结构和类对象数组的内存分配 [英] Memory Allocation for an Array of Struct and Class Object
问题描述
昨天，我正在阅读C#参考，在那里我看到了一条声明.请看下面的语句.
Last day I was reading C# reference and there I saw a statement. Kindly have a look at the following statement.
上下文:
对Point使用struct而不是class可以大大减少 在运行时执行的内存分配.下面的程序创建并初始化一个100点的数组. 通过将Point实现为一个类，可以实例化101个单独的对象-一个用于数组，另一个每个 为100个元素.
the use of a struct rather than a class for a Point can make a large difference in the number of memory allocations performed at run time. The program below creates and initializes an array of 100 points. With Point implemented as a class, 101 separate objects are instantiated—one for the array and one each for the 100 elements.
class Point
{
public int x, y;
public Point(int x, int y) {
this.x = x;
this.y = y;
}
}
class Test
{
static void Main() {
Point[] points = new Point[100];
for (int i = 0; i < 100; i++)
points[i] = new Point(i, i*i);
}
}
如果将Point实施为结构，如
If Point is instead implemented as a struct, as in
struct Point
{
public int x, y;
public Point(int x, int y) {
this.x = x;
this.y = y;
}
}
仅实例化一个对象-数组的一个对象. Point实例是在 大批.这种优化可能会被滥用.使用结构而不是类也可以使应用程序运行缓慢或占用更多内存，因为按值传递结构实例会导致该结构的副本被复制. 已创建.
only one object is instantiated—the one for the array. The Point instances are allocated in-line within the array. This optimization can be misused. Using structs instead of classes can also make an application run slower or take up more memory, as passing a struct instance by value causes a copy of that struct to be created.
问题: 在这里，我的问题是在值类型"和引用类型"的情况下如何进行内存分配?
Question: Here my question is how memory allocation is done in case of Value Type and Reference Type?
困惑: 为什么在《参考指南》中提到只能初始化1个对象.根据我对Array中每个对象的理解，将分配一个单独的内存.
Confusion: Why it is mentioned in Reference Guide that Only 1 Object will be intialized. As per my understanding for each object in Array a separate memory will be allocated.
修改:可能重复 这个问题与jason建议的可能重复的问题有点不同.我关心的是仅在值类型和引用类型的情况下如何分配内存，而这个问题只是解释值类型和引用类型的概述.
Possible Duplicate This question is bit different from possible duplicate question as suggested by jason. My concern is about how memory is allocated in case of Value Type and Referenece Type solely while that question just explain the overview of Value Type and Reference Type.
推荐答案
也许通过插图更容易理解引用类型的数组和值类型的数组之间的区别:
Perhaps the difference between an array of a reference type and an array of a value type is easier to understand with an illustration:
每个Point以及数组都在堆上分配，并且数组存储对每个Point的引用.总共需要N + 1个分配，其中N是点数.您还需要额外的间接访问权限来访问特定Point的字段，因为您必须通过引用.
Each Point as well as the array is allocated on the heap and the array stores references to each Point. In total you need N + 1 allocations where N is the number of points. You also need an extra indirection to access a field of a particular Point because you have to go through a reference.
每个Point直接存储在数组中.堆上只有一个分配.访问字段不涉及间接.可以直接从数组的内存地址，数组中项目的索引以及字段在值类型内部的位置直接计算出字段的内存地址.
Each Point is stored directly in the array. There is only one allocation on the heap. Accessing a field does not involve indirection. The memory address of the field can be computed directly from the memory address of the array, the index of the item in the array and the location of the field inside the value type.
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