How to impove the performence of this code?

Question

feng 2014-11-24

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关闭： MATLAB Answer Bot 2021-8-20

Hello,

I am doing a for-loop, but this computing cost is too huge for me. Therefore I am trying to find a shut-cut way to reduce the cost, I have no ideas how to do this vectorization.

Any suggestions are greatly appreciated.

Many thanks

Code:

--------------------------------------------------------

felspar(197992,128);

felspar(:,1:3)=alldatafel(:,1:3);

for j = 1:197992

    for i=1:337945   
        if strcmp(alldata(i,1),alldatafel(j,1)) && strcmp(alldata(i,2),alldatafel(j,2));
            felspar(j,4:128)=alldata(i,1:125);
        end                     
    end
end
xlswrite('match.xlsx',felspar)

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Answer 1

Hugo 2014-11-24

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https://ww2.mathworks.cn/matlabcentral/answers/164048-how-to-impove-the-performence-of-this-code#answer_160023

编辑：Hugo 2014-11-24

在 MATLAB Online 中打开

As far as I can see, there is a problem in the code. Wheneven the condition

strcmp(alldata(i,1),alldatafel(j,1)) && strcmp(alldata(i,2),alldatafel(j,2))

is TRUE, then

felspar(j,4:128)=alldata(i,1:125)

But that means that the value stored in felspar(j,4:128) for each j corresponds to the largest value of i for which the condition is fulfilled. Therefore, you can save time by searching i from the end, and breaking the loop as soon as the condition is fulfilled. The could should look like this:

felspar(197992,128);
felspar(:,1:3)=alldatafel(:,1:3);
for j = 1:197992
    for i=337945:-1:1   
        if strcmp(alldata(i,1),alldatafel(j,1)) &&  strcmp(alldata(i,2),alldatafel(j,2));
            felspar(j,4:128)=alldata(i,1:125);
            break;
  end                     
    end
  end