ROOT 6.08/07 Reference Guide 
Gradient interface (abstract class) defining the signature for calculating the gradient of a multidimensional function.
Three methods are provided:
Concrete classes should derive from ROOT::Math::IGradientFunctionMultiDim and not from this class.
Definition at line 196 of file IFunction.h.
Public Member Functions  
virtual  ~IGradientMultiDim () 
virual destructor More...  
double  Derivative (const double *x, unsigned int icoord=0) const 
Return the partial derivative with respect to the passed coordinate. More...  
virtual void  FdF (const double *x, double &f, double *df) const =0 
Optimized method to evaluate at the same time the function value and derivative at a point x. More...  
virtual void  Gradient (const double *x, double *grad) const =0 
Evaluate all the vector of function derivatives (gradient) at a point x. More...  
Private Member Functions  
virtual double  DoDerivative (const double *x, unsigned int icoord) const =0 
function to evaluate the derivative with respect each coordinate. More...  
#include <Math/IFunction.h>

inlinevirtual 
virual destructor
Definition at line 201 of file IFunction.h.

inline 
Return the partial derivative with respect to the passed coordinate.
Definition at line 212 of file IFunction.h.

privatepure virtual 
function to evaluate the derivative with respect each coordinate.
To be implemented by the derived class
Implemented in ROOT::Math::GradFunctor, ROOT::Math::LSResidualFunc, ROOT::Math::MultiNumGradFunction, ROOT::Math::MinimTransformFunction, and TPyMultiGradFunction.

pure virtual 
Optimized method to evaluate at the same time the function value and derivative at a point x.
Often both value and derivatives are needed and it is often more efficient to compute them at the same time. Derived class should implement this method if performances play an important role and if it is faster to evaluate value and derivative at the same time
Implemented in ROOT::Math::IGradientFunctionMultiDim, ROOT::Math::LSResidualFunc, and TPyMultiGradFunction.

pure virtual 
Evaluate all the vector of function derivatives (gradient) at a point x.
Derived classes must reimplement if it is more efficient than evaluting one at a time
Implemented in ROOT::Math::IGradientFunctionMultiDim, ROOT::Math::LSResidualFunc, and TPyMultiGradFunction.