python 多程序並行程式設計 ProcessPoolExecutor的實現
阿新 • • 發佈:2020-01-09
使用 ProcessPoolExecutor
from concurrent.futures import ProcessPoolExecutor,as_completed import random
斐波那契數列
當 n 大於 30 時丟擲異常
def fib(n): if n > 30: raise Exception('can not > 30,now %s' % n) if n <= 2: return 1 return fib(n-1) + fib(n-2)
準備陣列
nums = [random.randint(0,33) for _ in range(0,10)] ''' [13,17,22,19,33,7,12,8,16] '''
方案一:submit
submit 輸出結果按照子程序執行結束的先後順序,不可控
with ProcessPoolExecutor(max_workers=3) as executor: futures = {executor.submit(fib,n):n for n in nums} for f in as_completed(futures): try: print('fib(%s) result is %s.' % (futures[f],f.result())) except Exception as e: print(e) ''' fib(13) result is 233. fib(17) result is 1597. fib(0) result is 1. fib(22) result is 17711. fib(19) result is 4181. can not > 30,now 33 fib(7) result is 13. fib(12) result is 144. fib(8) result is 21. fib(16) result is 987. '''
等價寫法:
with ProcessPoolExecutor(max_workers=3) as executor: futures = {} for n in nums: job = executor.submit(fib,n) futures[job] = n for job in as_completed(futures): try: re = job.result() n = futures[job] print('fib(%s) result is %s.' % (n,re)) except Exception as e: print(e) ''' fib(13) result is 233. fib(17) result is 1597. fib(0) result is 1. fib(22) result is 17711. can not > 30,now 33 fib(7) result is 13. fib(19) result is 4181. fib(8) result is 21. fib(12) result is 144. fib(16) result is 987. '''
方案二:map
map 輸出結果按照輸入陣列的順序
缺點:某一子程序異常會導致整體中斷
with ProcessPoolExecutor(max_workers=3) as executor: try: results = executor.map(fib,nums) for num,result in zip(nums,results): print('fib(%s) result is %s.' % (num,result)) except Exception as e: print(e) ''' fib(13) result is 233. fib(17) result is 1597. fib(0) result is 1. fib(22) result is 17711. fib(19) result is 4181. can not > 30,now 33 '''
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