{
  "schemaVersion": 1,
  "slug": "hdf5-checksum-coverage",
  "title": "HDF5 checksum coverage and reader-state observations",
  "summary": "Controlled HDF5 1.14.6 observations separate declared Fletcher32, partial-edge coverage, failure callbacks and reuse of unchecked cached values.",
  "published": "2026-10-19",
  "updated": "2026-10-19",
  "generatedAt": "2026-10-19T04:26:19.845456+00:00",
  "evidenceType": "controlled-native-library-observations",
  "license": "CC0-1.0 for Hesela's original code and observations; upstream materials retain their licenses.",
  "licenseUrl": "https://creativecommons.org/publicdomain/zero/1.0/",
  "humanPage": "https://hesela.com/analyses/checksums-identity-and-lost-writes/#hdf5-coverage",
  "sourceUrl": "https://hesela.com/analyses/checksums-identity-and-lost-writes/#hdf5-coverage",
  "downloadPath": "/data/datasets/hdf5-checksum-coverage.csv",
  "rawPath": "/research/hdf5-verification/observations.json",
  "readerPath": "/research/hdf5-verification/reader-policy-observations.json",
  "codePath": "/research/hdf5-verification/hdf5_filter_coverage.py",
  "generatorPath": "/research/hdf5-verification/build-dataset.mjs",
  "requirementsPath": "/research/hdf5-verification/requirements.txt",
  "method": "One-dimensional synthetic uint32 arrays, eight-element chunks, one-bit payload mutations and intact controls. Seven coverage cases, eight fresh-reader combinations and four cache sequences, each repeated three times; three growth sequences and one fill control remain in raw JSON.",
  "environment": {
    "python": "3.12.3",
    "h5py": "3.15.0",
    "hdf5": "1.14.6",
    "numpy": "2.3.3",
    "system": "Linux",
    "machine": "x86_64",
    "formatBounds": [
      "v110",
      "v110"
    ],
    "fileDriver": "fileobj/BytesIO"
  },
  "rowCount": 57,
  "columns": [
    {
      "name": "phase",
      "type": "string",
      "description": "Coverage mutation, fresh-reader policy, or strict read after permissive cache priming."
    },
    {
      "name": "case",
      "type": "string",
      "description": "Designed case identifier; reader-policy cases include clean/damaged fixture."
    },
    {
      "name": "repetition",
      "type": "number",
      "description": "Repeat on one build, not an independent population sample."
    },
    {
      "name": "mask",
      "type": "number",
      "description": "Stored chunk filter mask; zero alone does not establish checksum coverage."
    },
    {
      "name": "storedBytes",
      "type": "number",
      "description": "Stored target-chunk bytes, including checksum when present."
    },
    {
      "name": "edcEnabled",
      "type": "boolean",
      "description": "Requested checking policy, not proof that checking ran."
    },
    {
      "name": "cacheBytes",
      "type": "number-or-null",
      "description": "Explicit budget in reader cases; null in coverage cases, whose cache budget was not recorded."
    },
    {
      "name": "outcome",
      "type": "string",
      "description": "returned-values or read-error; success does not establish agreement with the clean fixture."
    }
  ],
  "rows": [
    {
      "phase": "coverage",
      "case": "default-full",
      "repetition": 1,
      "mask": 0,
      "storedBytes": 36,
      "edcEnabled": true,
      "cacheBytes": null,
      "outcome": "read-error"
    },
    {
      "phase": "coverage",
      "case": "default-partial",
      "repetition": 1,
      "mask": 0,
      "storedBytes": 36,
      "edcEnabled": true,
      "cacheBytes": null,
      "outcome": "read-error"
    },
    {
      "phase": "coverage",
      "case": "edge-option-full",
      "repetition": 1,
      "mask": 0,
      "storedBytes": 36,
      "edcEnabled": true,
      "cacheBytes": null,
      "outcome": "read-error"
    },
    {
      "phase": "coverage",
      "case": "edge-option-partial",
      "repetition": 1,
      "mask": 0,
      "storedBytes": 32,
      "edcEnabled": true,
      "cacheBytes": null,
      "outcome": "returned-values"
    },
    {
      "phase": "coverage",
      "case": "edge-option-grown-before-mutation",
      "repetition": 1,
      "mask": 0,
      "storedBytes": 36,
      "edcEnabled": true,
      "cacheBytes": null,
      "outcome": "read-error"
    },
    {
      "phase": "coverage",
      "case": "direct-writer-skips-checksum",
      "repetition": 1,
      "mask": 1,
      "storedBytes": 32,
      "edcEnabled": true,
      "cacheBytes": null,
      "outcome": "returned-values"
    },
    {
      "phase": "coverage",
      "case": "reader-disables-edc",
      "repetition": 1,
      "mask": 0,
      "storedBytes": 36,
      "edcEnabled": false,
      "cacheBytes": null,
      "outcome": "returned-values"
    },
    {
      "phase": "coverage",
      "case": "default-full",
      "repetition": 2,
      "mask": 0,
      "storedBytes": 36,
      "edcEnabled": true,
      "cacheBytes": null,
      "outcome": "read-error"
    },
    {
      "phase": "coverage",
      "case": "default-partial",
      "repetition": 2,
      "mask": 0,
      "storedBytes": 36,
      "edcEnabled": true,
      "cacheBytes": null,
      "outcome": "read-error"
    },
    {
      "phase": "coverage",
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      "mask": 0,
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      "outcome": "read-error"
    },
