Coder
```C#
using BenchmarkDotNet.Attributes;
using BenchmarkDotNet.Configs;
using BenchmarkDotNet.Diagnosers;
using BenchmarkDotNet.Running;
using System.Diagnostics;
using BenchmarkDotNet.Jobs;
using System.Runtime.CompilerServices;
using System.Collections.Generic;
using System;
using System.Numerics;
using System.Linq;
using System.Runtime.Intrinsics.X86;
class Program
{
static void Main()
{
var fastConfig = new ManualConfig();
fastConfig.Add(DefaultConfig.Instance);
fastConfig.AddJob(Job.ShortRun);
BenchmarkRunner.Run(fastConfig);
}
}
public class AclBench
{
const int N = 1_000_000;
[Benchmark]
public long Orig()
{
var rnd = new Random(42);
long sum = 0;
for (int i = 0; i < N; i++)
{
sum += BSF((uint)rnd.Next());
}
return sum;
}
[Benchmark]
public long New()
{
var rnd = new Random(42);
long sum = 0;
for (int i = 0; i < N; i++)
{
sum += BSF2((uint)rnd.Next());
}
return sum;
}
[MethodImpl(MethodImplOptions.AggressiveInlining)]
public static int BSF(uint n)
{
Debug.Assert(n >= 1);
if (Bmi1.IsSupported)
{
// O(1)
return (int)Bmi1.TrailingZeroCount(n);
}
else if (Popcnt.IsSupported)
{
// O(1)
return (int)Popcnt.PopCount(~n & (n - 1));
}
else
{
// O(logn)
return BitOperations.TrailingZeroCount(n);
}
}
[MethodImpl(MethodImplOptions.AggressiveInlining)]
public static int BSF2(uint n)
{
Debug.Assert(n >= 1);
return BitOperations.TrailingZeroCount(n);
}
}
```
key-moon
commented
4 years ago
BitOperations.TrailingZeroCountの中でBmi1.TrailingZeroCountが呼ばれるので呼び分け不要です。Benchmark
BenchmarkDotNet=v0.12.1, OS=Windows 10.0.18363.1082 (1909/November2018Update/19H2) Intel Core i7-4790 CPU 3.60GHz (Haswell), 1 CPU, 8 logical and 4 physical cores .NET Core SDK=3.1.401 [Host] : .NET Core 3.1.7 (CoreCLR 4.700.20.36602, CoreFX 4.700.20.37001), X64 RyuJIT ShortRun : .NET Core 3.1.7 (CoreCLR 4.700.20.36602, CoreFX 4.700.20.37001), X64 RyuJIT
Job=ShortRun IterationCount=3 LaunchCount=1 WarmupCount=3
Coder
```C# using BenchmarkDotNet.Attributes; using BenchmarkDotNet.Configs; using BenchmarkDotNet.Diagnosers; using BenchmarkDotNet.Running; using System.Diagnostics; using BenchmarkDotNet.Jobs; using System.Runtime.CompilerServices; using System.Collections.Generic; using System; using System.Numerics; using System.Linq; using System.Runtime.Intrinsics.X86; class Program { static void Main() { var fastConfig = new ManualConfig(); fastConfig.Add(DefaultConfig.Instance); fastConfig.AddJob(Job.ShortRun); BenchmarkRunner.Run