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// Lab. Calcolo II - Esempio di codice
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// Example code: gaussian-distributed random numbers
// (20060911 francesco.prelz@mi.infn.it)
#include <iostream>
#include <iomanip>
#include <random>
#include <cmath>
int
main (int argc, char *argv[])
{
const int n_repeats = 10;
double x,y;
double sigma = 1;
double max = 10;
double min = -10;
double sqr2pi = std::sqrt(2*M_PI);
bool found;
// Pick random coordinates inside a (max-min)x(1/(sqr(2PI)*sigma)) square
std::random_device rndgen;
std::uniform_real_distribution<double> rndstx(min, max);
std::uniform_real_distribution<double> rndsty(0,1/sqr2pi/sigma);
for (int i=1; i<=n_repeats; i++)
{
found = false;
while (!found)
{
x = rndstx(rndgen);
y = rndsty(rndgen);
if (y < (1/(sigma*sqr2pi)) * exp(-x*x/(2*sigma*sigma)))
{
found = true;
}
}
std::cout << "Number # " << std::setw(2) << i << " is " << x << std::endl;
}
// For reference: same exercise using c++11 'random' library:
std::normal_distribution<double> gaussdist(0, sigma);
for (int i=1; i<=n_repeats; i++)
{
x = gaussdist(rndgen);
std::cout << "STD Number # " << std::setw(2) << i << " is " << x << std::endl;
}
return 0;
}
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