Changeset 17603

Timestamp:

06/16/20 13:37:57 (4 years ago)

Author:

pfleck

Message:

#3040

• Added additive simplification rules for stdev and variance symbols.
• Extended simplifications of constants to simplification of all scalar-nodes for aggregation symbols.

File:

• branches/3040_VectorBasedGP/HeuristicLab.Problems.DataAnalysis.Symbolic/3.4/Converters/VectorTreeSimplifier.cs (modified) (5 diffs)

branches/3040_VectorBasedGP/HeuristicLab.Problems.DataAnalysis.Symbolic/3.4/Converters/VectorTreeSimplifier.cs

@@ -1399 +1399 @@
 
     private ISymbolicExpressionTreeNode MakeSumAggregation(ISymbolicExpressionTreeNode node) {
-      if (IsConstant(node)) { // assumes scalar constant
+      if (IsScalarNode(node)) {
         return node;
       } else if (IsAddition(node) || IsSubtraction(node)) {
@@ -1467 +1467 @@
 
     private ISymbolicExpressionTreeNode MakeMeanAggregation(ISymbolicExpressionTreeNode node) {
-      if (IsConstant(node)) { // assumes scalar constant
+      if (IsScalarNode(node)) {
         return node;
       } else if (IsAddition(node) || IsSubtraction(node)) {
@@ -1532 +1532 @@
 
     private ISymbolicExpressionTreeNode MakeLengthAggregation(ISymbolicExpressionTreeNode node) {
-      if (IsConstant(node)) { // assumes scalar constant
+      if (IsScalarNode(node)) {
         return MakeConstant(1.0);
       } else if (IsAddition(node) || IsSubtraction(node)) {
@@ -1584 +1584 @@
 
     private ISymbolicExpressionTreeNode MakeStandardDeviationAggregation(ISymbolicExpressionTreeNode node) {
-      if (IsConstant(node)) {
+      if (IsScalarNode(node)) {
         return MakeConstant(0.0);
+      } else if (IsAddition(node) || IsSubtraction(node)) { // scalars drop out
+        var terms = node.Subtrees;
+
+        var scalarTerms = terms.Where(IsScalarNode).ToList();
+        var remainingTerms = terms.Except(scalarTerms).ToList();
+
+        if (remainingTerms.Any()) {
+          var vectorNode = remainingTerms.Aggregate(MakeSum);
+
+          var stdevNode = standardDeviationSymbol.CreateTreeNode();
+          stdevNode.AddSubtree(vectorNode);
+
+          return stdevNode;
+        } else if (scalarTerms.Any()) {
+          return MakeConstant(0.0);
+        } else
+          throw new InvalidOperationException("Addition does not contain any terms to simplify.");
       } else if (IsMultiplication(node) || IsDivision(node)) {
         var factors = node.Subtrees;
@@ -1625 +1642 @@
 
     private ISymbolicExpressionTreeNode MakeVarianceAggregation(ISymbolicExpressionTreeNode node) {
-      if (IsConstant(node)) {
+      if (IsScalarNode(node)) {
         return MakeConstant(0.0);
+      } else if (IsAddition(node) || IsSubtraction(node)) { // scalars drop out
+        var terms = node.Subtrees;
+
+        var scalarTerms = terms.Where(IsScalarNode).ToList();
+        var remainingTerms = terms.Except(scalarTerms).ToList();
+
+        if (remainingTerms.Any()) {
+          var vectorNode = remainingTerms.Aggregate(MakeSum);
+
+          var varNode = varianceSymbol.CreateTreeNode();
+          varNode.AddSubtree(vectorNode);
+
+          return varNode;
+        } else if (scalarTerms.Any()) {
+          return MakeConstant(0.0);
+        } else
+          throw new InvalidOperationException("Addition does not contain any terms to simplify.");
       } else if (IsMultiplication(node) || IsDivision(node)) {
         var factors = node.Subtrees;