    {
      "phase": "coverage",
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      "edcEnabled": true,
      "cacheBytes": null,
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    },
    {
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    },
    {
      "phase": "coverage",
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      "outcome": "returned-values"
    },
    {
      "phase": "coverage",
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      "edcEnabled": false,
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    },
    {
      "phase": "coverage",
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    },
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      "phase": "coverage",
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    },
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      "storedBytes": 36,
      "edcEnabled": true,
      "cacheBytes": 0,
      "outcome": "read-error"
    }
  ],
  "coverageRows": [
    {
      "case": "default-full",
      "mask": 0,
      "storedBytes": 36,
      "outcome": "read-error"
    },
    {
      "case": "default-partial",
      "mask": 0,
      "storedBytes": 36,
      "outcome": "read-error"
    },
    {
      "case": "edge-option-full",
      "mask": 0,
      "storedBytes": 36,
      "outcome": "read-error"
    },
    {
      "case": "edge-option-partial",
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      "storedBytes": 32,
      "outcome": "returned-values"
    },
    {
      "case": "edge-option-grown-before-mutation",
      "mask": 0,
      "storedBytes": 36,
      "outcome": "read-error"
    },
    {
      "case": "direct-writer-skips-checksum",
      "mask": 1,
      "storedBytes": 32,
      "outcome": "returned-values"
    },
    {
      "case": "reader-disables-edc",
      "mask": 0,
      "storedBytes": 36,
      "outcome": "returned-values"
    }
  ],
  "cacheRows": [
    {
      "primer": "edc-disabled",
      "cacheBytes": 1048576,
      "same": "returned-values",
      "fresh": "read-error"
    },
    {
      "primer": "edc-disabled",
      "cacheBytes": 0,
      "same": "read-error",
      "fresh": "read-error"
    },
    {
      "primer": "callback-continue",
      "cacheBytes": 1048576,
      "same": "returned-values",
      "fresh": "read-error"
    },
    {
      "primer": "callback-continue",
      "cacheBytes": 0,
      "same": "read-error",
      "fresh": "read-error"
    }
  ],
  "growthRunCount": 3,
  "inputHashes": {
    "observations.json": "1b4d95778bf72ede007bd7fd55ca63c2ff6c5072ae5ab3b558c73cecc4afe74c",
    "reader-policy-observations.json": "888aba60ea85f98da9a29acad5c591e3e18114bd9032d75876ec65d641c341e4"
  },
  "limits": [
    "One Linux x86_64 build: h5py 3.15.0, HDF5 1.14.6, NumPy 2.3.3. Fileobj/BytesIO and v110/v110 format bounds.",
    "Designed cases establish behavior, not corruption incidence, confidence intervals, throughput or hardware-fault results.",
    "Edge skipping, EDC disabling and callback continuation are explicit opt-outs, not ordinary h5py defaults.",
    "Mask inspection is a coverage precondition, not checksum verification; raw chunk reads bypass filters.",
    "No SWMR, parallel I/O, compression chains, third-party filters, power failure or cross-version claim.",
    "Later handle/refresh anomaly research is deliberately excluded from this dataset and its recommendations."
  ],
  "citations": [
    {
      "id": "h5-edge-api",
      "title": "HDF Group: H5Pset_chunk_opts, Dataset Creation Properties",
      "url": "https://support.hdfgroup.org/documentation/hdf5/latest/group___d_c_p_l.html",
      "accessed": "2026-10-19"
    },
    {
      "id": "h5-chunk-source",
      "title": "HDF5 1.14.6 H5Dchunk.c: chunk flush and partial-edge read paths",
      "url": "https://github.com/HDFGroup/hdf5/blob/hdf5_1.14.6/src/H5Dchunk.c",
      "accessed": "2026-10-19"
    },
    {
      "id": "h5-direct-api",
      "title": "HDF Group: H5Dwrite_chunk and H5Dread_chunk",
      "url": "https://docs.hdfgroup.org/archive/support/HDF5/doc/RM/RM_H5D.html",
      "accessed": "2026-10-19"
    },
    {
      "id": "h5py-low",
      "title": "h5py DatasetID API: chunk information and direct chunk methods",
      "url": "https://api.h5py.org/h5d.html",
      "accessed": "2026-10-19"
    },
    {
      "id": "h5-edc-api",
      "title": "HDF Group: H5Pset_edc_check and H5Pget_edc_check",
      "url": "https://support.hdfgroup.org/documentation/hdf5/latest/group___d_x_p_l.html",
      "accessed": "2026-10-19"
    },
    {
      "id": "h5-fletcher-source",
      "title": "HDF5 1.14.6 H5Zfletcher32.c",
      "url": "https://github.com/HDFGroup/hdf5/blob/hdf5_1.14.6/src/H5Zfletcher32.c",
      "accessed": "2026-10-19"
    },
    {
      "id": "h5py-high",
      "title": "h5py 3.15.1: Datasets and filter pipeline",
      "url": "https://docs.h5py.org/en/3.15.1/high/dataset.html",
      "accessed": "2026-10-19"
    },
    {
      "id": "h5-header",
      "title": "HDF5 1.14.6 H5Dpublic.h",
      "url": "https://github.com/HDFGroup/hdf5/blob/hdf5_1.14.6/src/H5Dpublic.h",
      "accessed": "2026-10-19"
    },
    {
      "id": "h5-pipeline",
      "title": "HDF5 1.14.6: H5Z_pipeline filter-failure callback",
      "url": "https://github.com/HDFGroup/hdf5/blob/hdf5_1.14.6/src/H5Z.c#L1446",
      "accessed": "2026-10-19"
    }
  ]
}