ROOT   6.08/07 Reference Guide

Interface (abstract class) for multi-dimensional functions providing a gradient calculation.

It implements both the ROOT::Math::IBaseFunctionMultiDim and ROOT::Math::IGradientMultiDim interfaces. The method ROOT::Math::IFunction::Gradient calculates the full gradient vector, ROOT::Math::IFunction::Derivative calculates the partial derivative for each coordinate and ROOT::Math::Fdf calculates the gradient and the function value at the same time. The pure private virtual method DoDerivative() must be implemented by the derived classes, while Gradient and FdF are by default implemented using DoDerivative, butthey can be overloaded by the derived classes to improve the efficiency in the derivative calculation.

Definition at line 322 of file IFunction.h.

## Public Types

typedef IBaseFunctionMultiDim BaseFunc

Public Types inherited from ROOT::Math::IBaseFunctionMultiDim
typedef IBaseFunctionMultiDim BaseFunc

## Public Member Functions

Virtual Destructor (no operations) More...

virtual void FdF (const double *x, double &f, double *df) const
Optimized method to evaluate at the same time the function value and derivative at a point x. More...

Evaluate all the vector of function derivatives (gradient) at a point x. More...

Public Member Functions inherited from ROOT::Math::IBaseFunctionMultiDim
IBaseFunctionMultiDim ()

virtual ~IBaseFunctionMultiDim ()
virtual destructor More...

virtual IBaseFunctionMultiDimClone () const =0
Clone a function. More...

virtual unsigned int NDim () const =0
Retrieve the dimension of the function. More...

double operator() (const double *x) const
Evaluate the function at a point x[]. More...

Public Member Functions inherited from ROOT::Math::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...

#include <Math/IFunction.h>

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## ◆ BaseFunc

Definition at line 329 of file IFunction.h.

Definition at line 330 of file IFunction.h.

## Constructor & Destructor Documentation

inlinevirtual

Virtual Destructor (no operations)

Definition at line 336 of file IFunction.h.

## ◆ FdF()

 virtual void ROOT::Math::IGradientFunctionMultiDim::FdF ( const double * x, double & f, double * df ) const
inlinevirtual

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

Definition at line 358 of file IFunction.h.

inlinevirtual

Evaluate all the vector of function derivatives (gradient) at a point x.

Derived classes must re-implement it if more efficient than evaluting one at a time