Avoid adding duplicated nodes and edges when building the graph. These can look like cut lines and get removed in weird ways, so it is better to just not create duplicates in the first place.

git-svn-id: http://svn.stsci.edu/svn/ssb/stsci_python/stsci_python/branches/sphere@17219 fe389314-cf27-0410-b35b-8c050e845b92

Former-commit-id: 51d0e8176c7eecdea00e478ef7efaa77c08aab70

1 files changed, 42 insertions, 6 deletions

diff --git a/lib/graph.py b/lib/graph.py
index 58b918d..d64074a 100644
--- a/lib/graph.py
+++ b/lib/graph.py
@@ -156,6 +156,26 @@ class Graph:
             except IndexError:
                 raise ValueError("Following from disconnected node")
 
+        def equals(self, other):
+            """
+            Returns True if the other edge is between the same two nodes.
+
+            Parameters
+            ----------
+            other : `Edge` instance
+
+            Returns
+            -------
+            equals : bool
+            """
+            if (self._nodes[0].equals(other._nodes[0]) and
+                self._nodes[1].equals(other._nodes[1])):
+                return True
+            if (self._nodes[1].equals(other._nodes[0]) and
+                self._nodes[0].equals(other._nodes[1])):
+                return True
+            return False
+
 
     def __init__(self, polygons):
         """
@@ -234,9 +254,17 @@ class Graph:
         node : `Node` instance
             The new node
         """
-        node = self.Node(point, source_polygons)
-        self._nodes.add(node)
-        return node
+        new_node = self.Node(point, source_polygons)
+
+        # Don't add nodes that already exist.  Update the existing
+        # node's source_polygons list to include the new polygon.
+        for node in self._nodes:
+            if node.equals(new_node):
+                node._source_polygons.update(source_polygons)
+                return node
+
+        self._nodes.add(new_node)
+        return new_node
 
     def remove_node(self, node):
         """
@@ -279,9 +307,17 @@ class Graph:
         assert A in self._nodes
         assert B in self._nodes
 
-        edge = self.Edge(A, B, source_polygons)
-        self._edges.add(edge)
-        return edge
+        new_edge = self.Edge(A, B, source_polygons)
+
+        # Don't add any edges that already exist.  Update the edge's
+        # source polygons list to include the new polygon.
+        for edge in self._edges:
+            if edge.equals(new_edge):
+                edge._source_polygons.update(source_polygons)
+                return edge
+
+        self._edges.add(new_edge)
+        return new_edge
 
     def remove_edge(self, edge):
         """