What is the maximum of the trace? and saving with pickle?


I mainly three questions as follow.

The first one is,
What is the maximum of the trace in pymc3?
After I generated a trace with more than 20 free parameters and length of 5 million with 4 chains, it tells me like this:
multiprocessing.pool.MaybeEncodingError: Error sending result: ‘[<pymc3.backends.ndarray.NDArray object at 0x1c524d9f28>]’. Reason: ‘error("‘i’ format requires -2147483648 <= number <= 2147483647",)’
and finally failed.

Then, I also tried the same length and parameter situation of only one chain, it is okay to finish the trace, but when I wanted to save it with pickle, it saids
pickle.dump({‘model’: basic_model, ‘trace’: trace}, buff)
OSError: [Errno 22] Invalid argument

The reason why I generate a chain like that is due to the relatively complicated model. The chain is hard to converge quickly with MH-sampling with this model. I tried the NUTS sampling but it IS NO USE because it got stuck and never finished when generating a nuts-sampling with my model.

Is there any idea about these kinds of problem?

Thank you very much!