libstdc++-v3/testsuite/util/testsuite_rng.h

   1 // -*- C++ -*-
   2
   3 // Copyright (C) 2005-2020 Free Software Foundation, Inc.
   4 //
   5 // This file is part of the GNU ISO C++ Library.  This library is free
   6 // software; you can redistribute it and/or modify it under the terms
   7 // of the GNU General Public License as published by the Free Software
   8 // Foundation; either version 3, or (at your option) any later
   9 // version.
  10
  11 // This library is distributed in the hope that it will be useful, but
  12 // WITHOUT ANY WARRANTY; without even the implied warranty of
  13 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14 // General Public License for more details.
  15
  16 // You should have received a copy of the GNU General Public License along
  17 // with this library; see the file COPYING3.  If not see
  18 // <http://www.gnu.org/licenses/>.
  19
  20
  21 // Copyright (C) 2004 Ami Tavory and Vladimir Dreizin, IBM-HRL.
  22
  23 // Permission to use, copy, modify, sell, and distribute this software
  24 // is hereby granted without fee, provided that the above copyright
  25 // notice appears in all copies, and that both that copyright notice
  26 // and this permission notice appear in supporting documentation. None
  27 // of the above authors, nor IBM Haifa Research Laboratories, make any
  28 // representation about the suitability of this software for any
  29 // purpose. It is provided "as is" without express or implied
  30 // warranty.
  31
  32 /**
  33  * @file testsuite_rng.h
  34  */
  35
  36 #ifndef _GLIBCXX_TESTSUITE_RNG_H
  37 #define _GLIBCXX_TESTSUITE_RNG_H
  38
  39 #include <ctime>
  40 #include <climits>
  41 #include <debug/debug.h>
  42 #include <tr1/random>
  43
  44 namespace __gnu_pbds
  45 {
  46   namespace test
  47   {
  48     class twister_rand_gen
  49     {
  50     public:
  51       twister_rand_gen(unsigned int seed =
  52                        static_cast<unsigned int>(std::time(0)))
  53       : m_base_generator(seed)
  54       {
  55         // Do nothing.
  56       }
  57
  58       void
  59       init(unsigned int seed)
  60       { m_base_generator.seed(seed); }
  61
  62       static unsigned int
  63       get_time_determined_seed()
  64       { return(static_cast<unsigned int>(std::time(0))); }
  65
  66       unsigned long
  67       get_unsigned_long(unsigned long min = 0,
  68                         unsigned long max = UINT_MAX - 1)
  69       {
  70         _GLIBCXX_DEBUG_ASSERT(max >= min);
  71         const double prob = get_prob();
  72         const unsigned long r = (unsigned long)((max - min + 1) * prob) + min;
  73         _GLIBCXX_DEBUG_ASSERT(r <= max);
  74         return r;
  75       }
  76
  77       double
  78       get_prob()
  79       {
  80         const double min = m_base_generator.min();
  81         const double max = m_base_generator.max();
  82         const double range = static_cast<double>(max - min);
  83         const double res = static_cast<double>(m_base_generator() - min);
  84         const double ret = res / range;
  85         _GLIBCXX_DEBUG_ASSERT(ret >= 0 && ret <= 1);
  86         return ret;
  87       }
  88
  89     private:
  90       typedef std::tr1::mt19937 base_generator_t;
  91
  92       base_generator_t m_base_generator;
  93     };
  94   } // namespace test
  95 } // namespace __gnu_pbds
  96
  97 #endif // #ifndef _GLIBCXX_TESTSUITE_RNG_H