cpp_vs_python.ipynb

{
 "cells": [
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Compare speed of cpp-program with pure python"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 1,
   "metadata": {},
   "outputs": [],
   "source": [
    "from __future__ import print_function, division"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 2,
   "metadata": {
    "collapsed": true
   },
   "outputs": [],
   "source": [
    "def main():\n",
    "    z = 0.0\n",
    "    for idx in xrange(10**8):\n",
    "        z += idx / (idx * idx * idx + 700.0)\n",
    "    print('z =', z)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 3,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "z = 0.136066788376\n",
      "CPU times: user 49.4 s, sys: 129 ms, total: 49.5 s\n",
      "Wall time: 49.4 s\n"
     ]
    }
   ],
   "source": [
    "%%time\n",
    "main()"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "#### python spend ~ 50 seconds for the task"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 4,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "Overwriting calc.cpp\n"
     ]
    }
   ],
   "source": [
    "%%file calc.cpp\n",
    "#include <iostream>\n",
    "#include <cstddef>\n",
    "\n",
    "int main() {\n",
    "    double z = 0.0;\n",
    "    double idx_d;\n",
    "    for (std::size_t idx = 0; idx < 100000000; ++idx) {\n",
    "    idx_d = idx;\n",
    "    z += idx_d / (idx_d * idx_d * idx_d + 700.0);\n",
    "    }  \n",
    "    std::cout << \"z = \" << z << std::endl; \n",
    "}"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 5,
   "metadata": {
    "collapsed": true
   },
   "outputs": [],
   "source": [
    "!g++ -std=c++11 calc.cpp -o calc"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 6,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "z = 0.136067\n",
      "CPU times: user 25 ms, sys: 6 ms, total: 31 ms\n",
      "Wall time: 849 ms\n"
     ]
    }
   ],
   "source": [
    "%%time\n",
    "!./calc"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "#### cpp-program spend ~ 0.8 second for the task"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## cpp-program is almost 100 times faster than python on that simple example"
   ]
  }
 ],
 "metadata": {
  "kernelspec": {
   "display_name": "Python 2",
   "language": "python",
   "name": "python2"
  },
  "language_info": {
   "codemirror_mode": {
    "name": "ipython",
    "version": 2
   },
   "file_extension": ".py",
   "mimetype": "text/x-python",
   "name": "python",
   "nbconvert_exporter": "python",
   "pygments_lexer": "ipython2",
   "version": "2.7.13"
  }
 },
 "nbformat": 4,
 "nbformat_minor": 2
}