"""
This program runs a loop that adds +1 to different cells in an array.

Run it as:
  python threading_example.py WORKERS ITERATIONS
where WORKERS is the number of threads,
and ITERATIONS is how much work each thread does.

In the single threaded case, when N == 1, the 'counters' variable
below starts out as
  [0, 0, 0]
then becomes
  [1, 0, 0]
then
  [1, 1, 0]
... and a little bit later
  [2, 1, 1]
and at the end
  [N, N, N]

What happens in the multi-threaded case, when N > 1? Try and see!
"""

import sys
import threading

def count(where, how_much):
    for i in range(how_much):
        # Execute where[i % len(where)] += 1, print what is hapenning
        cell = i % len(where)
        value = where[cell]
        thread = threading.get_native_id()
        end = '\r' if i < how_much - 1 else '\n'
        print(f'{thread=} {cell=} {value=}→{value + 1}', end=end)
        where[cell] = value + 1

workers = int(sys.argv[1])
how_much = int(sys.argv[2])

counters = [0] * 3
print(f'start: {counters=}')

threads = [threading.Thread(target=count, args=(counters, how_much))
           for _ in range(workers)]

for t in threads:
    t.start()
for t in threads:
    t.join()

print(f'final: {counters=}')
print(f'       {sum(counters)=}')