在我们的c++课程中,他们建议不要再在新项目中使用c++数组。据我所知,Stroustroup本人建议不要使用数组。但是否存在显著的性能差异?


当前回答

我认为最主要的问题不是性能,而是安全性。使用数组可能会犯很多错误(例如,考虑调整大小),而使用向量可以省去很多麻烦。

其他回答

如果不需要动态调整大小,则会有存储容量的内存开销(一个指针/size_t)。就是这样。

There is no argument about which of them is the best or good to use.They both have there own use cases,they both have their pros and cons.The behavior of both containers are different in different places.One of the main difficulty with arrays is that they are fixed in size if once they are defined or initialized then you can not change values and on the other side vectors are flexible, you can change vectors value whenever you want it's not fixed in size like arrays,because array has static memory allocation and vector has dynamic memory or heap memory allocation(we can push and pop elements into/from vector) and the creator of c++ Bjarne Stroustrup said that vectors are flexible to use more than arrays.

应该避免使用带有new的c++数组(即使用动态数组)。有一个问题是,你必须跟踪它们的大小,你需要手动删除它们,并做所有的家务工作。

我们还可以很容易地在向量中插入、推入和拉出值,这在数组中是不容易做到的。

如果我们讨论性能,那么如果你处理小的值,那么你应该使用数组,如果你处理大规模的代码,那么你应该使用向量(向量比数组更擅长处理大的值)。

对于定长数组,在发布版本中性能是相同的(相对于vector<>),但在调试版本中,根据我的经验,低级数组的优势是20倍(MS Visual Studio 2015, c++ 11)。

因此,如果您(或您的同事)倾向于在数组使用中引入错误,那么支持STL的“节省调试时间”参数可能是有效的,但如果您的调试时间主要用于等待代码运行到您当前正在处理的位置,以便您可以逐步检查它,则可能不是有效的。

处理数字密集型代码的有经验的开发人员有时属于第二组(特别是如果他们使用vector:))。

如果使用向量表示多维行为,则会对性能造成影响。

2d+向量会导致性能下降吗?

其要点是,每个子向量都有大小信息,因此会有少量开销,并且不一定会有数据序列化(与多维c数组不同)。这种串行化的缺乏可以提供比微优化更大的机会。如果你在做多维数组,最好扩展std::vector并滚动你自己的get/set/resize bits函数。

STL is a heavily optimized library. In fact, it's even suggested to use STL in games where high performance might be needed. Arrays are too error prone to be used in day to day tasks. Today's compilers are also very smart and can really produce excellent code with STL. If you know what you are doing, STL can usually provide the necessary performance. For example by initializing vectors to required size (if you know from start), you can basically achieve the array performance. However, there might be cases where you still need arrays. When interfacing with low level code (i.e. assembly) or old libraries that require arrays, you might not be able to use vectors.