/*

* Random Number Generation Example

*

* Copyright 2012-2014 cppreference.com Contributors

* Copyright 2014-2017 Melissa O'Neill <oneill@pcg-random.org>

* and the PCG Project contributors.

*

* SPDX-License-Identifier: (CC-BY-SA-3.0 OR Apache-2.0 OR MIT)

*

* Code in this file is based on code from cppreference.com, specifically

* the sample code at http://en.cppreference.com/w/cpp/numeric/random

* which is distributed under the Creative Commons Attribution-Share Alike

* license. You may distribute this file (and only this file) under

* that license, see http://creativecommons.org/licenses/by-sa/3.0/.

*

* Also licensed under the Apache License, Version 2.0 (provided in

* LICENSE-APACHE.txt and at http://www.apache.org/licenses/LICENSE-2.0)

* or under the MIT license (provided in LICENSE-MIT.txt and at

* http://opensource.org/licenses/MIT), at your option. This file may not

* be copied, modified, or distributed except according to those terms.

*

* Distributed on an "AS IS" BASIS, WITHOUT WARRANTY OF ANY KIND, either

* express or implied. See your chosen license for details.

*

* For additional information about the PCG random number generation scheme,

* visit http://www.pcg-random.org/.

*/

/*

*/

/*

* Produce a histogram of a normal distribution.

*/

#include <iostream>

#include <iomanip>

#include <string>

#include <map>

#include <random>

#include <cmath>

#include "pcg_random.hpp"

int main()

{

// Seed with a real random value, if available

pcg_extras::seed_seq_from<std::random_device> seed_source;

// Make a random number engine

pcg32 rng(seed_source);

// Choose a random mean between 1 and 6

std::uniform_int_distribution<int> uniform_dist(1, 6);

int mean = uniform_dist(rng);

std::cout << "Randomly-chosen mean: " << mean << '\n';

// Generate a normal distribution around that mean

std::normal_distribution<> normal_dist(mean, 2);

// Make a copy of the RNG state to use later

pcg32 rng_checkpoint = rng;

std::map<int, int> hist;

for (int n = 0; n < 10000; ++n) {

++hist[std::round(normal_dist(rng))];

}

std::cout << "Normal distribution around " << mean << ":\n";

for (auto p : hist) {

std::cout << std::fixed << std::setprecision(1) << std::setw(2)

<< p.first << ' ' << std::string(p.second/30, '*')

<< '\n';

}

std::cout << "Required " << (rng - rng_checkpoint) << " random numbers.\n";

}