Fix stack overflow in case of loops in the graph

In case of loops in the graph, more precisely, in the situation, when the last spot of a branch has an outgoing edge to itself, label spots systematically got to a stack overflow situation due to a recursion that does not finish. This commit adds conditions to leave the recursion and extends the unit test to proof, the fix is working

Author: Stefan Hahmann

src/main/java/org/mastodon/mamut/tomancak/label_systematically/LabelSpotsSystematically.java

@@ -78,8 +78,10 @@ private static void renameDescendants( ModelGraph graph, Predicate<Spot> filter,
 			Spot child1 = edges.next().getTarget(ref2);
 			Spot child2 = edges.next().getTarget(ref3);
 			boolean b = correctOrder.test( branchEnd );
-			renameDescendants(graph, filter, correctOrder, spot, child1, b );
-			renameDescendants(graph, filter, correctOrder, spot, child2, !b );
+			if ( !branchEnd.equals( child1 ) ) // NB: edge linking to itself. this normally should not happen but occurs in real data.
+				renameDescendants( graph, filter, correctOrder, spot, child1, b );
+			if ( !branchEnd.equals( child2 ) ) // NB: edge linking to itself. this normally should not happen but occurs in real data.
+				renameDescendants( graph, filter, correctOrder, spot, child2, !b );
 		}
 		finally
 		{

src/test/java/org/mastodon/mamut/tomancak/label_systematically/LabelSpotsSystematicallyTest.java

@@ -83,20 +83,33 @@ private double[] array( double... values )
 	}
 
 	@Test
-	public void testRenameCellsAsExternIntern() {
+	public void testRenameCellsAsExternIntern()
+	{
 		ModelGraph graph = new ModelGraph();
-		Spot a = addSpot(graph, "a", array(2, 2, 2));
-		Spot a1 = addSpotAsDescendantOf(graph, "2", a, array(1, 2, 2)); // extern
-		Spot a2 = addSpotAsDescendantOf(graph, "1", a, array(3, 2, 2)); // intern
-		Spot center = addSpot(graph, "center", array(4, 2, 2));
-		Spot b = addSpot(graph, "b", array(6, 2, 2));
-		Spot b2 = addSpotAsDescendantOf(graph, "4", b, array(5, 2, 2)); // intern
-		Spot b1 = addSpotAsDescendantOf(graph, "3", b, array(7, 2, 2)); // extern
-		LabelSpotsSystematically.setLabelsBasedOnExternIntern( graph, Collections.singleton( center ), graph.vertices(), true, false);
-		assertEquals("a1", a1.getLabel());
-		assertEquals("a2", a2.getLabel());
-		assertEquals("b1", b1.getLabel());
-		assertEquals("b2", b2.getLabel());
+		Spot a = addSpot( graph, "a", array( 2, 2, 2 ) );
+		Spot a1 = addSpotAsDescendantOf( graph, "2", a, array( 1, 2, 2 ) ); // extern
+		Spot a2 = addSpotAsDescendantOf( graph, "1", a, array( 3, 2, 2 ) ); // intern
+		Spot center = addSpot( graph, "center", array( 4, 2, 2 ) );
+		Spot b = addSpot( graph, "b", array( 6, 2, 2 ) );
+		Spot b2 = addSpotAsDescendantOf( graph, "4", b, array( 5, 2, 2 ) ); // intern
+		Spot b1 = addSpotAsDescendantOf( graph, "3", b, array( 7, 2, 2 ) ); // extern
+		Spot c = addSpot( graph, "c", array( 8, 2, 2 ) );
+		Spot c2 = addSpotAsDescendantOf( graph, "5", c, array( 9, 2, 2 ) ); // intern
+		Spot c1 = addSpotAsDescendantOf( graph, "6", c, array( 10, 2, 2 ) ); // extern
+		Spot c12 = addSpotAsDescendantOf( graph, "7", c1, array( 11, 2, 2 ) ); // intern
+		Spot c11 = addSpotAsDescendantOf( graph, "8", c1, array( 12, 2, 2 ) ); // extern
+		Spot c21 = addSpotAsDescendantOf( graph, "9", c2, array( 13, 2, 2 ) );
+		graph.addEdge( c2, c2 ).init(); // deliberately create a cycle to test the robustness of the algorithm
+		LabelSpotsSystematically.setLabelsBasedOnExternIntern( graph, Collections.singleton( center ), graph.vertices(), true, false );
+		assertEquals( "a1", a1.getLabel() );
+		assertEquals( "a2", a2.getLabel() );
+		assertEquals( "b1", b1.getLabel() );
+		assertEquals( "b2", b2.getLabel() );
+		assertEquals( "c1", c1.getLabel() );
+		assertEquals( "c2", c2.getLabel() );
+		assertEquals( "c11", c11.getLabel() );
+		assertEquals( "c12", c12.getLabel() );
+		assertEquals( "c21", c21.getLabel() );
 	}
 
 	//	Handling: