Python rpy2 and matplotlib conflict when using multiprocessing

Question

I am trying to calculate and generate plots using multiprocessing. On Linux the code below runs correctly, however on the Mac (ML) it doesn\'t, giving the error below:

Answer 1

I had a similar issue with my worker, which was loading some data, generating a plot, and saving it to a file. Note that this is slightly different than what the OP's case, which seems to be oriented around interactive plotting. Still, I think it's relevant.

A simplified version of my code:

def worker(id):
    data = load_data(id)
    plot_data_to_file(data) # Generates a plot and saves it to a file.

def plot_something_parallel(ids):
    pool = multiprocessing.Pool()
    pool.map(worker, ids)

plot_something_parallel(ids=[1,2,3])

This caused the same error others mention:

The process has forked and you cannot use this CoreFoundation functionality safely. You MUST exec().
Break on __THE_PROCESS_HAS_FORKED_AND_YOU_CANNOT_USE_THIS_COREFOUNDATION_FUNCTIONALITY___YOU_MUST_EXEC__() to debug.

Following @bbbruce's train of thought, I solved my problem by switching the matplotlib backend from TKAgg to the default. Specifically, I commented out the following line in my matplotlibrc file:

#backend : TkAgg