
//===----------------------------------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// REQUIRES: long_tests

// <random>

// template<class IntType = int>
// class binomial_distribution

// template<class _URNG> result_type operator()(_URNG& g);

#include <random>
#include <numeric>
#include <vector>
#include <cassert>

template <class T>
inline
T
sqr(T x)
{
    return x * x;
}

void
test1()
{
    typedef std::binomial_distribution<> D;
    typedef std::mt19937_64 G;
    G g;
    D d(5, .75);
    const int N = 1000000;
    std::vector<D::result_type> u;
    for (int i = 0; i < N; ++i)
    {
        D::result_type v = d(g);
        assert(d.min() <= v && v <= d.max());
        u.push_back(v);
    }
    double mean = std::accumulate(u.begin(), u.end(),
                                          double(0)) / u.size();
    double var = 0;
    double skew = 0;
    double kurtosis = 0;
    for (unsigned i = 0; i < u.size(); ++i)
    {
        double dbl = (u[i] - mean);
        double d2 = sqr(dbl);
        var += d2;
        skew += dbl * d2;
        kurtosis += d2 * d2;
    }
    var /= u.size();
    double dev = std::sqrt(var);
    skew /= u.size() * dev * var;
    kurtosis /= u.size() * var * var;
    kurtosis -= 3;
    double x_mean = d.t() * d.p();
    double x_var = x_mean*(1-d.p());
    double x_skew = (1-2*d.p()) / std::sqrt(x_var);
    double x_kurtosis = (1-6*d.p()*(1-d.p())) / x_var;
    assert(std::abs((mean - x_mean) / x_mean) < 0.01);
    assert(std::abs((var - x_var) / x_var) < 0.01);
    assert(std::abs((skew - x_skew) / x_skew) < 0.01);
    assert(std::abs((kurtosis - x_kurtosis) / x_kurtosis) < 0.04);
}

void
test2()
{
    typedef std::binomial_distribution<> D;
    typedef std::mt19937 G;
    G g;
    D d(30, .03125);
    const int N = 100000;
    std::vector<D::result_type> u;
    for (int i = 0; i < N; ++i)
    {
        D::result_type v = d(g);
        assert(d.min() <= v && v <= d.max());
        u.push_back(v);
    }
    double mean = std::accumulate(u.begin(), u.end(),
                                          double(0)) / u.size();
    double var = 0;
    double skew = 0;
    double kurtosis = 0;
    for (unsigned i = 0; i < u.size(); ++i)
    {
        double dbl = (u[i] - mean);
        double d2 = sqr(dbl);
        var += d2;
        skew += dbl * d2;
        kurtosis += d2 * d2;
    }
    var /= u.size();
    double dev = std::sqrt(var);
    skew /= u.size() * dev * var;
    kurtosis /= u.size() * var * var;
    kurtosis -= 3;
    double x_mean = d.t() * d.p();
    double x_var = x_mean*(1-d.p());
    double x_skew = (1-2*d.p()) / std::sqrt(x_var);
    double x_kurtosis = (1-6*d.p()*(1-d.p())) / x_var;
    assert(std::abs((mean - x_mean) / x_mean) < 0.01);
    assert(std::abs((var - x_var) / x_var) < 0.01);
    assert(std::abs((skew - x_skew) / x_skew) < 0.01);
    assert(std::abs((kurtosis - x_kurtosis) / x_kurtosis) < 0.01);
}

void
test3()
{
    typedef std::binomial_distribution<> D;
    typedef std::mt19937 G;
    G g;
    D d(40, .25);
    const int N = 100000;
    std::vector<D::result_type> u;
    for (int i = 0; i < N; ++i)
    {
        D::result_type v = d(g);
        assert(d.min() <= v && v <= d.max());
        u.push_back(v);
    }
    double mean = std::accumulate(u.begin(), u.end(),
                                          double(0)) / u.size();
    double var = 0;
    double skew = 0;
    double kurtosis = 0;
    for (unsigned i = 0; i < u.size(); ++i)
    {
        double dbl = (u[i] - mean);
        double d2 = sqr(dbl);
        var += d2;
        skew += dbl * d2;
        kurtosis += d2 * d2;
    }
    var /= u.size();
    double dev = std::sqrt(var);
    skew /= u.size() * dev * var;
    kurtosis /= u.size() * var * var;
    kurtosis -= 3;
    double x_mean = d.t() * d.p();
    double x_var = x_mean*(1-d.p());
    double x_skew = (1-2*d.p()) / std::sqrt(x_var);
    double x_kurtosis = (1-6*d.p()*(1-d.p())) / x_var;
    assert(std::abs((mean - x_mean) / x_mean) < 0.01);
    assert(std::abs((var - x_var) / x_var) < 0.01);
    assert(std::abs((skew - x_skew) / x_skew) < 0.03);
    assert(std::abs((kurtosis - x_kurtosis) / x_kurtosis) < 0.3);
}

void
test4()
{
    typedef std::binomial_distribution<> D;
    typedef std::mt19937 G;
    G g;
    D d(40, 0);
    const int N = 100000;
    std::vector<D::result_type> u;
    for (int i = 0; i < N; ++i)
    {
        D::result_type v = d(g);
        assert(d.min() <= v && v <= d.max());
        u.push_back(v);
    }
    double mean = std::accumulate(u.begin(), u.end(),
                                          double(0)) / u.size();
    double var = 0;
    double skew = 0;
    double kurtosis = 0;
    for (unsigned i = 0; i < u.size(); ++i)
    {
        double dbl = (u[i] - mean);
        double d2 = sqr(dbl);
        var += d2;
        skew += dbl * d2;
        kurtosis += d2 * d2;
    }
    var /= u.size();
    double dev = std::sqrt(var);
    // In this case:
    //   skew     computes to 0./0. == nan
    //   kurtosis computes to 0./0. == nan
    //   x_skew     == inf
    //   x_kurtosis == inf
    skew /= u.size() * dev * var;
    kurtosis /= u.size() * var * var;
    kurtosis -= 3;
    double x_mean = d.t() * d.p();
    double x_var = x_mean*(1-d.p());
    double x_skew = (1-2*d.p()) / std::sqrt(x_var);
    double x_kurtosis = (1-6*d.p()*(1-d.p())) / x_var;
    assert(mean == x_mean);
    assert(var == x_var);
    // assert(skew == x_skew);
    (void)skew; (void)x_skew;
    // assert(kurtosis == x_kurtosis);
    (void)kurtosis; (void)x_kurtosis;
}

void
test5()
{
    typedef std::binomial_distribution<> D;
    typedef std::mt19937 G;
    G g;
    D d(40, 1);
    const int N = 100000;
    std::vector<D::result_type> u;
    for (int i = 0; i < N; ++i)
    {
        D::result_type v = d(g);
        assert(d.min() <= v && v <= d.max());
        u.push_back(v);
    }
    double mean = std::accumulate(u.begin(), u.end(),
                                          double(0)) / u.size();
    double var = 0;
    double skew = 0;
    double kurtosis = 0;
    for (unsigned i = 0; i < u.size(); ++i)
    {
        double dbl = (u[i] - mean);
        double d2 = sqr(dbl);
        var += d2;
        skew += dbl * d2;
        kurtosis += d2 * d2;
    }
    var /= u.size();
    double dev = std::sqrt(var);
    // In this case:
    //   skew     computes to 0./0. == nan
    //   kurtosis computes to 0./0. == nan
    //   x_skew     == -inf
    //   x_kurtosis == inf
    skew /= u.size() * dev * var;
    kurtosis /= u.size() * var * var;
    kurtosis -= 3;
    double x_mean = d.t() * d.p();
    double x_var = x_mean*(1-d.p());
    double x_skew = (1-2*d.p()) / std::sqrt(x_var);
    double x_kurtosis = (1-6*d.p()*(1-d.p())) / x_var;
    assert(mean == x_mean);
    assert(var == x_var);
    // assert(skew == x_skew);
    (void)skew; (void)x_skew;
    // assert(kurtosis == x_kurtosis);
    (void)kurtosis; (void)x_kurtosis;
}

