隐含的DO循环效率低下吗? [英] Are implied DO loops inefficient?
问题描述
我有一个基于隐式do循环的数组初始化，给定的大小为N.
I have an array initialization based on an implied do loop, given an odd size N.
J=(N+1)/2
XLOC(1:N) = (/ (I-J, I=1,N) /)
在F90 +的上下文中，建议使用(/../)语法，或者使用FORALL语句更有效.
In the context of F90+ is it recommended to use the (/ .. /) syntax, or is more efficient to use a FORALL statement.
示例:先N=19然后XLOC=(-9,-8,-7,-6,-5,-4,-3,-2,-1,0,1,2,3,4,5,6,7,8,9)
您还将如何初始化此数组?
How else would you initialize this array?
编辑1
您将如何使用更具可读性的代码初始化此数组?
How would you initialize this array with more readable code?
推荐答案
对于这样一个简单的结构，两者都可能导致相同的代码，因为编译器擅长优化. FORALL语句不是一个循环语句，而是一个初始化语句，它具有许多可能会抑制优化的限制.如果一个简单的循环可行，我会用它.
For such a simple construct both are likely to lead to the same code because compilers are good at optimizing. The FORALL statement is not so much a looping statement but an initialization statement that has many restrictions that can inhibit optimizations. If a simple loop will work, I'd use it.
Also see this previous answer: Do Fortran 95 constructs such as WHERE, FORALL and SPREAD generally result in faster parallel code?
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