Changeset 17780

Timestamp:

11/02/20 16:27:25 (4 years ago)

Author:

gkronber

Message:

#3073 added (limited) support for power symbol (only for integer exponents)

File:

• branches/3073_IA_constraint_splitting/HeuristicLab.Problems.DataAnalysis.Symbolic/3.4/Converters/DerivativeCalculator.cs (modified) (2 diffs)

branches/3073_IA_constraint_splitting/HeuristicLab.Problems.DataAnalysis.Symbolic/3.4/Converters/DerivativeCalculator.cs

@@ -149 +149 @@
         return Product(Product(CreateConstant(3.0), Square(f)), Derive(f, variableName));
       }
+      if (branch.Symbol is Power) {
+        // HL evaluators handle power strangely (exponent is rounded to an integer)
+        // here we only support the case when the exponent is a constant integer and 
+        var exponent = branch.GetSubtree(1) as ConstantTreeNode;
+        if (exponent != null && Math.Truncate(exponent.Value) == exponent.Value) {
+          var newPower = (ISymbolicExpressionTreeNode)branch.Clone();
+          var newExponent = (ConstantTreeNode)newPower.GetSubtree(1);
+          newExponent.Value -= 1;
+          return Product(CreateConstant(exponent.Value), newPower);
+        } else throw new NotSupportedException("Cannot derive non-integer powers");
+      }
       if (branch.Symbol is Absolute) {
         var f = (ISymbolicExpressionTreeNode)branch.GetSubtree(0).Clone();
@@ -263 +274 @@
           !(n.Symbol is Cube) &&
           !(n.Symbol is CubeRoot) &&
+          !(n.Symbol is Power) &&
           !(n.Symbol is Absolute) &&
           !(n.Symbol is AnalyticQuotient) &&