void
test6()
{
    typedef std::binomial_distribution<> D;
    typedef std::mt19937 G;
    G g;
    D d(400, 0.5);
    const int N = 100000;
    std::vector<D::result_type> u;
    for (int i = 0; i < N; ++i)
    {
        D::result_type v = d(g);
        assert(d.min() <= v && v <= d.max());
        u.push_back(v);
    }
    double mean = std::accumulate(u.begin(), u.end(),
                                          double(0)) / u.size();
    double var = 0;
    double skew = 0;
    double kurtosis = 0;
    for (unsigned i = 0; i < u.size(); ++i)
    {
        double dbl = (u[i] - mean);
        double d2 = sqr(dbl);
        var += d2;
        skew += dbl * d2;
        kurtosis += d2 * d2;
    }
    var /= u.size();
    double dev = std::sqrt(var);
    skew /= u.size() * dev * var;
    kurtosis /= u.size() * var * var;
    kurtosis -= 3;
    double x_mean = d.t() * d.p();
    double x_var = x_mean*(1-d.p());
    double x_skew = (1-2*d.p()) / std::sqrt(x_var);
    double x_kurtosis = (1-6*d.p()*(1-d.p())) / x_var;
    assert(std::abs((mean - x_mean) / x_mean) < 0.01);
    assert(std::abs((var - x_var) / x_var) < 0.01);
    assert(std::abs(skew - x_skew) < 0.01);
    assert(std::abs(kurtosis - x_kurtosis) < 0.01);
}

void
test7()
{
    typedef std::binomial_distribution<> D;
    typedef std::mt19937 G;
    G g;
    D d(1, 0.5);
    const int N = 100000;
    std::vector<D::result_type> u;
    for (int i = 0; i < N; ++i)
    {
        D::result_type v = d(g);
        assert(d.min() <= v && v <= d.max());
        u.push_back(v);
    }
    double mean = std::accumulate(u.begin(), u.end(),
                                          double(0)) / u.size();
    double var = 0;
    double skew = 0;
    double kurtosis = 0;
    for (unsigned i = 0; i < u.size(); ++i)
    {
        double dbl = (u[i] - mean);
        double d2 = sqr(dbl);
        var += d2;
        skew += dbl * d2;
        kurtosis += d2 * d2;
    }
    var /= u.size();
    double dev = std::sqrt(var);
    skew /= u.size() * dev * var;
    kurtosis /= u.size() * var * var;
    kurtosis -= 3;
    double x_mean = d.t() * d.p();
    double x_var = x_mean*(1-d.p());
    double x_skew = (1-2*d.p()) / std::sqrt(x_var);
    double x_kurtosis = (1-6*d.p()*(1-d.p())) / x_var;
    assert(std::abs((mean - x_mean) / x_mean) < 0.01);
    assert(std::abs((var - x_var) / x_var) < 0.01);
    assert(std::abs(skew - x_skew) < 0.01);
    assert(std::abs((kurtosis - x_kurtosis) / x_kurtosis) < 0.01);
}

void
test8()
{
    const int N = 100000;
    std::mt19937 gen1;
    std::mt19937 gen2;

    std::binomial_distribution<>         dist1(5, 0.1);
    std::binomial_distribution<unsigned> dist2(5, 0.1);

    for(int i = 0; i < N; ++i) {
        int r1 = dist1(gen1);
        unsigned r2 = dist2(gen2);
        assert(r1 >= 0);
        assert(static_cast<unsigned>(r1) == r2);
    }
}

void
test9()
{
    typedef std::binomial_distribution<> D;
    typedef std::mt19937 G;
    G g;
    D d(0, 0.005);
    const int N = 100000;
    std::vector<D::result_type> u;
    for (int i = 0; i < N; ++i)
    {
        D::result_type v = d(g);
        assert(d.min() <= v && v <= d.max());
        u.push_back(v);
    }
    double mean = std::accumulate(u.begin(), u.end(),
                                          double(0)) / u.size();
    double var = 0;
    double skew = 0;
    double kurtosis = 0;
    for (unsigned i = 0; i < u.size(); ++i)
    {
        double dbl = (u[i] - mean);
        double d2 = sqr(dbl);
        var += d2;
        skew += dbl * d2;
        kurtosis += d2 * d2;
    }
    var /= u.size();
    double dev = std::sqrt(var);
    // In this case:
    //   skew     computes to 0./0. == nan
    //   kurtosis computes to 0./0. == nan
    //   x_skew     == inf
    //   x_kurtosis == inf
    skew /= u.size() * dev * var;
    kurtosis /= u.size() * var * var;
    kurtosis -= 3;
    double x_mean = d.t() * d.p();
    double x_var = x_mean*(1-d.p());
    double x_skew = (1-2*d.p()) / std::sqrt(x_var);
    double x_kurtosis = (1-6*d.p()*(1-d.p())) / x_var;
    assert(mean == x_mean);
    assert(var == x_var);
    // assert(skew == x_skew);
    (void)skew; (void)x_skew;
    // assert(kurtosis == x_kurtosis);
    (void)kurtosis; (void)x_kurtosis;
}

