"Bad message length" error


Operating System: OS X 10.10.5
Python Version: 2.7.10 (Anaconda 2.0.1)
Interface Version:


Just pip upgraded to Pystan 2.15 from 2.9, and now getting the following error:

Traceback (most recent call last):
File “sample_softmax_choice_learning.py”, line 58, in
fit = model_code_obj.sampling(data=model_data, iter=2000, chains=4)
File “//anaconda/lib/python2.7/site-packages/pystan/model.py”, line 725, in sampling
ret_and_samples = _map_parallel(call_sampler_star, call_sampler_args, n_jobs)
File “//anaconda/lib/python2.7/site-packages/pystan/model.py”, line 81, in _map_parallel
map_result = pool.map(function, args)
File “//anaconda/lib/python2.7/multiprocessing/pool.py”, line 251, in map
return self.map_async(func, iterable, chunksize).get()
File “//anaconda/lib/python2.7/multiprocessing/pool.py”, line 567, in get
raise self._value
multiprocessing.pool.MaybeEncodingError: Error sending result: ‘[(0, <stanfit4softmax_choice_learning_2d589e109e324d5ba96b6f064cf3aa6b_787095412542364527.PyStanHolder object at 0x10be3f170>)]’. Reason: ‘IOError(‘bad message length’,)’

The code throwing the error is:

model_code_obj = pystan.StanModel(file=‘softmax_choice_learning.stan.cpp’, model_name=‘softmax_choice_learning’, verbose=True) # Specific to model
fit = model_code_obj.sampling(data=model_data, iter=2000, chains=4)

Any help much appreciated!



Are you using a pickled model or anything like that?


Nope, it compiles from a script file.


Haven’t seen this error before. Can you try running it one chain at a
time using n_jobs=1? The error might be a bit more informative.

If the problem persists, it’s likely a bug (in Python). If you have a
Github account, you might open an issue on the PyStan repository.


How is your memory usage? How large is your dataset. This could be somehow related to low amount of free RAM available.


Running the chains sequentially worked. It’s also worked when sampling in parallel but with 50 iterations instead of 2,000. I thought it might be related to the upgrade, since I haven’t gotten this before, but I reverted back to 2.9 and got the same error. The dataset is only 9 matrices of 48 x 360, but I was saving a lot of big generated quantities matrices (the fit pickle is 39 GB), so I’ve trimmed it up and now it’s working fine. Sounds like a memory issue then. Thanks for your help!