Process another TODO comment

Author: flowtoolz

Code/Graph+Algorithms/Graph+NonEssentialEdges.swift

@@ -20,62 +20,55 @@ public extension Graph
     func findEssentialEdges() -> EdgeIDs
     {
         var idsOfEssentialEdges = EdgeIDs()
+            
+        // TODO: Do we even need to create the MEG of the condensation graph here? AS SOON AS our algorithm to find all transitive edges (or inverted: the transitive reduction) correctly returns all edges that ARE NOT in cycles (even if the graph is cyclic) then we only need to filter out the edges which ARE in cycles for which we only need the SCCs ... this is about making the code more straight forward, we'll assess performance much later and based on measurement ...
+        
+        // make condensation graph
+        let condensationGraph = makeCondensationGraph()
+        
+        // remember in which condensation node each original node is contained
+        var condensationNodeIDByNodeID = [NodeID: StronglyConnectedComponent.ID]()
 
-        // TODO: decomposing the graph into its components is probably legacy from before the algorithm extraction from Codeface ... this also seems to have no performance benefit here ... better just ensure makeCondensationGraph() (or find SCCs) and makeMinimumEquivalentGraph() work on disconnected graphs and then do this algorithm here on the whole graph in one go ...
-        // for each component graph individually ...
-        for component in findComponents()
+        for condensationNode in condensationGraph.nodes
         {
-            let componentGraph = subGraph(nodeIDs: component)
-            
-            // TODO: Do we even need to create the MEG of the condensation graph here? AS SOON AS our algorithm to find all transitive edges (or inverted: the transitive reduction) correctly returns all edges that ARE NOT in cycles (even if the graph is cyclic) then we only need to filter out the edges which ARE in cycles for which we only need the SCCs ... this is about making the code more straight forward, we'll assess performance much later and based on measurement ...
+            for node in condensationNode.value.nodeIDs
+            {
+                condensationNodeIDByNodeID[node] = condensationNode.id
+            }
+        }
+        
+        // make minimum equivalent condensation graph
+        let minimumCondensationGraph = condensationGraph.makeMinimumEquivalentGraph()
+        
+        // for each original edge in the component graph ...
+        for edge in edges
+        {
+            guard let originCondensationNodeID = condensationNodeIDByNodeID[edge.originID],
+                  let destinationCondensationNodeID = condensationNodeIDByNodeID[edge.destinationID]
+            else
+            {
+                log(error: "Nodes don't have their condensation node IDs set (but must have at this point)")
+                continue
+            }
 
-            // make condensation graph
-            let condensationGraph = componentGraph.makeCondensationGraph()
-
-            // remember in which condensation node each original node is contained
-            var condensationNodeIDByNodeID = [NodeID: StronglyConnectedComponent.ID]()
+            // add this edge if it is within the same condensation node (within a strongly connected component and thereby within a cycle)
 
-            for condensationNode in condensationGraph.nodes
+            if originCondensationNodeID == destinationCondensationNodeID
             {
-                for node in condensationNode.value.nodeIDs
-                {
-                    condensationNodeIDByNodeID[node] = condensationNode.id
-                }
+                idsOfEssentialEdges += edge.id
+                continue
             }
 
-            // make minimum equivalent condensation graph
-            let minimumCondensationGraph = condensationGraph.makeMinimumEquivalentGraph()
-
-            // for each original edge in the component graph ...
-            for edge in componentGraph.edges
+            // the non-cyclic edge is essential if its equivalent is in the minimum equivalent condensation graph
+            
+            let condensationEdgeID = CondensationEdge.ID(originCondensationNodeID,
+                                                         destinationCondensationNodeID)
+            
+            let edgeIsEssential = minimumCondensationGraph.contains(condensationEdgeID)
+            
+            if edgeIsEssential
             {
-                guard let originCondensationNodeID = condensationNodeIDByNodeID[edge.originID],
-                      let destinationCondensationNodeID = condensationNodeIDByNodeID[edge.destinationID]
-                else
-                {
-                    log(error: "Nodes don't have their condensation node IDs set (but must have at this point)")
-                    continue
-                }
-                
-                // add this edge if it is within the same condensation node (within a strongly connected component and thereby within a cycle)
-
-                if originCondensationNodeID == destinationCondensationNodeID
-                {
-                    idsOfEssentialEdges += edge.id
-                    continue
-                }
-
-                // the non-cyclic edge is essential if its equivalent is in the minimum equivalent condensation graph
-                
-                let condensationEdgeID = CondensationEdge.ID(originCondensationNodeID,
-                                                             destinationCondensationNodeID)
-                
-                let edgeIsEssential = minimumCondensationGraph.contains(condensationEdgeID)
-
-                if edgeIsEssential
-                {
-                    idsOfEssentialEdges += edge.id
-                }
+                idsOfEssentialEdges += edge.id
             }
         }