2个进程之间的raspberry pi 3多处理队列同步

Question

I have done a simple code using the multiprocessing library to build an extra process apart from the main code (2 processes in total). I did this code on W7 Professional x64 through Anaconda-spyder v3.2.4 and it works almost as I want except for the fact that when I run the code it increase the memory consumption of my second process (not the main one) until it reaches the total capacity and the computer got stuck and freezed (you can notice this at the whindows task manager).

"""
Example to print data from a function using multiprocessing library
Created on Thu Jan 30 12:07:49 2018
author: Kevin Machado Gamboa
Contct: ing.kevin@hotmail.com
"""
from time import time
import numpy as np
from multiprocessing import Process, Queue, Event

t0=time()

def ppg_parameters(hr, minR, ampR, minIR, ampIR, t):
    HR = float(hr)
    f= HR * (1/60)
    # Spo2 Red signal function
    sR = minR + ampR * (0.05*np.sin(2*np.pi*t*3*f)
                       + 0.4*np.sin(2*np.pi*t*f) + 0.25*np.sin(2*np.pi*t*2*f+45))
    # Spo2 InfraRed signal function
    sIR = minIR + ampIR * (0.05*np.sin(2*np.pi*t*3*f)
                          + 0.4*np.sin(2*np.pi*t*f) + 0.25*np.sin(2*np.pi*t*2*f+45))
    return sR, sIR

def loop(q):
    """
    generates the values of the function ppg_parameters
    """
    hr =  60
    ampR = 1.0814       # amplitud for Red signal
    minR = 0.0   # Desplacement from zero for Red signal
    ampIR = 1.12       # amplitud for InfraRed signal
    minIR = 0.7   # Desplacement from zero for Red signal
    # infinite loop to generate the signal
    while True:
        t = time()-t0
        y = ppg_parameters(hr, minR, ampR, minIR, ampIR, t)
        q.put([t, y[0], y[1]])

if __name__ == "__main__":
    _exit = Event()
    q = Queue()
    p = Process(target=loop, args=(q,))
    p.start()
    # starts the main process
    while q.qsize() != 1:
        try:
            data = q.get(True,2) # takes each data from the queue
            print(data[0], data[1], data[2])
        except KeyboardInterrupt:
            p.terminate()
            p.join()
            print('supposed to stop')
            break

Why is this happening? Perhaps is the while loop of my 2nd process? I don't know. I haven't seen this issue nowhere.

Moreover, if I run the same code on my Rpi 3 model B, there is a point when it pops an error that said "the queue is empty" something like if the main process is running faster than process two.

Please any guess of why is this happening, suggestion or link would be helpful.

Thanks

Answer 1

It looks like inside your infinite loop you are adding to the queue and I'm guessing that you are adding data faster than it can be taken off of the queue by the other process.

You could check the queue size periodically from inside the infinite loop and if it is over a certain amount (say 500 items), then you could sleep for a few seconds and then check again.

https://docs.python.org/2/library/queue.html#Queue.Queue.qsize