{"abstract":"Coordinate descent sweep reads stale coordinates.","category":"Optimization solver contracts","checks":6,"contract":"For f=(x-a)^2+(y-b)^2+(x-y)^2 perform one exact x-then-y sweep; return [x,y].","contract_signature":"x, y, a, b","evaluation_group":"model-0c0d174bdde36f22","failed_approach":"Reversing the update order changes the specified sweep.","family":"z-optimization-coordinate-sweep","id":"FA-12031","implementations":{"attempt":{"sha256":"e2f011039b898982ea51129b2318cea8eb143ccafc6bac7a519c9d9a188d748e","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(x, y, a, b):\n    new_y=(b+x)/2\n    return [(a+new_y)/2,new_y]\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('coupling', solve(0, 0, 4*N, 0), [2*N,N])\ncheck('shifted target', solve(0, 0, 0, 4*N), [0,2*N])\ncheck('initial x discarded', solve(9*N, 0, 0, 0), [0,0])\ncheck('initial y retained', solve(0, 4*N, 0, 0), [2*N,N])\ncheck('fixed point', solve(N,N,N,N), [N,N])\ncheck('signed targets', solve(0,0,-4*N,4*N), [-2*N,N])\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":"552b0e088276c7d0a00c46e424490b3bf3917825842a2140895f3dc10996ede9","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(x, y, a, b):\n    return [(a+y)/2,(b+x)/2]\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('coupling', solve(0, 0, 4*N, 0), [2*N,N])\ncheck('shifted target', solve(0, 0, 0, 4*N), [0,2*N])\ncheck('initial x discarded', solve(9*N, 0, 0, 0), [0,0])\ncheck('initial y retained', solve(0, 4*N, 0, 0), [2*N,N])\ncheck('fixed point', solve(N,N,N,N), [N,N])\ncheck('signed targets', solve(0,0,-4*N,4*N), [-2*N,N])\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":"Controlled finite inputs and explicit one-step contracts; this is not a production solver or a numerical stability benchmark. 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":"z-optimization-coordinate-sweep","generated_at":"2026-09-29T14:38:53.109790+00:00","license":"CC0-1.0","python":"3.12.14","seed":1,"split":"open-access"},"relevance":"This deterministic solver-step model isolates an algorithmic invariant used by iterative optimization implementations.","root_cause":"Both exact coordinate minimizers read the initial state.","sha256":"79d53fdf42349689cda0704bf88fe2de07b4a560e433e40f2be5c0ee25d3528d","title":"Coordinate descent sweep reads stale coordinates · case 01","variant":1,"variant_policy":"Five numbered records share a model and may reuse boundary fixtures.","verified":true,"visibility":"public","verification":{"attempt":{"elapsed_ms":39.759,"exit_code":1,"observations":[{"actual":[2.0,0.0],"check":"coupling","expected":[2,1],"passed":false},{"actual":[1.0,2.0],"check":"shifted target","expected":[0,2],"passed":false},{"actual":[2.25,4.5],"check":"initial x discarded","expected":[0,0],"passed":false},{"actual":[0.0,0.0],"check":"initial y retained","expected":[2,1],"passed":false},{"actual":[1.0,1.0],"check":"fixed point","expected":[1,1],"passed":true},{"actual":[-1.0,2.0],"check":"signed targets","expected":[-2,1],"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"coupling\", \"actual\": [2.0, 0.0], \"expected\": [2, 1], \"passed\": false}, {\"check\": \"shifted target\", \"actual\": [1.0, 2.0], \"expected\": [0, 2], \"passed\": false}, {\"check\": \"initial x discarded\", \"actual\": [2.25, 4.5], \"expected\": [0, 0], \"passed\": false}, {\"check\": \"initial y retained\", \"actual\": [0.0, 0.0], \"expected\": [2, 1], \"passed\": false}, {\"check\": \"fixed point\", \"actual\": [1.0, 1.0], \"expected\": [1, 1], \"passed\": true}, {\"check\": \"signed targets\", \"actual\": [-1.0, 2.0], \"expected\": [-2, 1], \"passed\": false}], \"passed\": false}\n"},"broken":{"elapsed_ms":40.774,"exit_code":1,"observations":[{"actual":[2.0,0.0],"check":"coupling","expected":[2,1],"passed":false},{"actual":[0.0,2.0],"check":"shifted target","expected":[0,2],"passed":true},{"actual":[0.0,4.5],"check":"initial x discarded","expected":[0,0],"passed":false},{"actual":[2.0,0.0],"check":"initial y retained","expected":[2,1],"passed":false},{"actual":[1.0,1.0],"check":"fixed point","expected":[1,1],"passed":true},{"actual":[-2.0,2.0],"check":"signed targets","expected":[-2,1],"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"coupling\", \"actual\": [2.0, 0.0], \"expected\": [2, 1], \"passed\": false}, {\"check\": \"shifted target\", \"actual\": [0.0, 2.0], \"expected\": [0, 2], \"passed\": true}, {\"check\": \"initial x discarded\", \"actual\": [0.0, 4.5], \"expected\": [0, 0], \"passed\": false}, {\"check\": \"initial y retained\", \"actual\": [2.0, 0.0], \"expected\": [2, 1], \"passed\": false}, {\"check\": \"fixed point\", \"actual\": [1.0, 1.0], \"expected\": [1, 1], \"passed\": true}, {\"check\": \"signed targets\", \"actual\": [-2.0, 2.0], \"expected\": [-2, 1], \"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."}}