/* boost random/linear_congruential.hpp header file

 *

 * Copyright Jens Maurer 2000-2001

 * Distributed under the Boost Software License, Version 1.0. (See

 * accompanying file LICENSE_1_0.txt or copy at

 * http://www.boost.org/LICENSE_1_0.txt)

 *

 * See http://www.boost.org for most recent version including documentation.

 *

 * $Id: linear_congruential.hpp,v 1.22 2005/05/21 15:57:00 dgregor Exp $

 *

 * Revision history

 *  2001-02-18  moved to individual header files

 */

#ifndef BOOST_RANDOM_LINEAR_CONGRUENTIAL_HPP

#define BOOST_RANDOM_LINEAR_CONGRUENTIAL_HPP

#include <iostream>

#include <cassert>

#include <stdexcept>

#include <boost/config.hpp>

#include <boost/limits.hpp>

#include <boost/static_assert.hpp>

#include <boost/random/detail/const_mod.hpp>

#include <boost/detail/workaround.hpp>

namespace boost {

namespace random {

// compile-time configurable linear congruential generator

template<class IntType, IntType a, IntType c, IntType m, IntType val>

class linear_congruential

{

public:

  typedef IntType result_type;

#ifndef BOOST_NO_INCLASS_MEMBER_INITIALIZATION

  static const bool has_fixed_range = true;

  static const result_type min_value = ( c == 0 ? 1 : 0 );

  static const result_type max_value = m-1;

#else

  BOOST_STATIC_CONSTANT(bool, has_fixed_range = false);

#endif

  BOOST_STATIC_CONSTANT(IntType, multiplier = a);

  BOOST_STATIC_CONSTANT(IntType, increment = c);

  BOOST_STATIC_CONSTANT(IntType, modulus = m);

  // MSVC 6 and possibly others crash when encountering complicated integral

  // constant expressions.  Avoid the check for now.

  // BOOST_STATIC_ASSERT(m == 0 || a < m);

  // BOOST_STATIC_ASSERT(m == 0 || c < m);

  explicit linear_congruential(IntType x0 = 1)

    : _modulus(modulus), _x(_modulus ? (x0 % _modulus) : x0)

  { 

    assert(c || x0); /* if c == 0 and x(0) == 0 then x(n) = 0 for all n */

    // overflow check

    // disabled because it gives spurious "divide by zero" gcc warnings

    // assert(m == 0 || (a*(m-1)+c) % m == (c < a ? c-a+m : c-a)); 

    // MSVC fails BOOST_STATIC_ASSERT with std::numeric_limits at class scope

#ifndef BOOST_NO_LIMITS_COMPILE_TIME_CONSTANTS

    BOOST_STATIC_ASSERT(std::numeric_limits<IntType>::is_integer);

#endif

  }

  template<class It>

  linear_congruential(It& first, It last) { seed(first, last); }

  // compiler-generated copy constructor and assignment operator are fine

  void seed(IntType x0 = 1)

  {

    assert(c || x0);

    _x = (_modulus ? (x0 % _modulus) : x0);

  }

  template<class It>

  void seed(It& first, It last)

  {

    if(first == last)

      throw std::invalid_argument("linear_congruential::seed");

    IntType value = *first++;

    _x = (_modulus ? (value % _modulus) : value);

  }

  result_type min BOOST_PREVENT_MACRO_SUBSTITUTION () const { return c == 0 ? 1 : 0; }

  result_type max BOOST_PREVENT_MACRO_SUBSTITUTION () const { return modulus-1; }

  IntType operator()()

  {

    _x = const_mod<IntType, m>::mult_add(a, _x, c);

    return _x;

  }

  static bool validation(IntType x) { return val == x; }

#ifdef BOOST_NO_OPERATORS_IN_NAMESPACE

  // Use a member function; Streamable concept not supported.

  bool operator==(const linear_congruential& rhs) const

  { return _x == rhs._x; }

  bool operator!=(const linear_congruential& rhs) const

  { return !(*this == rhs); }

#else 

  friend bool operator==(const linear_congruential& x,

                         const linear_congruential& y)

  { return x._x == y._x; }

  friend bool operator!=(const linear_congruential& x,

                         const linear_congruential& y)

  { return !(x == y); }

#if !defined(BOOST_NO_MEMBER_TEMPLATE_FRIENDS) && !BOOST_WORKAROUND(__BORLANDC__, BOOST_TESTED_AT(0x551))

  template<class CharT, class Traits>

  friend std::basic_ostream<CharT,Traits>&

  operator<<(std::basic_ostream<CharT,Traits>& os,

             const linear_congruential& lcg)

  {

    return os << lcg._x;

  }

  template<class CharT, class Traits>

  friend std::basic_istream<CharT,Traits>&

  operator>>(std::basic_istream<CharT,Traits>& is,

             linear_congruential& lcg)

  {

    return is >> lcg._x;

  }

private:

#endif

#endif

  IntType _modulus;   // work-around for gcc "divide by zero" warning in ctor

  IntType _x;

};

// probably needs the "no native streams" caveat for STLPort

#if !defined(__SGI_STL_PORT) && BOOST_WORKAROUND(__GNUC__, == 2)

template<class IntType, IntType a, IntType c, IntType m, IntType val>

std::ostream&

operator<<(std::ostream& os,

           const linear_congruential<IntType,a,c,m,val>& lcg)

