How MATLAB scheduler is doing the parallelization between the workers in one computer ?

Dear all,

Please, I have a question: I read about the parallel toolbox in MATLAB and how to use some functions and iteration loops like parfor and spmd. I implement some examples from the documents which are very useful and let me understand how to use these tools.

My question is: How MATLAB scheduler is doing the parallelisation for us ? in other words, when we write our parallel code (this code contain parfor or spmd) how MATLAB divide and copy the code and send it to all workers ?

Kind regards Ammar

Answer 1

[Edric Ellis]

For spmd, the model is simple: each worker executes the body of the block simultaneously.

For parfor, the iterations of the loop are split up into "intervals", and these are sent out to workers. The aim of the parfor scheduler is to divide the work in such a way as to minimise overheads, while minimising "stragglers". There is no way as a user of parfor to influence the way the work is divided.

[Ammar]

Dear Edric, I would like to thank you for this answer. Really it is useful. Please, can I ask: Can I use the pmode tool for implement the same code and get the same results with the same execution time as parfor ? i.e. in pmode tool designated a number of iterations for each worker using (if labindex==...) and collect the results using (labSend, labRecieve, labBroadcast).

Regards Ammar

[Edric Ellis]

You can't use parfor together with pmode. The commands that you enter at the P>> prompt are essentially executed as if they were inside an spmd block. However, you can use the for-drange loop there.