SPMD to process different iteration on different worker

I'm trying to use the spmd to process different iteration. The current problem I have is the spmd function is repeating the same processing on different worker. I have tried to use parfor but the parfor cannot guarantee the iteration is process in order. What I am looking for is to have the iteration process in order. For example, from 0>1>2>3>4,.... Below is the sample code.

clear
clc
iCellNum = 1;
activeUeNums = 1;

tic
ticBytes(gcp)
for ttiNum = 1 : 20
   spmd
        if true
            fprintf('%s processing subframe: %d\n', getTimeNow, ttiNum-1);
        end    
   end
end
toc
tocBytes(gcp)

Answer 1

[Edric Ellis]

It's not entirely clear to me quite what you're after. You might want for (drange) which spreads the iterations of a for loop over different workers in spmd.

parpool("local");

Starting parallel pool (parpool) using the 'local' profile ...
Connected to the parallel pool (number of workers: 2).

spmd
    for ii = drange(1:20)
        fprintf('Worker %d processing iteration %d\n', labindex, ii);
    end
end

Worker 1: 
  Worker 1 processing iteration 1
  Worker 1 processing iteration 2
  Worker 1 processing iteration 3
  Worker 1 processing iteration 4
  Worker 1 processing iteration 5
  Worker 1 processing iteration 6
  Worker 1 processing iteration 7
  Worker 1 processing iteration 8
  Worker 1 processing iteration 9
  Worker 1 processing iteration 10
Worker 2: 
  Worker 2 processing iteration 11
  Worker 2 processing iteration 12
  Worker 2 processing iteration 13
  Worker 2 processing iteration 14
  Worker 2 processing iteration 15
  Worker 2 processing iteration 16
  Worker 2 processing iteration 17
  Worker 2 processing iteration 18
  Worker 2 processing iteration 19
  Worker 2 processing iteration 20

[Yi Xien Yap]

Let's say I have 4 workers to process in parallel. How can I force worker 1 to process on iteration 1, worker 2 > iteration 2, worker 3 >iteration 3 and so on. Once worker 1 finished to process, it will proceed to iteration 4 and so on.

[Walter Roberson]

Suppose that worker 1 finished iteration 4 before worker 2 begins iteration 5. Should worker 1 start the next available iteration (5), or should it be strictly round-robin that worker 1 does 1:3:end and 2 does 2:3:end?

[Yi Xien Yap]

I see what you mean, the worker will start whenever they are free.

[Walter Roberson]

Do you need spmd specifically? That is, are you doing labSend(), or using labBarrier to control access to a resource?

If not then consider queuing a bunch of jobs using parfeval.