{"abstract":"An upside-down tube reads -180 instead of 180.","category":"Solar tracker geometry","checks":7,"contract":"ax (across-axis) and az (normal) are gravity components in g. The magnitude must be within [0.8, 1.2] g, else [None, 'fault']. Rotation = atan2(ax, az) in degrees, negated for a sensor mounted on the west side, then minus the calibration offset, normalised to (-180, 180]. Return [angle rounded 2, 'ok'].","contract_signature":"ax, az, mount, offset","evaluation_group":"w2-solar_tracker_geometry-inclinometer-rotation","failed_approach":"Remapping everything below -179 corrupts valid angles near the flip.","family":"w2-solar_tracker_geometry-inclinometer-rotation-half-turn-canonical-value","id":"FA-93616","implementations":{"attempt":{"sha256":"b6838cc36d292bf4393403677ab4f974e9908004ac206130d88df3e017c659a8","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\nimport math\nN = 1\nobservations = []\ndef solve(ax, az, mount, offset):\n    mag = math.hypot(ax, az)\n    if not 0.8 <= mag <= 1.2:\n        return [None, 'fault']\n    ang = math.degrees(math.atan2(ax, az))\n    if mount == 'west':\n        ang = -ang\n    ang -= offset\n    ang = (ang + 180) % 360 - 180\n    if ang < -179:\n        ang = 180.0\n    return [round(ang, 2), 'ok']\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\nfixtures = [[['boundary: magnitude at lower bound', [0.0, 0.8, 'east', 0], [0.0, 'ok']],\n  ['boundary: magnitude at upper bound', [1.2, 0.0, 'east', 0], [90.0, 'ok']],\n  ['boundary: upside-down reading', [0.0, -1.0, 'east', 0], [180.0, 'ok']],\n  ['regression: angle just inside the flip', [-0.0175, -0.9998, 'east', 0.5], [-179.5, 'ok']],\n  ['regression: half-turn canonical value', [0.0, -1.1, 'east', 0], [180.0, 'ok']],\n  ['control 1', [-1.1, 0.0, 'west', 0], [90.0, 'ok']],\n  ['control 2', [-0.4, 0.6928, 'east', 0], [None, 'fault']]],\n [['boundary: magnitude at lower bound', [0.0, 0.8, 'east', 0], [0.0, 'ok']],\n  ['boundary: magnitude at upper bound', [1.2, 0.0, 'east', 0], [90.0, 'ok']],\n  ['boundary: upside-down reading', [0.0, -1.0, 'east', 0], [180.0, 'ok']],\n  ['regression: angle just inside the flip', [-0.0175, -0.9998, 'east', 0.5], [-179.5, 'ok']],\n  ['regression: half-turn canonical value', [0.0, -0.8, 'west', 0], [180.0, 'ok']],\n  ['control 1', [-0.7778, 0.7778, 'east', 0], [-45.0, 'ok']],\n  ['control 2', [0.5657, -0.5657, 'west', 2], [-137.0, 'ok']]],\n [['boundary: magnitude at lower bound', [0.0, 0.8, 'east', 0], [0.0, 'ok']],\n  ['boundary: magnitude at upper bound', [1.2, 0.0, 'east', 0], [90.0, 'ok']],\n  ['boundary: upside-down reading', [0.0, -1.0, 'east', 0], [180.0, 'ok']],\n  ['regression: angle just inside the flip', [-0.0175, -0.9998, 'east', 0.5], [-179.5, 'ok']],\n  ['regression: half-turn canonical value', [0.0, -0.8, 'west', 0], [180.0, 'ok']],\n  ['control 1', [0.25, 0.433, 'west', 2], [None, 'fault']],\n  ['control 2', [0.8485, -0.8485, 'west', -3], [-132.0, 'ok']]],\n [['boundary: magnitude at lower bound', [0.0, 0.8, 'east', 0], [0.0, 'ok']],\n  ['boundary: magnitude at upper bound', [1.2, 0.0, 'east', 0], [90.0, 'ok']],\n  ['boundary: upside-down reading', [0.0, -1.0, 'east', 0], [180.0, 'ok']],\n  ['regression: angle just inside the flip', [-0.0175, -0.9998, 'east', 0.5], [-179.5, 'ok']],\n  ['regression: half-turn canonical value', [0.0, -1.0, 'west', 0], [180.0, 'ok']],\n  ['control 1', [0.5657, -0.5657, 'east', -3], [138.0, 'ok']],\n  ['control 2', [-0.6, 1.0392, 'east', 0], [-30.0, 'ok']]],\n [['boundary: magnitude at lower bound', [0.0, 0.8, 'east', 0], [0.0, 'ok']],\n  ['boundary: magnitude at upper bound', [1.2, 0.0, 'east', 0], [90.0, 'ok']],\n  ['boundary: upside-down reading', [0.0, -1.0, 'east', 0], [180.0, 'ok']],\n  ['regression: angle just inside the flip', [-0.0175, -0.9998, 'east', 0.5], [-179.5, 'ok']],\n  ['regression: half-turn canonical value', [0.0, -1.1, 'east', 0], [180.0, 'ok']],\n  ['control 1', [0.6928, 0.4, 'east', 5], [None, 'fault']],\n  ['control 2', [-0.55, 0.9526, 'east', 2], [-32.0, 'ok']]]]\nfor label, args, expected in fixtures[N-1]:\n    check(label, solve(*args), expected)\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":"9fa3efbded14319d8d3141a7e83943f0a4053fc0d8b34bdcc3e06bdaaa0ea0c4","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\nimport math\nN = 1\nobservations = []\ndef solve(ax, az, mount, offset):\n    mag = math.hypot(ax, az)\n    if not 0.8 <= mag <= 1.2:\n        return [None, 'fault']\n    ang = math.degrees(math.atan2(ax, az))\n    if mount == 'west':\n        ang = -ang\n    ang -= offset\n    ang = (ang + 180) % 360 - 180\n    return [round(ang, 2), 'ok']\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\nfixtures = [[['boundary: magnitude at lower bound', [0.0, 0.8, 'east', 0], [0.0, 'ok']],\n  ['boundary: magnitude at upper bound', [1.2, 0.0, 'east', 0], [90.0, 'ok']],\n  ['boundary: upside-down reading', [0.0, -1.0, 'east', 0], [180.0, 'ok']],\n  ['regression: angle just inside the flip', [-0.0175, -0.9998, 'east', 0.5], [-179.5, 'ok']],\n  ['regression: half-turn canonical value', [0.0, -1.1, 'east', 0], [180.0, 'ok']],\n  ['control 1', [-1.1, 0.0, 'west', 0], [90.0, 'ok']],\n  ['control 2', [-0.4, 0.6928, 'east', 0], [None, 'fault']]],\n [['boundary: magnitude at lower bound', [0.0, 0.8, 'east', 0], [0.0, 'ok']],\n  ['boundary: magnitude at upper bound', [1.2, 0.0, 'east', 0], [90.0, 'ok']],\n  ['boundary: upside-down reading', [0.0, -1.0, 'east', 0], [180.0, 'ok']],\n  ['regression: angle just inside the flip', [-0.0175, -0.9998, 'east', 0.5], [-179.5, 'ok']],\n  ['regression: half-turn canonical value', [0.0, -0.8, 'west', 0], [180.0, 'ok']],\n  ['control 1', [-0.7778, 0.7778, 'east', 0], [-45.0, 'ok']],\n  ['control 2', [0.5657, -0.5657, 'west', 2], [-137.0, 'ok']]],\n [['boundary: magnitude at lower bound', [0.0, 0.8, 'east', 0], [0.0, 'ok']],\n  ['boundary: magnitude at upper bound', [1.2, 0.0, 'east', 0], [90.0, 'ok']],\n  ['boundary: upside-down reading', [0.0, -1.0, 'east', 0], [180.0, 'ok']],\n  ['regression: angle just inside the flip', [-0.0175, -0.9998, 'east', 0.5], [-179.5, 'ok']],\n  ['regression: half-turn canonical value', [0.0, -0.8, 'west', 0], [180.0, 'ok']],\n  ['control 1', [0.25, 0.433, 'west', 2], [None, 'fault']],\n  ['control 2', [0.8485, -0.8485, 'west', -3], [-132.0, 'ok']]],\n [['boundary: magnitude at lower bound', [0.0, 0.8, 'east', 0], [0.0, 'ok']],\n  ['boundary: magnitude at upper bound', [1.2, 0.0, 'east', 0], [90.0, 'ok']],\n  ['boundary: upside-down reading', [0.0, -1.0, 'east', 0], [180.0, 'ok']],\n  ['regression: angle just inside the flip', [-0.0175, -0.9998, 'east', 0.5], [-179.5, 'ok']],\n  ['regression: half-turn canonical value', [0.0, -1.0, 'west', 0], [180.0, 'ok']],\n  ['control 1', [0.5657, -0.5657, 'east', -3], [138.0, 'ok']],\n  ['control 2', [-0.6, 1.0392, 'east', 0], [-30.0, 'ok']]],\n [['boundary: magnitude at lower bound', [0.0, 0.8, 'east', 0], [0.0, 'ok']],\n  ['boundary: magnitude at upper bound', [1.2, 0.0, 'east', 0], [90.0, 'ok']],\n  ['boundary: upside-down reading', [0.0, -1.0, 'east', 0], [180.0, 'ok']],\n  ['regression: angle just inside the flip', [-0.0175, -0.9998, 'east', 0.5], [-179.5, 'ok']],\n  ['regression: half-turn canonical value', [0.0, -1.1, 'east', 0], [180.0, 'ok']],\n  ['control 1', [0.6928, 0.4, 'east', 5], [None, 'fault']],\n  ['control 2', [-0.55, 0.9526, 'east', 2], [-32.0, 'ok']]]]\nfor label, args, expected in fixtures[N-1]:\n    check(label, solve(*args), expected)\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":"Deterministic stipulated toy contract for teaching; no claim of conformance with any standard, vendor protocol or production controller. 