Vectorization of a for loop

Question

David Valle 2020-3-19

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/511732-vectorization-of-a-for-loop

评论： David Valle 2020-3-23

采纳的回答： Aditya Patil

在 MATLAB Online 中打开

Hello,

I have to do a large calculation and the next foor loop takes like 99% of runtime in the script:

for n = 1:iteraciones-1 
   x(n+1) = a - x(n)^2 + b*y(n); 
   y(n+1) = x(n); 
end

I've read that if I manage to vectorize it, it will improve my code performance, but im stuck with

x(1) = 1;
y(1) = 1;
x(2) = a - x(1)^2 + b*x(1);
for n = 2:iteraciones-1 
   x(n+1) = a - x(n)^2 + b*x(n-1);
end
y(2:iteraciones) = x(1:iteraciones-1);

And I cant think of a way to vectorize that for loop since it uses previous generated values

If someone could take the time to figure this out or link a good resource on how to vectorize, it would be much apreciated

Thanks in advice :)

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darova 2020-3-19

I think your code can't be vectorized. As your value of x(i+1) depends on previous x(i)

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Answer 1

Aditya Patil 2020-3-23

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/511732-vectorization-of-a-for-loop#answer_421417

I understand that you want to vectorize the for loop to improve performance.

However vectorization of for loops requires that each iteration is independent of each other. This is not the case in your code, as x(n + 1) depends upon x(n). Hence I think it is not possible to vectorize this code.