在性能方面有什么好处？键入[,]或类型[] []？

Question

在C#中使用二维数组(type[,])或数组()数组会更高效type[][]吗？

特别是对于初始分配和项目访问

Answer 1

当然,如果一切都失败了......试试吧!以下给出(在"发布"中,在控制台):

Size 1000, Repeat 1000
    int[,] set: 3460
    int[,] get: 4036 (chk=1304808064)
    int[][] set: 2441
    int[][] get: 1283 (chk=1304808064)

因此,至少在此测试中,锯齿状阵列更快.有趣!然而,这是一个相对较小的因素,所以我仍然会坚持用更好的描述我的要求.除了某些特定(高CPU /处理)方案之外,可读性/可维护性应该优于小的性能增益.不过,由你决定.

请注意,此测试假定您访问阵列的次数比创建时更频繁,因此我没有包含创建时间,我希望矩形更快,除非内存高度分散.

using System;
using System.Diagnostics;
static class Program
{
    static void Main()
    {
        Console.WriteLine("First is just for JIT...");
        Test(10,10);
        Console.WriteLine("Real numbers...");
        Test(1000,1000);

        Console.ReadLine();
    }

    static void Test(int size, int repeat)
    {
        Console.WriteLine("Size {0}, Repeat {1}", size, repeat);
        int[,] rect = new int[size, size];
        int[][] jagged = new int[size][];
        for (int i = 0; i < size; i++)
        { // don't cound this in the metrics...
            jagged[i] = new int[size];
        }
        Stopwatch watch = Stopwatch.StartNew();
        for (int cycle = 0; cycle < repeat; cycle++)
        {
            for (int i = 0; i < size; i++)
            {
                for (int j = 0; j < size; j++)
                {
                    rect[i, j] = i * j;
                }
            }
        }
        watch.Stop();
        Console.WriteLine("\tint[,] set: " + watch.ElapsedMilliseconds);

        int sum = 0;
        watch = Stopwatch.StartNew();
        for (int cycle = 0; cycle < repeat; cycle++)
        {
            for (int i = 0; i < size; i++)
            {
                for (int j = 0; j < size; j++)
                {
                    sum += rect[i, j];
                }
            }
        }
        watch.Stop();
        Console.WriteLine("\tint[,] get: {0} (chk={1})", watch.ElapsedMilliseconds, sum);

        watch = Stopwatch.StartNew();
        for (int cycle = 0; cycle < repeat; cycle++)
        {
            for (int i = 0; i < size; i++)
            {
                for (int j = 0; j < size; j++)
                {
                    jagged[i][j] = i * j;
                }
            }
        }
        watch.Stop();
        Console.WriteLine("\tint[][] set: " + watch.ElapsedMilliseconds);

        sum = 0;
        watch = Stopwatch.StartNew();
        for (int cycle = 0; cycle < repeat; cycle++)
        {
            for (int i = 0; i < size; i++)
            {
                for (int j = 0; j < size; j++)
                {
                    sum += jagged[i][j];
                }
            }
        }
        watch.Stop();
        Console.WriteLine("\tint[][] get: {0} (chk={1})", watch.ElapsedMilliseconds, sum);
    }
}