void
test10()
{
    typedef std::binomial_distribution<> D;
    typedef std::mt19937 G;
    G g;
    D d(0, 0);
    const int N = 100000;
    std::vector<D::result_type> u;
    for (int i = 0; i < N; ++i)
    {
        D::result_type v = d(g);
        assert(d.min() <= v && v <= d.max());
        u.push_back(v);
    }
    double mean = std::accumulate(u.begin(), u.end(),
                                          double(0)) / u.size();
    double var = 0;
    double skew = 0;
    double kurtosis = 0;
    for (unsigned i = 0; i < u.size(); ++i)
    {
        double dbl = (u[i] - mean);
        double d2 = sqr(dbl);
        var += d2;
        skew += dbl * d2;
        kurtosis += d2 * d2;
    }
    var /= u.size();
    double dev = std::sqrt(var);
    // In this case:
    //   skew     computes to 0./0. == nan
    //   kurtosis computes to 0./0. == nan
    //   x_skew     == inf
    //   x_kurtosis == inf
    skew /= u.size() * dev * var;
    kurtosis /= u.size() * var * var;
    kurtosis -= 3;
    double x_mean = d.t() * d.p();
    double x_var = x_mean*(1-d.p());
    double x_skew = (1-2*d.p()) / std::sqrt(x_var);
    double x_kurtosis = (1-6*d.p()*(1-d.p())) / x_var;
    assert(mean == x_mean);
    assert(var == x_var);
    // assert(skew == x_skew);
    (void)skew; (void)x_skew;
    // assert(kurtosis == x_kurtosis);
    (void)kurtosis; (void)x_kurtosis;
}

void
test11()
{
    typedef std::binomial_distribution<> D;
    typedef std::mt19937 G;
    G g;
    D d(0, 1);
    const int N = 100000;
    std::vector<D::result_type> u;
    for (int i = 0; i < N; ++i)
    {
        D::result_type v = d(g);
        assert(d.min() <= v && v <= d.max());
        u.push_back(v);
    }
    double mean = std::accumulate(u.begin(), u.end(),
                                          double(0)) / u.size();
    double var = 0;
    double skew = 0;
    double kurtosis = 0;
    for (unsigned i = 0; i < u.size(); ++i)
    {
        double dbl = (u[i] - mean);
        double d2 = sqr(dbl);
        var += d2;
        skew += dbl * d2;
        kurtosis += d2 * d2;
    }
    var /= u.size();
    double dev = std::sqrt(var);
    // In this case:
    //   skew     computes to 0./0. == nan
    //   kurtosis computes to 0./0. == nan
    //   x_skew     == -inf
    //   x_kurtosis == inf
    skew /= u.size() * dev * var;
    kurtosis /= u.size() * var * var;
    kurtosis -= 3;
    double x_mean = d.t() * d.p();
    double x_var = x_mean*(1-d.p());
    double x_skew = (1-2*d.p()) / std::sqrt(x_var);
    double x_kurtosis = (1-6*d.p()*(1-d.p())) / x_var;
    assert(mean == x_mean);
    assert(var == x_var);
    // assert(skew == x_skew);
    (void)skew; (void)x_skew;
    // assert(kurtosis == x_kurtosis);
    (void)kurtosis; (void)x_kurtosis;
}

int main(int, char**)
{
    test1();
    test2();
    test3();
    test4();
    test5();
    test6();
    test7();
    test8();
    test9();
    test10();
    test11();

    return 0;
}
