Speed up code:: Code is working but slow..

Hi ,

The code is working fine, but it's very slow... any suggestions ?

clearvars; 
clc; 

C(1:3,1:3,1:3,1:3)    =                             rand(3,3,3,3)
T                     =                            [cos(theta) sin(theta) 0;
                                                   -sin(theta) cos(theta) 0;
                                                      0           0      1];
T_z                 =                            T;
tensor_order        =                            ndims(C);
el_n                =                            numel(C);
 
C_tran              =                              C;
C_tran(:)           =                              0;
 
iie                 =                            zeros(tensor_order,1);              % initialise vector with indices of input tensor element
ioe                 =                            zeros(tensor_order,1);              % initialise vector with indices of output tensor element
 
cum_vector          =                            cumprod(3*ones(tensor_order,1))/3;
for i = 1:el_n,                                   % loop over all output elements
        ioe         =                            mod(floor((i-1)./cum_vector),3)+1;          % calculate indices of current output tensor element
   for j = 1:el_n,                                % loop over all input elements
       pmxx         =                             1;                                 % initialise product of transformation matrices
       iie                  =                    mod(floor((j-1)./cum_vector),3)+1;          % calculate indices of current input tensor element
      for k = 1:tensor_order                            % loop over all dimensions
         pmxx               =                    pmxx * T_z( ioe(k), iie(k) );       
      end
 
         C_tran(i)          =                    C_tran(i) + pmxx * C(j);       % add product of transformation matrices and input tensor element to output tensor element
   end
end

Answer 1

[per isakson]

See: Profile Your Code to Improve Performance and Techniques to Improve Performance

[Mark Sc]

@per isakson

Thanks for your answer... actually, I still do not know why, and which lines are the main problem.. I also asked for any modifications in the code, specially converting sum functions into a for loop

[per isakson]

"but it's very slow" Do you mean more than one millisecond? What is an acceptable execution time?

"specially converting sum functions into a for loop" The function, sum(), doesn't appear in your code.