How to run N threads of the same functions with different parameters in parallel? - python

Question

From Concurrently run two functions that take parameters and return lists?, i can run 2 functions in parallel by specifying 2 queues.

from threading import Thread
from Queue import Queue

def func1(x):
    return [i*i for i in x]

nums1 = [1,2,3,4,5]; nums2 = [112,32,53,64,25]

def wrapper(func, arg, queue):
    queue.put(func(arg))

q1, q2 = Queue(), Queue()
Thread(target=wrapper, args=(func1, nums1, q1)).start() 
Thread(target=wrapper, args=(func1, nums2, q2)).start() 

print q1.get(), q2.get()

How to run N threads of the same functions with different parameters in parallel?

Currently, I'm hard coding and doing:

nums1 = [1,2,3,4,5]; nums2 = [112,32,53,64,25]
nums3 = [11,522,33,467,85]; nums4 = [12,2,5,4,1125]
q1, q2, q3, q4 = Queue(), Queue(), Queue(), Queue()
Thread(target=wrapper, args=(func1, nums1, q1)).start() 
Thread(target=wrapper, args=(func1, nums2, q2)).start() 
Thread(target=wrapper, args=(func1, nums3, q3)).start() 
Thread(target=wrapper, args=(func1, nums4, q4)).start() 
print q1.get(), q2.get(), q3.get()

Answer 1

Queues are threadsafe. So you should be able to get away with two queues, to be shared between all your threads:

from threading import Thread
from multiprocessing import Queue

def func1(x):
    return [i*i for i in x]

nums = [1,2,3,4,5,112,32,53,64,25]

def wrapper(func, qIn, qOut):
    for arg in iter(qIn.get, None):
        qOut.put(func(arg))

qIn, qOut = Queue(), Queue()
chunksize = len(nums)/numThreads
for i in xrange(numThreads):
    qIn.put(nums[i*chunksize : (i+1)*chunksize])
numThreads = 2  # or N
for _ in xrange(numThreads):
    qIn.put(None)
for _ in xrange(numThreads):
    Thread(target=wrapper, args=(func1, qIn, qOut)).start() 

for _ in xrange(numThreads):
    print qOut.get()