H3 Cell iterator ideas

cell_iterators.ipynb

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    "We could probably do something similar in C if we defined an iterator struct with some helper functions like option 2 here:\n",
    "\n",
    "https://www.cs.yale.edu/homes/aspnes/pinewiki/C(2f)Iterators.html\n",
    "\n",
    "This iterator pattern would be very flexible, allowing us to do the \"exhaustive\" testing in C without code duplication or function pointers.\n",
    "\n",
    "Would this help speed up or reduce memory usage of:\n",
    "\n",
    "- testing code (yes!)\n",
    "- `uncompact` (probably?)\n",
    "- `polyfill` (maybe?)\n",
    "\n",
    "\n",
    "## Questions\n",
    "\n",
    "- does it make more sense to have depth parameterized in absolute terms (resolution), or in relative terms (\"how many resolution hops down\")?\n",
    "- i think we had a similar discussion at some point on if `h3.h3_to_children` should be in relative or absolute terms"
   ]
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   "execution_count": 1,
   "metadata": {},
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   "source": [
    "import h3\n",
    "\n",
    "# actually, this function is almost an exact duplicate of `h3_to_children`! (just the iterator/relative version)\n",
    "def iter_children(h, depth=0):\n",
    "    assert depth >= 0\n",
    "    \n",
    "    if depth == 0:\n",
    "        yield h\n",
    "    else:\n",
    "        for c in h3.h3_to_children(h):\n",
    "            yield from iter_children(c, depth-1)\n",
    "\n",
    "            \n",
    "def iter_all_cells_at_res(res):\n",
    "    for c in h3.get_res0_indexes():\n",
    "        yield from iter_children(c, res)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 2,
   "metadata": {},
   "outputs": [],
   "source": [
    "h0 = h3.geo_to_h3(0,0,0)\n",
    "depth = 6"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "- Things seem to run a little bit slower when we recursively iterate through children.\n",
    "- I wonder if the recursive/iterative pattern wins out when it is all done in C?"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 3,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "489 ms ± 11.3 ms per loop (mean ± std. dev. of 7 runs, 1 loop each)\n"
     ]
    }
   ],
   "source": [
    "%%timeit\n",
    "sum(\n",
    "    h3.cell_area(h)\n",
    "    for h in h3.uncompact({h0}, depth)\n",
    ")"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 4,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "641 ms ± 16.4 ms per loop (mean ± std. dev. of 7 runs, 1 loop each)\n"
     ]
    }
   ],
   "source": [
    "%%timeit\n",
    "sum(\n",
    "    h3.cell_area(h)\n",
    "    for h in iter_children(h0, depth)\n",
    ")"
   ]
  },
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   "execution_count": 5,
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       "842"
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     "execution_count": 5,
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   ],
   "source": [
    "len(list(iter_all_cells_at_res(1)))"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
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