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bindings/python/cntk/graph.py

@@ -3,33 +3,59 @@
 # for full license information.
 # ==============================================================================
 
-def dfs_walk(node, visitor, accum):
+def dfs_walk(node, visitor, accum, visited):
+    '''
+    Generic function to walk the graph.
+
+    Args:
+        node (graph node): the node to start the journey from
+        visitor (Python function or lambda): function that takes a node as
+         argument and returns `True` if that node should be returned.
+        accum (`list`): accumulator of nodes while traversing the graph
+        visited (`set`): set of nodes that have already been visited.
+         Initialize with empty set.
+    '''
+    if node in visited:
+        return
+    visited.add(node)
     if hasattr(node, 'root_function'):
         node = node.root_function
         for child in node.inputs:
-            dfs_walk(child, visitor, accum)
+            dfs_walk(child, visitor, accum, visited)
     elif hasattr(node, 'is_output') and node.is_output:
-        dfs_walk(node.owner, visitor, accum)
+        dfs_walk(node.owner, visitor, accum, visited)
 
     if visitor(node):
         accum.append(node)
 
-def visit(root_node, visitor):
-    nodes = []
-    dfs_walk(root_node, visitor, nodes)
-    return nodes
-
-def find_nodes_by_name(root_node, node_name):
+def visit(node, visitor):
     '''
-    Return a list of nodes having the given name
+    Generic function that walks through the graph starting at `node` and
+    applies function `visitor` on each of those.
 
     Args:
-        root_node (node in the graph): root node from where the search should
-         start
-        node_name (`str`): name of the nodes
+        node (graph node): the node to start the journey from
+        visitor (Python function or lambda): function that takes a node as
+         argument and returns `True` if that node should be returned.
 
     Returns:
-       a list of nodes having the given name
-
+        List of nodes, for which `visitor` was `True`
     '''
-    return visit(root_node, lambda x: x.name == node_name)
+    nodes = []
+    dfs_walk(node, visitor, nodes, set())
+    return nodes
+
+def find_nodes_by_name(node, node_name):
+    '''
+    Finds nodes in the graph starting from `node` and doing a depth-first
+    search.
+
+    Args:
+        node (graph node): the node to start the journey from
+        node_name (`str`): name for which we are search nodes
+
+    Returns:
+        List of nodes having the specified name
+    '''
+    return visit(node, lambda x: x.name == node_name)
+

bindings/python/cntk/tests/initializer_test.py

@@ -8,7 +8,7 @@ import numpy as np
 import pytest
 
 from ..initializer import *
-from .. import parameter, input_variable, momentums_per_sample
+from .. import parameter
 
 
 def _check(init, name):