EdmistonRuedenberg.h

/*
   CheMPS2: a spin-adapted implementation of DMRG for ab initio quantum chemistry
   Copyright (C) 2013-2016 Sebastian Wouters

   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.

   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.

   You should have received a copy of the GNU General Public License along
   with this program; if not, write to the Free Software Foundation, Inc.,
   51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*/

#ifndef EDMISTONRUEDENBERG_CHEMPS2_H
#define EDMISTONRUEDENBERG_CHEMPS2_H

#include "Options.h"
#include "DMRGSCFunitary.h"
#include "Hamiltonian.h"

namespace CheMPS2{
   class EdmistonRuedenberg{

      public:
      

         EdmistonRuedenberg( const FourIndex * Vmat, const int group, const int printLevelIn=1 );
         
         virtual ~EdmistonRuedenberg();
         

         double Optimize(double * temp1, double * temp2, const bool startFromRandomUnitary, const double gradThreshold=EDMISTONRUED_gradThreshold, const int maxIter=EDMISTONRUED_maxIter);
         

         void FiedlerExchange(const int maxlinsize, double * temp1, double * temp2);


         void FiedlerGlobal( int * dmrg2ham ) const;


         DMRGSCFunitary * getUnitary();
         
      private:
      
         //Pointer to the active space two-electron integrals
         const FourIndex * VMAT_ORIG;
         
         //The print level
         int printLevel;
         
         //The symmetry information object
         Irreps SymmInfo;
         
         //The DMRGSCF index handler (in order to be able to recycle the DMRGSCFunitary object)
         DMRGSCFindices * iHandler;
         
         //DMRGSCF unitary
         DMRGSCFunitary * unitary;
         
         //The rotated two-body matrix elements
         FourIndex * VmatRotated;
         
         //Calculate the gradient, hessian and update
         double augmentedHessianNewtonRaphson(double * gradient, double * temp1, double * temp2) const;
         double calcGradientValue(const int irrep, const int p, const int q) const;
         double calcHessianValue( const int irrep, const int p, const int q, const int r, const int s) const;
         
         //Calculate the cost function
         double costFunction() const;
         
         //Fiedler vector helper function
         double FiedlerExchangeCost() const;
         static double FiedlerGlobalCost( const DMRGSCFindices * idx, const FourIndex * VMAT_LOCAL, int * dmrg2ham );
         void Fiedler(const int irrep, int * reorder, double * laplacian, double * temp2);
         
   };
}

#endif