[Documentation] Explain how to access the executorlib_worker_id for debugging

[jan-janssen]

The functionality was added in: #748

Basically, the worker ID is available as input parameter to your functions named executorlib_worker_id, so if you have a function like this:

def my_function(a, b, executorlib_worker_id): 
    ...

And you submit it to an executor like this:

exe.submit(my_function, a=1, b=2)

Then executorlib automatically sets the executorlib_worker_id input parameter at the point when the function is executed on the worker, in analogy to the init_function: https://executorlib.readthedocs.io/en/latest/1-single-node.html#performance-optimization

[jan-janssen]

Example from @mgt16-LANL :

import os
from concurrent.futures import as_completed
from executorlib import SingleNodeExecutor
 
def gpu_init_simple(executorlib_worker_id):
    import os
    cuda_inds = os.environ.get('CUDA_VISIBLE_DEVICES','1').split(',')
    sel_ind = int(executorlib_worker_id) % len(cuda_inds)
    cuda_ind = cuda_inds[sel_ind]
    print('Device is cuda init:' + cuda_ind)
    print('executorlib worker_id init: ', executorlib_worker_id)
    return {}
 
def run_parallel(ind, executorlib_worker_id):
    print('Ind: ', ind, 'executorlib worker_id: ', executorlib_worker_id)
 
with SingleNodeExecutor(max_workers=4, init_function=gpu_init_simple,
                        block_allocation=True) as exe:
    futs = []
    print('Starting')
    for ind in range(8):
        fut = exe.submit(run_parallel, ind)
        futs.append(fut)
    print('Submitted')
    count = 0
    for done in as_completed(futs):
        print('Done: ',count)
        count += 1