which for loop will completed first ??

1 次查看（过去 30 天）
Anil Kumar
Anil Kumar 2018-12-9
评论： Stephen23 2018-12-9
for i=1:5
for j=1:4
v(i,j)=w*v(i,j)+c1*rand()*(pbest(i,j)-x(i,j))+c2*rand()*(gbest(1,j)-x(i,j));
end
end
how this loops will work.
thanks in advance
  2 个评论
madhan ravi
madhan ravi 2018-12-9
a=rand(3);
m=size(a,1);
n=size(a,2);
b=zeros(size(a,1),size(a,2));
for i=1:m
for j=1:n
b(i,j)=a(i,j) % this will make you understand the working of nested for loops
end
end
Stephen23
Stephen23 2018-12-9
"which for loop will completed first ??"
Of any nested loops, the innermost one will finish first.

请先登录，再进行评论。

请先登录，再回答此问题。

回答（1 个）

Image Analyst
Image Analyst 2018-12-9
The inner j loop will finish first, for any given i. The j loop will execute its 4 iterations 5 times - one iteration of 4 times for every one of the 5 i values.
If the loops got very large (tens of thousands of iterations), you might notice a speed up if you switched the i and j loop because MATLAB is "column major" so it goes down rows (left most index) first before jumping over to the next column. So it would be faster if the inner most loop variable were the left most index.

类别

在 Help Center 和 File Exchange 中查找有关 Loops and Conditional Statements 的更多信息

标签

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by