# pp-web / pp_examples / sum_primes.py

 ``` 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81``` ```#!/usr/bin/env python # File: sum_primes.py # Author: Vitalii Vanovschi # Desc: This program demonstrates parallel computations with pp module # It calculates the sum of prime numbers below a given integer in parallel # Parallel Python Software: http://www.parallelpython.com import math import sys from pp import pp def isprime(n): """Returns True if n is prime and False otherwise""" if not isinstance(n, int): raise TypeError("argument passed to is_prime is not of 'int' type") if n < 2: return False if n == 2: return True max = int(math.ceil(math.sqrt(n))) i = 2 while i <= max: if n % i == 0: return False i += 1 return True def sum_primes(n): """Calculates sum of all primes below given integer n""" return sum([x for x in xrange(2, n) if isprime(x)]) print """Usage: python sum_primes.py [ncpus] [ncpus] - the number of workers to run in parallel, if omitted it will be set to the number of processors in the system""" # tuple of all parallel python servers to connect with ppservers = () #ppservers = ("127.0.0.1:60000", ) if len(sys.argv) > 1: ncpus = int(sys.argv[1]) # Creates jobserver with ncpus workers job_server = pp.Server(ncpus, ppservers=ppservers) else: # Creates jobserver with automatically detected number of workers job_server = pp.Server(ppservers=ppservers) print "Starting pp with", job_server.get_ncpus(), "workers" # Submit a job of calulating sum_primes(100) for execution. # sum_primes - the function # (100,) - tuple with arguments for sum_primes # (isprime,) - tuple with functions on which function sum_primes depends # ("math",) - tuple with module names which must be imported before # sum_primes execution # Execution starts as soon as one of the workers will become available job1 = job_server.submit(sum_primes, (100, ), (isprime, ), ("math", )) # Retrieves the result calculated by job1 # The value of job1() is the same as sum_primes(100) # If the job has not been finished yet, execution will # wait here until result is available result = job1() print "Sum of primes below 100 is", result # The following submits 8 jobs and then retrieves the results inputs = (100000, 100100, 100200, 100300, 100400, 100500, 100600, 100700) jobs = [(input, job_server.submit(sum_primes, (input, ), (isprime, ), ("math", ))) for input in inputs] for input, job in jobs: print "Sum of primes below", input, "is", job() job_server.print_stats() # Parallel Python Software: http://www.parallelpython.com ```