Changeset 16737

Timestamp:

04/01/19 19:15:54 (5 years ago)

Author:

gkronber

Message:

#2948: fixed a bug for products with >2 factors

Location:

trunk

Files:

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

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

@@ -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

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

@@ -65 +65 @@
 
       Assert.AreEqual("0", Derive("(a+b)/(x+SQR(x))", "y")); // df(a,b,x) / dy = 0
+
+
+      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")); 
 
       {