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// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.
//
// Newton's method adapted from Conte and De Boor
using Microsoft.Xunit.Performance;
using System;
using System.Runtime.CompilerServices;
using Xunit;
[assembly: OptimizeForBenchmarks]
[assembly: MeasureInstructionsRetired]
public static class NewtR
{
#if DEBUG
public const int Iterations = 1;
#else
public const int Iterations = 80000000;
#endif
public static volatile object VolatileObject;
[MethodImpl(MethodImplOptions.NoInlining)]
private static void Escape(object obj)
{
VolatileObject = obj;
}
[MethodImpl(MethodImplOptions.NoInlining)]
private static bool Bench()
{
int idbg, iflag;
double x0, fx0;
iflag = 0;
idbg = 0;
fx0 = 0.0;
x0 = 1.0;
for (int i = 1; i <= Iterations; i++)
{
Inner(ref x0, 0.0000001, 0.0000001, 10, out iflag);
if (iflag > 1)
{
goto L888;
}
fx0 = FF(x0);
if (idbg != 0)
{
System.Console.WriteLine(" THE ROOT IS {0:e} F(ROOT) := {1:E}\n", x0, fx0);
}
L888:
{
}
}
// Escape iflag, x0, and fx0 so that they appear live
Escape(iflag);
Escape(x0);
Escape(fx0);
return true;
}
private static double FF(double x)
{
return (-1.0 - ((x) * (1.0 - ((x) * (x)))));
}
private static double FFDer(double x)
{
return (3.0 * (x) * (x) - 1.0);
}
private static void Inner(ref double x0, double xtol, double ftol, int ntol, out int iflag)
{
double fx0, deriv, deltax;
iflag = 0;
for (int n = 1; n <= ntol; n++)
{
fx0 = FF(x0);
if (System.Math.Abs(fx0) < ftol)
{
goto L999;
}
deriv = FFDer(x0);
if (deriv == 0.0)
{
goto L999;
}
deltax = fx0 / deriv;
x0 = x0 - deltax;
if (System.Math.Abs(deltax) < xtol)
{
goto L999;
}
}
L999:
iflag = 2;
}
[Benchmark]
public static void Test()
{
foreach (var iteration in Benchmark.Iterations)
{
using (iteration.StartMeasurement())
{
Bench();
}
}
}
private static bool TestBase()
{
bool result = Bench();
return result;
}
public static int Main()
{
bool result = TestBase();
return (result ? 100 : -1);
}
}
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