Matlab parallel for loop or Matlab open pool

I am trying to to some computations and I would like to do it in parallel using parfor or by Opening the matlabpool.. as the current implementations is too slow:

   result=zeros(25,16000);
   for i = 1:length(vector1) % length is 25

     for j = 1:length(vector2) % length is 16000 

              temp1 = vector1(i); 
              temp2 = vector2(j);
              t1 = load(matfiles1(temp1).name) %load image1 from matfile1
              t2 = load(matfiles2(temp2).name) % load image2 from matfile2
              result(i,j)=t1.*t2
     end
   end

It work fine but I would really like to know if there is a way to speed thing up ... Thanks a lot in advance!

Answer 1

[Walter Roberson]

load() is slow. Only load what you have to.

   result=zeros(25,16000);
   for K = 1 : length(vector1) % length is 25
     temp1 = vector1(K);
     all_t1{K} = load(matfiles1(temp1).name) %load image1 from matfile1
   end
   for K = 1 : length(vector2) % length is 16000 
     temp2 = vector2(K);
     all_t2{K} = load(matfiles2(temp2).name) % load image2 from matfile2
   end

   for K1 = 1 : length(vector1)
     t1 = all_t1{K1};
     for K2 = 1 : length(vector2)
       t2 = all_t2{K2};
       result(i,j) = t1 .* t2;
     end
   end

Note: the fact that you store the element-by-element multiplication into a single numeric entry implies that the files you load might all consist of single scalar values. If that is the case, then the storage use can be improved and the multiplication can be sped up. Store the values into row vectors and then,

result = bsxfun(@times, all_t1(:), all_t2 )

[Nitin]

Thanks Walter!