MarlinKinfit  0.4.0
Public Member Functions | Protected Attributes | List of all members
BaseSoftConstraint Class Referenceabstract

Abstract base class for soft constraints of kinematic fits. More...

#include <BaseSoftConstraint.h>

Inheritance diagram for BaseSoftConstraint:
BaseConstraint SoftGaussParticleConstraint SoftGaussMassConstraint SoftGaussMomentumConstraint

Public Member Functions

virtual ~BaseSoftConstraint ()
 Virtual destructor.
 
virtual double getChi2 () const =0
 Returns the chi2.
 
virtual void add2ndDerivativesToMatrix (double *M, int idim) const =0
 Adds second order derivatives to global covariance matrix M. More...
 
virtual void addToGlobalChi2DerVector (double *y, int idim) const =0
 Add derivatives of chi squared to global derivative matrix. More...
 
- Public Member Functions inherited from BaseConstraint
 BaseConstraint ()
 Creates an empty BaseConstraint object.
 
 BaseConstraint (const BaseConstraint &rhs)
 Copy constructor. More...
 
BaseConstraintoperator= (const BaseConstraint &rhs)
 Assignment. More...
 
virtual ~BaseConstraint ()
 Virtual destructor.
 
virtual double getValue () const =0
 Returns the value of the constraint function.
 
virtual double getError () const
 Returns the error on the value of the constraint.
 
virtual const char * getName () const
 Returns the name of the constraint.
 
virtual void setName (const char *name_)
 Set object's name.
 
virtual void getDerivatives (int idim, double der[]) const =0
 Get first order derivatives of the constraint function Call this with a predefined array "der" with the necessary number of entries! More...
 
virtual std::ostream & print (std::ostream &os) const
 print object to ostream More...
 

Protected Attributes

char * name
 
- Protected Attributes inherited from BaseConstraint
char * name
 

Additional Inherited Members

Detailed Description

Abstract base class for soft constraints of kinematic fits.

This class defines the minimal functionality any constraint class must provide. First of all a constraint should know on with particles (or FitObject) it is applied. Where as for example a constraint on the total transvese momentum takes into account all particles in the event, an invariant mass constraint usually applies only to a subset of particles.

The particle list is implemented as a vector containing pointers to objects derived from BaseFitObject and can be either set a whole (setFOList) or enlarged by adding a single BaseFitObject (addToFOList).

From the four–momenta of all concerned fit objects the constraint has to be able to calculate its current value (getValue). Constraints should be formulated such that a value of zero corresponds to a perfectly fulfilled constraint.

In order to find a solution to the constrained minimisation problem, fit algorithms usually need the first order derivatives of the constraint with respect to the fit parameters. Since many constraints can be most easily expressed in terms of E, px, py, pz, the constraints supply their derivatives w.r.t. these parameters. If a FitObject uses a different parametrisation, it is its own task to provide the additional derivatives of E, px, py, pz w.r.t. the parameters of the FitObject. Thus it is easily possible to use FitObjects with different kinds of parametrisations under the same constraint. Some fit algorithms also need the second derivatives of the constraint, i.e. the NewtonFitter.

First and second order derivatives of each constraint can be added directly to the global covariance matrix containing the derivatives of all constraints w.r.t. to all parameters (add1stDerivativesToMatrix, add2ndDerivativesToMatrix). This requires the constraint to know its position in the overall list of constraints (globalNum).

Author: Jenny List, Benno List Last update:

Date:
2011/03/03 15:03:02

by:

Author:
blist

Member Function Documentation

virtual void BaseSoftConstraint::add2ndDerivativesToMatrix ( double *  M,
int  idim 
) const
pure virtual

Adds second order derivatives to global covariance matrix M.

Parameters
MGlobal covariance matrix, dimension at least idim x idim
idimFirst dimension of array der

Implemented in SoftGaussParticleConstraint.

virtual void BaseSoftConstraint::addToGlobalChi2DerVector ( double *  y,
int  idim 
) const
pure virtual

Add derivatives of chi squared to global derivative matrix.

Parameters
yVector of chi2 derivatives
idimVector size

Implemented in SoftGaussParticleConstraint.


The documentation for this class was generated from the following files: