import numpy as np
from multiprocessing import Process, Manager, Value, Array
import time
import humanize


#actual computation
def f(a):
    return a-1.0;
# obs: with such a simple computation, there will advantage will be no computation time advantage.
# use this for hardcore stuff that deals with peripherals such as a disk read

#computation wrapper
def process_target(pidx, Global, res, count, N, P):

    for i in range(pidx, N, P):

        with count.get_lock():
            count.value += 1;


        res[i] =  f(Global.mat[i])

        if Global.run is False:
            break;


if __name__ == '__main__':

    manager = Manager()
    Global = manager.Namespace()


    N = 100000;                      #job size

    P = 12;                          #process number

    Global.mat = np.random.rand(N);  #input vector

    res = Array('d', N, lock = False) #output vector

    count = Value('i', 0)             #counter

    Global.run = True;                #used for greceful halt


    #init procecess
    proc_list = [Process(target=process_target, args=(i, Global, res, count, N, P)) for i in range(P)]

    #start procecess
    [p.start() for p in proc_list]


    ts = time.time()
    elapsed = 0;
    c = 0;
    while any([p.is_alive() for p in proc_list]):
        try:
            time.sleep(2)
            elapsed_old = elapsed;
            elapsed = time.time();

            c_old = c
            c = count.value

            remaining = (elapsed - elapsed_old)*(N  - c)/(c + -c_old)

            print(humanize.naturaltime(remaining, future=True));

        except KeyboardInterrupt:
            print("KeyboardInterrupt")
            Global.run = False;
            [p.terminate() for p in proc_list]
            break;
        except ZeroDivisionError:
            time.sleep(1)



    [p.join() for p in proc_list]

    print("Final time: " + humanize.naturaldelta(time.time() - ts))


    print("{} out of {} elements were processed".format(count.value, N))

    #get results
    res_npy =  np.frombuffer(res, dtype='d');