The trick is to pass the Queue as an argument to the initializer. Appears to work with all the Pool dispatch methods. import multiprocessing as mp def f(x): f.q.put(‘Doing: ‘ + str(x)) return x*x def f_init(q): f.q = q def main(): jobs = range(1,6) q = mp.Queue() p = mp.Pool(None, f_init, [q]) results = p.imap(f, … Read more
Regarding the fact that all of your processes are running on the same CPU, see my answer here. During import, numpy changes the CPU affinity of the parent process, such that when you later use Pool all of the worker processes that it spawns will end up vying for for the same core, rather than … Read more
You could use the blocking capabilities of queue to spawn multiple process at startup (using multiprocessing.Pool) and letting them sleep until some data are available on the queue to process. If your not familiar with that, you could try to “play” with that simple program: import multiprocessing import os import time the_queue = multiprocessing.Queue() def … Read more
Trying again as I just saw the bounty 😉 Basically I think the error message means what it said – multiprocessing shared memory Arrays can’t be passed as arguments (by pickling). It doesn’t make sense to serialise the data – the point is the data is shared memory. So you have to make the shared … Read more
The multiprocessing.pool.Pool class creates the worker processes in its __init__ method, makes them daemonic and starts them, and it is not possible to re-set their daemon attribute to False before they are started (and afterwards it’s not allowed anymore). But you can create your own sub-class of multiprocesing.pool.Pool (multiprocessing.Pool is just a wrapper function) and … Read more
This is a Python bug. When waiting for a condition in threading.Condition.wait(), KeyboardInterrupt is never sent. Repro: import threading cond = threading.Condition(threading.Lock()) cond.acquire() cond.wait(None) print “done” The KeyboardInterrupt exception won’t be delivered until wait() returns, and it never returns, so the interrupt never happens. KeyboardInterrupt should almost certainly interrupt a condition wait. Note that this … Read more
Heap memory The heap memory is the runtime data area from which the Java VM allocates memory for all class instances and arrays. The heap may be of a fixed or variable size. The garbage collector is an automatic memory management system that reclaims heap memory for objects. Eden Space: The pool from which memory … Read more
The problem is that multiprocessing must pickle things to sling them among processes, and bound methods are not picklable. The workaround (whether you consider it “easy” or not;-) is to add the infrastructure to your program to allow such methods to be pickled, registering it with the copy_reg standard library method. For example, Steven Bethard’s … Read more