How can i remove for loops?
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I'm trying to remove for loops from a code I wrote long time ago.
function [Rup] = updateR(A,E,S)
[imax,jmax,zmax] = size(A);
for z = 1 : zmax
Stmp = S(:,:,setdiff(1:zmax,z));
Atmp = A(:,:,setdiff(1:zmax,z));
Etmp = E(:,:,:,:,setdiff(1:zmax,z));
for i = 1 : imax
for j = 1 : jmax
sumtmp = permute(sum(sum(Etmp(i,j,:,:,:), 3), 4),[1 2 5 3 4]);
beta = (Stmp(i,j,:)+Atmp(i,j,:)+sumtmp);
n = - max(beta);
EEtmp = E(i,j,:,:,z);
Rup (i,j,z) = S(i,j,z) + n + sum(EEtmp(:));
end
end
end
A,R,S are [N x M x P] matrices.
I tried a lot by myself, but I have no confidence with the tricks useful to remove loops. Can anyone help me?
Matteo
采纳的回答
Sean de Wolski
2014-1-10
Just preallocating Rup should speed this up:
First line:
Rup = zeros(size(A));
更多回答（1 个）
Matteo
2014-1-10
0 个投票
2 个评论
Sean de Wolski
2014-1-10
Unless this is going into production or being run millions of times, the time it would take to "vectorize" this will take longer than the running time of the code. Preallocating will speed it up most of the way.
As for how much you will see for a speedup? Try it!
Matteo
2014-1-13
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