/* boost random/mersenne_twister.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: mersenne_twister.hpp,v 1.20 2005/07/21 22:04:31 jmaurer Exp $

 *

 * Revision history

 *  2001-02-18  moved to individual header files

 */

#ifndef BOOST_RANDOM_MERSENNE_TWISTER_HPP

#define BOOST_RANDOM_MERSENNE_TWISTER_HPP

#include <iostream>

#include <algorithm>     // std::copy

#include <stdexcept>

#include <boost/config.hpp>

#include <boost/limits.hpp>

#include <boost/static_assert.hpp>

#include <boost/integer_traits.hpp>

#include <boost/cstdint.hpp>

#include <boost/random/linear_congruential.hpp>

#include <boost/detail/workaround.hpp>

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

namespace boost {

namespace random {

// http://www.math.keio.ac.jp/matumoto/emt.html

template<class UIntType, int w, int n, int m, int r, UIntType a, int u,

  int s, UIntType b, int t, UIntType c, int l, UIntType val>

class mersenne_twister

{

public:

  typedef UIntType result_type;

  BOOST_STATIC_CONSTANT(int, word_size = w);

  BOOST_STATIC_CONSTANT(int, state_size = n);

  BOOST_STATIC_CONSTANT(int, shift_size = m);

  BOOST_STATIC_CONSTANT(int, mask_bits = r);

  BOOST_STATIC_CONSTANT(UIntType, parameter_a = a);

  BOOST_STATIC_CONSTANT(int, output_u = u);

  BOOST_STATIC_CONSTANT(int, output_s = s);

  BOOST_STATIC_CONSTANT(UIntType, output_b = b);

  BOOST_STATIC_CONSTANT(int, output_t = t);

  BOOST_STATIC_CONSTANT(UIntType, output_c = c);

  BOOST_STATIC_CONSTANT(int, output_l = l);

  BOOST_STATIC_CONSTANT(bool, has_fixed_range = false);

  mersenne_twister() { seed(); }

#if defined(__SUNPRO_CC) && (__SUNPRO_CC <= 0x520)

  // Work around overload resolution problem (Gennadiy E. Rozental)

  explicit mersenne_twister(const UIntType& value)

#else

  explicit mersenne_twister(UIntType value)

#endif

  { seed(value); }

  template<class It> mersenne_twister(It& first, It last) { seed(first,last); }

  template<class Generator>

  explicit mersenne_twister(Generator & gen) { seed(gen); }

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

  void seed() { seed(UIntType(5489)); }

#if defined(__SUNPRO_CC) && (__SUNPRO_CC <= 0x520)

  // Work around overload resolution problem (Gennadiy E. Rozental)

  void seed(const UIntType& value)

#else

  void seed(UIntType value)

#endif

  {

    // New seeding algorithm from 

    // http://www.math.sci.hiroshima-u.ac.jp/~m-mat/MT/MT2002/emt19937ar.html

    // In the previous versions, MSBs of the seed affected only MSBs of the

    // state x[].

    const UIntType mask = ~0u;

    x[0] = value & mask;

    for (i = 1; i < n; i++) {

      // See Knuth "The Art of Computer Programming" Vol. 2, 3rd ed., page 106

      x[i] = (1812433253UL * (x[i-1] ^ (x[i-1] >> (w-2))) + i) & mask;

    }

  }

  // For GCC, moving this function out-of-line prevents inlining, which may

  // reduce overall object code size.  However, MSVC does not grok

  // out-of-line definitions of member function templates.

  template<class Generator>

  void seed(Generator & gen)

  {

#ifndef BOOST_NO_LIMITS_COMPILE_TIME_CONSTANTS

    BOOST_STATIC_ASSERT(!std::numeric_limits<result_type>::is_signed);

#endif

    // I could have used std::generate_n, but it takes "gen" by value

    for(int j = 0; j < n; j++)

      x[j] = gen();

    i = n;

  }

  template<class It>

  void seed(It& first, It last)

  {

    int j;

    for(j = 0; j < n && first != last; ++j, ++first)

      x[j] = *first;

    i = n;

    if(first == last && j < n)

