chiSquare.h

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/***************************************************************************
 *   Copyright (C) 2005 by Christophe GONZALES and Pierre-Henri WUILLEMIN  *
 *   {prenom.nom}_at_lip6.fr                                               *
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 *   This program is free software; you can redistribute it and/or modify  *
 *   it under the terms of the GNU General Public License as published by  *
 *   the Free Software Foundation; either version 2 of the License, or     *
 *   (at your option) any later version.                                   *
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 *   This program is distributed in the hope that it will be useful,       *
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of        *
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the         *
 *   GNU General Public License for more details.                          *
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 *   Free Software Foundation, Inc.,                                       *
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 ***************************************************************************/
#ifndef GUM_CHI_SQUARE_H
#  define GUM_CHI_SQUARE_H

#  include <agrum/core/math/math.h>
#  include <agrum/core/hashTable.h>


namespace gum {

  class ChiSquare {
    public:
    static double probaChi2(double x, Size df);

    private:

    static constexpr double __Z_MAX = 6.0;

    static constexpr double __CHI_EPSILON = 0.000001;

    static constexpr double __CHI_MAX = 99999.0;

    static constexpr double __LOG_SQRT_PI = 0.5723649429247000870717135;

    static constexpr double __I_SQRT_PI = 0.5641895835477562869480795;

    static constexpr double __BIGX = 20.0;




    static double __exp(double x) { return (((x) < -__BIGX) ? 0.0 : exp(x)); }

    static double __probaZValue(double z);
  };

} /* namespace gum */

#endif   // GUM_CHI_SQUARE_H


// static HashTable<std::pair<double, unsigned long>, double> __chi2Cache;
// static HashTable<double, double> __ZCache;
// static Idx nbZ;
// static Idx nbChi;
// static Idx nbZt;
// static Idx nbChit;