How do I use multprocessing.Value (or other shared resources) on Mac with Spawn? Question: Example: import multiprocessing as mp counter = mp.Value(‘i’, 0) def test_fun(i): global counter with counter.get_lock(): counter.value += 1 def main(): global counter with mp.Pool(4) as p: result = p.map(test_fun, range(4)) print(counter.value) if __name__ == "__main__": main() The expected output is 4, …
python – accessing manager object in shared state multiprocessing Question: I have a program that populates a shared data structure between processes. This is a customised implementation of a HashMap with separate chaining functionality for items with the same key (hash). The class is defined as follows: class HashMapChain: """A HashMap with Separate Chaining for …
Connecting a C++ program to a Python script with shared memory Question: I’m trying to connect a C++ program to python using shared memory but I don’t know how to pass the name of the memory segment to python. Here is my C++ code: key_t key = ftok("address", 1); int shm_o; char* msg = "hello …
How to properly close and unlink shared memory of multiprocessing? Question: I’m trying to use the multiprocessing module and to add 1 to the shared memory in each process. But, I see the errors when running the following code. Can anyone tell how to close and unlink the shared momery? Here is the code. from …
'unlink()' does not work in Python's shared_memory on Windows Question: I am using Python 3.8’s new shared_memory module and fail to free the shared memory without terminating the processes using it. After creating and using a block shm of shared memory, I close it via shm.close() in all processes and finally free it via shm.unlink …
Right way to share opencv video frame as Numpy array between multiprocessing processes Question: I want to share my captured frame in OpenVC with my multiprocessing subprocess but video_capture.read() creates a new object and doesnt write in to my numpy array that iam going to share by wrapping it with multiprocessing.Array() Here is the code: …
Share Large, Read-Only Numpy Array Between Multiprocessing Processes Question: I have a 60GB SciPy Array (Matrix) I must share between 5+ multiprocessing Process objects. I’ve seen numpy-sharedmem and read this discussion on the SciPy list. There seem to be two approaches–numpy-sharedmem and using a multiprocessing.RawArray() and mapping NumPy dtypes to ctypes. Now, numpy-sharedmem seems to …
What is the possible source of error in Runge-Kutta 4 algorithm in python for solving SHM Question: I wrote a simple RK4 program in python to solve SHM equation: y”[t] = -w^2*y[t] by writing: z'[t] = -w^2*y y'[t] = z Following is the RK4 code: def rk4_gen(t, y, z, h): k1 = h*f1(y, z, t) …
Shared memory in multiprocessing Question: I have three large lists. First contains bitarrays (module bitarray 0.8.0) and the other two contain arrays of integers. l1=[bitarray 1, bitarray 2, … ,bitarray n] l2=[array 1, array 2, … , array n] l3=[array 1, array 2, … , array n] These data structures take quite a bit of …
Shared-memory objects in multiprocessing Question: Suppose I have a large in memory numpy array, I have a function func that takes in this giant array as input (together with some other parameters). func with different parameters can be run in parallel. For example: def func(arr, param): # do stuff to arr, param # build array …
