哪个更快/首选:memset 或 for 循环将双精度数组归零?

2021-12-20 00:00:00 performance optimization c c++

double d[10];
int length = 10;

memset(d, length * sizeof(double), 0);

//or

for (int i = length; i--;)
  d[i] = 0.0;

推荐答案

请注意，对于 memset，您必须传递字节数，而不是元素数，因为这是一个旧的 C 函数:

Note that for memset you have to pass the number of bytes, not the number of elements because this is an old C function:

memset(d, 0, sizeof(double)*length);

memset 可以更快，因为它是用汇编程序编写的，而 std::fill 是一个模板函数，它只是在内部执行循环.

memset can be faster since it is written in assembler, whereas std::fill is a template function which simply does a loop internally.

但是为了类型安全和更易读的代码我会推荐 std::fill() - 这是 C++ 做事的方式，并考虑 memset 如果需要在代码中的这个地方进行性能优化.

But for type safety and more readable code I would recommend std::fill() - it is the c++ way of doing things, and consider memset if a performance optimization is needed at this place in the code.

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