Changeset 6009 for trunk/sources/HeuristicLab.Encodings.SymbolicExpressionTreeEncoding/3.4/Creators

Timestamp:

04/13/11 16:02:40 (14 years ago)

Author:

gkronber

Message:

#1472 implemented a check in PTC2 operator, fixed bugs in SymbolicExpressionGrammarBase and made some small changes in both classes to prevent numeric overflow exceptions.

File:

• trunk/sources/HeuristicLab.Encodings.SymbolicExpressionTreeEncoding/3.4/Creators/ProbabilisticTreeCreator.cs (modified) (3 diffs)

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

@@ -103 +103 @@
     public static void PTC2(IRandom random, ISymbolicExpressionTreeNode seedNode,
       int maxLength, int maxDepth) {
+      // make sure it is possible to create a trees smaller than maxLength and maxDepth
+      if (seedNode.Grammar.GetMinimumExpressionLength(seedNode.Symbol) > maxLength)
+        throw new ArgumentException("Cannot create trees of length " + maxLength + " or shorter because of grammar constraints.", "maxLength");
+      if (seedNode.Grammar.GetMinimumExpressionDepth(seedNode.Symbol) > maxDepth)
+        throw new ArgumentException("Cannot create trees of depth " + maxDepth + " or smaller because of grammar constraints.", "maxDepth");
+
       // tree length is limited by the grammar and by the explicit size constraints
       int allowedMinLength = seedNode.Grammar.GetMinimumExpressionLength(seedNode.Symbol);
@@ -149 +155 @@
         int argumentIndex = nextExtension.ChildIndex;
         int extensionDepth = nextExtension.ExtensionPointDepth;
-        if (extensionDepth + parent.Grammar.GetMinimumExpressionDepth(parent.Symbol) >= maxDepth) {
+        if (parent.Grammar.GetMinimumExpressionDepth(parent.Symbol) >= maxDepth - extensionDepth) {
           ReplaceWithMinimalTree(random, root, parent, argumentIndex);
         } else {
@@ -155 +161 @@
                                 where s.InitialFrequency > 0.0
                                 where parent.Grammar.IsAllowedChildSymbol(parent.Symbol, s, argumentIndex)
-                                where parent.Grammar.GetMinimumExpressionDepth(s) + extensionDepth - 1 < maxDepth
+                                where parent.Grammar.GetMinimumExpressionDepth(s) < maxDepth - extensionDepth + 1
                                 where parent.Grammar.GetMaximumExpressionLength(s) > targetLength - totalListMinLength - currentLength
                                 select s)