使用std :: vector的开销？ [英] Overhead to using std::vector?

问题描述

我知道手动动态分配内存通常不是一个好主意，但是有时候它比使用 std :: vector 更好吗？

I know that manual dynamic memory allocation is a bad idea in general, but is it sometimes a better solution than using, say, std::vector?

举一个简单的例子，如果我必须存储一个 n 整数数组，其中 n < = 16，例如。我可以使用

To give a crude example, if I had to store an array of n integers, where n <= 16, say. I could implement it using

int* data = new int[n]; //assuming n is set beforehand

或使用向量：

std::vector<int> data;

使用 std :: vector绝对是一个更好的主意吗？ / code>还是在实际情况下手动分配动态内存会更好，以提高效率？

Is it absolutely always a better idea to use a std::vector or could there be practical situations where manually allocating the dynamic memory would be a better idea, to increase efficiency?

推荐答案

总是最好使用 std :: vector / std :: array ，至少直到可以（通过概要分析）结论性地证明，在特定情况下 T * a = new T [100]; 解决方案要快得多。这不太可能发生： vector / array 是围绕普通旧数组的极其薄的一层。使用 vector :: at 进行边界检查会有一些开销，但是您可以使用 operator [] 来规避。

It is always better to use std::vector/std::array, at least until you can conclusively prove (through profiling) that the T* a = new T[100]; solution is considerably faster in your specific situation. This is unlikely to happen: vector/array is an extremely thin layer around a plain old array. There is some overhead to bounds checking with vector::at, but you can circumvent that by using operator[].

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