FastRng/FastRngTests/Distributions/CauchyLorentzX1.cs

using System;
using System.Diagnostics.CodeAnalysis;
using System.Linq;
using System.Threading.Tasks;
using FastRng;
using NUnit.Framework;

namespace FastRngTests.Distributions;

[ExcludeFromCodeCoverage]
public class CauchyLorentzX1
{
    [Test]
    [Category(TestCategories.COVER)]
    [Category(TestCategories.NORMAL)]
    public async Task TestCauchyDistribution01()
    {
        // The properties of the cauchy distribution cannot be tested by mean, media or variance,  
        // cf. https://en.wikipedia.org/wiki/Cauchy_distribution#Explanation_of_undefined_moments
            
        using var rng = new MultiThreadedRng<float>();
        var dist = new FastRng.Distributions.CauchyLorentzX1<float>(rng);
        var fqa = new FrequencyAnalysis();

        for (var n = 0; n < 100_000; n++)
            fqa.CountThis(await dist.NextNumber());
            
        var result = fqa.NormalizeAndPlotEvents(TestContext.WriteLine);
            
        Assert.That(result[0], Is.EqualTo(0.009966272570142f).Within(0.003f));
        Assert.That(result[1], Is.EqualTo(0.010168596941156f).Within(0.004f));
        Assert.That(result[2], Is.EqualTo(0.010377123221893f).Within(0.005f));
            
        Assert.That(result[21], Is.EqualTo(0.015956672819692f).Within(0.005f));
        Assert.That(result[22], Is.EqualTo(0.016366904083094f).Within(0.005f));
        Assert.That(result[23], Is.EqualTo(0.016793067514802f).Within(0.005f));
            
        Assert.That(result[50], Is.EqualTo(0.039454644029179f).Within(0.015f));
            
        Assert.That(result[75], Is.EqualTo(0.145970509936354f).Within(0.03f));
        Assert.That(result[85], Is.EqualTo(0.333365083503296f).Within(0.1f));
        Assert.That(result[90], Is.EqualTo(0.545171628270584f).Within(0.1f));
            
        Assert.That(result[97], Is.EqualTo(0.948808314586302f).Within(0.06f));
        Assert.That(result[98], Is.EqualTo(0.976990739772032f).Within(0.03f));
        Assert.That(result[99], Is.EqualTo(0.986760647169751f).Within(0.02f));
    }

    [Test]
    [Category(TestCategories.COVER)]
    [Category(TestCategories.NORMAL)]
    public async Task TestCauchyGeneratorWithRange01()
    {
        using var rng = new MultiThreadedRng<float>();
        var dist = new FastRng.Distributions.CauchyLorentzX0<float>(rng);
        var samples = new float[1_000];
        for (var n = 0; n < samples.Length; n++)
            samples[n] = await dist.NextNumber(-1.0f, 1.0f);
            
        Assert.That(samples.Min(), Is.GreaterThanOrEqualTo(-1.0f), "Min is out of range");
        Assert.That(samples.Max(), Is.LessThanOrEqualTo(1.0f), "Max is out of range");
    }
        
    [Test]
    [Category(TestCategories.COVER)]
    [Category(TestCategories.NORMAL)]
    public async Task TestCauchyGeneratorWithRange02()
    {
        using var rng = new MultiThreadedRng<float>();
        var dist = new FastRng.Distributions.CauchyLorentzX0<float>(rng);
        var samples = new float[1_000];
        for (var n = 0; n < samples.Length; n++)
            samples[n] = await dist.NextNumber(0.0f, 1.0f);
            
        Assert.That(samples.Min(), Is.GreaterThanOrEqualTo(0.0f), "Min is out of range");
        Assert.That(samples.Max(), Is.LessThanOrEqualTo(1.0f), "Max is out of range");
    }

    [Test]
    [Category(TestCategories.COVER)]
    [Category(TestCategories.NORMAL)]
    public void NoRandomNumberGenerator01()
    {
        Assert.Throws<ArgumentNullException>(() => new FastRng.Distributions.CauchyLorentzX1<float>(null));
    }
}