Changeset 17193 for branches/2974_Constants_Optimization/HeuristicLab.Problems.DataAnalysis.Symbolic/3.4/Converters/DerivativeCalculator.cs

Timestamp:

08/07/19 13:32:09 (5 years ago)

Author:

mkommend

Message:

#2974: Merged trunk changes into branch.

Location:

branches/2974_Constants_Optimization/HeuristicLab.Problems.DataAnalysis.Symbolic

Files:

• . (modified) (1 prop)
• 3.4/Converters/DerivativeCalculator.cs (modified) (4 diffs)

branches/2974_Constants_Optimization/HeuristicLab.Problems.DataAnalysis.Symbolic/3.4/Converters/DerivativeCalculator.cs

@@ -1 +1 @@
 #region License Information
 /* HeuristicLab
- * Copyright (C) 2002-2019 Heuristic and Evolutionary Algorithms Laboratory (HEAL)
+ * Copyright (C) Heuristic and Evolutionary Algorithms Laboratory (HEAL)
  *
  * This file is part of HeuristicLab.
@@ -83 +83 @@
         if (branch.SubtreeCount >= 2) {
           var f = (ISymbolicExpressionTreeNode)branch.GetSubtree(0).Clone();
-          var g = (ISymbolicExpressionTreeNode)branch.GetSubtree(1).Clone();
           var fprime = Derive(f, variableName);
-          var gprime = Derive(g, variableName);
-          var fgPrime = Sum(Product(f, gprime), Product(fprime, g));
-          for (int i = 2; i < branch.SubtreeCount; i++) {
+          for (int i = 1; i < branch.SubtreeCount; i++) {
+            var g = (ISymbolicExpressionTreeNode)branch.GetSubtree(i).Clone();
             var fg = Product((ISymbolicExpressionTreeNode)f.Clone(), (ISymbolicExpressionTreeNode)g.Clone());
-            var h = (ISymbolicExpressionTreeNode)branch.GetSubtree(i).Clone();
-            var hPrime = Derive(h, variableName);
-            fgPrime = Sum(Product(fgPrime, h), Product(fg, hPrime));
+            var gPrime = Derive(g, variableName);
+            var fgPrime = Sum(Product(fprime, g), Product(gPrime, f));
+            // prepare for next iteration
+            f = fg;
+            fprime = fgPrime;
           }
-          return fgPrime;
+          return fprime;
         } else
           // multiplication with only one argument has no effect -> derive the argument
@@ -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) {
@@ -179 +179 @@
         var u = (ISymbolicExpressionTreeNode)branch.GetSubtree(0).Clone();
         return Div(fxp, Square(Cosine(u)));
+      }
+      if (branch.Symbol is HyperbolicTangent) {
+        // tanh(f(x))' = f(x)'sech²(f(x)) = f(x)'(1 - tanh²(f(x)))
+        var fxp = Derive(branch.GetSubtree(0), variableName);
+        var tanh = (ISymbolicExpressionTreeNode)branch.Clone();
+        return Product(fxp, Subtract(CreateConstant(1.0), Square(tanh)));
       }
       throw new NotSupportedException(string.Format("Symbol {0} is not supported.", branch.Symbol));