可枚举范围和内存分配 [英] Enumerable.Range and Memory allocation

问题描述

我有以下代码:

IEnumerable<int> elements = Enumerable.Range(1, Int32.MaxValue);
Console.WriteLine("Size of System.Int32: {0}", sizeof(int));
Console.Write("Iterating over {0} elements... ", elements.Count());
Parallel.ForEach(elements, _ => { });
Console.WriteLine("Done.");

打印输出:

> Size of System.Int32: 4
> Iterating over 2147483647 elements... Done.

但是，我不明白为什么它没有抛出OutOfMemoryException.

However, I don't understand why is this not throwing an OutOfMemoryException.

知道每个int值占用4个字节的空间，分配Int32.MaxValue个int的量应该占用〜8GB

Knowing that each int value takes up 4 bytes of space, allocating Int32.MaxValue amount of int should take up ~ 8GB

检查我的应用程序，该过程占用了大约aprox. 〜5.200KB.

Inspecting my application, the process is taking up aprox. ~ 5.200KB.

元素正在成功迭代，因此必须将它们分配到某个地方，对吧?

The elements are being iterated successfully so they must be allocated somewhere, right?

LINQ如何实现这一目标?

How does LINQ achieve this?

推荐答案

IEnumerable<int>不是数组.它本身不存储任何信息.实现它的类能够循环一组值.

IEnumerable<int> is not an array. It doesn't store any information itself. The class implementing it is capable of looping over a set of values.

此处的值未存储在数组中，而是仅进行迭代并产生每次迭代的结果.

The values here are not stored in an array, instead of that is just iterates and yields the result of every iteration.

类似这样的东西:

public IEnumerable<int> GetRange(int start, int number)
{
    for (int i = start; i < start + number; i++)
    {
        yield return i;
    }
}

请参阅，没有数组，没有存储.它只记住迭代器中的当前位置，并且可以执行适当的步骤来获取下一个位置.这段代码是由C#编译器即时生成的.

See, no arrays, no storage. It just remembers the current position in the iterator and can execute the appropriate steps to get the next one. This code is generated by the C# compiler on the fly.

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