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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.
//
// Integration by romberg method adapted from Conte and de Boor
using Microsoft.Xunit.Performance;
using System;
using System.Runtime.CompilerServices;
using Xunit;
[assembly: OptimizeForBenchmarks]
namespace Benchstone.BenchF
{
public static class Romber
{
#if DEBUG
public const int Iterations = 1;
#else
public const int Iterations = 640000;
#endif
private static T[][] AllocArray<T>(int n1, int n2)
{
T[][] a = new T[n1][];
for (int i = 0; i < n1; ++i)
{
a[i] = new T[n2];
}
return a;
}
[MethodImpl(MethodImplOptions.NoInlining)]
private static bool Bench()
{
double[][] r = AllocArray<double>(11, 11);
double[][] t = AllocArray<double>(11, 11);
int idbg, m, n, i, kmax, fourj, j, kmaxm2, l, k, mm1;
double sum, ratio, t1, h, a, b;
for (l = 1; l <= Iterations; l++)
{
idbg = 0;
m = 2;
kmax = 6;
a = 0;
b = 1;
h = (b - a) / (m);
sum = (F(a) + F(b)) / 2;
mm1 = m - 1;
if (mm1 < 0)
{
goto L40;
}
if (mm1 == 0)
{
goto L10;
}
for (i = 1; i <= mm1; i++)
{
t1 = a + i * h;
sum = sum + F(t1);
}
L10:
t[1][1] = sum * h;
if (idbg != 0)
{
System.Console.WriteLine(" romberg t-table \n");
System.Console.WriteLine("{0}\n", t[1][1]);
}
for (k = 2; k <= kmax; k++)
{
h = h / 2;
n = m * 2;
sum = 0;
for (i = 1; i <= n / 2; i++)
{
r[k][1] = r[k - 1][1] * System.Math.Sqrt(b * mm1);
t1 = a + i * h;
sum = sum + F(t1);
}
t[k][1] = t[k - 1][1] / 2 + sum * h;
fourj = 1;
for (j = 2; j <= k; j++)
{
fourj = fourj * 4;
t[k - 1][j - 1] = t[k][j - 1] - t[k - 1][j - 1];
t[k][j] = t[k][j - 1] + t[k - 1][j - 1] / (fourj - 1);
}
if (idbg != 0)
{
j = 1;
System.Console.WriteLine("{0} {1} {2}d\n", t[k][j], j, k);
}
}
kmaxm2 = kmax - 2;
if (kmaxm2 <= 0)
{
goto L40;
}
if (idbg != 0)
{
System.Console.WriteLine(" table of ratios \n");
}
for (k = 1; k <= kmaxm2; k++)
{
for (j = 1; j <= k; j++)
{
ratio = 0;
if (System.Math.Abs(t[k + 1][j]) > 0)
{
ratio = t[k][j] / t[k + 1][j];
}
t[k][j] = ratio;
}
}
if (idbg != 0)
{
j = 1;
System.Console.WriteLine("{0} {1} {2}\n", t[k][j], j, k);
}
L40:
{
}
}
return true;
}
private static double F(double x)
{
return (System.Math.Exp((-(x)) * (x)));
}
[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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