AS3矢量阵列

Question

将数组存储在Array类型的Vector中是否有任何性能优势？

例如选项1

private var _arrays:Vector.<Array> =  new Vector.<Array>(2); 
_arrays[0] = new Array(10);
_arrays[1] = new Array(10);

选项2

private var _arrays:Array =  new Array(2); 
_arrays[0] = new Array(10);
_arrays[1] = new Array(10);

我也可以有矢量或矢量吗？

 private var _vectors:Vector.<Vector> = new Vector.<Vector>(2);

_vectors[0] = new Vector.<String>(10);
_vectors[1] = new Vector.<String>(10);

谢谢,

标记

Answer 1

编辑

我的原始答案是错误的,除了最后一部分,我必须为此道歉.我知道Vector在"引擎盖下"有四个实现.(你可以找到从FP 10的playerglobal.swc在后由罗伯特·彭纳反编译源在这里)那些三是号码类型(INT,UINT和数字).一个是对象类型.最后一个用作catch-all并接受从Object派生的所有类.这就是为什么我认为它Vector.<Object>仍然比Array更快,依赖于Adobe提供的有关矢量和数组的信息.

但是,似乎这些信息是错误的,或者至少它遗漏了一些重要的部分:

1. 虽然Vector.<AnyClassDerivedFromObject>允许严格键入,但此类型信息仅在编译时评估(因此您获得更多类型安全性),但不在运行时评估 - 因此,严格键入对象向量的好处实际上不适用于性能.有关详细信息,请参阅此博客文章.

2. 因此,Vector中比Array快的唯一实现是数字类型(!).

事实上,我已经对此进行了一些广泛的测试,并且得出的结论是,虽然Vector.<int>比int of int快60%,但所有的衍生物Vector.<Object>不仅速度Vector.<Object>相同(即执行相同Vector.<String>,它们也是比Array 低约20%.我对此进行了双重和三重检查,因此我认为结果相当准确.

数字类型向量仍然更快,因此您应该使用这些向量而不是数组.但:

结束编辑

只有当你要使用sort(),sortOn()或任何其它的阵列的方便排序功能,您可能还是会另作决定,因为这些都是原生功能,这样真的快.在Vector上实现自己的排序方法可能与它们的速度不匹配.

Answer 2

我个人看不到任何性能优势.如果有,它将是最小的.拥有vector类的重点是严格键入数组的元素.但是,一个数组对象本身被设计为容纳多种类型的对象,甚至是无类型的......所以严格地将一个向量键入一个基本上无类型的容器,该容器可以填充无类型或多个不同类型的内容......当这样思考时它只是在逻辑上听起来像它几乎没有效果.

更新

这里有一些性能测试结果来证明我的观点.我们可以看到,当受到压力时,数组的向量等于作为数组数组的性能,并且在一个测试用例中,它实际上更糟糕:

/ =============================================================================================
                                     Array  Tests                                               
 ============================================================================================= /
Testing Array of Arrays push performance:
Total time for 100000 push calls on Array of Arrays: 24

Testing Array of Arrays random assignment performance:
Total time for 100000 random assignment calls on Array of Arrays: 40

Testing Array of Arrays sequential read performance:
Total time for 100000 sequential read calls on Array of Arrays: 14

Testing Array of Arrays random read performance:
Total time for 100000 random read calls on Array of Arrays: 41
/ ============================================================================================= /

/ =============================================================================================
                                     Vector Tests                                               
 ============================================================================================= /
Testing Vector of Arrays push performance:
Total time for 100000 push calls on Vector of Arrays: 24

Testing Vector of Arrays random assignment performance:
Total time for 100000 random assignment calls on Vector of Arrays: 49

Testing Vector of Arrays sequential read performance:
Total time for 100000 sequential read calls on Vector of Arrays: 14

Testing Vector of Arrays random read performance:
Total time for 100000 random read calls on Vector of Arrays: 41
/ ============================================================================================= /

和测试代码:

import flash.events.Event;
import flash.utils.getTimer;

//Performance timer related
var startTime:Number; //ms
//

//Our two container types we're testing IO on
var arrayOfArrays:Array = new Array();
var vectorOfArrays:Vector.<Array> = new Vector.<Array>();
//

