boost/random/inversive_congruential.hpp

   1 /* boost random/inversive_congruential.hpp header file
   2  *
   3  * Copyright Jens Maurer 2000-2001
   4  * Distributed under the Boost Software License, Version 1.0. (See
   5  * accompanying file LICENSE_1_0.txt or copy at
   6  * http://www.boost.org/LICENSE_1_0.txt)
   7  *
   8  * See http://www.boost.org for most recent version including documentation.
   9  *
  10  * $Id$
  11  *
  12  * Revision history
  13  *  2001-02-18  moved to individual header files
  14  */
  15
  16 #ifndef BOOST_RANDOM_INVERSIVE_CONGRUENTIAL_HPP
  17 #define BOOST_RANDOM_INVERSIVE_CONGRUENTIAL_HPP
  18
  19 #include <iostream>
  20 #include <cassert>
  21 #include <stdexcept>
  22 #include <boost/config.hpp>
  23 #include <boost/static_assert.hpp>
  24 #include <boost/random/detail/config.hpp>
  25 #include <boost/random/detail/const_mod.hpp>
  26
  27 namespace boost {
  28 namespace random {
  29
  30 // Eichenauer and Lehn 1986
  31 template<class IntType, IntType a, IntType b, IntType p, IntType val>
  32 class inversive_congruential
  33 {
  34 public:
  35   typedef IntType result_type;
  36 #ifndef BOOST_NO_INCLASS_MEMBER_INITIALIZATION
  37   static const bool has_fixed_range = true;
  38   static const result_type min_value = (b == 0 ? 1 : 0);
  39   static const result_type max_value = p-1;
  40 #else
  41   BOOST_STATIC_CONSTANT(bool, has_fixed_range = false);
  42 #endif
  43   BOOST_STATIC_CONSTANT(result_type, multiplier = a);
  44   BOOST_STATIC_CONSTANT(result_type, increment = b);
  45   BOOST_STATIC_CONSTANT(result_type, modulus = p);
  46
  47   result_type min BOOST_PREVENT_MACRO_SUBSTITUTION () const { return b == 0 ? 1 : 0; }
  48   result_type max BOOST_PREVENT_MACRO_SUBSTITUTION () const { return p-1; }
  49
  50   explicit inversive_congruential(IntType y0 = 1) : value(y0)
  51   {
  52     BOOST_STATIC_ASSERT(b >= 0);
  53     BOOST_STATIC_ASSERT(p > 1);
  54     BOOST_STATIC_ASSERT(a >= 1);
  55     if(b == 0)
  56       assert(y0 > 0);
  57   }
  58   template<class It> inversive_congruential(It& first, It last)
  59   { seed(first, last); }
  60
  61   void seed(IntType y0 = 1) { value = y0; if(b == 0) assert(y0 > 0); }
  62   template<class It> void seed(It& first, It last)
  63   {
  64     if(first == last)
  65       throw std::invalid_argument("inversive_congruential::seed");
  66     value = *first++;
  67   }
  68   IntType operator()()
  69   {
  70     typedef const_mod<IntType, p> do_mod;
  71     value = do_mod::mult_add(a, do_mod::invert(value), b);
  72     return value;
  73   }
  74
  75   static bool validation(result_type x) { return val == x; }
  76
  77 #ifndef BOOST_NO_OPERATORS_IN_NAMESPACE
  78
  79 #ifndef BOOST_RANDOM_NO_STREAM_OPERATORS
  80   template<class CharT, class Traits>
  81   friend std::basic_ostream<CharT,Traits>&
  82   operator<<(std::basic_ostream<CharT,Traits>& os, inversive_congruential x)
  83   { os << x.value; return os; }
  84
  85   template<class CharT, class Traits>
  86   friend std::basic_istream<CharT,Traits>&
  87   operator>>(std::basic_istream<CharT,Traits>& is, inversive_congruential& x)
  88   { is >> x.value; return is; }
  89 #endif
  90
  91   friend bool operator==(inversive_congruential x, inversive_congruential y)
  92   { return x.value == y.value; }
  93   friend bool operator!=(inversive_congruential x, inversive_congruential y)
  94   { return !(x == y); }
  95 #else
  96   // Use a member function; Streamable concept not supported.
  97   bool operator==(inversive_congruential rhs) const
  98   { return value == rhs.value; }
  99   bool operator!=(inversive_congruential rhs) const
 100   { return !(*this == rhs); }
 101 #endif
 102 private:
 103   IntType value;
 104 };
 105
 106 #ifndef BOOST_NO_INCLASS_MEMBER_INITIALIZATION
 107 //  A definition is required even for integral static constants
 108 template<class IntType, IntType a, IntType b, IntType p, IntType val>
 109 const bool inversive_congruential<IntType, a, b, p, val>::has_fixed_range;
 110 template<class IntType, IntType a, IntType b, IntType p, IntType val>
 111 const typename inversive_congruential<IntType, a, b, p, val>::result_type inversive_congruential<IntType, a, b, p, val>::min_value;
 112 template<class IntType, IntType a, IntType b, IntType p, IntType val>
 113 const typename inversive_congruential<IntType, a, b, p, val>::result_type inversive_congruential<IntType, a, b, p, val>::max_value;
 114 template<class IntType, IntType a, IntType b, IntType p, IntType val>
 115 const typename inversive_congruential<IntType, a, b, p, val>::result_type inversive_congruential<IntType, a, b, p, val>::multiplier;
 116 template<class IntType, IntType a, IntType b, IntType p, IntType val>
 117 const typename inversive_congruential<IntType, a, b, p, val>::result_type inversive_congruential<IntType, a, b, p, val>::increment;
 118 template<class IntType, IntType a, IntType b, IntType p, IntType val>
 119 const typename inversive_congruential<IntType, a, b, p, val>::result_type inversive_congruential<IntType, a, b, p, val>::modulus;
 120 #endif
 121
 122 } // namespace random
 123
 124 typedef random::inversive_congruential<int32_t, 9102, 2147483647-36884165,
 125   2147483647, 0> hellekalek1995;
 126
 127 } // namespace boost
 128
 129 #endif // BOOST_RANDOM_INVERSIVE_CONGRUENTIAL_HPP