對於我正在處理的項目,我需要在函數中生成一個隨機數的向量。問題是我最終每次都會生成相同的數字向量。我有這樣的例子,重現我的問題:C++在函數中生成隨機數
#include <iostream>
#include <random>
std::vector<double> generate(std::default_random_engine generator, double mean, double sigma, int n)
{
std::vector<double> generated(n,0);
std::normal_distribution<double> distribution(mean,sigma);
for (int i = 0;i<n;i++)
generated[i] = distribution(generator);
return generated;
}
std::vector<double> generate(double mean, double sigma, int n)
{
std::vector<double> generated(n,0);
std::default_random_engine generator;
std::normal_distribution<double> distribution(mean,sigma);
for (int i = 0;i<n;i++)
generated[i] = distribution(generator);
return generated;
}
int main(int argc, char** argv)
{
// Read inputs
int nrolls = 20; // number of experiments
int ntimes = 50;
double mean = 100;
double sigma = 4;
bool useFunction(false);
if (argc>1)
useFunction=true;
// crates series
std::vector< std::vector<double> > results(ntimes,std::vector<double>());
std::default_random_engine generator;
for (int i = 0;i<ntimes/4;i++){
std::vector<double> generated(nrolls,0);
std::normal_distribution<double> distribution(mean,sigma);
for (int i = 0;i<nrolls;i++)
generated[i] = distribution(generator);
results[i] = generated;
}
for (int i = ntimes/4;i<ntimes/2;i++)
results[i] = generate(generator,mean,sigma,nrolls);
for (int i = ntimes/2;i<3*ntimes/4;i++){
std::vector<double> generated(nrolls,0);
std::normal_distribution<double> distribution(mean,sigma);
for (int i = 0;i<nrolls;i++)
generated[i] = distribution(generator);
results[i] = generated;
}
for (int i = 3*ntimes/4;i<ntimes;i++)
results[i] = generate(mean,sigma,nrolls);
//
// Display all random numbers
for (int i = 0;i<ntimes;i++){
std::cout<<i;
for (int j = 0;j<nrolls;j++)
std::cout<<" "<<results[i][j];
std::cout<<std::endl;
}
// Check number of equal results
int n_equal(0);
int n_total(0);
for (int i=0;i<ntimes;i++){
for (int k = 0;k<nrolls;k++){
for (int j=i+1;j<ntimes;j++){
n_total++;
if (results[i][k] == results[j][k])
n_equal++;
}
}
}
std::cout<<n_equal<<"/"<<n_total<<std::endl;
// Exit
return 0;
}
我曾嘗試通過將發電機到產生隨機數的數組,但顯然,這也不行功能來解決這個問題。有人可以給我一個暗示,我應該怎麼做,每次我調用生成函數時獲得不同的數組?
非常感謝。
您可以讓您的引擎每次獲得不同的值 – CoryKramer