74 lines
1.9 KiB
Python
74 lines
1.9 KiB
Python
#!/usr/bin/env python3
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"""
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threads.py: shows that Python threads are slower
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than sequential code for CPU-intensive work.
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"""
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import os
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import sys
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from queue import SimpleQueue
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from time import perf_counter
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from typing import NamedTuple
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from threading import Thread
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from primes import is_prime, NUMBERS
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class PrimeResult(NamedTuple):
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n: int
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prime: bool
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elapsed: float
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JobQueue = SimpleQueue[int] # <4>
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ResultQueue = SimpleQueue[PrimeResult] # <5>
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def check(n: int) -> PrimeResult: # <6>
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t0 = perf_counter()
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res = is_prime(n)
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return PrimeResult(n, res, perf_counter() - t0)
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def worker(jobs: JobQueue, results: ResultQueue) -> None: # <7>
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while n := jobs.get(): # <8>
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results.put(check(n)) # <9>
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results.put(PrimeResult(0, False, 0.0))
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def start_jobs(workers: int, jobs: JobQueue, results: ResultQueue) -> None:
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for n in NUMBERS: # <3>
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jobs.put(n)
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for _ in range(workers):
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proc = Thread(target=worker, args=(jobs, results)) # <4>
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proc.start() # <5>
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jobs.put(0) # <6>
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def report(workers: int, results: ResultQueue) -> int:
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checked = 0
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workers_done = 0
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while workers_done < workers:
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n, prime, elapsed = results.get()
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if n == 0:
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workers_done += 1
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else:
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checked += 1
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label = 'P' if prime else ' '
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print(f'{n:16} {label} {elapsed:9.6f}s')
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return checked
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def main() -> None:
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if len(sys.argv) < 2:
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workers = os.cpu_count()
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else:
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workers = int(sys.argv[1])
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print(f'Checking {len(NUMBERS)} numbers with {workers} threads:')
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t0 = perf_counter()
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jobs: JobQueue = SimpleQueue()
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results: ResultQueue = SimpleQueue()
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start_jobs(workers, jobs, results)
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checked = report(workers, results)
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elapsed = perf_counter() - t0
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print(f'{checked} checks in {elapsed:.2f}s')
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if __name__ == '__main__':
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main()
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