A managers.dict() allow to share a dictionary across process and perform thread-safe operation.
In my case each a coordinator process create the shared dict with m elements and n worker processes read and write to/from a single dict key.
Do managers.dict() have one single lock for the dict or m locks, one for every key in it?
Is there an alternative way to share m elements to n workers, other than a shared dict, when the workers do not have to communicate with each other?
Related python-manager-dict-is-very-slow-compared-to-regular-dict
After some tries I can say there is only one lock per managers dict.
Here is the code that proves it:
import time
import multiprocessing as mp
def process_f(key, shared_dict):
values = [i for i in range(64 * 1024 * 1024)]
print "Writing {}...".format(key)
a = time.time()
shared_dict[key] = values
b = time.time()
print "released {} in {}ms".format(key, (b-a)*1000)
def main():
process_manager = mp.Manager()
n = 5
keys = [i for i in range(n)]
shared_dict = process_manager.dict({i: i * i for i in keys})
pool = mp.Pool(processes=n)
for i in range(n):
pool.apply_async(process_f, (keys[i], shared_dict))
time.sleep(20)
if __name__ == '__main__':
main()
output:
Writing 4...
Writing 3...
Writing 1...
Writing 2...
Writing 0...
released 4 in 3542.7968502ms
released 0 in 4416.22900963ms
released 1 in 6247.48706818ms
released 2 in 7926.97191238ms
released 3 in 9973.71196747ms
Process finished with exit code 0
The increasing time for writing show the waiting which is happening.
