52 lines
1.2 KiB
Python
52 lines
1.2 KiB
Python
"""
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This program runs a loop that adds +1 to different cells in an array.
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Run it as:
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python threading_example.py WORKERS ITERATIONS
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where WORKERS is the number of threads,
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and ITERATIONS is how much work each thread does.
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In the single threaded case, when N == 1, the 'counters' variable
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below starts out as
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[0, 0, 0]
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then becomes
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[1, 0, 0]
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then
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[1, 1, 0]
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... and a little bit later
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[2, 1, 1]
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and at the end
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[N, N, N]
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What happens in the multi-threaded case, when N > 1? Try and see!
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"""
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import sys
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import threading
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def count(where, how_much):
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for i in range(how_much):
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# Execute where[i % len(where)] += 1, print what is hapenning
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cell = i % len(where)
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value = where[cell]
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thread = threading.get_native_id()
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end = '\r' if i < how_much - 1 else '\n'
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print(f'{thread=} {cell=} {value=}→{value + 1}', end=end)
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where[cell] = value + 1
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workers = int(sys.argv[1])
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how_much = int(sys.argv[2])
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counters = [0] * 3
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print(f'start: {counters=}')
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threads = [threading.Thread(target=count, args=(counters, how_much))
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for _ in range(workers)]
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for t in threads:
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t.start()
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for t in threads:
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t.join()
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print(f'final: {counters=}')
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print(f' {sum(counters)=}')
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