//Used to store a bunch of arrays we're going to use to test
var testArrays:Array = new Array();
//

var randomIndex:uint = 0;
var i:uint = 0;
var arr:Array;

//Generate a bunch of arrays of mixed typed content
for(i = 0; i < 100000; ++i) {
    generateTestArray();
}

/*======================================================================================================
***********************************      Array  Tests      *********************************************
*=====================================================================================================*/
//Test push on array of arrays
trace("Testing Array of Arrays push performance:");
startTime = getTimer();
for(i = 0; i < 100000; ++i) {
    arrayOfArrays.push(testArrays[i]);
}
trace("Total time for 100000 push calls on Array of Arrays: " + (getTimer() - startTime));
trace(" ");
//

//Test random write on array of arrays
trace("Testing Array of Arrays random assignment performance:");
startTime = getTimer();
for(i = 0; i < 100000; ++i) {
    randomIndex = Math.round(Math.random() * 99999) as uint;
    arrayOfArrays[randomIndex] = testArrays[randomIndex];
}
trace("Total time for 100000 random assignment calls on Array of Arrays: " + (getTimer() - startTime));
trace(" ");
//

//Test sequential read on array of arrays
trace("Testing Array of Arrays sequential read performance:");
startTime = getTimer();
for(i = 0; i < 100000; ++i) {
    arr = arrayOfArrays[i];
}
trace("Total time for 100000 sequential read calls on Array of Arrays: " + (getTimer() - startTime));
trace(" ");
//

//Test random read on array of arrays
trace("Testing Array of Arrays sequential read performance:");
startTime = getTimer();
for(i = 0; i < 100000; ++i) {
    randomIndex = Math.round(Math.random() * 99999) as uint;
    arr = arrayOfArrays[randomIndex];
}
trace("Total time for 100000 random read calls on Array of Arrays: " + (getTimer() - startTime));
trace(" ");
//
/*====================================================================================================*/


/*======================================================================================================
***********************************      Vector Tests      *********************************************
*=====================================================================================================*/
//Test push on vector of arrays
trace("Testing Vector of Arrays push performance:");
startTime = getTimer();
for(i = 0; i < 100000; ++i) {
    vectorOfArrays.push(testArrays[i]);
}
trace("Total time for 100000 push calls on Vector of Arrays: " + (getTimer() - startTime));
trace(" ");
//

//Test random write on vector of arrays
trace("Testing Vector of Arrays random assignment performance:");
startTime = getTimer();
for(i = 0; i < 100000; ++i) {
    randomIndex = Math.round(Math.random() * 99999) as uint;
    vectorOfArrays[randomIndex] = testArrays[randomIndex];
}
trace("Total time for 100000 random assignment calls on Vector of Arrays: " + (getTimer() - startTime));
trace(" ");
//

//Test sequential read on vector of arrays
trace("Testing Vector of Arrays sequential read performance:");
startTime = getTimer();
for(i = 0; i < 100000; ++i) {
    arr = vectorOfArrays[i];
}
trace("Total time for 100000 sequential read calls on Vector of Arrays: " + (getTimer() - startTime));
trace(" ");
//

//Test random read on vector of arrays
trace("Testing Vector of Arrays sequential read performance:");
startTime = getTimer();
for(i = 0; i < 100000; ++i) {
    randomIndex = Math.round(Math.random() * 99999) as uint;
    arr = vectorOfArrays[randomIndex];
}
trace("Total time for 100000 random read calls on Vector of Arrays: " + (getTimer() - startTime));
trace(" ");
//
/*====================================================================================================*/

function generateTestArray():void
{
    var newArray:Array = new Array();

    var totalItems:uint = Math.round(Math.random() * 50 + 1);

    var i:uint = 0;

    var dice:uint = 0;

    for(i; i < totalItems; ++i) {

        dice = Math.round(Math.random() * 5);

        switch(dice) {
            case 0:
                newArray.push(new int(Math.random()));
            break;

            case 1:
                newArray.push(new String(Math.random()));
            break;

            case 2:
                newArray.push(new Array());
            break;

            case 3:
                newArray.push(new MovieClip());
            break;

            case 4:
                newArray.push(new Date());
            break;

            case 5:
                newArray.push(new Event(Event.COMPLETE, false, false));
            break;  

        }
    }

    testArrays.push(newArray);
}