How to speed up calculation taking inputs from 2 separate and very large matrices (working code below)

Question

klb 2018-10-25

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/426010-how-to-speed-up-calculation-taking-inputs-from-2-separate-and-very-large-matrices-working-code-belo

编辑： per isakson 2018-10-28

Hi. The code below works. updated portion the REAL is 'a' is at 10600X5 and and 'b' at 60X5 and takes forever to run. How can I massively speed up the calculation?

 *updated*
 tic
 a = randi([0,100],10600,5)   % example only to run the code
 b = randi([0,20],60,5)
 new = zeros(size(a,1)*size(b,1),size(a,2));
 w = 0;
 for s= 1:size(a,1)
    for t= 1:size(b,1)
        new(w+t,:)= [(3*a(s,1)+b(t,1)), (5*a(s,2)+b(t,2)), (1*a(s,3)+b(t,3)),   (5*a(s,4)+b(t,4)) , (2*a(s,5)+b(t,5))];
    end
    w=w+size(b,1);
 end
 toc

4 个评论
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Jan 2018-10-26

@klb: Do I understand correctly: The posted code works with the needed speed, but some other code, which you do not show, is much slower? We cannot know the reason of this difference without seeing the other code. So all I can do is to suggest letting the profile find out, where the time is spent.

per isakson 2018-10-28

"massively speed up" How much is that?

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Answer 1

per isakson 2018-10-28

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/426010-how-to-speed-up-calculation-taking-inputs-from-2-separate-and-very-large-matrices-working-code-belo#answer_343798

编辑：per isakson 2018-10-28

在 MATLAB Online 中打开

Try

>> cssm()
Elapsed time is 0.073258 seconds.
Elapsed time is 0.073459 seconds.
Elapsed time is 0.042250 seconds.
Elapsed time is 0.019368 seconds.
ans =
  1×3 logical array
   1   1   1

where

function  cssm()
      a = randi([0,100],10800,5);   % example only to run the code
      b = randi([0,20],60,5);
      tic, new1 = cssm_1( a, b ); toc
      tic, new2 = cssm_2( a, b ); toc
      tic, new3 = cssm_3( a, b ); toc
      tic, new4 = cssm_4( a, b ); toc
      [ all(new1(:)==new2(:)), all(new1(:)==new3(:)), ll(new1(:)==new4(:)) ]
  end
  function    new = cssm_1( a, b )
      %%*updated*
      new = zeros(size(a,1)*size(b,1),size(a,2));
      w = 0;
      for s = 1:size(a,1)
          for t = 1:size(b,1)
              new(w+t,:)= [(3*a(s,1)+b(t,1))  ...
                          ,(5*a(s,2)+b(t,2))  ...
                          ,(1*a(s,3)+b(t,3))  ...
                          ,(5*a(s,4)+b(t,4))  ...
                          ,(2*a(s,5)+b(t,5))  ];
          end
          w=w+size(b,1);
      end
  end
  function    new = cssm_2( a, b )
      new = zeros(size(a,1)*size(b,1),size(a,2));
      w = 0;
      a = [3,5,1,5,2].*a;
      for s = 1:size(a,1)
          for t = 1:size(b,1)
              new(w+t,:)= [(a(s,1)+b(t,1))  ...
                          ,(a(s,2)+b(t,2))  ...
                          ,(a(s,3)+b(t,3))  ...
                          ,(a(s,4)+b(t,4))  ...
                          ,(a(s,5)+b(t,5))  ];
          end
          w=w+size(b,1);
      end
  end
  function    new = cssm_3( a, b )
      new = zeros(size(a,1)*size(b,1),size(a,2));
      w = 0;
      a = [3,5,1,5,2].*a;
      for s = 1:size(a,1)
          for t = 1:size(b,1)
              new(w+t,:)= a(s,:)+b(t,:);
          end
          w=w+size(b,1);
      end
  end
  function    new = cssm_4( a, b )
      new = zeros(size(a,1)*size(b,1),size(a,2));
      w = size(b,1);
      a = [3,5,1,5,2].*a;
      for s = 1:size(a,1)
          new( ( 1+(s-1)*w : s*w ), : ) = a(s,:)+b;
      end
  end