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How increase calculate speed in for loop

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kisik KIM
kisik KIM on 14 Sep 2021
Commented: Jan on 15 Sep 2021
Hi all.
I have a problem in my code about too long calculate time.
This is my part of code
=============================================
Depth=5000;
Num_Alines=400;
Num_Bscan=300;
Alines=180
half=Alines/2;
ReconImage=zeros(Depth,Num_Alines,Num_Bscan);
for i=1:Depth
Sampledist2=Sampledist;
Sampledist2(Sampledist2==Sampledist2(i,round(half),round(half)))=1;
Sampledist2(Sampledist2~=1)=0;
Sampledist2=Sampledist2*D313; %D313 is one data not array.
for j=round(half):Num_Alines-round(half)
for k=round(half):Num_Bscan-round(half)
ReconImage(:,1+j-round(half):j+round(half),1+k-round(half):k+round(half))=ReconImage(:,1+j-round(half):j+round(half),1+k-round(half):k+round(half))+fftimage(i,j,k).*Sampledist2/1000;
end
end
end
=============================================================================
In my code, Sampledist is (Depth,Alines,Alines) size aray.
Ultimately, I want sum "fftimage(i,j,k).*Sampledist2/1000" to "ReconImage" array. But in my code, 'for k=~' part spend 0.8 sec during one cycle. So actually, expected spend time is up to ten thousands hours.
I never agree my code is the best.
When i search to increase calculation, i found 'parfor' but i can't apply that because for loop refer the result.(underline)
Anyone have nice idea?
Thank you.
Kim.

Answers (1)

Jan
Jan on 14 Sep 2021
Edited: Jan on 14 Sep 2021
Start with a simplification of the code:
Depth = 5000;
Num_Alines = 400;
Num_Bscan = 300;
Alines = 180
h = round(Alines / 2); % Call round() once only
R = zeros(Depth, Num_Alines, Num_Bscan);
for i = 1:Depth
S = Sampledist;
S(S == S(i, h, h)) = 1;
S(S ~= 1) = 0;
S = S * D313 / 1000;
for j = h:Num_Alines - h
for k = h:Num_Bscan - h
R(:, 1+j-h:j+h, 1+k-h:k+h) = ...
R(:, 1+j-h:j+h, 1+k-h:k+h) + fftimage(i,j,k) .* S;
end
end
end
Please provide some values for Sampledist and fftimage - maybe produced by rand().
  3 Comments
Jan
Jan on 15 Sep 2021
Sorry, I tried to guess the sized of the inputs, but the code still stops with errors.
Please do not let the readers guess, what your input arguments are. If I cannot run your code, it is very hard to improve its speed.

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