Vectorization of double for loop

I am vectorizing following code,doesnt seem to work. I will appreciate any help !

              aux=1; 
              n = sqrt(max(size(u)));
              cut = n / Nx;
              u = reshape(u, n, n);   
              for i = 0 : Nx-1
                  for j = 0 : Nx-1
                  P{aux}{1} = u(1+ i*cut: (i+1)*cut,1+ j*cut: (j+1)*cut); 
                  aux = aux +1;
                  end
              end

[Jon]

What do you mean "doesn't seem to work?" Please be specific, and if you can provide an example, it would really help.

[ak135AK]

this code works, but my implementations of vectorization do not... I am not sure, if it is even possible, is it?

[Jon]

It doesn't seem possible to me, but one of the more experienced users here might be able to make it happen.

[ak135AK]

u is vector 1 x n2, then is gets reshaped and is cut into 4 partitions in middle, something like:

              % omega 1 | omega 2
              % ------------------
              % omega 3 | omega 4
and each part is saved into P

Answer 1

[Sean de Wolski]

Just preallocating P will speed this up a lot

P = cell(Nx^2,1)

before the loop