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":"w2-solar_tracker_geometry-inclinometer-rotation-half-turn-canonical-value","generated_at":"2026-09-29T14:51:56.829362+00:00","license":"CC0-1.0","python":"3.12.14","seed":1,"split":"open-access"},"relevance":"Single-axis and dual-axis solar trackers turn a sun direction into actuator commands; a sign, frame or limit mistake points a whole plant away from the sun or into a mechanical stop.","root_cause":"The -180 representation is not canonicalised.","sha256":"b16cc67bc7380072ee07989e91d5e9600e8239ead82bd25eaabfb3622e5680c1","title":"Torque-tube inclinometer rotation: half-turn canonical value · 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":41.521,"exit_code":1,"observations":[{"actual":[0.0,"ok"],"check":"boundary: magnitude at lower bound","expected":[0.0,"ok"],"passed":true},{"actual":[90.0,"ok"],"check":"boundary: magnitude at upper bound","expected":[90.0,"ok"],"passed":true},{"actual":[180.0,"ok"],"check":"boundary: upside-down reading","expected":[180.0,"ok"],"passed":true},{"actual":[180.0,"ok"],"check":"regression: angle just inside the flip","expected":[-179.5,"ok"],"passed":false},{"actual":[180.0,"ok"],"check":"regression: half-turn canonical value","expected":[180.0,"ok"],"passed":true},{"actual":[90.0,"ok"],"check":"control 1","expected":[90.0,"ok"],"passed":true},{"actual":[null,"fault"],"check":"control 2","expected":[null,"fault"],"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"boundary: magnitude at lower bound\", \"actual\": [0.0, \"ok\"], \"expected\": [0.0, \"ok\"], \"passed\": true}, {\"check\": \"boundary: magnitude at upper bound\", \"actual\": [90.0, \"ok\"], \"expected\": [90.0, \"ok\"], \"passed\": true}, {\"check\": \"boundary: upside-down reading\", \"actual\": [180.0, \"ok\"], \"expected\": [180.0, \"ok\"], \"passed\": true}, {\"check\": \"regression: angle just inside the flip\", \"actual\": [180.0, \"ok\"], \"expected\": [-179.5, \"ok\"], \"passed\": false}, {\"check\": \"regression: half-turn canonical value\", \"actual\": [180.0, \"ok\"], \"expected\": [180.0, \"ok\"], \"passed\": true}, {\"check\": \"control 1\", \"actual\": [90.0, \"ok\"], \"expected\": [90.0, \"ok\"], \"passed\": true}, {\"check\": \"control 2\", \"actual\": [null, \"fault\"], \"expected\": [null, \"fault\"], \"passed\": true}], \"passed\": false}\n"},"broken":{"elapsed_ms":41.177,"exit_code":1,"observations":[{"actual":[0.0,"ok"],"check":"boundary: magnitude at lower bound","expected":[0.0,"ok"],"passed":true},{"actual":[90.0,"ok"],"check":"boundary: magnitude at upper bound","expected":[90.0,"ok"],"passed":true},{"actual":[-180.0,"ok"],"check":"boundary: upside-down reading","expected":[180.0,"ok"],"passed":false},{"actual":[-179.5,"ok"],"check":"regression: angle just inside the flip","expected":[-179.5,"ok"],"passed":true},{"actual":[-180.0,"ok"],"check":"regression: half-turn canonical value","expected":[180.0,"ok"],"passed":false},{"actual":[90.0,"ok"],"check":"control 1","expected":[90.0,"ok"],"passed":true},{"actual":[null,"fault"],"check":"control 2","expected":[null,"fault"],"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"boundary: magnitude at lower bound\", \"actual\": [0.0, \"ok\"], \"expected\": [0.0, \"ok\"], \"passed\": true}, {\"check\": \"boundary: magnitude at upper bound\", \"actual\": [90.0, \"ok\"], \"expected\": [90.0, \"ok\"], \"passed\": true}, {\"check\": \"boundary: upside-down reading\", \"actual\": [-180.0, \"ok\"], \"expected\": [180.0, \"ok\"], \"passed\": false}, {\"check\": \"regression: angle just inside the flip\", \"actual\": [-179.5, \"ok\"], \"expected\": [-179.5, \"ok\"], \"passed\": true}, {\"check\": \"regression: half-turn canonical value\", \"actual\": [-180.0, \"ok\"], \"expected\": [180.0, \"ok\"], \"passed\": false}, {\"check\": \"control 1\", \"actual\": [90.0, \"ok\"], \"expected\": [90.0, \"ok\"], \"passed\": true}, {\"check\": \"control 2\", \"actual\": [null, \"fault\"], \"expected\": [null, \"fault\"], \"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."}}