ループは関数にする.ipynb

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 "cells": [
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "# 基本的に関数（function）にまとめる  \n",
    "\n",
    "いろいろなところで説明されているように、Juliaでは関数で書かないと速度が出ません。  \n",
    "書き方により差は出ますが、百倍以上の差があります。"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 1,
   "metadata": {},
   "outputs": [],
   "source": [
    "using BenchmarkTools"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "### 下記に$1$から$10^8$まで足していく計算例を示します。  "
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 2,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "  9.758943 seconds (400.00 M allocations: 7.451 GiB, 2.91% gc time)\n",
      "5000000050000000"
     ]
    }
   ],
   "source": [
    "a = 0\n",
    "N0 = 10^8\n",
    "@time for x in 1:N0\n",
    "    global a\n",
    "    a += x\n",
    "end\n",
    "print(a)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 3,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "  0.006952 seconds (2.39 k allocations: 168.797 KiB, 99.45% compilation time)\n",
      "5000000050000000"
     ]
    }
   ],
   "source": [
    "a = 0\n",
    "N0 = 10^8\n",
    "function f(a, N0)\n",
    "    a = 0\n",
    "    for x in 1:N0\n",
    "        a += x\n",
    "    end\n",
    "    return a\n",
    "end\n",
    "\n",
    "@time b = f(a, N0)\n",
    "print(b)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": []
  }
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