/**
 *  @file   MtRand.h
 *  @brief  MT 乱数 クラス (unsigned生成限定)
 *  @note
 *      -   http://www.math.sci.hiroshima-u.ac.jp/~m-mat/MT/MT2002/mt19937ar.html
 *          の mt19937ar-cok.c を簡略化(出力型をuint32のみしシード生成を1種類に)してクラス化したもの.
 *      -   inlineでない関数をヘッダに書くためダミーでtemplateクラス化している.
 */
/*
   A C-program for MT19937, with initialization improved 2002/2/10.
   Coded by Takuji Nishimura and Makoto Matsumoto.
   This is a faster version by taking Shawn Cokus's optimization,
   Matthe Bellew's simplification, Isaku Wada's real version.

   //Before using, initialize the state by using init_genrand(seed)
   //or init_by_array(init_key, key_length).

   Copyright (C) 1997 - 2002, Makoto Matsumoto and Takuji Nishimura,
   All rights reserved.

   Redistribution and use in source and binary forms, with or without
   modification, are permitted provided that the following conditions
   are met:

     1. Redistributions of source code must retain the above copyright
        notice, this list of conditions and the following disclaimer.

     2. Redistributions in binary form must reproduce the above copyright
        notice, this list of conditions and the following disclaimer in the
        documentation and/or other materials provided with the distribution.

     3. The names of its contributors may not be used to endorse or promote
        products derived from this software without specific prior written
        permission.

   THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
   "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
   LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
   A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT OWNER OR
   CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
   EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
   PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
   PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
   LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
   NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
   SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.


   Any feedback is very welcome.
   http://www.math.sci.hiroshima-u.ac.jp/~m-mat/MT/emt.html
   email: m-mat @ math.sci.hiroshima-u.ac.jp (remove space)
*/

#ifndef MTRAND_H
#define MTRAND_H

/// MT 法の乱数発生クラス
template<unsigned DMY=0>
class MtRandT {
    enum {  // Period parameters
        N           = 624,
        M           = 397,
        MATRIX_A    = 0x9908b0dfU,      ///< constant vector a
        UMASK       = 0x80000000U,      ///< most significant w-r bits
        LMASK       = 0x7fffffffU,      ///< least significant r bits
    };

public:
    enum { MAX = 0xFFFFFFFF };
    MtRandT(unsigned s=1) { init(s); }
    void        init(unsigned s=1);     ///< initializes state_[N] with a seed
    unsigned    get();                  ///< generates a random number on [0,0xffffffff]-interval
    unsigned    operator()() { return get(); }

private:
    unsigned    mixBits(unsigned u, unsigned v) { return ( ((u) & UMASK) | ((v) & LMASK) ); }
    unsigned    twist  (unsigned u, unsigned v) { return ((mixBits(u,v) >> 1) ^ ((v & 1U) ? MATRIX_A : 0U)); }
    void        next_state();

private:
    unsigned    *next_;
    unsigned    left_ ;
    unsigned    state_[N];
};



/** initializes state_[N] with a seed
 */
template<unsigned DMY>
void MtRandT<DMY>::init(unsigned s) {
    state_[0] = s & 0xffffffffU;
    for (unsigned j = 1; j < N; ++j) {
        state_[j] = (1812433253U * (state_[j-1] ^ (state_[j-1] >> 30)) + j);
        //  /* See Knuth TAOCP Vol2. 3rd Ed. P.106 for multiplier.  */
        //  /* In the previous versions, MSBs of the seed affect    */
        //  /* only MSBs of the array state_[].                     */
        //  /* 2002/01/09 modified by Makoto Matsumoto              */
        //  state_[j] &= 0xffffffffU;  /* for >32 bit machines      */
    }
  #if 1
    next_state();
    next_++;
  #else
    left_ = 1;
    get();
  #endif
}


template<unsigned DMY>
void MtRandT<DMY>::next_state() {
    left_ = N;
    next_ = state_;

    unsigned *p = state_;
    unsigned  j;
    for (j=N-M+1; --j; p++)
        *p = p[M] ^ twist(p[0], p[1]);

    for (j=M; --j; p++)
        *p = p[M-N] ^ twist(p[0], p[1]);

    *p = p[M-N] ^ twist(p[0], state_[0]);
}


/** generates a random number on [0,0xffffffff]-interval
 */
template<unsigned DMY> inline
unsigned MtRandT<DMY>::get() {
    if (--left_ == 0)
        next_state();
    unsigned y = *next_++;
    /* Tempering */
    y ^= (y >> 11);
    y ^= (y <<  7) & 0x9d2c5680U;
    y ^= (y << 15) & 0xefc60000U;
    y ^= (y >> 18);
    return y;
}


typedef MtRandT<>       MtRand;


#endif