ROOT   Reference Guide
ROOT::Math::IGradientFunctionMultiDimTempl< T > Class Template Reference
template<class T>

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

It implements both the ROOT::Math::IBaseFunctionMultiDimTempl and ROOT::Math::IGradientMultiDimTempl 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 342 of file IFunction.h.

## Public Types

typedef IBaseFunctionMultiDimTempl< T > BaseFunc

Public Types inherited from ROOT::Math::IBaseFunctionMultiDimTempl< T >
typedef T BackendType

typedef IBaseFunctionMultiDimTempl< T > BaseFunc

## Public Member Functions

Virtual Destructor (no operations) More...

virtual void FdF (const T *x, T &f, T *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...

In some cases, the gradient algorithm will use information from the previous step, these can be passed in with this overload. More...

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

virtual bool returnsInMinuit2ParameterSpace () const

Public Member Functions inherited from ROOT::Math::IBaseFunctionMultiDimTempl< T >
IBaseFunctionMultiDimTempl ()

virtual ~IBaseFunctionMultiDimTempl ()
virtual destructor More...

virtual IBaseFunctionMultiDimTempl< T > * Clone () const =0
Clone a function. More...

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

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

Public Member Functions inherited from ROOT::Math::IGradientMultiDimTempl< T >
virual destructor More...

Derivative (const T *x, unsigned int icoord, T *previous_grad, T *previous_g2, T *previous_gstep) const
In some cases, the derivative algorithm will use information from the previous step, these can be passed in with this overload. More...

Derivative (const T *x, unsigned int icoord=0) const
Return the partial derivative with respect to the passed coordinate. More...

virtual void FdF (const T *x, T &f, T *df) const =0
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...

#include <Math/IFunction.h>

Inheritance diagram for ROOT::Math::IGradientFunctionMultiDimTempl< T >:
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## ◆ BaseFunc

template<class T >

Definition at line 346 of file IFunction.h.

template<class T >

Definition at line 347 of file IFunction.h.

## Constructor & Destructor Documentation

template<class T >
inlinevirtual

Virtual Destructor (no operations)

Definition at line 352 of file IFunction.h.

## ◆ FdF()

template<class T >
 virtual void ROOT::Math::IGradientFunctionMultiDimTempl< T >::FdF ( const T * x, T & f, T * 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 383 of file IFunction.h.

template<class T >
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

Definition at line 358 of file IFunction.h.

template<class T >
 virtual void ROOT::Math::IGradientFunctionMultiDimTempl< T >::GradientWithPrevResult ( const T * x, T * grad, T * previous_grad, T * previous_g2, T * previous_gstep ) const
inlinevirtual

In some cases, the gradient algorithm will use information from the previous step, these can be passed in with this overload.

The previous_* arrays can also be used to return second derivative and step size so that these can be passed forward again as well at the call site, if necessary.

Definition at line 368 of file IFunction.h.

## ◆ NDim()

template<class T >
 virtual unsigned int ROOT::Math::IBaseFunctionMultiDimTempl< T >::NDim ( ) const
virtual

Retrieve the dimension of the function.

Implements ROOT::Math::IBaseFunctionMultiDimTempl< T >.

## ◆ returnsInMinuit2ParameterSpace()

template<class T >
 virtual bool ROOT::Math::IGradientFunctionMultiDimTempl< T >::returnsInMinuit2ParameterSpace ( ) const
inlinevirtual