MATLAB: Fastest way to implement the given lines of code.

speedtimevectorization

Let A, B, C be any random matrices of order mxn; m,n would be large enough. What is the fastest way to implement the following lines:
A = rand(m,n) ;
B = rand(m,n) ; 
C = rand(m,n) ; 
t1 = tic ;
for j = 2:n
    for i = 2:m
        H = 0.5*(A(i,j) + A(i+1,j)) ;
        if (H > 0.0)
            C(i,j) = C(i,j)-H*(B(i+1,j)-B(i,j)) ;
        end 
    end 
end 
toc(t1)
cheers...
Sreenivas

Best Answer

I suspect you're looking for something like the following,
      A = rand(m,n) ;
      B = rand(m,n) ; 
      C = rand(m,n) ; 
   H=0.5*conv2(A,[1;1],'same');    %EDITED
   deltaB=conv2(B,[1;-1],'same');
   idx=H>0;
   C(idx)=C(idx)-H(idx).*deltaB(idx);
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