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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.
//
using Microsoft.Xunit.Performance;
using System;
using System.Runtime.CompilerServices;
using Xunit;
[assembly: OptimizeForBenchmarks]
namespace Benchstone.BenchI
{
public static class HeapSort
{
#if DEBUG
public const int Iterations = 1;
#else
public const int Iterations = 2500;
#endif
const int ArraySize = 5500;
static void Inner(int[] x, int n) {
int i, j, k, m;
// pass1 -- put vector in heap form
// that is to say, guarantee that x(i)>=x(2*i) and x(i)>=x(2*i+1).
// after pass 1, the largest item will be at x(1).
for (i = 2; i <= n; i++) {
j = i;
k = j / 2;
m = x[i];
// 0 < k <= (n / 2)
// 1 <= j <= n
while (k > 0) {
if (m <= x[k]) {
break;
}
x[j] = x[k];
j = k;
k = k / 2;
}
x[j] = m;
}
// pass 2 -- swap first and last items. now with the last
// item correctly placed, consider the list shorter by one item.
// restore the shortened list to heap sort, and repeat
// process until list is only two items long.
i = n;
do {
// do i = n to 2 by -1;
m = x[i];
x[i] = x[1]; // last item, i.e. item(i) now correct.
j = 1; // we now find the appropriate resting point for m
k = 2;
// 2 <= k < i ==> 2 <= k < n
// 1 <= j < n
while (k < i) {
if ((k + 1) < i) {
if (x[k + 1] > x[k]) {
k = k + 1;
}
}
if (x[k] <= m) {
break;
}
x[j] = x[k];
j = k;
k = k + k;
}
x[j] = m;
i = i - 1;
} while (i >= 2);
}
[MethodImpl(MethodImplOptions.NoInlining)]
static bool Bench() {
int[] x = new int[ArraySize + 1];
for (int i = 1; i <= ArraySize; i++) {
x[i] = ArraySize - i + 1;
}
Inner(x, ArraySize);
for (int j = 1; j <= ArraySize; j++) {
if (x[j] != j) {
return false;
}
}
return true;
}
[Benchmark]
public static void Test() {
foreach (var iteration in Benchmark.Iterations) {
using (iteration.StartMeasurement()) {
for (int i = 0; i < Iterations; i++) {
Bench();
}
}
}
}
static bool TestBase() {
bool result = true;
for (int i = 0; i < Iterations; i++) {
result &= Bench();
}
return result;
}
public static int Main() {
bool result = TestBase();
return (result ? 100 : -1);
}
}
}
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