Multiprocessing Tutorial Example Not Working

General information:

• emcee version: 3.0.2
• platform: python, jupyter notebook
• installation method (pip/conda/source/other?): pip

Problem description:

Expected behavior: That the multiprocessing example using "pool" would work in a jupyter notebook for the example shown in the multiprocessing example.

Actual behavior: Using "pool" in the sampler does not converge and continues to run indefinitely. However, the example in the tutorial shows that it should finish running and run faster than the serial code.

What have you tried so far?: Modified the code, tried different notebooks, tried to use pool.close()

Minimal example:

from multiprocessing import Pool

with Pool() as pool:
    sampler = emcee.EnsembleSampler(nwalkers, ndim, log_prob, pool=pool)
    start = time.time()
    sampler.run_mcmc(initial, nsteps, progress=True)
    end = time.time()
    multi_time = end - start
    print("Multiprocessing took {0:.1f} seconds".format(multi_time))
    print("{0:.1f} times faster than serial".format(serial_time / multi_time))

Start by reproducing the multiprocessing tutorial's minimal example in a Jupyter notebook with emcee 3.0.2 and compare it with the serial run. Investigate why the sampler does not finish when given a multiprocessing.Pool; the work is done when the documented example completes and reports its runtime.