parfor and nested loop

hi,

can I use parfor with nested loop?

for ex.

parfor i=1:5
for j=1:2

%%whatever
end
end

should I use par with each for or with one.

please, I need somebody can solve my problem.

Thanks in advance

Answer 1

[Mischa Kim]

Hello huda, there are no nested parfor loops. Parallelization with parfor only works on the outermost loop.

[huda nawaf]

thanks,

ok, do u mean it is not problem if i use parfor for outermost loop and the inside loop stay as it.

I just wonder because when I used parfor for only outermost loop, I did not find any improvement in terms of running time.

Please, I badly need that.

Answer 2

[Matt J]

To combine the loops into a single parfor loop,

 parfor k=1:10

   [i,j]=ind2sub([5,2],k);

    %%whatever

 end

[huda nawaf]

thanks,

but I did not find any improvement in terms of time if I compare this code with other without parfor even for high iteration.

[Matt J]

The effectiveness of parfor depends a lot on what you're doing inside the loop.

[huda nawaf]

yes, but I read if I have large array it is best to use spmd.

this function will distribute the array among workers.

but I have problem. Also I used pmode .

I did not find the efficiency of these functions. I hope to find simple example show me the difference between parallel and serial processing.

thanks