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Add tests for Hypotenuse (float and double) and fix Hypotenuse to pass the tests #1145

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Add tests for Hypotenuse (float and double) and fix Hypotenuse to pass the tests #1145

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170 changes: 170 additions & 0 deletions src/Numerics.Tests/SpecialFunctionsTests/StabilityTests.cs
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Original file line number Diff line number Diff line change
@@ -0,0 +1,170 @@
// <copyright file="StabilityTests.cs" company="Math.NET">
// Math.NET Numerics, part of the Math.NET Project
// https://numerics.mathdotnet.com
// https://github.com/mathnet/mathnet-numerics
//
// Copyright (c) 2009-$CURRENT_YEAR$ Math.NET
//
// Permission is hereby granted, free of charge, to any person
// obtaining a copy of this software and associated documentation
// files (the "Software"), to deal in the Software without
// restriction, including without limitation the rights to use,
// copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the
// Software is furnished to do so, subject to the following
// conditions:
//
// The above copyright notice and this permission notice shall be
// included in all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
// OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
// NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
// HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
// WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
// OTHER DEALINGS IN THE SOFTWARE.
// </copyright>

using NUnit.Framework;

namespace MathNet.Numerics.Tests.SpecialFunctionsTests
{
/// <summary>
/// Special functions tests.
/// </summary>
[TestFixture, Category("Functions")]
public class StabilityTests
{
/// <summary>
/// Hypotenuse function (double).
/// </summary>
/// <param name="x">Input X value.</param>
/// <param name="y">Input Y value.</param>
/// <param name="f">Function result.</param>
[TestCase(double.NaN, 0, double.NaN)]
[TestCase(0, double.NaN, double.NaN)]
[TestCase(double.NaN, double.NaN, double.NaN)]
[TestCase(double.NegativeInfinity, double.NaN, double.NaN)]
[TestCase(double.NaN, double.NegativeInfinity, double.NaN)]
[TestCase(double.PositiveInfinity, double.NaN, double.NaN)]
[TestCase(double.NaN, double.PositiveInfinity, double.NaN)]
[TestCase(double.NegativeInfinity, 0, double.PositiveInfinity)]
[TestCase(double.NegativeInfinity, double.NegativeInfinity, double.PositiveInfinity)]
[TestCase(double.NegativeInfinity, double.PositiveInfinity, double.PositiveInfinity)]
[TestCase(0, double.NegativeInfinity, double.PositiveInfinity)]
[TestCase(double.PositiveInfinity, 0, double.PositiveInfinity)]
[TestCase(double.PositiveInfinity, double.PositiveInfinity, double.PositiveInfinity)]
[TestCase(double.PositiveInfinity, double.NegativeInfinity, double.PositiveInfinity)]
[TestCase(0, double.NegativeInfinity, double.PositiveInfinity)]
[TestCase(0, double.MaxValue, double.MaxValue)]
[TestCase(double.MaxValue, 0, double.MaxValue)]
[TestCase(0, -double.MinValue, -double.MinValue)]
[TestCase(0, double.MinValue, -double.MinValue)]
[TestCase(-double.MinValue, 0, -double.MinValue)]
[TestCase(double.MinValue, 0, -double.MinValue)]
[TestCase(0, double.Epsilon, double.Epsilon)]
[TestCase(0, -double.Epsilon, double.Epsilon)]
[TestCase(double.Epsilon, 0, double.Epsilon)]
[TestCase(-double.Epsilon, 0, double.Epsilon)]
[TestCase(0, 0, 0)]
[TestCase(0, 7, 7)]
[TestCase(0, -7, 7)]
[TestCase(7, 0, 7)]
[TestCase(-7, 0, 7)]
[TestCase(3, 4, 5)]
[TestCase(3, -4, 5)]
[TestCase(-3, 4, 5)]
[TestCase(-3, -4, 5)]
[TestCase(4, 3, 5)]
[TestCase(4, -3, 5)]
[TestCase(-4, 3, 5)]
[TestCase(-4, -3, 5)]
[TestCase(1, 2.98023223876953125E-8, 1.000000000000000444089210)] // TwoToThePowerOfMinus25 = 2.98023223876953125E-8;
[TestCase(1, -2.98023223876953125E-8, 1.000000000000000444089210)]
[TestCase(-1, 2.98023223876953125E-8, 1.000000000000000444089210)]
[TestCase(-1, -2.98023223876953125E-8, 1.000000000000000444089210)]
[TestCase(2.98023223876953125E-8, 1, 1.000000000000000444089210)]
[TestCase(2.98023223876953125E-8, -1, 1.000000000000000444089210)]
[TestCase(-2.98023223876953125E-8, 1, 1.000000000000000444089210)]
[TestCase(-2.98023223876953125E-8, -1, 1.000000000000000444089210)]
public void Hypotenuse(double x, double y, double f)
{
var h = SpecialFunctions.Hypotenuse(x, y);
if (double.IsNaN(f))
{
Assert.IsTrue(double.IsNaN(h));
}
else
{
Assert.AreEqual(f, h);
}
}