{

    return os << lcg._x;

}

template<class IntType, IntType a, IntType c, IntType m, IntType val>

std::istream&

operator>>(std::istream& is,

           linear_congruential<IntType,a,c,m,val>& lcg)

{

    return is >> lcg._x;

}

#elif defined(BOOST_NO_OPERATORS_IN_NAMESPACE) || defined(BOOST_NO_MEMBER_TEMPLATE_FRIENDS) || BOOST_WORKAROUND(__BORLANDC__, BOOST_TESTED_AT(0x551))

template<class CharT, class Traits, class IntType, IntType a, IntType c, IntType m, IntType val>

std::basic_ostream<CharT,Traits>&

operator<<(std::basic_ostream<CharT,Traits>& os,

           const linear_congruential<IntType,a,c,m,val>& lcg)

{

    return os << lcg._x;

}

template<class CharT, class Traits, class IntType, IntType a, IntType c, IntType m, IntType val>

std::basic_istream<CharT,Traits>&

operator>>(std::basic_istream<CharT,Traits>& is,

           linear_congruential<IntType,a,c,m,val>& lcg)

{

    return is >> lcg._x;

}

#endif

#ifndef BOOST_NO_INCLASS_MEMBER_INITIALIZATION

//  A definition is required even for integral static constants

template<class IntType, IntType a, IntType c, IntType m, IntType val>

const bool linear_congruential<IntType, a, c, m, val>::has_fixed_range;

template<class IntType, IntType a, IntType c, IntType m, IntType val>

const typename linear_congruential<IntType, a, c, m, val>::result_type linear_congruential<IntType, a, c, m, val>::min_value;

template<class IntType, IntType a, IntType c, IntType m, IntType val>

const typename linear_congruential<IntType, a, c, m, val>::result_type linear_congruential<IntType, a, c, m, val>::max_value;

template<class IntType, IntType a, IntType c, IntType m, IntType val>

const IntType linear_congruential<IntType,a,c,m,val>::modulus;

#endif

} // namespace random

// validation values from the publications

typedef random::linear_congruential<int32_t, 16807, 0, 2147483647, 

  1043618065> minstd_rand0;

typedef random::linear_congruential<int32_t, 48271, 0, 2147483647,

  399268537> minstd_rand;

#if !defined(BOOST_NO_INT64_T) && !defined(BOOST_NO_INTEGRAL_INT64_T)

// emulate the lrand48() C library function; requires support for uint64_t

class rand48 

{

public:

  typedef int32_t result_type;

#ifndef BOOST_NO_INCLASS_MEMBER_INITIALIZATION

  static const bool has_fixed_range = true;

  static const int32_t min_value = 0;

  static const int32_t max_value = integer_traits<int32_t>::const_max;

#else

  enum { has_fixed_range = false };

#endif

  int32_t min BOOST_PREVENT_MACRO_SUBSTITUTION () const { return 0; }

  int32_t max BOOST_PREVENT_MACRO_SUBSTITUTION () const { return std::numeric_limits<int32_t>::max BOOST_PREVENT_MACRO_SUBSTITUTION (); }

  explicit rand48(int32_t x0 = 1) : lcf(cnv(x0)) { }

  explicit rand48(uint64_t x0) : lcf(x0) { }

  template<class It> rand48(It& first, It last) : lcf(first, last) { }

  // compiler-generated copy ctor and assignment operator are fine

  void seed(int32_t x0 = 1) { lcf.seed(cnv(x0)); }

  void seed(uint64_t x0) { lcf.seed(x0); }

  template<class It> void seed(It& first, It last) { lcf.seed(first,last); }

  int32_t operator()() { return static_cast<int32_t>(lcf() >> 17); }

  // by experiment from lrand48()

  static bool validation(int32_t x) { return x == 1993516219; }

#ifndef BOOST_NO_OPERATORS_IN_NAMESPACE

#ifndef BOOST_NO_MEMBER_TEMPLATE_FRIENDS

  template<class CharT,class Traits>

  friend std::basic_ostream<CharT,Traits>&

  operator<<(std::basic_ostream<CharT,Traits>& os, const rand48& r)

  { os << r.lcf; return os; }

  template<class CharT,class Traits>

  friend std::basic_istream<CharT,Traits>&

  operator>>(std::basic_istream<CharT,Traits>& is, rand48& r)

  { is >> r.lcf; return is; }

#endif

  friend bool operator==(const rand48& x, const rand48& y)

  { return x.lcf == y.lcf; }

  friend bool operator!=(const rand48& x, const rand48& y)

  { return !(x == y); }

#else

  // Use a member function; Streamable concept not supported.

  bool operator==(const rand48& rhs) const

  { return lcf == rhs.lcf; }

  bool operator!=(const rand48& rhs) const

  { return !(*this == rhs); }

#endif

private:

  random::linear_congruential<uint64_t,

    uint64_t(0xDEECE66DUL) | (uint64_t(0x5) << 32), // xxxxULL is not portable

    0xB, uint64_t(1)<<48, /* unknown */ 0> lcf;

  static uint64_t cnv(int32_t x) 

  { return (static_cast<uint64_t>(x) << 16) | 0x330e;  }

};

#endif /* !BOOST_NO_INT64_T && !BOOST_NO_INTEGRAL_INT64_T */

} // namespace boost

#endif // BOOST_RANDOM_LINEAR_CONGRUENTIAL_HPP