BaseHardConstraint Class Reference

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

#include <BaseHardConstraint.h>

Inheritance diagram for BaseHardConstraint:

Collaboration diagram for BaseHardConstraint:

Public Member Functions
virtual	~BaseHardConstraint ()
	Virtual destructor.
virtual void	add1stDerivativesToMatrix (double *M, int idim) const
	Adds first order derivatives to global covariance matrix M. More...
virtual void	add2ndDerivativesToMatrix (double *M, int idim, double lambda) const
	Adds second order derivatives to global covariance matrix M. More...
virtual void	addToGlobalChi2DerVector (double *y, int idim, double lambda) const
	Add lambda times derivatives of chi squared to global derivative vector. More...
virtual double	dirDer (double *p, double *w, int idim, double mu=1)
	Calculate directional derivative. More...
virtual double	dirDerAbs (double *p, double *w, int idim, double mu=1)
	Calculate directional derivative for abs(c) More...
virtual bool	secondDerivatives (int i, int j, double *derivatives) const =0
	Second derivatives with respect to the meta-variables of Fit objects i and j; result false if all derivatives are zero. More...
virtual bool	firstDerivatives (int i, double *derivatives) const =0
	First derivatives with respect to the meta-variables of Fit objects i; result false if all derivatives are zero. More...
virtual int	getVarBasis () const =0
virtual double	getValue () const override=0
	Returns the value of the constraint.
virtual double	getError () const override
	Returns the error on the value of the constraint.
virtual void	getDerivatives (int idim, double der[]) const override=0
	Get first order derivatives. More...
virtual int	getGlobalNum () const
	Accesses position of constraint in global constraint list.
virtual void	setGlobalNum (int iglobal)
	Sets position of constraint in global constraint list. More...
virtual void	printFirstDerivatives () const
virtual void	printSecondDerivatives () const
virtual void	test1stDerivatives ()
virtual void	test2ndDerivatives ()
virtual double	num1stDerivative (int ifo, int ilocal, double eps)
	Evaluates numerically the 1st derivative w.r.t. a parameter. More...
virtual double	num2ndDerivative (int ifo1, int ilocal1, double eps1, int ifo2, int ilocal2, double eps2)
	Evaluates numerically the 2nd derivative w.r.t. 2 parameters. More...
virtual const char *	getName () const
	Returns the name of the constraint.
void	setName (const char *name_)
	Set object's name.
virtual std::ostream &	print (std::ostream &os) const
	print object to ostream More...

Protected Types
typedef std::vector< BaseFitObject * >	FitObjectContainer
	Vector of pointers to ParticleFitObjects.
typedef FitObjectContainer::iterator	FitObjectIterator
	Iterator through vector of pointers to ParticleFitObjects.
typedef FitObjectContainer::const_iterator	ConstFitObjectIterator
	Constant iterator through vector of pointers to ParticleFitObjects.

Protected Attributes
FitObjectContainer	fitobjects
	The FitObjectContainer.
std::vector< double >	derivatives
	The derivatives.
std::vector< int >	flags
	The flags can be used to divide the FitObjectContainer into several subsets used for example to implement an equal mass constraint (see MassConstraint).
int	globalNum
	Position of constraint in global constraint list.
char *	name

Related Functions
(Note that these are not member functions.)
std::ostream &	operator<< (std::ostream &os, const BaseConstraint &bc)
	Prints out a BaseConstraint, using its print method. More...

Detailed Description

Abstract base class for 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

Definition at line 75 of file BaseHardConstraint.h.

Member Function Documentation

add1stDerivativesToMatrix()

void add1stDerivativesToMatrix ( double *  M, int  idim  ) const

virtual

Adds first order derivatives to global covariance matrix M.

Parameters

M	Global covariance matrix, dimension at least idim x idim
idim	First dimension of array der

Definition at line 37 of file BaseHardConstraint.cc.

    {
      double dgdpi[BaseDefs::MAXINTERVARS];
      for (unsigned int i = 0; i < fitobjects.size(); ++i) {
        const BaseFitObject* foi = fitobjects[i];
        assert(foi);
        if (firstDerivatives(i, dgdpi)) {
          foi->addTo1stDerivatives(M, idim, dgdpi, getGlobalNum(), getVarBasis());
        }
      }
    }

add2ndDerivativesToMatrix()

void add2ndDerivativesToMatrix ( double *  M, int  idim, double  lambda  ) const

virtual

Adds second order derivatives to global covariance matrix M.

