Tilted uniform distribution random number generator over min/max range, C++ (clang)

Tilted uniform distribution random number generator over min/max range

#include <iostream>
#include <iomanip>
#include <string>
#include <map>
#include <cmath>

// -------- CONFIG --------

float min = -10;
float max = 10;
float tilt = 1.;

// ------------------------

using std::cout;
using std::endl;
static bool debug = false;

float randomRange(float min, float max, float tilt = 0);

int main()
{
    srand(time(NULL));
    
    if (debug)
    {
        cout << randomRange(min, max, tilt) << endl;
        return 0;
    }
        
    std::map<int, int> hist;
    for (int i = 0; i < 1000000; ++i)
    {
        ++hist[round(randomRange(min, max, tilt))];
    }

for (auto p : hist) {
        std::cout << std::fixed << std::setprecision(1) << std::setw(3)
                  << p.first << ' ' << p.second << '\t' << std::string(p.second/2000, '*') << '\n';
    }
}

float randomRange(float min, float max, float tilt)
{
    float rnd = min + static_cast<float>(rand()) / static_cast<float>(RAND_MAX / (max - min));
    
    if (debug) cout << "rnd: " << rnd << endl;
    
    if (0 == tilt)
        return rnd;
    
    float middle = (min + max)/2.F;
    if (debug) cout << "middle: " << middle << endl;
    
    // Calculate probability
    float deviation = (((rnd - min)/(max - min)) - 0.5F) / 0.5F;
    if (debug) cout << "deviation: " << deviation << endl;
    float probability = -deviation * tilt;
    if (debug) cout << "probability: " << probability << endl;
    
    if (probability < 0)
    {
        if (debug) cout << "Negative probability. Return original random." << endl << endl;
        return rnd;
    }
    
    float dice = static_cast<float>(rand()) / static_cast<float>(RAND_MAX);
    if (debug) cout << dice << " ";
    
    if (dice > probability)
    {
        if (debug) cout << "--> no flip. Return original random." << endl << endl;
        return rnd;
    }

float counterpart = min + max - rnd;
    
    if (debug) cout << "--> FLIP! Return counterpart." << endl << endl;
    return counterpart;
}


run \| edit \| history \| help	0

λ

                                      .NET NoSQL database for rapid development