Question

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

its works fine but I would really like to know if there is a way to speed thing up …
Thanks a lot in advance!

Answer 1

Using a parfor loop and opening a matlabpool go together. Opening the matlabpool provides your MATLAB session with dedicated workers with which it can run the body of your parfor loop. So, you could change your code to something like this:

matlabpool open local 4 % or however many cores you have
parfor i = ...
   ...
end

Before running your code in parallel, I would definitely recommend using the MATLAB profiler to ensure you understand where the time is being spent running your code. (I’m a little surprised that hoisting the load into t1 into the outer loop has no effect – the profiler presumably should therefore show that the load calls take very little time compared to the rest of your algorithm).