speed up the calculation in multidimensional array

Question

aldo 2023-7-14

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1996238-speed-up-the-calculation-in-multidimensional-array

评论： aldo 2023-7-15

Array:RP_bin
Matrix: matrix
[~,c]=size(matrix);
xx=find(RP_bin);
q=length(xx);
[~,c]=size(matrix);
cor=zeros(c,c,q);
for i=1:q
  for gg=1:c
       for yy=1:c
              a=matrix(1:xx(i),gg);
              b=matrix(1:xx(i),yy);
              cc=sum((a>0 & b>0)|(a<0 & b<0));
              cc1=sum(a~=0 & b~=0);  
                cor(yy,gg,i)=round(100 * cc/cc1) / 100; %cc/cc1; %%array multidimension
              end            
       end
   end 
>> size(cor)
ans =
    82    82   188
to execution this code is :
Elapsed time is 21.425685 seconds.
is possibile to speed loop?

2 个评论
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James Tursa 2023-7-14

Can you provide a small example of matrix and RP_bin?

aldo 2023-7-15

yes ..attachment it

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Answer 1

Dyuman Joshi 2023-7-15

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1996238-speed-up-the-calculation-in-multidimensional-array#answer_1273538

在 MATLAB Online 中打开

You can reduce a for loop by vectorizing the code -

load('RP_BIN.mat')
load('matlab.mat')
[~,c]=size(matrix);
xx=find(RP_bin);
q=numel(xx);
%Preallocation
[cor,COR]=deal(zeros(c,c,q));
%%Original approach
tic
for i=1:q
    for gg=1:c
        for yy=1:c
            a=matrix(1:xx(i),gg);
            b=matrix(1:xx(i),yy);
            cc=sum((a>0 & b>0)|(a<0 & b<0));
            cc1=sum(a~=0 & b~=0);
            cor(yy,gg,i)=round(100 * cc./cc1)/100; %cc/cc1; %%array multidimension    
            
        end
    end
end
toc
Elapsed time is 18.790586 seconds.

%%Modified approach
tic
gg=1:c;
for i=1:q
    %As the array a is only dependent on the outer loop, bring it out of
    %the inner loop, so that it isn't re-calculated in every iteration of inner loop
    %thereby increasing the speed of the code
    a=matrix(1:xx(i),gg);
    for yy=1:c
        b=matrix(1:xx(i),yy);
        cc=sum((a>0 & b>0)|(a<0 & b<0),1);
        cc1=sum(a~=0 & b~=0,1);
        COR(yy,gg,i)=round(100 * cc./cc1)/100; %cc/cc1; %%array multidimension
    end
end
toc
Elapsed time is 9.287863 seconds.
%%Comparing the output obtained
%As the calculations have NaN data, use isequaln()
isequaln(cor,COR)
ans = logical
   1