calculating greens functions breaks pipes

[jboguski]

Using Windows 10, python 3.7.6, running the juypter notebook pleiades_intro.ipynb works great, but running the same code in a .py file in ipython causes the following error:

File "C:\Users\l284987\Documents\Python Scripts\pleiades-develop\temp.py", line 40, in
brb.grid = RZgrid

File "C:\Users\l284987\Documents\Python Scripts\pleiades-develop\pleiades\core.py", line 1751, in grid
comp.grid = grid

File "C:\Users\l284987\Documents\Python Scripts\pleiades-develop\pleiades\core.py", line 944, in grid
self.compute_greens()

File "C:\Users\l284987\Documents\Python Scripts\pleiades-develop\pleiades\core.py", line 885, in compute_greens
p.start()

File "C:\Users\l284987\anaconda3\lib\multiprocessing\process.py", line 112, in start
self._popen = self._Popen(self)

File "C:\Users\l284987\anaconda3\lib\multiprocessing\context.py", line 223, in _Popen
return _default_context.get_context().Process._Popen(process_obj)

File "C:\Users\l284987\anaconda3\lib\multiprocessing\context.py", line 322, in _Popen
return Popen(process_obj)

File "C:\Users\l284987\anaconda3\lib\multiprocessing\popen_spawn_win32.py", line 89, in init
reduction.dump(process_obj, to_child)

File "C:\Users\l284987\anaconda3\lib\multiprocessing\reduction.py", line 60, in dump
ForkingPickler(file, protocol).dump(obj)

BrokenPipeError: [Errno 32] Broken pipe

I tried inserting:

for c in brb.components:
c.nprocs=1

right before:
brb.grid = RZgrid

but it failed to set the number of processors used to 1, it gave the following error:

File "C:\Users\l284987\Documents\Python Scripts\pleiades-develop\temp.py", line 40, in
c.nprocs=1

File "C:\Users\l284987\Documents\Python Scripts\pleiades-develop\pleiades\core.py", line 963, in nprocs
if len(new_nprocs) != self._num_groups:

TypeError: object of type 'int' has no len()

[eepeterson]

Oh the type error at the end is because nprocs has to be iterable and be the same length as the number of groups in the component so replace c.nprocs = 1 with something like c.nprocs = [1]*c.num_groups. That should get rid of the TypeError.

As for the broken pipe, are you running the .py file in IPython itself or are you just running python test_pipe_error.py? where test_pipe_error.py is the name of your python file

[eepeterson]

So after a little digging I found this thread that describes that using the multiprocessing module in interactive Python especially on windows has a lot of problems associated with it. The way the multiprocessing is handled now in the code is not how I'd like it done so I may rewrite it and I'll keep this in mind when doing that, but I believe the solution to this for now is to use [Jupyter notebooks](<https://jupyter.org/) if you want an interactive environment. Or simply execute a standard .py file using the non-interactive interpreter.

[eepeterson]

If you care to read a little about why this doesn't work, you can check out the links here, here, and here. If you try putting all the code you're trying to execute inside an if __name__ == '__main__': clause as shown in this post I believe it should work for you as a python script on windows.