MATLAB缩放的repmat

2 回答

• 3

  我想你正在寻找kron：

  result = kron(B, A);
  

  回复于 2024-05-03T17:34:10+08:00
• 2

  您可能正在执行元素乘法，从而产生一个巨大的数组，然后进行置换 . 现在，大阵列上的 permute 将导致大量数据传输，这将无效 . 所以，我猜你在做这些事情：

  reshape(permute(bsxfun(@times,A,permute(B,[3,4,1,2])),[1,3,2,4]),N,[]) 
             ^ (kills performance)
  

  另一种方法是在输入数组之间执行元素乘法之前在 A 和 B 上执行 permute ，这样最终我们只需要 reshape . 比较 A 和 B 的效率应该更高效 .

  因此，一个有效的解决方案是 -

  n = size(A,1)*size(B,1);
  out = reshape(bsxfun(@times,permute(A,[1,3,2]),permute(B,[3,1,4,2])),n,[]);
  

  Runtime test

  让我们来两种方法来验证我们的性能改进，并且还包括@ Shai的帖子中建议的基于_1874240的方法，这似乎是一个干净的解决方案 -

  % Max sized input arrays that my system could handle
  A = randi(9,70,70);
  B = randi(9,70,70);
  
  disp('-------------- With permute on A and B and finally reshaping')
  tic
  n = size(A,1)*size(B,1);
  out0 = reshape(bsxfun(@times,permute(A,[1,3,2]),permute(B,[3,1,4,2])),n,[]);
  toc, clear out0 n
  
  disp('-------------- With permute on elementwise result')
  tic
  n = size(A,1)*size(B,1);
  out1 = reshape(permute(bsxfun(@times,A,permute(B,[3,4,1,2])),[1,3,2,4]),n,[]);
  toc, clear out1 n
  
  disp('-------------- With kron from @Shai post')
  tic,
  result1 = kron(B, A);
  toc
  

  计时 -

  -------------- With permute on A and B and finally reshaping
  Elapsed time is 0.161598 seconds.
  -------------- With permute on elementwise result
  Elapsed time is 0.413746 seconds.
  -------------- With kron from @Shai post
  Elapsed time is 0.612825 seconds.
  

  回复于 2024-05-03T17:34:10+08:00