)), 0.5)\ncheck('fixture 2', solve(*(1, 1, 1, 1)), 0)\ncheck('fixture 3', solve(*(0.25, 0.25, 0, 0)), 0.25)\ncheck('fixture 4', solve(*(0, 0, 0.5, 0.5)), 0.5)\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"},"fixed":{"sha256":"30f08a2ce013b190ca934f3ac98b644a9e20b51023cbc569c6736b8511bd40bd","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\nimport math\nN = 1\nobservations = []\ndef solve(source, sa, destination, da):\n    return source*(1-da)+destination*(1-sa)\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('fixture 1', solve(*(0.5, 0.5, 0.25, 0.25)), 0.5)\ncheck('fixture 2', solve(*(1, 1, 1, 1)), 0)\ncheck('fixture 3', solve(*(0.25, 0.25, 0, 0)), 0.25)\ncheck('fixture 4', solve(*(0, 0, 0.5, 0.5)), 0.5)\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":" 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":"xg-xor-disjoint-coverage","generated_at":"2026-09-29T14:38:40.243995+00:00","license":"CC0-1.0","python":"3.12.14","seed":1,"split":"open-access"},"relevance":"A deterministic software graphics stage with explicit channel and coordinate conventions; no hardware, device profile or API behavior is inferred.","repair":"Use the stage contract: Source and destination are premultiplied channel values with corresponding normalized alphas. Return Porter-Duff XOR channel.","root_cause":"Adding both channels retains their overlap during exclusive compositing.","sha256":"89473bc3deb4d7e1eaf9fd3e1ce3149a6430c320746fd2417348df01da74d081","title":"Xor disjoint coverage · case 01","variant":1,"variant_policy":"Five numbered records share a model and may reuse boundary fixtures.","verification":{"attempt":{"elapsed_ms":41.282,"exit_code":1,"observations":[{"actual":0.4375,"check":"fixture 1","expected":0.5,"passed":false},{"actual":0,"check":"fixture 2","expected":0,"passed":true},{"actual":0.1875,"check":"fixture 3","expected":0.25,"passed":false},{"actual":0.25,"check":"fixture 4","expected":0.5,"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"fixture 1\", \"actual\": 0.4375, \"expected\": 0.5, \"passed\": false}, {\"check\": \"fixture 2\", \"actual\": 0, \"expected\": 0, \"passed\": true}, {\"check\": \"fixture 3\", \"actual\": 0.1875, \"expected\": 0.25, \"passed\": false}, {\"check\": \"fixture 4\", \"actual\": 0.25, \"expected\": 0.5, \"passed\": false}], \"passed\": false}\n"},"broken":{"elapsed_ms":41.196,"exit_code":1,"observations":[{"actual":0.75,"check":"fixture 1","expected":0.5,"passed":false},{"actual":2,"check":"fixture 2","expected":0,"passed":false},{"actual":0.25,"check":"fixture 3","expected":0.25,"passed":true},{"actual":0.5,"check":"fixture 4","expected":0.5,"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"fixture 1\", \"actual\": 0.75, \"expected\": 0.5, \"passed\": false}, {\"check\": \"fixture 2\", \"actual\": 2, \"expected\": 0, \"passed\": false}, {\"check\": \"fixture 3\", \"actual\": 0.25, \"expected\": 0.25, \"passed\": true}, {\"check\": \"fixture 4\", \"actual\": 0.5, \"expected\": 0.5, \"passed\": true}], \"passed\": false}\n"},"fixed":{"elapsed_ms":40.58,"exit_code":0,"observations":[{"actual":0.5,"check":"fixture 1","expected":0.5,"passed":true},{"actual":0,"check":"fixture 2","expected":0,"passed":true},{"actual":0.25,"check":"fixture 3","expected":0.25,"passed":true},{"actual":0.5,"check":"fixture 4","expected":0.5,"passed":true}],"passed":true,"stderr":"","stdout":"{\"observations\": [{\"check\": \"fixture 1\", \"actual\": 0.5, \"expected\": 0.5, \"passed\": true}, {\"check\": \"fixture 2\", \"actual\": 0, \"expected\": 0, \"passed\": true}, {\"check\": \"fixture 3\", \"actual\": 0.25, \"expected\": 0.25, \"passed\": true}, {\"check\": \"fixture 4\", \"actual\": 0.5, \"expected\": 0.5, \"passed\": true}], \"passed\": true}\n"}},"verified":true,"visibility":"public"}