Changeset 442 for trunk/sources/HeuristicLab.StructureIdentification/Recombination

Timestamp:

08/04/08 23:06:15 (16 years ago)

Author:

gkronber

Message:

stop trying to cross trees that are not compatible with each other after a maximal number of tries (20).
Also weakened the final size-constraint check because trees generated with initial operators could be slightly larger than the size limit.
(ticket #225)

File:

• trunk/sources/HeuristicLab.StructureIdentification/Recombination/SizeFairCrossOver.cs (modified) (5 diffs)

trunk/sources/HeuristicLab.StructureIdentification/Recombination/SizeFairCrossOver.cs

@@ -34 +34 @@
 namespace HeuristicLab.StructureIdentification {
   public class SizeFairCrossOver : OperatorBase {
-
+    private const int MAX_RECOMBINATION_TRIES = 20;
     public override string Description {
       get {
@@ -95 +95 @@
       child.AddVariable(new HeuristicLab.Core.Variable(scope.TranslateName("TreeHeight"), new IntData(newTreeHeight)));
 
-      // check if the new tree is valid and if the size of is still in the allowed bounds
-      Debug.Assert(gardener.IsValidTree(newTree) &&
-        newTreeHeight <= maxTreeHeight && newTreeSize <= maxTreeSize);
+      // check if the new tree is valid and if the height of is still in the allowed bounds (we are not so strict for the max-size)
+      Debug.Assert(gardener.IsValidTree(newTree) && newTreeHeight <= maxTreeHeight);
       return gardener.CreateInitializationOperation(newBranches, child);
     }
@@ -114 +113 @@
         return CombineTerminals(gardener, tree0, tree1, random, maxTreeHeight, out newBranches);
       } else {
+        newBranches = new List<IFunctionTree>();
+
         // we are going to insert tree1 into tree0 at a random place so we have to make sure that tree0 is not a terminal
         // in case both trees are higher than 1 we swap the trees with probability 50%
@@ -155 +156 @@
           }
         }
+        int tries = 0;
         while(possibleChildIndices.Count == 0) {
+          if(tries++ > MAX_RECOMBINATION_TRIES) {
+            if(random.Next() > 0.5) return root1;
+            else return root0;
+          }
           // we couln't find a possible configuration given the current tree0 and tree1
           // possible reasons for this are: 
@@ -189 +195 @@
         tree0.RemoveSubTree(selectedIndex);
         tree0.InsertSubTree(selectedIndex, tree1);
-
-        // no new operators where needed
-        newBranches = new List<IFunctionTree>();
         return root0;
       }