Changeset 16905 for trunk/HeuristicLab.Problems.DataAnalysis.Symbolic/3.4/Converters

Timestamp:

05/07/19 14:20:33 (6 years ago)

Author:

gkronber

Message:

#2915: Corrected calculation of cuberoot function in all interpreters and updated all formatters.
I tested a run with all interpreters and got the same results with all of them.

Location:

trunk/HeuristicLab.Problems.DataAnalysis.Symbolic/3.4/Converters

Files:

• DerivativeCalculator.cs (modified) (1 diff)
• TreeToAutoDiffTermConverter.cs (modified) (2 diffs)

trunk/HeuristicLab.Problems.DataAnalysis.Symbolic/3.4/Converters/DerivativeCalculator.cs

@@ -143 +143 @@
         var f = (ISymbolicExpressionTreeNode)branch.Clone();
         var u = (ISymbolicExpressionTreeNode)branch.GetSubtree(0).Clone();
-        return Product(Div(CreateConstant(1.0), Product(CreateConstant(3.0), Square(f))), Derive(u, variableName));
+        return Product(Div(CreateConstant(1.0), Product(CreateConstant(3.0), Square(f))), Derive(u, variableName));  // 1/3 1/cbrt(f(x))^2 d/dx f(x)
       }
       if (branch.Symbol is Cube) {

trunk/HeuristicLab.Problems.DataAnalysis.Symbolic/3.4/Converters/TreeToAutoDiffTermConverter.cs

@@ -92 +92 @@
       );
 
+    private static readonly Func<Term, UnaryFunc> cbrt = UnaryFunc.Factory(
+      eval: x => x < 0 ? -Math.Pow(-x, 1.0 / 3) : Math.Pow(x, 1.0 / 3),
+      diff: x => { var cbrt_x = x < 0 ? -Math.Pow(-x, 1.0 / 3) : Math.Pow(x, 1.0 / 3); return 1.0 / (3 * cbrt_x * cbrt_x); }
+      );
+
+
+
     #endregion
 
@@ -250 +257 @@
       }
       if (node.Symbol is CubeRoot) {
-        return AutoDiff.TermBuilder.Power(
-          ConvertToAutoDiff(node.GetSubtree(0)), 1.0/3.0);
+        return cbrt(ConvertToAutoDiff(node.GetSubtree(0)));
       }
       if (node.Symbol is Sine) {