// @(#)root/mathcore:$Id: FitUtil.h 24477 2008-06-23 12:58:47Z moneta $
// Author: L. Moneta Tue Nov 28 10:52:47 2006

/**********************************************************************
 *                                                                    *
 * Copyright (c) 2006  LCG ROOT Math Team, CERN/PH-SFT                *
 *                                                                    *
 *                                                                    *
 **********************************************************************/

// Header file for class FitUtil

#ifndef ROOT_Fit_FitUtil
#define ROOT_Fit_FitUtil

#ifndef ROOT_Math_IParamFunctionfwd
#include "Math/IParamFunctionfwd.h"
#endif

#ifndef ROOT_Fit_DataVectorfwd
#include "Fit/DataVectorfwd.h"
#endif


namespace ROOT { 

   namespace Fit { 


   

/** 
   namespace defining utility free functions using in Fit for evaluating the various fit method 
   functions (chi2, likelihood, etc..)  given the data and the model function 

   @ingroup FitMain
*/ 
namespace FitUtil {

   typedef  ROOT::Math::IParamMultiFunction IModelFunction;
   typedef  ROOT::Math::IParamMultiGradFunction IGradModelFunction;

   /** Chi2 Functions */

   /** 
       evaluate the Chi2 given a model function and the data at the point x. 
       return also nPoints as the effective number of used points in the Chi2 evaluation
   */ 
   double EvaluateChi2(const IModelFunction & func, const BinData & data, const double * x, unsigned int & nPoints);  

   /** 
       evaluate the effective Chi2 given a model function and the data at the point x. 
       The effective chi2 uses the errors on the coordinates : W = 1/(sigma_y**2 + ( sigma_x_i * df/dx_i )**2 )
       return also nPoints as the effective number of used points in the Chi2 evaluation
   */ 
   double EvaluateChi2Effective(const IModelFunction & func, const BinData & data, const double * x, unsigned int & nPoints);  

   /** 
       evaluate the Chi2 gradient given a model function and the data at the point x. 
       return also nPoints as the effective number of used points in the Chi2 evaluation
   */ 
   void EvaluateChi2Gradient(const IModelFunction & func, const BinData & data, const double * x, double * grad, unsigned int & nPoints);  

   /** 
       evaluate the LogL given a model function and the data at the point x. 
       return also nPoints as the effective number of used points in the LogL evaluation
   */ 
   double EvaluateLogL(const IModelFunction & func, const UnBinData & data, const double * x, unsigned int & nPoints);  

   /** 
       evaluate the LogL gradient given a model function and the data at the point x. 
       return also nPoints as the effective number of used points in the LogL evaluation
   */ 
   void EvaluateLogLGradient(const IModelFunction & func, const UnBinData & data, const double * x, double * grad, unsigned int & nPoints);  

   /** 
       evaluate the Poisson LogL given a model function and the data at the point x. 
       return also nPoints as the effective number of used points in the LogL evaluation
   */ 
   double EvaluatePoissonLogL(const IModelFunction & func, const BinData & data, const double * x, unsigned int & nPoints);  

   /** 
       evaluate the Poisson LogL given a model function and the data at the point x. 
       return also nPoints as the effective number of used points in the LogL evaluation
   */ 
   void EvaluatePoissonLogLGradient(const IModelFunction & func, const BinData & data, const double * x, double * grad);  

//    /** 
//        Parallel evaluate the Chi2 given a model function and the data at the point x. 
//        return also nPoints as the effective number of used points in the Chi2 evaluation
//    */ 
//    double ParallelEvalChi2(const IModelFunction & func, const BinData & data, const double * x, unsigned int & nPoints);  

   // methods required by dedicate minimizer like Fumili 
 
   /** 
       evaluate the residual contribution to the Chi2 given a model function and the BinPoint data 
       and if the pointer g is not null evaluate also the gradient of the residual.
       If the function provides parameter derivatives they are used otherwise a simple derivative calculation 
       is used       
   */ 
   double EvaluateChi2Residual(const IModelFunction & func, const BinData & data, const double * x, unsigned int ipoint, double *g = 0);  

   /** 
       evaluate the pdf contribution to the LogL given a model function and the BinPoint data.
       If the pointer g is not null evaluate also the gradient of the pdf.
       If the function provides parameter derivatives they are used otherwise a simple derivative calculation 
       is used 
   */ 
   double EvaluatePdf(const IModelFunction & func, const UnBinData & data, const double * x, unsigned int ipoint, double * g = 0); 

   /** 
       evaluate the pdf contribution to the Poisson LogL given a model function and the BinPoint data. 
       If the pointer g is not null evaluate also the gradient of the Poisson pdf.
       If the function provides parameter derivatives they are used otherwise a simple derivative calculation 
       is used 
   */ 
   double EvaluatePoissonBinPdf(const IModelFunction & func, const BinData & data, const double * x, unsigned int ipoint, double * g = 0);  


   




} // end namespace FitUtil 

   } // end namespace Fit

} // end namespace ROOT


#endif /* ROOT_Fit_FitUtil */