How can I reduce the time complexity of this matlab code.. Its taking lot of time to execute when an image is fed as input.

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cnt1=0; cnt2=0; cnt3=0; cnt4=0; cnt5=0; cnt6=0; cnt7=0; cnt8=0;
p = 1;
row = 1;
while p<(size(Theta_deg_img,1))
q = 1;
while q<(size(Theta_deg_img,2))
for i=p:p+8
for j=q:q+8
if Theta_deg_img(i,j)>=-180 && Theta_deg_img(i,j)<=-135
cnt1 = cnt1+1;
elseif Theta_deg_img(i,j)>=-134 && Theta_deg_img(i,j)<=-90
cnt2 = cnt2 + 1;
elseif Theta_deg_img(i,j)>=-89 && Theta_deg_img(i,j)<=-45
cnt3 = cnt3 + 1;
elseif Theta_deg_img(i,j)>=-44 && Theta_deg_img(i,j)<=0
cnt4 = cnt4 + 1;
elseif Theta_deg_img(i,j)>=1 && Theta_deg_img(i,j)<=45
cnt5 = cnt5 + 1;
elseif Theta_deg_img(i,j)>=46 && Theta_deg_img(i,j)<=90
cnt6 = cnt6 + 1;
elseif Theta_deg_img(i,j)>=91 && Theta_deg_img(i,j)<=135
cnt7 = cnt7 + 1;
else
cnt8 = cnt8 + 1;
end
eval([fsrc '(row,1) = cnt1;']);
eval([fsrc '(row,2) = cnt2;']);
eval([fsrc '(row,3) = cnt3;']);
eval([fsrc '(row,4) = cnt4;']);
eval([fsrc '(row,5) = cnt5;']);
eval([fsrc '(row,6) = cnt6;']);
eval([fsrc '(row,7) = cnt7;']);
eval([fsrc '(row,8) = cnt8;']);
end
end
q = q + 9; row = row+1;
cnt1=0; cnt2=0; cnt3=0; cnt4=0; cnt5=0; cnt6=0; cnt7=0; cnt8=0;
end
p = p + 9;
end

采纳的回答

Harshit
Harshit 2012-11-23
Vectorize your code. Example you don't need inner loops you can use sum to get the value of counts. In the outer two loops you are calculating size again and again. Store it in a variable.
  5 个评论
Harshit
Harshit 2012-11-26
Yes it will just think about it. Whenver the condn is true 1 will be generated in the matrix and otherwise 0. sum will give the no of 1.

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Akiva Gordon
Akiva Gordon 2012-11-23

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