{"abstract":"Delta decompression carries a predictor across independent blocks.","category":"Compression format semantics","checks":6,"contract":"Each list is an independent delta-coded block whose predictor starts at zero. Return corresponding lists of prefix sums; empty blocks remain empty.","contract_signature":"blocks","evaluation_group":"model-d20c02c85a38f57d","failed_approach":"Treating each delta as absolute avoids carryover but loses within-block accumulation.","family":"z-compression-block-predictor-reset","id":"FA-11621","implementations":{"attempt":{"sha256":"308f0cf7d67bcef68f9e0693018243fad96a6450cc27f03423b5183bcf7c3cf7","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(blocks):\n    return blocks\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('reset boundary',solve([[N,1],[2,1]]),[[N,N+1],[2,3]])\ncheck('empty',solve([]),[])\ncheck('empty block',solve([[],[1]]),[[],[1]])\ncheck('negative delta',solve([[3,-2]]),[[3,1]])\ncheck('zero delta',solve([[2,0,0]]),[[2,2,2]])\ncheck('singletons',solve([[2],[3]]),[[2],[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":"a099b071455873a11594683fdd6ce3598f51df22d35dd2605b070037c0bc65e2","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(blocks):\n    out=[]; previous=0\n    for block in blocks:\n        row=[]\n        for d in block: previous+=d; row.append(previous)\n        out.append(row)\n    return out\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('reset boundary',solve([[N,1],[2,1]]),[[N,N+1],[2,3]])\ncheck('empty',solve([]),[])\ncheck('empty block',solve([[],[1]]),[[],[1]])\ncheck('negative delta',solve([[3,-2]]),[[3,1]])\ncheck('zero delta',solve([[2,0,0]]),[[2,2,2]])\ncheck('singletons',solve([[2],[3]]),[[2],[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":"Controlled educational model, not a complete implementation of a production compression format. 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-compression-block-predictor-reset","generated_at":"2026-09-29T14:38:49.542241+00:00","license":"CC0-1.0","python":"3.12.14","seed":1,"split":"open-access"},"relevance":"A small offline codec model isolates a compression-specific failure without external files or libraries.","root_cause":"The previous block last value seeds the next independent block.","sha256":"2eb0a22a4f6c5ded25665cbeeff330e922318d62b28752a10736d12fee90a51e","title":"Delta decompression carries a predictor across independent blocks · 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":37.81,"exit_code":1,"observations":[{"actual":[[1,1],[2,1]],"check":"reset boundary","expected":[[1,2],[2,3]],"passed":false},{"actual":[],"check":"empty","expected":[],"passed":true},{"actual":[[],[1]],"check":"empty block","expected":[[],[1]],"passed":true},{"actual":[[3,-2]],"check":"negative delta","expected":[[3,1]],"passed":false},{"actual":[[2,0,0]],"check":"zero delta","expected":[[2,2,2]],"passed":false},{"actual":[[2],[3]],"check":"singletons","expected":[[2],[3]],"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"reset boundary\", \"actual\": [[1, 1], [2, 1]], \"expected\": [[1, 2], [2, 3]], \"passed\": false}, {\"check\": \"empty\", \"actual\": [], \"expected\": [], \"passed\": true}, {\"check\": \"empty block\", \"actual\": [[], [1]], \"expected\": [[], [1]], \"passed\": true}, {\"check\": \"negative delta\", \"actual\": [[3, -2]], \"expected\": [[3, 1]], \"passed\": false}, {\"check\": \"zero delta\", \"actual\": [[2, 0, 0]], \"expected\": [[2, 2, 2]], \"passed\": false}, {\"check\": \"singletons\", \"actual\": [[2], [3]], \"expected\": [[2], [3]], \"passed\": true}], \"passed\": false}\n"},"broken":{"elapsed_ms":39.485,"exit_code":1,"observations":[{"actual":[[1,2],[4,5]],"check":"reset boundary","expected":[[1,2],[2,3]],"passed":false},{"actual":[],"check":"empty","expected":[],"passed":true},{"actual":[[],[1]],"check":"empty block","expected":[[],[1]],"passed":true},{"actual":[[3,1]],"check":"negative delta","expected":[[3,1]],"passed":true},{"actual":[[2,2,2]],"check":"zero delta","expected":[[2,2,2]],"passed":true},{"actual":[[2],[5]],"check":"singletons","expected":[[2],[3]],"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"reset boundary\", \"actual\": [[1, 2], [4, 5]], \"expected\": [[1, 2], [2, 3]], \"passed\": false}, {\"check\": \"empty\", \"actual\": [], \"expected\": [], \"passed\": true}, {\"check\": \"empty block\", \"actual\": [[], [1]], \"expected\": [[], [1]], \"passed\": true}, {\"check\": \"negative delta\", \"actual\": [[3, 1]], \"expected\": [[3, 1]], \"passed\": true}, {\"check\": \"zero delta\", \"actual\": [[2, 2, 2]], \"expected\": [[2, 2, 2]], \"passed\": true}, {\"check\": \"singletons\", \"actual\": [[2], [5]], \"expected\": [[2], [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."}}