What does it mean can not pickle due to not finding function for parallel chain sampling

Questions
1

I tried running the example arbitrary_stochstic.py. It bumps out an error

CustomizablePickler(buffer, self._reducers).dump(obj)

AttributeError: Can’t pickle local object ‘build_model..logp’

There is one post which explains this is due to “it cannot pickle a function for parallel chain sampling”. This is code from git, I did not make any changes. Can someone explain what is wrong and how to fix. I see the same error in my own code and don’t get what is the problem. I do have an idea about parallel sampling, but how does this code violate parallel chain sampling?

2

Multiprocessing requires everything passed to thread to be picklable. Lambdas defined in local namespace are not picklable.
PicklingError with njobs>1 using DensityDist · Issue #1995 · pymc-devs/pymc · GitHub

I submitted a PR today actually to fix the example Update pymc3\examples by junpenglao · Pull Request #2947 · pymc-devs/pymc · GitHub

3

Thank you, I fixed it according to the instructions.