Error when using MPI
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Question
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Description
I'm only seeing this error at the end when using MPIPool in the emcee sampler, it works fine with a multiprocessing pool.
> Traceback (most recent call last):
> File "mpiemcee.py", line 121, in <module>
> pos, prob, state = sampler.run_mcmc(p0, 10)
> File "/home/sash7676/anaconda2/lib/python2.7/site-packages/emcee/sampler.py", line 172, in run_mcmc
> **kwargs):
> File "/home/sash7676/anaconda2/lib/python2.7/site-packages/emcee/ensemble.py", line 198, in sample
> lnprob, blobs = self._get_lnprob(p)
> File "/home/sash7676/anaconda2/lib/python2.7/site-packages/emcee/ensemble.py", line 382, in _get_lnprob
> results = list(M(self.lnprobfn, [p[i] for i in range(len(p))]))
> TypeError: 'NoneType' object is not iterable
Has anybody had this problem?
Contributor guide
First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
Research direction
Start with mpiemcee.py at line 121 and compare the MPIPool path with the working multiprocessing-pool path. Trace the call through emcee/sampler.py line 172 and emcee/ensemble.py lines 198 and 382 to determine why the MPI mapping result is None rather than iterable; completion requires reproducing the traceback and confirming corrected MPI behavior.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- python
- Domain
- distributed-systems
- Issue type
- Bug
- Difficulty
- 4/5
- Estimated time
- 3-5 days
- Activity status
- Stale
- Clarity
- Needs clarification
- Newbie friendliness
- 25/100