Changeset 14883 for branches/RBFRegression/HeuristicLab.Algorithms.DataAnalysis/3.4/RadialBasisFunctions/KernelFunctions/MultiquadraticKernel.cs

Timestamp:

04/24/17 13:17:43 (7 years ago)

Author:

bwerth

Message:

#2699 checked and reformulated gradient functions for kernels

File:

• branches/RBFRegression/HeuristicLab.Algorithms.DataAnalysis/3.4/RadialBasisFunctions/KernelFunctions/MultiquadraticKernel.cs (modified) (1 diff)

branches/RBFRegression/HeuristicLab.Algorithms.DataAnalysis/3.4/RadialBasisFunctions/KernelFunctions/MultiquadraticKernel.cs

@@ -48 +48 @@
     #endregion
     protected override double Get(double norm) {
-      return Math.Abs(Beta) < double.Epsilon ? 0 : Math.Sqrt(1 + norm * norm / Beta);
+      if (Math.Abs(Beta) < double.Epsilon) return double.NaN;
+      return Math.Sqrt(1 + norm * norm / Beta);
     }
 
     protected override double GetGradient(double norm) {
       if (Math.Abs(Beta) < double.Epsilon) return double.NaN;
-      norm *= norm;
-      return -norm / (2 * Beta * Beta * Math.Sqrt((norm + Beta) / Beta));
+      var dividend = 2 * Beta * Beta * Math.Sqrt((Beta + norm * norm) / Beta);
+      return -norm * norm / dividend;
     }
   }