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src/ell/SC_PartitionFunction.cc

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#include "ell/StateCollector.hh"

#include <cmath>

namespace ell
{
    
    SC_PartitionFunction::SC_PartitionFunction()
      : SC_Counting(), Z(0.0)
    {
    }
    
    SC_PartitionFunction::~SC_PartitionFunction()
    {
    }

    
    void
    SC_PartitionFunction::
	add(const State& s)
    {
          // increase the partition function
        Z += exp( - s.getEnergy() / LandscapeTopology::BOLTZMANN_KT );
          // store the state
        SC_Counting::add(s);
    }

    
    double
    SC_PartitionFunction::
	getZ( void ) const
    {
        return Z;
    }
    
    double
    SC_PartitionFunction::
	getEnergy( void ) const
    {
        return - LandscapeTopology::BOLTZMANN_KT * log( Z );
    }
    

}



namespace ell
{
    
    SC_PartitionFunction_Shifted::
	SC_PartitionFunction_Shifted( const LandscapeTopology& lt )
      : SC_Counting()
        , Z_shifted(0.0)
        , MIN_E( lt.getMFEState()->getEnergy() )
    {
    }
    
    SC_PartitionFunction_Shifted::
	SC_PartitionFunction_Shifted( const double MinE )
      : Z_shifted(0.0)
        , MIN_E( MinE )
    {
    }
    
    SC_PartitionFunction_Shifted::
	~SC_PartitionFunction_Shifted()
    {
    }

    
    void
    SC_PartitionFunction_Shifted::
	add(const State& s)
    {
        assertbiu(s.getEnergy() >= MIN_E
            , "the used MIN_E is HIGHER than the energy of the collected State");
          // increase the shifted partition function
        Z_shifted += exp( (MIN_E - s.getEnergy()) 
                            / LandscapeTopology::BOLTZMANN_KT );
          // store the state
        SC_Counting::add(s);
    }

    
    double
    SC_PartitionFunction_Shifted::
	getZ( void ) const
    {
        return Z_shifted / exp( MIN_E / LandscapeTopology::BOLTZMANN_KT );
    }
    
    double
    SC_PartitionFunction_Shifted::
	getEnergy( void ) const
    {
        return MIN_E - LandscapeTopology::BOLTZMANN_KT * log( Z_shifted );
    }
    

}