PyMC causes theano to crash

[vhaasteren]

I am trying out a tutorial of Theano, and I notice that pymc3 makes it throw a ValueError. The code below fails. However, if I simply remove the pymc3 import, it runs fine. Example:

import pymc3 as pm
import theano as th

print(pm.version)

3.0

print(th.version)

0.7.0.dev-3e84371d4e0f4d24c5bc784291ee8c0d85e84005

a = th.tensor.dscalar()
b = th.tensor.dscalar()
c = a + b

ValueError Traceback (most recent call last)
in ()
4
5 # create a simple expression
----> 6 c = a + b

/Users/vhaaster/env/pint/lib/python2.7/site-packages/theano/tensor/var.pyc in add(self, other)
131 def add(self, other):
132 try:
--> 133 return theano.tensor.basic.add(self, other)
134 # We should catch the minimum number of exception here.
135 # Otherwise this will convert error when Theano flags

/Users/vhaaster/env/pint/lib/python2.7/site-packages/theano/gof/op.pyc in call(self, _inputs, *_kwargs)
524 run_perform = False
525 elif config.compute_test_value == 'raise':
--> 526 raise ValueError('Cannot compute test value: input %i (%s) of Op %s missing default value' % (i, ins, node))
527 elif config.compute_test_value == 'ignore':
528 # silently skip test

ValueError: Cannot compute test value: input 0 (<TensorType(float64, scalar)>) of Op Elemwise{add,no_inplace}(<TensorType(float64, scalar)>, <TensorType(float64, scalar)>) missing default value

[twiecki]

This is probably caused by #566

[jsalvatier]

@vhaasteren there's some ideas on how to do this in #566 like thomas said. Would you be interested in making a pull request to fix this?

[vhaasteren]

@jsalvatier I am definitely willing to contribute. However, given that my first experience with PyMC was two days ago (looks very cool, btw), I am not sure of how much help I can be until I familiarize myself a bit more with the codebase. I will look into it

[jsalvatier]

Makes sense: the relevant things are in https://github.com/pymc-devs/pymc3/blob/master/pymc3/model.py. The class Model inherits from Context, and theano.config.compute_test_value = 'raise' is done at the bottom of the file, which are likely the things you want to change.

Let me know if you want to chat for help.

[vhaasteren]

Thank you for the pointers, that is a good start. I will be in touch if I need help.

[fonnesbeck]

Closing. Please re-open if you need additional support.