Changeset 17155

Timestamp:

07/23/19 20:15:32 (5 years ago)

Author:

gkronber

Message:

#2948: merged r17125 (support for symbolic derivation of tanh) from trunk to stable

Location:

stable

Files:

• . (modified) (1 prop)
• HeuristicLab.Problems.DataAnalysis.Symbolic (modified) (1 prop)
• HeuristicLab.Problems.DataAnalysis.Symbolic/3.4/Converters/DerivativeCalculator.cs (modified) (1 diff)
• HeuristicLab.Tests (modified) (1 prop)
• HeuristicLab.Tests/HeuristicLab.Problems.DataAnalysis.Symbolic-3.4/DeriveTest.cs (modified) (1 diff)

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

@@ -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));

stable/HeuristicLab.Tests/HeuristicLab.Problems.DataAnalysis.Symbolic-3.4/DeriveTest.cs

@@ -68 +68 @@
 
       Assert.AreEqual("('a' * 'b' * 'c')", Derive("a*b*c*d", "d"));
-      Assert.AreEqual("('a' / ('b' * 'c' * SQR('d') * (-1)))", Derive("a/b/c/d", "d")); 
+      Assert.AreEqual("('a' / ('b' * 'c' * SQR('d') * (-1)))", Derive("a/b/c/d", "d"));
+
+      Assert.AreEqual("('x' * ((SQR(TANH(SQR('x'))) * (-1)) + 1) * 2)", Derive("tanh(sqr(x))", "x")); // (2*'x'*(1 - SQR(TANH(SQR('x'))))
 
       {