List.Sort IComparer性能

Question

我正在尝试排序一对int数组(int [] a; int [] b;)

如果我使用Array.Sort(a,b)那么性能很好.

但是,我更喜欢使用List <>并在结构中加载int对.我可以使用带有重载的Array.Sort()来实现这一点,该重载为结构提供了一个简单的比较器,但它比Array.Sort(a,b)慢大约4倍

这是正常的吗？

Answer 1

这听起来很现实; 你正在引入更多的复杂性(更多的查找等,更多的虚拟方法,更多的范围检查),所以它只会变慢(数组访问非常直接,非常快).

看起来你可以通过实现IComparer<T>代替方法来更快地获得它(但不像数组那么快); (编辑)并再次使用IComparable<T>:

Array.Sort: 2241ms
List.Sort (delegate): 8714ms
List.Sort (interface): 6976ms
List.Sort (comparable): 5456ms

使用代码:

using System;
using System.Collections.Generic;
using System.Diagnostics;

struct MyStruct : IComparable<MyStruct>
{
    private readonly int key, value;
    public int Key { get { return key; } }
    public int Value { get { return value; } }
    public MyStruct(int key, int value)
    {
        this.key = key;
        this.value = value;
    }
    public int CompareTo(MyStruct other)
    {
        return key.CompareTo(other.key);
    }
}
static class Program
{
    static void Main()
    {
        const int SIZE = 10000000;
        int[] a = new int[SIZE], b = new int[SIZE];
        Random rand = new Random();
        for(int i = 0 ; i < SIZE ; i++) {
            a[i] = rand.Next();
            b[i] = i;
        }
        var list = new List<MyStruct>(SIZE);
        for (int i = 0; i < SIZE; i++)
        {
            list.Add(new MyStruct(a[i], b[i]));
        }
        var list2 = new List<MyStruct>(list);
        var list3 = new List<MyStruct>(list);

        var watch = Stopwatch.StartNew();
        Array.Sort(a, b);
        watch.Stop();
        Console.WriteLine("Array.Sort: " + watch.ElapsedMilliseconds + "ms");

        watch = Stopwatch.StartNew();
        list.Sort((x, y) => x.Key.CompareTo(y.Key));
        watch.Stop();
        Console.WriteLine("List.Sort (delegate): " + watch.ElapsedMilliseconds + "ms");

        watch = Stopwatch.StartNew();
        list2.Sort(MyComparer.Default);
        watch.Stop();
        Console.WriteLine("List.Sort (interface): " + watch.ElapsedMilliseconds + "ms");

        watch = Stopwatch.StartNew();
        list3.Sort();
        watch.Stop();
        Console.WriteLine("List.Sort (comparable): " + watch.ElapsedMilliseconds + "ms");
    }
    sealed class MyComparer : IComparer<MyStruct>
    {
        private MyComparer() { }
        public static readonly MyComparer Default = new MyComparer();
        public int Compare(MyStruct x, MyStruct y)
        {
            return x.Key.CompareTo(y.Key);
        }
    }
}