mersenne_twister::seed

Seeds the engine.

template<class Gen>
   void seed(Gen& gen)
void seed(unsigned long x0 = default_seed);

Parameters

• Gen
  The type of the seed generator.

• gen
  The seed generator.

• x0
  The seed value.

Remarks

Precondition: 0 < x0

The first seed function generates N values from the values of type unsigned long returned by successive invocations of gen and then twists the resulting large integer value. Each value is gen() % 2W.

The second seed function sets the oldest historical value h[0] to x0 mod 2W, then iteratively sets each successive historical value h[i] to (i + 1812433253 * (h[i - 1] >> (W - 2))) mod 2W, for i ranging from 1 to N - 1.

Example

// std_tr1__random__mersenne_twister_seed.cpp 
// compile with: /EHsc 
#include <random> 
#include <iostream> 
 
typedef std::minstd_rand Myeng; 
typedef std::mersenne_twister<unsigned int, 32, 624, 
    397, 31, 0x9908b0df, 11, 7, 0x9d2c5680, 
    15, 0xefc60000, 18> Myceng;  // same as mt19937 
int main() 
    { 
    Myeng eng; 
    Myceng ceng; 
    Myceng::result_type compval = ceng(); 
 
    compval = compval;  // to quiet "unused" warnings 
 
    std::cout << "W == " << Myceng::word_size << std::endl; 
    std::cout << "N == " << Myceng::state_size << std::endl; 
    std::cout << "M == " << Myceng::shift_size << std::endl; 
    std::cout << "R == " << Myceng::mask_bits << std::endl; 
    std::cout << "A == " << Myceng::parameter_a << std::endl; 
    std::cout << "U == " << Myceng::output_u << std::endl; 
    std::cout << "S == " << Myceng::output_s << std::endl; 
    std::cout << "B == " << Myceng::output_b << std::endl; 
    std::cout << "T == " << Myceng::output_t << std::endl; 
    std::cout << "C == " << Myceng::output_c << std::endl; 
    std::cout << "L == " << Myceng::output_l << std::endl; 
 
    std::cout << "min == " << ceng.min() << std::endl; 
    std::cout << "max == " << ceng.max() << std::endl; 
 
    ceng.seed(); // reseed base engine 
    std::cout << "a random value == " << ceng() << std::endl; 
    std::cout << "a random value == " << ceng() << std::endl; 
    std::cout << "a random value == " << ceng() << std::endl; 
 
    Myceng ceng2(eng); // construct with generator 
    ceng2.seed(eng);  // seed with generator 
 
    Myceng ceng3(5UL);  // construct with unsigned long seed 
    ceng3.seed(5UL);  // seed with unsigned long 
 
    return (0); 
    } 
 

W == 32
N == 624
M == 397
R == 31
A == 2567483615
U == 11
S == 7
B == 2636928640
T == 15
C == 4022730752
L == 18
min == 0
max == 4294967295
a random value == 3499211612
a random value == 581869302
a random value == 3890346734

Requirements

Header: <random>

Namespace: std

See Also

Reference

<random>

mersenne_twister Class

Other Resources

<random> Members