高效执行Java中多维数组的？ [英] Efficient implementation of multi-dimensional arrays in Java?

问题描述

据我所知（从答案，如<一个href=\"http://stackoverflow.com/questions/732684/implementing-a-matrix-which-is-more-efficient-using-an-array-of-arrays-2d-or/732688#732688\">this), Java没有本地多维连续存储器阵列（不像C＃，例如）。

As far as I understand (from answers such as this), java has no native multi-dimensional continuous memory arrays (unlike C#, for example).

虽然交错数组语法（数组的数组）可能是好于大多数应用，我还是想知道什么是最好的做法，如果你确实需要一个连续存储器阵列的原始效率（避免不必要的内存读取）

While the jagged array syntax (arrays of arrays) might be good for most applications, I would still like to know what's the best practice if you do want the raw efficiency of a continuous-memory array (avoiding unneeded memory reads)

我当然可以使用映射到一个二维一个一维数组，但我preFER事情更有条理。

I could of course use a single-dimensional array that maps to a 2D one, but I prefer something more structured.

推荐答案

这取决于您的访问模式。使用这个简单的程序，比较了 INT [] [] 与2D映射，以作为基质处理一维 INT [] 阵列，本地Java 2D矩阵是：

It depends on your access pattern. Using this simple program, comparing an int[][] with a 2D mapped over a 1D int[] array treated as a matrix, a native Java 2D matrix is:

1. 25％的速度时，行上的缓存，即：按行访问：


2. 慢100％，当行不在缓存中，即：由colums访问：

例如：

// Case #1
for (y = 0; y < h; y++)
    for (x = 0; x < w; x++)
        // Access item[y][x]

// Case #2
for (x = 0; x < w; x++)
    for (y = 0; y < h; y++)
        // Access item[y][x]

一维矩阵的计算公式为：

The 1D matrix is calculated as:

public int get(int x, int y) {
    return this.m[y * width + x];
}

这篇关于高效执行Java中多维数组的？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！