// http://www.math.sci.hiroshima-u.ac.jp/m-mat/MT/VERSIONS/C-LANG/mt19937-64.c

/*
   A C-program for MT19937-64 (2004/9/29 version).
   Coded by Takuji Nishimura and Makoto Matsumoto.

   This is a 64-bit version of Mersenne Twister pseudorandom number
   generator.

   Before using, initialize the state by using init_genrand64(seed)
   or init_by_array64(init_key, key_length).

   Copyright (C) 2004, 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.

   References:
   T. Nishimura, ``Tables of 64-bit Mersenne Twisters''
   ACM Transactions on Modeling and
   Computer Simulation 10. (2000) 348--357.
   M. Matsumoto and T. Nishimura,
   ``Mersenne Twister: a 623-dimensionally equidistributed
     uniform pseudorandom number generator''
   ACM Transactions on Modeling and
   Computer Simulation 8. (Jan. 1998) 3--30.

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

/*
Modifications:

- Remove stdio.h and the main() function.
- Replace 'unsigned long long' with 'uint64_t' (include stdint.h).
- Remove the global state and instead store the generator's state in the new
  mt19937_64 struct.
- Naming and formatting.
*/

#include <random/mt19937-64.h>

#include <assert.h>

#define NN 312
#define MM 156
#define MATRIX_A 0xB5026F5AA96619E9ULL
#define UM 0xFFFFFFFF80000000ULL /* Most significant 33 bits */
#define LM 0x7FFFFFFFULL /* Least significant 31 bits */

mt19937_64 mt19937_64_make() {
  mt19937_64 rng;
  rng.mti = NN+1;  // Not initialized.
  return rng;
}

/* initializes mt[NN] with a seed */
void mt19937_64_init(mt19937_64* rng, uint64_t seed) {
  assert(rng);
  rng->mt[0] = seed;
  for (rng->mti = 1; rng->mti < NN; rng->mti++) {
    rng->mt[rng->mti] =
        (6364136223846793005ULL * (rng->mt[rng->mti - 1] ^ (rng->mt[rng->mti - 1] >> 62)) + rng->mti);
  }
}

/* initialize by an array with array-length */
/* init_key is the array for initializing keys */
/* key_length is its length */
void mt19937_64_init_by_array64(mt19937_64* rng, uint64_t init_key[], uint64_t key_length) {
  assert(rng);
  uint64_t i, j, k;
  mt19937_64_init(rng, 19650218ULL);
  i=1; j=0;
  k = (NN>key_length ? NN : key_length);
  for (; k; k--) {
    rng->mt[i] = (rng->mt[i] ^ ((rng->mt[i-1] ^ (rng->mt[i-1] >> 62)) * 3935559000370003845ULL))
      + init_key[j] + j; /* non linear */
    i++; j++;
    if (i>=NN) { rng->mt[0] = rng->mt[NN-1]; i=1; }
    if (j>=key_length) j=0;
  }
  for (k=NN-1; k; k--) {
    rng->mt[i] = (rng->mt[i] ^ ((rng->mt[i-1] ^ (rng->mt[i-1] >> 62)) * 2862933555777941757ULL))
      - i; /* non linear */
    i++;
    if (i>=NN) { rng->mt[0] = rng->mt[NN-1]; i=1; }
  }

  rng->mt[0] = 1ULL << 63; /* MSB is 1; assuring non-zero initial array */
}

/* generates a random number on [0, 2^64-1]-interval */
uint64_t mt19937_64_gen64u(mt19937_64* rng) {
  assert(rng);
  int i;
  uint64_t x;
  static uint64_t mag01[2]={0ULL, MATRIX_A};

  if (rng->mti >= NN) { /* generate NN words at one time */

    /* if mt19937_64_init() has not been called, */
    /* a default initial seed is used   */
    if (rng->mti == NN+1)
      mt19937_64_init(rng, 5489ULL);

    for (i=0;i<NN-MM;i++) {
      x = (rng->mt[i]&UM)|(rng->mt[i+1]&LM);
      rng->mt[i] = rng->mt[i+MM] ^ (x>>1) ^ mag01[(int)(x&1ULL)];
    }
    for (;i<NN-1;i++) {
      x = (rng->mt[i]&UM)|(rng->mt[i+1]&LM);
      rng->mt[i] = rng->mt[i+(MM-NN)] ^ (x>>1) ^ mag01[(int)(x&1ULL)];
    }
    x = (rng->mt[NN-1]&UM)|(rng->mt[0]&LM);
    rng->mt[NN-1] = rng->mt[MM-1] ^ (x>>1) ^ mag01[(int)(x&1ULL)];

    rng->mti = 0;
  }

  x = rng->mt[rng->mti++];

  x ^= (x >> 29) & 0x5555555555555555ULL;
  x ^= (x << 17) & 0x71D67FFFEDA60000ULL;
  x ^= (x << 37) & 0xFFF7EEE000000000ULL;
  x ^= (x >> 43);

  return x;
}

/* generates a random number on [0, 2^63-1]-interval */
int64_t mt19937_64_gen64i(mt19937_64* rng) {
  return (int64_t)(mt19937_64_gen64u(rng) >> 1);
}

/* generates a random number on [0,1]-real-interval */
double mt19937_64_gen_real1(mt19937_64* rng) {
  return (mt19937_64_gen64u(rng) >> 11) * (1.0/9007199254740991.0);
}

/* generates a random number on [0,1)-real-interval */
double mt19937_64_gen_real2(mt19937_64* rng) {
  return (mt19937_64_gen64u(rng) >> 11) * (1.0/9007199254740992.0);
}

/* generates a random number on (0,1)-real-interval */
double mt19937_64_gen_real3(mt19937_64* rng) {
  return ((mt19937_64_gen64u(rng) >> 12) + 0.5) * (1.0/4503599627370496.0);
}

/* generates a random number on (-1,+1)-real-interval */
double mt19937_64_gen_real4(mt19937_64* rng) {
  const double x01 = mt19937_64_gen_real3(rng);  // (0,1) interval.
  const double x11 = x01 * 2. - 1.;  // (-1, +1) interval.
  return x11;
}