Choose between for and parfor.

Hi,

I want to run many simulations. For this I wrote "for" loop. I used parallel computing, using parfor instead; It works well.

Now I would like to have a binary parameter, say P, at the beginning of my program activating or not parallel computing. (if P == 0, use for loop. If P == 1, use parfor loop).

A way to do that is to copy paste the whole loop, write for on the first one, and parfor on the second one. But I would like to avoid that, to keep my program compact and easily modifiable. Do you think it is at all possible?

Answer 1

[Friedrich]

Hi,

always use parfor as loop type. When no worker pool is open the parfor loop runs as for loop but backwards. But that should not matter. Note: In R2013b there was a new feature introduced which automatically open a new parallel pool when SPMD or PARFOR is executed. You might want to disable that feature in the parallel preference setting of your MATLAB in the case you use R2013b or newer.

Or in the case you dont like that put the whole body of the loop in a function which takes the index as input, e.g.

if run_in_parallel
 parfor i=1:n
   result(i) = myfun(i, other_args)
 end
else
 for i=1:n
   result(i) = myfun(i, other_args)
 end
end

[Martin]

Ok, thanks. I'll stick with parfor. :)