First, the function advances the internal state by one using a transition algorithm that produces a twist on the selected element in the state as if this wasx[i]in the following piece of code
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UIntType Mask = (1u<<w)-1, UMask= (Mask << r) & Mask, LMask = (~UMask) & Mask,
Y = (x[i]&UMask)|(x[(i+1)%n]&LMask); // upper bits of x[i] and lower of x[i+1]
x[i]=x[(i+m)%n]^(Y>>1)^((Y&1)*a); // mersenne twister linear transformation
With each of the values being their corresponding class template parameters.
To improve the uniformity of the random value produced, the function uses a generation algorithm to return a tempered version of the selected element in the state sequence: it applies the same transformation applied onyin the following piece of code
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y^=(y>>u)&d;
y^=(y<<s)&b;
y^=(y<<t)&c;
y^=y>>l;
With each of the values being again their corresponding class template parameters.
Note: not fully tested, plese report any inaccuracies.
参数
无
返回值
A new random number. （一个新的随机数。） result_type是一个成员类型，定义为第一个类模板参数的别名 (UIntType).
示例
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// mersenne_twister_engine::operator()
#include <iostream>
#include <chrono>
#include <random>
int main ()
{
// obtain a seed from the system clock:
unsigned seed = std::chrono::system_clock::now().time_since_epoch().count();
std::mt19937 generator (seed); // mt19937 is a standard mersenne_twister_engine
std::cout << "Random value: " << generator() << std::endl;
return 0;
}