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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.
//
// The modified regula-falsi routine adapted from Conte and De Boor
using Microsoft.Xunit.Performance;
using System;
using System.Runtime.CompilerServices;
using Xunit;
[assembly: OptimizeForBenchmarks]
[assembly: MeasureInstructionsRetired]
namespace Benchstone.BenchF
{
public static class Regula
{
#if DEBUG
public const int Iterations = 1;
#else
public const int Iterations = 4000000;
#endif
public static volatile object VolatileObject;
[MethodImpl(MethodImplOptions.NoInlining)]
private static void Escape(object obj)
{
VolatileObject = obj;
}
[MethodImpl(MethodImplOptions.NoInlining)]
private static bool Bench()
{
double error, fxi;
double a, b, xi;
int idbg, iflag;
iflag = 0;
idbg = 0;
xi = 0;
error = 0.0;
fxi = 0.0;
for (int i = 1; i <= Iterations; i++)
{
a = 1.0;
b = 2.0;
Inner(ref a, ref b, 0.0000001, 0.0000000001, 30, out iflag);
if (iflag > 2)
{
goto L999;
}
xi = (a + b) / 2.0;
error = System.Math.Abs(b - a) / 2.0;
fxi = FG(xi);
if (idbg != 0)
{
System.Console.WriteLine(" the root is {0:E}", xi);
System.Console.WriteLine(" plus/minus {0}\n", error);
System.Console.WriteLine(" fg(root):= {0:E}\n", fxi);
}
L999:
{
}
}
// Escape iflag, xi, error, and fxi so that they appear live
Escape(iflag);
Escape(xi);
Escape(error);
Escape(fxi);
return true;
}
private static double FG(double x)
{
return (-1.0 - (x * (1.0 - (x * x))));
}
private static void Inner(ref double a, ref double b, double xtol, double ftol, int ntol, out int iflag)
{
double signfa, prevfw, fa, fb, fw, w;
iflag = 0;
fa = FG(a);
if (fa < 0.0)
{
signfa = -1.0;
}
else
{
signfa = 1.0;
}
fb = FG(b);
if (signfa * fb <= 0.0)
{
goto L5;
}
iflag = 3;
goto L99;
L5:
w = a;
fw = fa;
for (int i = 1; i <= ntol; i++)
{
if (System.Math.Abs(b - a) / 2.0 <= xtol)
{
goto L99;
}
if (System.Math.Abs(fw) > ftol)
{
goto L9;
}
a = w;
b = w;
iflag = 1;
goto L99;
L9:
w = (fa * b - fb * a) / (fa - fb);
if (fw < 0.0)
{
prevfw = -1.0;
}
else
{
prevfw = 1.0;
}
fw = FG(w);
if (signfa * fw < 0.0)
{
goto L10;
}
a = w;
fa = fw;
if (fw * prevfw > 0.0)
{
fb = fb / 2.0;
}
goto L20;
L10:
b = w;
fb = fw;
if (fw * prevfw > 0.0)
{
fa = fa / 2.0;
}
L20:
{
}
}
iflag = 2;
L99:
{
}
}
[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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