Modify model_graph to handle new pm.Data

Mark Data nodes in graph: previously these were incorrectly marked as
`Deterministic`.
Mark Potential nodes in graph.
Also distinguish between Deterministic, Data, and Potential nodes by node shape.

Put observations below observed nodes: Now that there are `Data`
objects that are graphable, they need to be placed correctly with
respect to other nodes: if they are inputs they should be above, and
if they are observations, they should be below.

Author: rpgoldman

RELEASE-NOTES.md

@@ -1,5 +1,10 @@
 # Release Notes
 
+## PyMC3 3.8 (on deck)
+
+### New features
+- Distinguish between `Data` and `Deterministic` variables when graphing models with graphviz. PR [#3491](https://github.com/pymc-defs/pymc3/pulls/3491).
+
 ## PyMC3 3.7 (May 29 2019)
 
 ### New features

pymc3/data.py

@@ -390,7 +390,7 @@ def align_minibatches(batches=None):
 
 class Data:
     """Data container class that wraps the theano SharedVariable class
-    and let the model be aware of its inputs and outputs.
+    and lets the model be aware of its inputs and outputs.
 
     Parameters
     ----------

pymc3/model_graph.py

@@ -1,17 +1,16 @@
 from collections import deque
-from typing import Iterator, Optional, MutableSet
+from typing import Dict, Iterator, Set, Optional
+
+VarName = str
 
 from theano.gof.graph import stack_search
 from theano.compile import SharedVariable
 from theano.tensor import Tensor
 
 from .util import get_default_varnames
+from .model import ObservedRV
 import pymc3 as pm
 
-# this is a placeholder for a better characterization of the type
-# of variables in a model.
-RV = Tensor
-
 
 class ModelGraph:
     def __init__(self, model):
@@ -30,16 +29,16 @@ def get_deterministics(self, var):
                 deterministics.append(v)
         return deterministics
 
-    def _get_ancestors(self, var, func) -> MutableSet[RV]:
+    def _get_ancestors(self, var: Tensor, func) -> Set[Tensor]:
         """Get all ancestors of a function, doing some accounting for deterministics.
         """
 
         # this contains all of the variables in the model EXCEPT var...
         vars = set(self.var_list)
         vars.remove(var)
 
-        blockers = set()
-        retval = set()
+        blockers = set() # type: Set[Tensor]
+        retval = set()  # type: Set[Tensor]
         def _expand(node) -> Optional[Iterator[Tensor]]:
             if node in blockers:
                 return None
@@ -58,9 +57,9 @@ def _expand(node) -> Optional[Iterator[Tensor]]:
                      mode='bfs')
         return retval
 
-    def _filter_parents(self, var, parents):
+    def _filter_parents(self, var, parents) -> Set[VarName]:
         """Get direct parents of a var, as strings"""
-        keep = set()
+        keep = set() # type: Set[VarName]
         for p in parents:
             if p == var:
                 continue
@@ -73,7 +72,7 @@ def _filter_parents(self, var, parents):
                 raise AssertionError('Do not know what to do with {}'.format(str(p)))
         return keep
 
-    def get_parents(self, var):
+    def get_parents(self, var: Tensor) -> Set[VarName]:
         """Get the named nodes that are direct inputs to the var"""
         if hasattr(var, 'transformed'):
             func = var.transformed.logpt
@@ -85,11 +84,26 @@ def get_parents(self, var):
         parents = self._get_ancestors(var, func)
         return self._filter_parents(var, parents)
 
-    def make_compute_graph(self):
+    def make_compute_graph(self) -> Dict[str, Set[VarName]]:
         """Get map of var_name -> set(input var names) for the model"""
-        input_map = {}
+        input_map = {} # type: Dict[str, Set[VarName]]
+        def update_input_map(key: str, val: Set[VarName]):
+            if key in input_map:
+                input_map[key] = input_map[key].union(val)
+            else:
+                input_map[key] = val
+
         for var_name in self.var_names:
-            input_map[var_name] = self.get_parents(self.model[var_name])
+            var = self.model[var_name]
+            update_input_map(var_name, self.get_parents(var))
+            if isinstance(var, ObservedRV):
+                try:
+                    obs_name = var.observations.name
+                    if obs_name:
+                        input_map[var_name] = input_map[var_name].difference(set([obs_name]))
+                        update_input_map(obs_name, set([var_name]))
+                except AttributeError:
+                    pass
         return input_map
 
     def _make_node(self, var_name, graph):
@@ -101,12 +115,19 @@ def _make_node(self, var_name, graph):
         if isinstance(v, pm.model.ObservedRV):
             attrs['style'] = 'filled'
 
+        # make Data be roundtangle, instead of rectangle
         if isinstance(v, SharedVariable):
-            attrs['style'] = 'filled'
+            attrs['style'] = 'rounded, filled'
 
         # Get name for node
-        if hasattr(v, 'distribution'):
+        if v in self.model.potentials:
+            distribution = 'Potential'
+            attrs['shape'] = 'octagon'
+        elif hasattr(v, 'distribution'):
             distribution = v.distribution.__class__.__name__
+        elif isinstance(v, SharedVariable):
+            distribution = 'Data'
+            attrs['shape'] = 'box'
         else:
             distribution = 'Deterministic'
             attrs['shape'] = 'box'

pymc3/tests/test_data_container.py

@@ -101,5 +101,12 @@ def test_model_to_graphviz_for_model_with_data_container(self):
             pm.sample(1000, init=None, tune=1000, chains=1)
 
         g = pm.model_to_graphviz(model)
-        text = 'x [label="x ~ Deterministic" shape=box style=filled]'
+
+        # Data node rendered correctly?
+        text = 'x [label="x ~ Data" shape=box style="rounded, filled"]'
+        assert text in g.source
+        # Didn't break ordinary variables?
+        text = 'beta [label="beta ~ Normal"]'
+        assert text in g.source
+        text = 'obs [label="obs ~ Normal" style=filled]'
         assert text in g.source