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#include "random.h"
#include <chrono>
#include <type_traits>
#include <cmath>
Random::Random()
: Random(std::chrono::system_clock::now().time_since_epoch().count())
{
}
Random::Random(unsigned int seed)
{
setSeed(seed);
}
void Random::setSeed(unsigned int seed)
{
generator.seed(seed);
}
int Random::intInRange(int lower_bound, int upper_bound)
{
auto generate = [this]()
{
return (int)generator() - generator.min();
};
const int in_range = generator.max() - generator.min();
const int out_range = upper_bound - lower_bound;
int rand;
if (in_range > out_range)
{
const int rand_inv_range = in_range / (out_range + 1);
do
{
rand = generate();
}
while (rand >= (out_range + 1) * rand_inv_range);
rand = lower_bound + rand/rand_inv_range;
}
else if (in_range < out_range)
{
int scale = out_range / (in_range + 1);
do
{
rand = generate() + intInRange(0, scale) * (in_range + 1);
}
while (rand < lower_bound && rand > upper_bound);
rand = lower_bound + rand;
}
else
{
rand = lower_bound + generate();
}
return rand;
}
float Random::floatInRange(float lower_bound, float upper_bound)
{
return generateFloat() * (upper_bound - lower_bound) + lower_bound;
}
float Random::normalDistribution(float mean, float stddev)
{
if (has_saved_value)
{
has_saved_value = false;
return saved_value * stddev + mean;
}
else
{
float u, v, s;
do
{
u = 2.0f*generateFloat() - 1;
v = 2.0f*generateFloat() - 1;
s = (u * u) + (v * v);
}
while (s > 1.0f || s == 0.0f);
s = std::sqrt(-2*std::log(s) / s);
saved_value = u * s;
has_saved_value = true;
return mean + stddev * (v * s);
}
}
float Random::generateFloat()
{
return std::generate_canonical<float,
std::numeric_limits<float>::digits,
decltype(generator)>(generator);
}
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