Convert matlabpool to parpool in matlab

Question

I have a code from matlab 2010a that I want to run it in matlab 2019a, I'm using parallelism.

matlabpool open 4 %prepares matlab to run in 4 parallel procesors
j1 = batch('parallel1', 'matlabpool', 0);
pause(1)
j2 = batch('parallel2', 'matlabpool', 0);
pause(1)
j3 = batch('parallel3', 'matlabpool', 0);
pause(1)
j4 = batch('parallel4', 'matlabpool', 0);

matlabpool close

But, the code dosen't run in this version of matlab, because I have to use parpool. So, I'm asking to someone who know how to convert or how to change this part of the code to run in my new matlab version.

Answer 1

First step is to check the original documentation, since 2010a is no longer online here the corresponding 2013a documentation. It still has matlabpool explained:

'Matlabpool' — An integer specifying the number of workers to make into a MATLAB pool for the job in addition to the worker running the batch job itself. The script or function uses this pool for execution of statements such as parfor and spmd that are inside the batch code. Because the MATLAB pool requires N workers in addition to the worker running the batch, there must be at least N+1 workers available on the cluster. You do not have to have a MATLAB pool already running to execute batch; and the new pool that batch opens is not related to a MATLAB pool you might already have open. (See Run a Batch Parallel Loop.) The default value is 0, which causes the script or function to run on only the single worker without a MATLAB pool.

In current MATLAB-Versions this option is replaced by the pool parameter. 0 Is still the default behavior, you can use:

j1 = batch('parallel1');

Answer 2

The literal translation of your code is to do this:

parpool(4) % Creates a parallel pool with 4 workers
j1 = batch('parallel1', 'Pool', 0) % creates a batch job with no pool
... % etc.

However, I'm curious as to whether this is actually what you want to do. The parpool(4) command launches 4 worker processes to be used by your desktop MATLAB - for when you use parfor, spmd, or parfeval. Each batch command spawns an additional worker process, which cannot access the workers from the parallel pool.