Parallel 并发编程实例

算法计算小于数的所有  素数和

不用Parallel

# sum_primes_without_pp.py
import math, sys, time

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)])

start_time = time.time()
start=time.clock()
inputs = (100000, 100100, 100200, 100300, 100400, 100500, 100600, 100700,676899,646899,677899,676099,675899,646899,677099,606099)
for input in inputs:
        print "Sum of primes below", input, "is", sum_primes(input)

elapsed = (time.clock() - start)
print "Time elapsed: ", elapsed, "s"
print "Time elapsed: ", time.time() - start_time, "s"

运行结果

Sum of primes below 100000 is 454396537
Sum of primes below 100100 is 454996777
Sum of primes below 100200 is 455898156
Sum of primes below 100300 is 456700218
Sum of primes below 100400 is 457603451
Sum of primes below 100500 is 458407033
Sum of primes below 100600 is 459412387
Sum of primes below 100700 is 460217613
Sum of primes below 676899 is 17725655031
Sum of primes below 646899 is 16245807217
Sum of primes below 677899 is 17773746096
Sum of primes below 676099 is 17690477739
Sum of primes below 675899 is 17679661703
Sum of primes below 646899 is 16245807217
Sum of primes below 677099 is 17739194685
Sum of primes below 606099 is 14352855223
Time elapsed:  100.017748574 s
Time elapsed:  100.016000032 s

用Parallel 并发编程

import math, sys, time
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 = ("10.0.0.1",)

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

start_time = time.time()

# The following submits 8 jobs and then retrieves the results
inputs = (100000, 100100, 100200, 100300, 100400, 100500, 100600, 100700,676899,646899,677899,676099,675899,646899,677099,606099)
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()

print "Time elapsed: ", time.time() - start_time, "s"
job_server.print_stats()

运行结果

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

Starting pp with 4 workers
Sum of primes below 100 is 1060
Sum of primes below 100000 is 454396537
Sum of primes below 100100 is 454996777
Sum of primes below 100200 is 455898156
Sum of primes below 100300 is 456700218
Sum of primes below 100400 is 457603451
Sum of primes below 100500 is 458407033
Sum of primes below 100600 is 459412387
Sum of primes below 100700 is 460217613
Sum of primes below 676899 is 17725655031
Sum of primes below 646899 is 16245807217
Sum of primes below 677899 is 17773746096
Sum of primes below 676099 is 17690477739
Sum of primes below 675899 is 17679661703
Sum of primes below 646899 is 16245807217
Sum of primes below 677099 is 17739194685
Sum of primes below 606099 is 14352855223
Time elapsed:  39.5499999523 s
Job execution statistics:
 job count | % of all jobs | job time sum | time per job | job server
        17 |        100.00 |     154.4120 |     9.083059 | local
Time elapsed since server creation 39.5599999428
0 active tasks, 4 cores