Closed
Description
Description of your problem
This issue summarizes two inconsistent behaviors of pymc3's random method. One happens for distributions that are declared with shape (1,). The other happens when a distribution's random method is called with size=1.
Singleton array distributions
>>> import pymc3 as pm
>>> pm.Normal.dist(0, 1, shape=1).random().shape
()
>>> pm.Normal.dist(0, 1, shape=1).random(size=10).shape
(10,)These two calls should output shapes (1,) and (10, 1) respectively. The singleton distribution dimension is incorrectly reduced.
Random draws of a single value
>>> import pymc3 as pm
>>> pm.Normal.dist(0, 1).random(size=1).shape
()
>>> pm.Normal.dist(0, 1, shape=1).random(size=1).shape
()
>>> pm.Normal.dist(0, 1, shape=10).random(size=1).shape
(10,)These calls should output (1,), (1, 1) and (1, 10) respectively, but the single draw is incorrectly reduced. In particular, this behavior should only happen when we supply size=None or size=().
Versions and main components
- PyMC3 Version: 3.9.3
- Theano Version: 1.0.5
- Python Version: 3.7.6
- Operating system: Ubuntu
- How did you install PyMC3: (conda/pip) pip