```/* boost random/mersenne_twister.hpp header file
*
* accompanying file LICENSE_1_0.txt or copy at
*
*
* \$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 DLIB_BOOST_RANDOM_MERSENNE_TWISTER_HPP
#define DLIB_BOOST_RANDOM_MERSENNE_TWISTER_HPP

#include <iostream>
#include <algorithm>     // std::copy
#include <stdexcept>
#include "../uintn.h"
#include "../serialize.h"

namespace dlib
{
namespace random_helpers
{

// ------------------------------------------------------------------------------------

// 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;
const static int word_size = w;
const static int state_size = n;
const static int shift_size = m;
const static int mask_bits = r;
const static UIntType parameter_a = a;
const static int output_u = u;
const static int output_s = s;
const static UIntType output_b = b;
const static int output_t = t;
const static UIntType output_c = c;
const static int output_l = l;

const static bool has_fixed_range = false;

mersenne_twister() { seed(); }

explicit mersenne_twister(UIntType value) { seed(value); }

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

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

void seed(UIntType value)
{
// 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[].
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;
}
}

result_type min() const { return 0; }
result_type max() 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()();

friend void serialize(
const mersenne_twister& item,
std::ostream& out
)
{
dlib::serialize(item.x, out);
dlib::serialize(item.i, out);
}

friend void deserialize(
mersenne_twister& item,
std::istream& in
)
{
dlib::deserialize(item.x, in);
dlib::deserialize(item.i, in);
}

private:

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;
};

// ------------------------------------------------------------------------------------

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;

if(block == 0) {
for(int j = n; j < 2*n; j++) {
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++) {
x[j] = x[j+n+m] ^ (y >> 1) ^ (y&1 ? a : 0);
}
}

for(int j = n-m; j < n-1; j++) {
x[j] = x[j-(n-m)] ^ (y >> 1) ^ (y&1 ? a : 0);
}
// last iteration
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_helpers::mersenne_twister<uint32,32,351,175,19,0xccab8ee7,11,
7,0x31b6ab00,15,0xffe50000,17, 0xa37d3c92> mt11213b;

// validation by experiment from mt19937.c
typedef random_helpers::mersenne_twister<uint32,32,624,397,31,0x9908b0df,11,
7,0x9d2c5680,15,0xefc60000,18, 3346425566U> mt19937;

} // namespace dlib

#endif // DLIB_BOOST_RANDOM_MERSENNE_TWISTER_HPP

```