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

  }

  result_type min BOOST_PREVENT_MACRO_SUBSTITUTION () const { return 0; }

  result_type max BOOST_PREVENT_MACRO_SUBSTITUTION () const

  {

    // avoid "left shift count >= with of type" warning

    result_type res = 0;

    for(int i = 0; i < w; ++i)

      res |= (1u << i);

    return res;

  }

  result_type operator()();

  static bool validation(result_type v) { return val == v; }

#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 mersenne_twister& mt)

  {

    for(int j = 0; j < mt.state_size; ++j)

      os << mt.compute(j) << " ";

    return os;

  }

  template<class CharT, class Traits>

  friend std::basic_istream<CharT,Traits>&

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

  {

    for(int j = 0; j < mt.state_size; ++j)

      is >> mt.x[j] >> std::ws;

    // MSVC (up to 7.1) and Borland (up to 5.64) don't handle the template

    // value parameter "n" available from the class template scope, so use

    // the static constant with the same value

    mt.i = mt.state_size;

    return is;

  }

#endif

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

  {

    for(int j = 0; j < state_size; ++j)

      if(x.compute(j) != y.compute(j))

        return false;

    return true;

  }

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

  { return !(x == y); }

#else

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

  bool operator==(const mersenne_twister& rhs) const

  {

    for(int j = 0; j < state_size; ++j)

      if(compute(j) != rhs.compute(j))

        return false;

    return true;

  }

  bool operator!=(const mersenne_twister& rhs) const

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

#endif

private:

  // returns x(i-n+index), where index is in 0..n-1

  UIntType compute(unsigned int index) const

  {

    // equivalent to (i-n+index) % 2n, but doesn't produce negative numbers

    return x[ (i + n + index) % (2*n) ];

  }

  void twist(int block);

  // state representation: next output is o(x(i))

  //   x[0]  ... x[k] x[k+1] ... x[n-1]     x[n]     ... x[2*n-1]   represents

  //  x(i-k) ... x(i) x(i+1) ... x(i-k+n-1) x(i-k-n) ... x[i(i-k-1)]

  // The goal is to always have x(i-n) ... x(i-1) available for

  // operator== and save/restore.

  UIntType x[2*n]; 

  int i;

};

#ifndef BOOST_NO_INCLASS_MEMBER_INITIALIZATION

//  A definition is required even for integral static constants

template<class UIntType, int w, int n, int m, int r, UIntType a, int u,

  int s, UIntType b, int t, UIntType c, int l, UIntType val>

const bool mersenne_twister<UIntType,w,n,m,r,a,u,s,b,t,c,l,val>::has_fixed_range;

template<class UIntType, int w, int n, int m, int r, UIntType a, int u,

  int s, UIntType b, int t, UIntType c, int l, UIntType val>

const int mersenne_twister<UIntType,w,n,m,r,a,u,s,b,t,c,l,val>::state_size;

template<class UIntType, int w, int n, int m, int r, UIntType a, int u,

  int s, UIntType b, int t, UIntType c, int l, UIntType val>

const int mersenne_twister<UIntType,w,n,m,r,a,u,s,b,t,c,l,val>::shift_size;

template<class UIntType, int w, int n, int m, int r, UIntType a, int u,

  int s, UIntType b, int t, UIntType c, int l, UIntType val>

const int mersenne_twister<UIntType,w,n,m,r,a,u,s,b,t,c,l,val>::mask_bits;

template<class UIntType, int w, int n, int m, int r, UIntType a, int u,

  int s, UIntType b, int t, UIntType c, int l, UIntType val>

const UIntType mersenne_twister<UIntType,w,n,m,r,a,u,s,b,t,c,l,val>::parameter_a;

template<class UIntType, int w, int n, int m, int r, UIntType a, int u,

  int s, UIntType b, int t, UIntType c, int l, UIntType val>

const int mersenne_twister<UIntType,w,n,m,r,a,u,s,b,t,c,l,val>::output_u;