Calculates the second derivative of the constraint g w.r.t.

the various parameters, multiplies it by lambda and adds it to the global covariance matrix

in case of particlefitobject: We denote with P_i the 4-vector of the i-th ParticleFitObject, then $$ \frac{\partial ^2 g}{\partial a_k \partial a_l} = \sum_i \sum_j \frac{\partial ^2 g}{\partial P_i \partial P_j} \cdot \frac{\partial P_i}{\partial a_k} \cdot \frac{\partial P_j}{\partial a_l}

• \sum_i \frac{\partial g}{\partial P_i} \cdot \frac{\partial^2 P_i}{\partial a_k \partial a_l} $$ Here, $\frac{\partial P_i}{\partial a_k}$ is a $4 \times n_i$ Matrix, where $n_i$ is the number of parameters of FitObject i; Correspondingly, $\frac{\partial^2 P_i}{\partial a_k \partial a_l}$ is a $4 \times n_i \times n_i$ matrix. Also, $\frac{\partial ^2 g}{\partial P_i \partial P_j}$ is a $4\times 4$ matrix for a given i and j, and $\frac{\partial g}{\partial P_i}$ is a 4-vector (though not a Lorentz-vector!).

but here it's been generalised

First, treat the part $$ \frac{\partial ^2 g}{\partial P_i \partial P_j} \cdot \frac{\partial P_i}{\partial a_k} \cdot \frac{\partial P_j}{\partial a_l} $$

Second, treat the part $$ \sum_i \frac{\partial g}{\partial P_i} \cdot \frac{\partial^2 P_i}{\partial a_k \partial a_l} $$ Here, $\frac{\partial g}{\partial P_i}$ is a 4-vector, which we pass on to the FitObject

Parameters

M	Global covariance matrix, dimension at least idim x idim
idim	First dimension of array der
lambda	Lagrange multiplier for this constraint

Definition at line 75 of file BaseHardConstraint.cc.

addToGlobalChi2DerVector()

void addToGlobalChi2DerVector ( double *  y, int  idim, double  lambda  ) const

virtual

Add lambda times derivatives of chi squared to global derivative vector.

Parameters

y	Vector of chi2 derivatives
idim	Vector size

Definition at line 201 of file BaseHardConstraint.cc.

dirDer()

double dirDer ( double *  p, double *  w, int  idim, double  mu = 1  )

virtual

Calculate directional derivative.

Parameters

p	Vector of direction
w	Work vector
idim	Vector size
mu	optional multiplier

Definition at line 229 of file BaseHardConstraint.cc.

dirDerAbs()

double dirDerAbs ( double *  p, double *  w, int  idim, double  mu = 1  )

virtual

Calculate directional derivative for abs(c)

Parameters

p	Vector of direction
w	Work vector
idim	Vector size
mu	optional multiplier

Definition at line 239 of file BaseHardConstraint.cc.

firstDerivatives()

virtual bool firstDerivatives ( int  i, double *  derivatives  ) const

pure virtual

First derivatives with respect to the meta-variables of Fit objects i; result false if all derivatives are zero.

Parameters

i	number of 1st FitObject
derivatives	The result 4-vector

Implemented in RecoilMassConstraint, MomentumConstraint, and MassConstraint.

getDerivatives()

virtual void getDerivatives ( int  idim, double  der[]  ) const

overridepure virtual

Get first order derivatives.

Call this with a predefined array "der" with the necessary number of entries!

Parameters

idim	First dimension of the array
der	Array of derivatives, at least idim x idim

Implements BaseConstraint.

Implemented in RecoilMassConstraint, MomentumConstraint, and MassConstraint.

num1stDerivative()

double num1stDerivative ( int  ifo, int  ilocal, double  eps  )

virtual

Evaluates numerically the 1st derivative w.r.t. a parameter.

Parameters

ifo	Number of FitObject
ilocal	Local parameter number
eps	variation of local parameter

Definition at line 304 of file BaseHardConstraint.cc.

num2ndDerivative()

double num2ndDerivative ( int  ifo1, int  ilocal1, double  eps1, int  ifo2, int  ilocal2, double  eps2  )

virtual

Evaluates numerically the 2nd derivative w.r.t. 2 parameters.

Parameters

ifo1	Number of 1st FitObject
ilocal1	1st local parameter number
eps1	variation of 1st local parameter
ifo2	Number of 1st FitObject
ilocal2	1st local parameter number
eps2	variation of 2nd local parameter

Definition at line 318 of file BaseHardConstraint.cc.

print()

std::ostream & print ( std::ostream &  os ) const

virtualinherited

print object to ostream

Parameters

os	The output stream

Definition at line 76 of file BaseConstraint.cc.

secondDerivatives()

virtual bool secondDerivatives ( int  i, int  j, double *  derivatives  ) const

pure virtual

Second derivatives with respect to the meta-variables of Fit objects i and j; result false if all derivatives are zero.

Parameters

i	number of 1st FitObject
j	number of 2nd FitObject
derivatives	The result 4x4 matrix

Implemented in RecoilMassConstraint, MomentumConstraint, and MassConstraint.

setGlobalNum()

virtual void setGlobalNum ( int  iglobal )

inlinevirtual

Sets position of constraint in global constraint list.

Parameters

iglobal

Global constraint number

Definition at line 140 of file BaseHardConstraint.h.

      {globalNum = iglobal;}

Friends And Related Function Documentation

operator<<()

std::ostream & operator<< ( std::ostream &  os, const BaseConstraint &  bc  )

related

Prints out a BaseConstraint, using its print method.

Parameters

os	The output stream
bc	The object to print

Definition at line 114 of file BaseConstraint.h.

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

• analysis/OrcaKinFit/include/BaseHardConstraint.h
• analysis/OrcaKinFit/src/BaseHardConstraint.cc