With a great success I am using for my project ostap (https://github.com/OstapHEP/ostap) a nice pathos suite (pathos, multiprocess and ppft) together with ROOT project (https://github.com/root-project/root). It helps me a lot - thank you very much for this powerful tool! Everything works for me with python2( e.g. 2.7.16), but dill (0.2.9) fails with python3 (3.6.5).
Surprisingly, a plain pickle works for this case.

import ROOT, pickle, dill 
h = ROOT.TH1D()
pickle.dumps ( h )  ## ok 
dill.dumps ( h ) ## fails

Is it a problem from the dill side?