packed dtype transformations demo

structured_hash.ipynb

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      "source": "import numpy",
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      "source": "full_type = numpy.dtype([\n    (\"id\", \"u8\"),\n    (\"ht\", \"f8\", (4, 4)),\n])\nhashed_type = numpy.dtype([(\"id\", \"u8\"), (\"hashed_ht\", \"u8\")])",
      "execution_count": 55,
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      "source": "def hash_ht(ht_array):\n    return (ht_array.sum(axis=-1).sum(axis=-1) * 1000).astype(\"u8\")",
      "execution_count": 56,
      "outputs": []
    },
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      "source": "def hash_full(full_array):\n    result = numpy.empty_like(full_array, dtype=hashed_type)\n    result[\"id\"] = full_array[\"id\"]\n    result[\"hashed_ht\"] = hash_ht(full_array[\"ht\"])\n    return result",
      "execution_count": 57,
      "outputs": []
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      "cell_type": "code",
      "source": "src_data = numpy.empty(10, full_type)\nsrc_data[\"id\"] = numpy.arange(10)\nsrc_data[\"ht\"] = numpy.random.random((10, 4, 4))",
      "execution_count": 58,
      "outputs": []
    },
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      "cell_type": "code",
      "source": "print(hash_full(src_data))",
      "execution_count": 59,
      "outputs": [
        {
          "output_type": "stream",
          "text": "[(0,  8039) (1, 10326) (2,  7956) (3,  7414) (4,  6769) (5,  8062)\n (6,  9912) (7,  7881) (8,  7764) (9,  9540)]\n",
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