template<class UIntType, int w, int n, int m, int r, UIntType a, int u,

  int s, UIntType b, int t, UIntType c, int l, UIntType val>

const int mersenne_twister<UIntType,w,n,m,r,a,u,s,b,t,c,l,val>::output_s;

template<class UIntType, int w, int n, int m, int r, UIntType a, int u,

  int s, UIntType b, int t, UIntType c, int l, UIntType val>

const UIntType mersenne_twister<UIntType,w,n,m,r,a,u,s,b,t,c,l,val>::output_b;

template<class UIntType, int w, int n, int m, int r, UIntType a, int u,

  int s, UIntType b, int t, UIntType c, int l, UIntType val>

const int mersenne_twister<UIntType,w,n,m,r,a,u,s,b,t,c,l,val>::output_t;

template<class UIntType, int w, int n, int m, int r, UIntType a, int u,

  int s, UIntType b, int t, UIntType c, int l, UIntType val>

const UIntType mersenne_twister<UIntType,w,n,m,r,a,u,s,b,t,c,l,val>::output_c;

template<class UIntType, int w, int n, int m, int r, UIntType a, int u,

  int s, UIntType b, int t, UIntType c, int l, UIntType val>

const int mersenne_twister<UIntType,w,n,m,r,a,u,s,b,t,c,l,val>::output_l;

#endif

template<class UIntType, int w, int n, int m, int r, UIntType a, int u,

  int s, UIntType b, int t, UIntType c, int l, UIntType val>

void mersenne_twister<UIntType,w,n,m,r,a,u,s,b,t,c,l,val>::twist(int block)

{

  const UIntType upper_mask = (~0u) << r;

  const UIntType lower_mask = ~upper_mask;

  if(block == 0) {

    for(int j = n; j < 2*n; j++) {

      UIntType y = (x[j-n] & upper_mask) | (x[j-(n-1)] & lower_mask);

      x[j] = x[j-(n-m)] ^ (y >> 1) ^ (y&1 ? a : 0);

    }

  } else if (block == 1) {

    // split loop to avoid costly modulo operations

    {  // extra scope for MSVC brokenness w.r.t. for scope

      for(int j = 0; j < n-m; j++) {

        UIntType y = (x[j+n] & upper_mask) | (x[j+n+1] & lower_mask);

        x[j] = x[j+n+m] ^ (y >> 1) ^ (y&1 ? a : 0);

      }

    }

    for(int j = n-m; j < n-1; j++) {

      UIntType y = (x[j+n] & upper_mask) | (x[j+n+1] & lower_mask);

      x[j] = x[j-(n-m)] ^ (y >> 1) ^ (y&1 ? a : 0);

    }

    // last iteration

    UIntType y = (x[2*n-1] & upper_mask) | (x[0] & lower_mask);

    x[n-1] = x[m-1] ^ (y >> 1) ^ (y&1 ? a : 0);

    i = 0;

  }

}

template<class UIntType, int w, int n, int m, int r, UIntType a, int u,

  int s, UIntType b, int t, UIntType c, int l, UIntType val>

inline typename mersenne_twister<UIntType,w,n,m,r,a,u,s,b,t,c,l,val>::result_type

mersenne_twister<UIntType,w,n,m,r,a,u,s,b,t,c,l,val>::operator()()

{

  if(i == n)

    twist(0);

  else if(i >= 2*n)

    twist(1);

  // Step 4

  UIntType z = x[i];

  ++i;

  z ^= (z >> u);

  z ^= ((z << s) & b);

  z ^= ((z << t) & c);

  z ^= (z >> l);

  return z;

}

} // namespace random

typedef random::mersenne_twister<uint32_t,32,351,175,19,0xccab8ee7,11,

  7,0x31b6ab00,15,0xffe50000,17, 0xa37d3c92> mt11213b;

// validation by experiment from mt19937.c

typedef random::mersenne_twister<uint32_t,32,624,397,31,0x9908b0df,11,

  7,0x9d2c5680,15,0xefc60000,18, 3346425566U> mt19937;

} // namespace boost

BOOST_RANDOM_PTR_HELPER_SPEC(boost::mt19937)

#endif // BOOST_RANDOM_MERSENNE_TWISTER_HPP