用C ++复制数组的最快便携式方法是什么 [英] What is the fastest portable way to copy an array in C++
问题描述
这个问题困扰了我一段时间.我正在考虑的可能性是
This question has been bothering me for some time. The possibilities I am considering are
- memcpy
- std :: copy
- cblas_dcopy
有人对这三者的利弊有什么线索吗?也欢迎其他建议.
Does anyone have any clue on what the pros and cons are with these three? Other suggestions are also welcome.
推荐答案
在C ++中，除非有充分的理由，否则默认情况下应使用std :: copy.原因是C ++类通过复制构造函数和复制赋值运算符定义了自己的复制语义，在列出的操作中，只有std :: copy遵守这些约定.
In C++ you should use std::copy by default unless you have good reasons to do otherwise. The reason is that C++ classes define their own copy semantics via the copy constructor and copy assignment operator, and of the operations listed, only std::copy respects those conventions.
memcpy()使用原始的按字节的数据副本(尽管可能对缓存行大小进行了优化，等等)，并且忽略了C ++复制语义(毕竟是C函数).
memcpy() uses raw, byte-wise copy of data (though likely heavily optimized for cache line size, etc.), and ignores C++ copy semantics (it's a C function, after all...).
cblas_dcopy()是一个专用函数，用于使用双精度浮点值的线性代数例程.它可能擅长于此，但不应被视为通用.
cblas_dcopy() is a specialized function for use in linear algebra routines using double precision floating point values. It likely excels at that, but shouldn't be considered general purpose.
如果您的数据是简单" POD类型的结构数据或原始基础类型数据，则memcpy可能会尽可能快.在这种情况下，std :: copy可能会被优化为使用memcpy，因此您永远不会知道它们之间的区别.
If your data is "simple" POD type struct data or raw fundamental type data, memcpy will likely be as fast as you can get. Just as likely, std::copy will be optimized to use memcpy in these situations, so you'll never know the difference.
简而言之，请使用std :: copy().
In short, use std::copy().
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