src/util/random.cpp

   1 /*********************                                                        */
   2 /*! \file random.cpp
   3  ** \verbatim
   4  ** Top contributors (to current version):
   5  **   Aina Niemetz
   6  ** This file is part of the CVC4 project.
   7  ** Copyright (c) 2009-2017 by the authors listed in the file AUTHORS
   8  ** in the top-level source directory) and their institutional affiliations.
   9  ** All rights reserved.  See the file COPYING in the top-level source
  10  ** directory for licensing information.\endverbatim
  11  **
  12  ** \brief A Random Number Generator.
  13  **
  14  ** A random number generator, implements the xorshift* generator
  15  ** (see S. Vigna, An experimental exploration of Marsaglia's xorshift
  16  ** generators, scrambled. ACM Trans. Math. Softw. 42(4): 30:1-30:23, 2016).
  17  **/
  18
  19 #include "util/random.h"
  20
  21 #include <cfloat>
  22 #include "base/cvc4_assert.h"
  23
  24 namespace CVC4 {
  25
  26 uint64_t Random::rand()
  27 {
  28   /* xorshift* generator (see S. Vigna, An experimental exploration of
  29    * Marsaglia's xorshift generators, scrambled. ACM Trans. Math. Softw.
  30    * 42(4): 30:1-30:23, 2016). */
  31   d_state ^= d_state >> 12;
  32   d_state ^= d_state << 25;
  33   d_state ^= d_state >> 27;
  34   d_state *= uint64_t{2685821657736338717};
  35   return d_state;
  36 }
  37
  38 uint64_t Random::pick(uint64_t from, uint64_t to)
  39 {
  40   Assert(from <= to);
  41   Assert(to < UINT64_MAX);
  42   return (Random::rand() % (to - from + 1)) + from;
  43 }
  44
  45 double Random::pickDouble(double from, double to)
  46 {
  47   Assert(from <= to);
  48   Assert(to <= DBL_MAX);
  49   return Random::rand() * (to - from) + from;
  50 }
  51
  52 bool Random::pickWithProb(double probability)
  53 {
  54   Assert(probability <= 1);
  55   uint64_t p = (uint64_t) (probability * 1000);
  56   uint64_t r = pick(0, 999);
  57   return r < p;
  58 }
  59
  60 }