Cannot execute matlabpool close on the labs.

Hi:

I'm just starting doing parallel programing and till now everything went fine, but now I get an error I don't understand.

*Error using ==> parallel_function at 598 Error in ==> matlabpool at 135 Cannot execute matlabpool close on the labs.

Error in ==> getallbiggervecs at 43 parfor i=1:m

Error in ==> getallbiggervecs at 36 y=[y;getallbiggervecs(Y,Xvar,nucleos)];

*

It's just my intuition, but I think that parallelism doesn't work fine with recursive functions.

Here's the routine (I added an extra if to use normal for.loop and compare):

http://dl.dropbox.com/u/14114808/getallbiggervecs.m

[Sean de Wolski]

Your intuition is correct.

[Sean de Wolski]

what is 'safestarmatlabpool'?

[kira]

safestarmatlabpool it's just a little routine that ask if matlabpool is open, before trying opennig...

Answer 1

[Edric Ellis]

You can nest a PARFOR loop invoke another PARFOR loop, but you will not get any additional parallelism. (due to a current limitation, the inner PARFOR loop cannot occur directly in the text of the outer PARFOR loop) There is no extra parallelism because you cannot open or close another MATLABPOOL on the workers. (One way to tell if you're on a worker is to ask "isempty(getCurrentJob)")

[kira]

I see. But what if for example, I have 4 workers available and I just start matlabpool with 2. Shouldn't the inner parfor-loop use the 2 unused workers?

[Walter Roberson]

Kira, you can do that by calling a function that opens the new pool and has a PARFOR. The limitation is on directly nested PARFOR.

[kira]

I see, so if the "inner" function use a parfor, there should be no problem, i mean, if i only have 4 cores, and i'm using them in the outer loop, the inner function can use them as well?

[Walter Roberson]

I have not worked in that area, but my understanding is that if you want the inner PARFOR to actually run distributed, it has to run in a different pool.

[kira]

i see... I'll check some routines and see what happens...

[kira]

Hi again:

After some experiments, i have this:

a parfor that calls a function that also has a parfor:

- the inner function works fine if executed by itself

- the parfor works fine if the inner function use a for-loop instead of a parfor

- nothing happens (ie, the program is not executed) if the inner function use the parfor... the error i get is the one i posted...

So, the problem is not with the function being recursive by itself, since it works. But executed inside the parfor-loop it can't be done... why, i don't now...