为什么人们在openmp的循环之前声明迭代值？ [英] why do people declare iterated values before loop for openmp?

问题描述

所以从我的理解，这些都是正确的所有版本的openmp：

So from what I understand, either of these are correct in ALL versions of openmp:

//int i declared in loop, explicitly private
#pragma omp parallel for
for (int i = 0; i < NUMEL; i++)
{
  foo(i);
}
//int i declared outsize loop, but is the iterated value, implicitly private
int i;
#pragma omp parallel for
for (i = 0; i < NUMEL; i++)
{
  foo(i);
}

但是，我通常看到第二个而不是第一个。为什么？

However, I more commonly see the second than the first. Why is that?

推荐答案

因为不是每个人都用C ++编写或者定义一个C99兼容的C编译器。一些人喜欢坚持在块的开始处声明变量的旧C要求，以便代码与旧的（C99之前的）C编译器更加兼容。

Because not everybody writes in C++ or targets a C99-compliant C compiler. Some prefer to stick with the old C requirement of having variables declared at the beginning of a block so that the code would be more compatible with older (pre-C99) C compilers.

这篇关于为什么人们在openmp的循环之前声明迭代值？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！