python-multiprocessing

When using multiprocessing in Python, I usually see examples where the join() function is called in a separate loop to where each process was actually created. For example, this: processes = [] for i in range(10): p = Process(target=my_func) processes.append(p) p.start() for p in processes: p.join() is more common than this: processes = [] for i in range(10): p = Process(target=my_func) processes.append(p) p.start() p.join() But from my understanding of join() , it just tells the script not to exit until that process has finished. Therefore, it shouldn't matter when join() is called. So why is

I'm trying to communicate between multiple threading.Thread (s) doing I/O-bound tasks and multiple multiprocessing.Process (es) doing CPU-bound tasks. Whenever a thread finds work for a process, it will be put on a multiprocessing.Queue , together with the sending end of a multiprocessing.Pipe(duplex=False) . The processes then do their part and send results back to the threads via the Pipe. This procedure seems to work in roughly 70% of the cases, the other 30% I receive an AttributeError: Can't get attribute 'DupFd' on <module 'multiprocessing.resource_sharer' from '/usr/lib/python3.5

This is my code: from multiprocessing import Pool, Lock from datetime import datetime as dt console_out = "/STDOUT/Console.out" chunksize = 50 lock = Lock() def writer(message): lock.acquire() with open(console_out, 'a') as out: out.write(message) out.flush() lock.release() def conf_wrapper(state): import ProcessingModule as procs import sqlalchemy as sal stcd, nrows = state engine = sal.create_engine('postgresql://foo:bar@localhost:5432/schema') writer("State {s} started at: {n}" "\n".format(s=str(stcd).zfill(2), n=dt.now())) with engine.connect() as conn, conn.begin(): procs.processor(conn,

I was learning about multi-processing and multi-threading. From what I understand, threads run on the same core, so I was wondering if I create multiple processes inside a child thread will they be limited to that single core too? I'm using python, so this is a question about that specific language but I would like to know if it is the same thing with other languages? I'm not a pyhton expert but I expect this is like in other languages, because it's an OS feature in general. Process A process is executed by the OS and owns one thread which will be executed. This is in general your programm.

I am doing some parallel processing, as follows: with mp.Pool(8) as tmpPool: results = tmpPool.starmap(my_function, inputs) where inputs look like: [(1,0.2312),(5,0.52) ...] i.e., tuples of an int and a float. The code runs nicely, yet I cannot seem to wrap it around a loading bar (tqdm), such as can be done with e.g., imap method as follows: tqdm.tqdm(mp.imap(some_function,some_inputs)) Can this be done for starmap also? Thanks! It's not possible with starmap() , but it's possible with a patch adding Pool.istarmap() . It's based on the code for imap() . All you have to do, is create the

I'm working on project named "Faciel Actions Units Detection" I'm using python2.7 and opencv 2.4 The error: pickle.PicklingError: Can't pickle <type 'cv2.Boost'>: it's not the same object as cv2.Boost A partial traceback, transcribed from a screenshot : Loading classifier for action unit 27 Traceback (most recent call last): File "C:\Python27\audetect-master\audetect-interactive.py", line 59, in <module> main() File "C:\Python27\audetect-master\audetect-interactive.py", line 18, in main active_aus = detector.detect() File "C:\Python27\audetect-master\detect.py", line 67, in detect initial