I want to change the "for loop" statement to a vectorizing code, but I've been stuck with this problem for many days, help!

Question

shelton David 2023-4-26

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https://ww2.mathworks.cn/matlabcentral/answers/1953249-i-want-to-change-the-for-loop-statement-to-a-vectorizing-code-but-i-ve-been-stuck-with-this-pro

回答： Bhanu Prakash 2023-5-13

I have heard that a vectorized version code is more efficient than a code written with " for-loop statement" when executing some math calculation, but I am not very familiar with Matlab's vectorized code writing style, is there any kind person willing to help to change the following code into a vectorized style code, or provide some tips for me, thank you very much !

Here is the mathmaetical expression that I want to calculate, denoted by sum1 and sum2

Here is Mycode

//c, h, g, e are all vector, here is their definition in my code.

c=zeros(q+1,1);

e=zeros(q+1,1);

h=zeros(q+1,1);

g=zeros(q+1,1);

....

// the part that i want to modify as vectorized code.

sum1=0;

sum2=0;

if(n>1)

for i=1:n-1

s=0;

for j=0:n-1-i

s=s+c(n-i-j+1)*(n-i-j)*h(j+1)-c(n-i-j)*h(j+2)*(j+1);

end

for j=0:n-i

s=s-h(n-i-j+1)*h(j+1)*i;

end

sum1=sum1+s*g(i+1);

end

for j=1:n-1

sum2=sum2+g(1)*(c(n-j+1)*(n-j)*h(j+1)-c(n-j)*h(j+2)*(j+1));

end

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Answer 1

Bhanu Prakash 2023-5-13

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Hi Shelton,

As per my understanding, you want to vectorize "for" loop in the given code.

To vectorize the "for" loops in a given code, you can use the "coder.loop.vectorize" function. Consider the code shown below:

% creating a 10x1 matrix with random values
x=rand(10,1);
% creating a 10x1 zero matrix to store the output
y=zeros(10,1);
for i=1:length(x)
    % vectorizing the "for" loop
    coder.loop.vectorize
    y(i)=sin(x(i));
end