Changeset 6888 for trunk/sources/HeuristicLab.Encodings.SymbolicExpressionTreeEncoding

Timestamp:

10/07/11 21:25:02 (13 years ago)

Author:

bburlacu

Message:

#1654: Small adjustments to the Grow and Full tree creators. Added corresponding classes and unit tests.

Location:

trunk/sources/HeuristicLab.Encodings.SymbolicExpressionTreeEncoding/3.4/Creators

Files:

• FullTreeCreator.cs (modified) (4 diffs)
• GrowTreeCreator.cs (modified) (4 diffs)

trunk/sources/HeuristicLab.Encodings.SymbolicExpressionTreeEncoding/3.4/Creators/FullTreeCreator.cs

@@ -51 +51 @@
 
     public IValueLookupParameter<ISymbolicExpressionGrammar> SymbolicExpressionTreeGrammarParameter {
-      get {
-        return
-            (IValueLookupParameter<ISymbolicExpressionGrammar>)
-            Parameters[SymbolicExpressionTreeGrammarParameterName];
-      }
+      get { return (IValueLookupParameter<ISymbolicExpressionGrammar>)Parameters[SymbolicExpressionTreeGrammarParameterName]; }
     }
 
     public ILookupParameter<ISymbolicExpressionGrammar> ClonedSymbolicExpressionTreeGrammarParameter {
-      get {
-        return
-            (ILookupParameter<ISymbolicExpressionGrammar>)
-            Parameters[ClonedSymbolicExpressionTreeGrammarParameterName];
-      }
+      get { return (ILookupParameter<ISymbolicExpressionGrammar>)Parameters[ClonedSymbolicExpressionTreeGrammarParameterName]; }
     }
 
@@ -144 +136 @@
 
       int arity = seedNode.Grammar.GetMaximumSubtreeCount(seedNode.Symbol);
-      if (arity <= 0) return; // should never happen
+      // Throw an exception if the seedNode happens to be a terminal, since in this case we cannot grow a tree.
+      if (arity <= 0)
+        throw new ArgumentException("Cannot grow tree. Seed node shouldn't have arity zero."); 
 
       for (var i = 0; i != arity; ++i) {
@@ -153 +147 @@
       }
 
-      foreach (var subTree in seedNode.Subtrees) {
-        RecursiveGrowFull(random, subTree, 0, maxDepth);
-      }
+      // Only iterate over the non-terminal nodes (those which have arity > 0)
+      // Start from depth 2 since the first two levels are formed by the rootNode and the seedNode
+      foreach (var subTree in seedNode.Subtrees.Where(subTree => subTree.Grammar.GetMaximumSubtreeCount(subTree.Symbol) != 0)) 
+        RecursiveGrowFull(random, subTree, 2, maxDepth);
     }
 
     public static void RecursiveGrowFull(IRandom random, ISymbolicExpressionTreeNode root, int currentDepth, int maxDepth) {
       var arity = root.Grammar.GetMaximumSubtreeCount(root.Symbol);
-      if (arity <= 0) return;
+      // In the 'Full' grow method, we cannot have terminals on the intermediate tree levels.
+      if (arity <= 0)
+        throw new ArgumentException("Cannot grow node of arity zero. Expected a function node.");
 
       var possibleSymbols = currentDepth < maxDepth ?
@@ -173 +170 @@
       }
 
-      foreach (var tree in root.Subtrees)
-        RecursiveGrowFull(random, tree, currentDepth + 1, maxDepth);
+      foreach (var subTree in root.Subtrees.Where(subTree => subTree.Grammar.GetMaximumSubtreeCount(subTree.Symbol) != 0))
+        RecursiveGrowFull(random, subTree, currentDepth + 1, maxDepth);
     }
   }

trunk/sources/HeuristicLab.Encodings.SymbolicExpressionTreeEncoding/3.4/Creators/GrowTreeCreator.cs

@@ -55 +55 @@
 
     public ILookupParameter<ISymbolicExpressionGrammar> ClonedSymbolicExpressionTreeGrammarParameter {
-      get {
-        return
-            (ILookupParameter<ISymbolicExpressionGrammar>)
-            Parameters[ClonedSymbolicExpressionTreeGrammarParameterName];
-      }
+      get { return (ILookupParameter<ISymbolicExpressionGrammar>)Parameters[ClonedSymbolicExpressionTreeGrammarParameterName]; }
     }
 
@@ -137 +133 @@
 
       var arity = SampleArity(random, seedNode);
-      if (arity <= 0) return; // maybe throw an exception here? But this should never happen.
+      // throw an exception if the seedNode happens to be a terminal, since in this case we cannot grow a tree
+      if (arity <= 0) 
+        throw new ArgumentException("Cannot grow tree. Seed node shouldn't have arity zero."); 
 
       var possibleSymbols = seedNode.Grammar.GetAllowedChildSymbols(seedNode.Symbol).Where(s => s.InitialFrequency > 0.0).ToList();
@@ -148 +146 @@
       }
 
-      foreach (var subTree in seedNode.Subtrees) {
-        RecursiveGrow(random, subTree, 0, maxDepth);
-      }
+      // Only iterate over the non-terminal nodes (those which have arity > 0)
+      // Start from depth 2 since the first two levels are formed by the rootNode and the seedNode
+      foreach (var subTree in seedNode.Subtrees.Where(subTree => subTree.Grammar.GetMaximumSubtreeCount(subTree.Symbol) != 0))
+        RecursiveGrow(random, subTree, 2, maxDepth);
     }
 
     public static void RecursiveGrow(IRandom random, ISymbolicExpressionTreeNode root, int currentDepth, int maxDepth) {
       var arity = SampleArity(random, root);
-      if (arity <= 0) return;
+      if (arity <= 0)
+        throw new ArgumentException("Cannot grow node of arity zero. Expected a function node.");
 
       var possibleSymbols = currentDepth < maxDepth ?
@@ -168 +168 @@
       }
 
-      foreach (var subTree in root.Subtrees) {
+      foreach (var subTree in root.Subtrees.Where(subTree => subTree.Grammar.GetMaximumSubtreeCount(subTree.Symbol) != 0))
         RecursiveGrow(random, subTree, currentDepth + 1, maxDepth);
-      }
     }