sc/source/core/tool/random.cxx

   1 /* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
   2 /*
   3  * This file is part of the LibreOffice project.
   4  *
   5  * This Source Code Form is subject to the terms of the Mozilla Public
   6  * License, v. 2.0. If a copy of the MPL was not distributed with this
   7  * file, You can obtain one at http://mozilla.org/MPL/2.0/.
   8  *
   9  * Contributor(s):
  10  *   Copyright (C) 2012 Tino Kluge <tino.kluge@hrz.tu-chemnitz.de>
  11  */
  12
  13 #include <boost/random.hpp>
  14
  15 // this is nothing but a simple wrapper around
  16 // the boost random generators
  17
  18 namespace sc
  19 {
  20 namespace rng
  21 {
  22
  23 // underlying random number generator
  24 // boost::mt19937 implements the Mersenne twister algorithm which
  25 // is fast and has good statistical properties, it produces integers
  26 // in the range of [0, 2^32-1] internally
  27 // memory requirement: 625*sizeof(uint32_t)
  28 // http://en.wikipedia.org/wiki/Mersenne_twister
  29 #define BOOST_RNG_ALGO  boost::mt19937
  30 BOOST_RNG_ALGO global_rng;
  31
  32 // initialises the state of the global random number generator
  33 // should only be called once at the start of the main programme
  34 // (note, a few boost::variate_generator<> (like normal) have their
  35 // own state which would need a reset as well to guarantee identical
  36 // sequence of numbers, e.g. via myrand.distribution().reset())
  37 void seed(int i)
  38 {
  39     global_rng.seed(i);
  40 }
  41
  42 // uniform [0,1) or [a,b) distribution
  43 double uniform()
  44 {
  45     static boost::uniform_01<BOOST_RNG_ALGO&> myrand(global_rng);
  46     return myrand();
  47 }
  48
  49 } // namespace
  50 } // namespace
  51
  52 /* vim:set shiftwidth=4 softtabstop=4 expandtab: */