libstdc++-v3/testsuite/util/rng/twister_rand_gen.cc

   1 // -*- C++ -*-
   2
   3 // Copyright (C) 2005, 2006 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 2, 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 COPYING.  If not, write to the Free
  18 // Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
  19 // USA.
  20
  21 // As a special exception, you may use this file as part of a free
  22 // software library without restriction.  Specifically, if other files
  23 // instantiate templates or use macros or inline functions from this
  24 // file, or you compile this file and link it with other files to
  25 // produce an executable, this file does not by itself cause the
  26 // resulting executable to be covered by the GNU General Public
  27 // License.  This exception does not however invalidate any other
  28 // reasons why the executable file might be covered by the GNU General
  29 // Public License.
  30
  31 // Copyright (C) 2004 Ami Tavory and Vladimir Dreizin, IBM-HRL.
  32
  33 // Permission to use, copy, modify, sell, and distribute this software
  34 // is hereby granted without fee, provided that the above copyright
  35 // notice appears in all copies, and that both that copyright notice
  36 // and this permission notice appear in supporting documentation. None
  37 // of the above authors, nor IBM Haifa Research Laboratories, make any
  38 // representation about the suitability of this software for any
  39 // purpose. It is provided "as is" without express or implied
  40 // warranty.
  41
  42 /**
  43  * @file twister_rand_gen.cc
  44  */
  45
  46 #include <ctime>
  47 #include <debug/debug.h>
  48 #include <util/rng/twister_rand_gen.hpp>
  49
  50 namespace pb_ds
  51 {
  52   namespace test
  53   {
  54     twister_rand_gen::
  55     twister_rand_gen(unsigned int seed)
  56     : m_base_generator(seed)
  57     {
  58       // Do nothing.
  59     }
  60
  61     void
  62     twister_rand_gen::
  63     init(unsigned int seed)
  64     { m_base_generator.seed(seed); }
  65
  66     unsigned long
  67     twister_rand_gen::
  68     get_unsigned_long(unsigned long min, unsigned long max)
  69     {
  70       _GLIBCXX_DEBUG_ASSERT(max >= min);
  71
  72       const double prob = get_prob();
  73
  74       const unsigned long rand_word =
  75         (unsigned long)((max - min + 1) * prob) + min;
  76
  77       _GLIBCXX_DEBUG_ASSERT(rand_word <= max);
  78
  79       return rand_word;
  80     }
  81
  82     double
  83     twister_rand_gen::
  84     get_prob()
  85     {
  86       const double eng_min = m_base_generator.min();
  87       const double eng_range =
  88         static_cast<const double>(m_base_generator.max() - eng_min);
  89
  90       const double eng_res =
  91         static_cast<const double>(m_base_generator() - eng_min);
  92
  93       const double ret = eng_res / eng_range;
  94
  95       _GLIBCXX_DEBUG_ASSERT(ret >=0 && ret <= 1);
  96
  97       return ret;
  98     }
  99   } // namespace test
 100 } // namespace pb_ds