pathos.multiprocessing ProcessingPool crashes in input integer np.int32 object into pool(the_integer), sometimes (tbd)

[jcb31416]

if replacing int(ncpu) into ncpu sometimes the process gets hanged, but it's avoided by wrapping the np.int32 object into int(). to be noted that type(ncpu) = np.int32

i don't fully understand why sometimes the problem is solved by wrapping np.int32 into int(), and others don't. should be something else, it's strange.. sth to be solved.

some context: Spyder 5.4.5 | Python 3.11.5 64-bit | Qt 5.15.2 | PyQt5 5.15.6 | Windows 10 (AMD64)

min repr example of crash: this example aims to group the parallelization in groups of 5.

import numpy as np
from pathos.multiprocessing import ProcessingPool as Pool

def f_phi(item):
    print(item)
# enddef f_phi

# Initialize a list to be grouped in blocks of 5 items
lis_1 = np.arange(0, 13)

# Total number of elements in lis_1
nn = len(lis_1)

# Create a vector to separate indices of lis_1 into groups of 5
vec = np.arange(0, nn, 5)

# Create lists for "from" (start) indices and "to" (end) indices
lis_frm = list(vec[:-1])  # "From" indices
lis_to = list(vec[1:])    # "To" indices

# Handle the remainder if the last group has fewer than 5 elements
if lis_to[-1] < (nn - 1):  # Handle the remainder group (e.g., 10 to 13)
    lis_frm += [lis_to[-1]]
    lis_to += [nn - 1]
#endif

# Number of groups to be processed
ngru = len(lis_frm)

# Initialize lists for the number of CPUs and results
lis_ncpu = [None] * ngru
lis_resp = [None] * ngru

# Loop through all groups and process them in parallel
for igro in range(len(lis_frm)):
    frm = lis_frm[igro]  # "From" index for the current group
    to = lis_to[igro]    # "To" index for the current group
    ncpu = int(lis_to[igro] - lis_frm[igro])  # Number of parallel threads (ensure it's an integer)

    # Slice the input list for the current group
    lis_argin = lis_1[frm:to]
    lis = []

    # Process the current group in parallel
    with Pool(ncpu) as pool:
        lis = pool.map(f_phi, lis_argin)
    # endwith

    # Store the results
    lis_resp[igro] = lis
# endfor