Hyperband.ipynb

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   "cell_type": "code",
   "execution_count": 1,
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   "outputs": [],
   "source": [
    "import numpy as np"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 2,
   "metadata": {},
   "outputs": [],
   "source": [
    "def hyperband(b_max, b_min=1, eta=3):\n",
    "\n",
    "    # ln (eta)\n",
    "    ln_eta = np.log(eta)\n",
    "\n",
    "    # ln (b_max/b_min)\n",
    "    ln_ratio = np.log(b_max) - np.log(b_min)\n",
    "\n",
    "    # log_eta (b_max/b_min)\n",
    "    # lg_eta_ratio = ln_ratio / ln_eta\n",
    "\n",
    "    # division for change of base then floor\n",
    "    s_max = int(np.floor_divide(ln_ratio, ln_eta))\n",
    "\n",
    "    for s in reversed(range(s_max+1)):\n",
    "\n",
    "        n = int(np.ceil(eta**s * (s_max + 1) / (s + 1)))\n",
    "        b = b_max // eta**s\n",
    "\n",
    "        yield n, b"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 3,
   "metadata": {},
   "outputs": [],
   "source": [
    "def successive_halving(n, b, b_max, eta=3):\n",
    "\n",
    "    yield n, b\n",
    "\n",
    "    if b * eta <= b_max:\n",
    "        yield from successive_halving(n // eta, b * eta, b_max, eta)"
   ]
  },
  {
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   "execution_count": 4,
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   "outputs": [
    {
     "data": {
      "text/plain": [
       "[[(81, 1), (27, 3), (9, 9), (3, 27), (1, 81)],\n",
       " [(34, 3), (11, 9), (3, 27), (1, 81)],\n",
       " [(15, 9), (5, 27), (1, 81)],\n",
       " [(8, 27), (2, 81)],\n",
       " [(5, 81)]]"
      ]
     },
     "execution_count": 4,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "[list(successive_halving(n, b, b_max=81)) for n, b in hyperband(b_max=81)]"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 5,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "[[(243, 1), (81, 3), (27, 9), (9, 27), (3, 81), (1, 243)],\n",
       " [(98, 3), (32, 9), (10, 27), (3, 81), (1, 243)],\n",
       " [(41, 9), (13, 27), (4, 81), (1, 243)],\n",
       " [(18, 28), (6, 84), (2, 252)],\n",
       " [(9, 85), (3, 255)],\n",
       " [(6, 256)]]"
      ]
     },
     "execution_count": 5,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "[list(successive_halving(n, b, b_max=256)) for n, b in hyperband(b_max=256)]"
   ]
  }
 ],
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