/* 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 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[].
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;
}
}
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;
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_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