空向量的开销成本是多少? [英] What is the overhead cost of an empty vector?

问题描述

拥有一个空向量与拥有一个指向向量的指针的内存开销是多少?

What is the memory overhead of having an empty vector vs having a pointer to a vector?

选项 A:

std::vector<int> v;

选项 B:

std::vector<int> *v = NULL;

我相信选项 B 需要 1 个 32 位指针(假设这里是 32 位)空的v"占用多少内存?

I believe that option B takes 1 32 bit pointer (assuming 32 bit here) How much memory does the empty 'v' take up?

推荐答案

至于问的问题:看实现.使用 MSVC 7.1:

As for the question as asked: It depends on the implementation. With MSVC 7.1 this:

std:: cout << sizeof(std::vector<int>) << std::endl;

给我 16(字节).(3个指针:容量的开始、结束和结束，加上一个分配器)

gives me 16 (bytes). (3 pointers: begin, end, and end of capacity, plus an allocator)

然而应该注意的是，指向向量的指针给了它更大的开销:

However it should be noted that the pointer-to-vector gives it a larger overhead:

• 非空情况下的时间和空间
• 在所有情况下都很复杂.

这篇关于空向量的开销成本是多少?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！