Exemplu de bariera in Python

Exemplu de bariera - 10 thread-uri pornesc unul dupa altul si sunt afisate in ordinea intrarii lor, dupa care se face o bariera care asigura ca thread-urile vor astepta ca toate sa termine intrarea pentru a merge mai departe.

Mai departe, sunt eliberate unul cate unul si tinute intr-o alta bariera.

import threading

import time

import random

bariera = threading.Semaphore(value=0)

bariera2 = threading.Semaphore(value=0)

regcritica = threading.Semaphore(value=1)

threads = 10

n=threads

threadlist = []

# asigura ca toate thread-urile ies odata

def folosire(x):

print "[INTRARE]: ",x

barrier()

print "[IESIRE]: ",x

barrier()

def barrier():

global bariera,bariera2, regcritica,n,threads

# prima bariera este de intrare (aduna toate thread-urile)

regcritica.acquire();

n = n - 1;

if n==0:

for i in range(threads):

bariera.release();

regcritica.release();

bariera.acquire();

# a doua bariera este de iesire ( --//-- )

regcritica.acquire()

n = n + 1

if n == threads:

for i in range(threads):

bariera2.release()

regcritica.release()

bariera2.acquire()

random.seed()

for i in range(threads):

thread = threading.Thread(target=folosire, args=(i,)) # arg o functie si arg. ei

thread.start()

threadlist.append(thread)

for i in range(len(threadlist)):

threadlist[i].join()