/// <summary>
/// Hypotenuse function (float).
/// </summary>
/// <param name="x">Input X value.</param>
/// <param name="y">Input Y value.</param>
/// <param name="f">Function result.</param>
[TestCase(float.NaN, 0, float.NaN)]
[TestCase(0, float.NaN, float.NaN)]
[TestCase(float.NaN, float.NaN, float.NaN)]
[TestCase(float.NegativeInfinity, float.NaN, float.NaN)]
[TestCase(float.NaN, float.NegativeInfinity, float.NaN)]
[TestCase(float.PositiveInfinity, float.NaN, float.NaN)]
[TestCase(float.NaN, float.PositiveInfinity, float.NaN)]
[TestCase(float.NegativeInfinity, 0, float.PositiveInfinity)]
[TestCase(float.NegativeInfinity, float.NegativeInfinity, float.PositiveInfinity)]
[TestCase(float.NegativeInfinity, float.PositiveInfinity, float.PositiveInfinity)]
[TestCase(0, float.NegativeInfinity, float.PositiveInfinity)]
[TestCase(float.PositiveInfinity, 0, float.PositiveInfinity)]
[TestCase(float.PositiveInfinity, float.PositiveInfinity, float.PositiveInfinity)]
[TestCase(float.PositiveInfinity, float.NegativeInfinity, float.PositiveInfinity)]
[TestCase(0, float.NegativeInfinity, float.PositiveInfinity)]
[TestCase(0, float.MaxValue, float.MaxValue)]
[TestCase(float.MaxValue, 0, float.MaxValue)]
[TestCase(0, -float.MinValue, -float.MinValue)]
[TestCase(0, float.MinValue, -float.MinValue)]
[TestCase(-float.MinValue, 0, -float.MinValue)]
[TestCase(float.MinValue, 0, -float.MinValue)]
[TestCase(0, float.Epsilon, float.Epsilon)]
[TestCase(0, -float.Epsilon, float.Epsilon)]
[TestCase(float.Epsilon, 0, float.Epsilon)]
[TestCase(-float.Epsilon, 0, float.Epsilon)]
[TestCase(0, 0, 0)]
[TestCase(0, 7, 7)]
[TestCase(0, -7, 7)]
[TestCase(7, 0, 7)]
[TestCase(-7, 0, 7)]
[TestCase(3, 4, 5)]
[TestCase(3, -4, 5)]
[TestCase(-3, 4, 5)]
[TestCase(-3, -4, 5)]
[TestCase(4, 3, 5)]
[TestCase(4, -3, 5)]
[TestCase(-4, 3, 5)]
[TestCase(-4, -3, 5)]
[TestCase(1, 0.00048828125f, 1.000000119209282445354739f)] // TwoToThePowerOfMinus11 = 0.00048828125f
[TestCase(1, -0.00048828125f, 1.000000119209282445354739f)]
[TestCase(-1, 0.00048828125f, 1.000000119209282445354739f)]
[TestCase(-1, -0.00048828125f, 1.000000119209282445354739f)]
[TestCase(0.00048828125f, 1, 1.000000119209282445354739f)]
[TestCase(0.00048828125f, -1, 1.000000119209282445354739f)]
[TestCase(-0.00048828125f, 1, 1.000000119209282445354739f)]
[TestCase(-0.00048828125f, -1, 1.000000119209282445354739f)]
public void Hypotenuse(float x, float y, float f)
{
var h = SpecialFunctions.Hypotenuse(x, y);
if (float.IsNaN(f))
{
Assert.IsTrue(float.IsNaN(h));
}
else
{
Assert.AreEqual(f, h);
}
}
}
}
73 changes: 40 additions & 33 deletions src/Numerics/SpecialFunctions/Stability.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -91,25 +91,26 @@ public static Complex32 Hypotenuse(Complex32 a, Complex32 b)
/// <returns>Returns <code>sqrt(a<sup>2</sup> + b<sup>2</sup>)</code> without underflow/overflow.</returns>
public static double Hypotenuse(double a, double b)
{
if (double.IsNaN(a) || double.IsNaN(b))
{
return double.NaN;
}

if (Math.Abs(a) > Math.Abs(b))
{
double r = b/a;
return Math.Abs(a)*Math.Sqrt(1 + (r*r));
}

if (b != 0.0)
{
// NOTE (ruegg): not "!b.AlmostZero()" to avoid convergence issues (e.g. in SVD algorithm)
double r = a/b;
return Math.Abs(b)*Math.Sqrt(1 + (r*r));
}

return 0d;
var min = Math.Abs(a);
var max = Math.Abs(b);
if (min > max)
{
(min, max) = (max, min);
}
if (min == 0)
{
return max;
}
else if (double.IsInfinity(min + max))
{
return double.PositiveInfinity;
}
else
{
// NOTE (ruegg): not "!b.AlmostZero()" to avoid convergence issues (e.g. in SVD algorithm)
var r = min / max;
return max * Math.Sqrt(1 + r * r);
}
}

/// <summary>
Expand All @@ -120,20 +121,26 @@ public static double Hypotenuse(double a, double b)
/// <returns>Returns <code>sqrt(a<sup>2</sup> + b<sup>2</sup>)</code> without underflow/overflow.</returns>
public static float Hypotenuse(float a, float b)
{
if (Math.Abs(a) > Math.Abs(b))
{
float r = b/a;
return Math.Abs(a)*(float)Math.Sqrt(1 + (r*r));
}

if (b != 0.0)
{
// NOTE (ruegg): not "!b.AlmostZero()" to avoid convergence issues (e.g. in SVD algorithm)
float r = a/b;
return Math.Abs(b)*(float)Math.Sqrt(1 + (r*r));
}

return 0f;
var min = Math.Abs(a);
var max = Math.Abs(b);
if (min > max)
{
(min, max) = (max, min);
}
if (min == 0)
{
return max;
}
else if (float.IsInfinity(min + max))
{
return float.PositiveInfinity;
}
else
{
// NOTE (ruegg): not "!b.AlmostZero()" to avoid convergence issues (e.g. in SVD algorithm)
var r = min / max;
return max * (float)Math.Sqrt(1 + r * r);
}
}
}
}