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::tr1::minstd_rand Myeng;
typedef std::tr1::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::tr1