/*   []----------------------------------------[]
      |            LangevinDynamics.h          |
     []----------------------------------------[]
      |                                        |
      |   AUTHOR:    MFSomers 2005.            |
      |   USE:       Defines a classical       |
      |              dynamics framework class  |
      |              to be used for different  |
      |              integrators of the        |
      |              Langevin equation of      |
      |              motion ...                |
      |                                        |
     []----------------------------------------[]
*/

// Copyright (C) 2005 M.F. Somers, Theoretical Chemistry Department, Leiden University
//
// This is free software; you can redistribute it and/or modify it under the terms of
// the GNU Lesser General Public License as published by the Free Software Foundation.
//
// http://www.gnu.org/licenses/lgpl.txt

#if !defined(__LANGEVIN_DYNAMICS_INCLUDED__)

#define __LANGEVIN_DYNAMICS_INCLUDED__

#include "Global.h"
#include "Vector.h"
#include "Rand.h"
#include "Constants.h"
#include "ClassicalDynamics.h"

#include "DistanceConstraint.h"

/* --------------------------------------------------------- */

class   LangevinDynamics;
typedef LangevinDynamics *LangevinDynamicsPointer;

class LangevinDynamics : public ClassicalDynamics
                       { public:
			  
			 LangevinDynamics( double theGamma = 0.0, double theBoltzmann = 0.0, double theTemperature = 0.0, unsigned int TheId = GET_NEW_ID ) : ClassicalDynamics( 2, TheId )
			 {
			  Type = LangevinClassicalDynamics;
                          // Gamma = ( theGamma < CONST_EPSILON ? 0.0 : ( theGamma < 1.0 ? theGamma : 1.0 ) );
                          Gamma = ( theGamma < CONST_EPSILON ? 0.0 : theGamma );
                          KbT = ( theBoltzmann < CONST_EPSILON ? 0.0 : theBoltzmann );
                          KbT *= ( theTemperature < CONST_EPSILON ? 0.0 : theTemperature );
			 };
			 LangevinDynamics( LangevinDynamics& D ) : ClassicalDynamics( D )
			 {
                          Gamma = D.Gamma;
                          KbT = D.KbT;
			 };
			  
			 virtual LangevinDynamics& operator=( LangevinDynamics& D )
			 {
			  if( &D == &(*this) ) return( (*this) );
			  ClassicalDynamics::operator=( D );
                          Gamma = D.Gamma;
                          KbT = D.KbT;
			  return( (*this) );
			 };
			  
			 virtual LangevinDynamicsPointer Clone()
			 {
			  return( new LangevinDynamics( (*this) ) );
			 }
			 virtual LangevinDynamicsPointer Create( double theGamma = 0.0, double theBoltzmann = 0.0, double theTemperature = 0.0, unsigned int TheId = GET_NEW_ID  )
			 {
			  return( new LangevinDynamics( theGamma, theBoltzmann, theTemperature, TheId ) );
			 }			  
			  
			 virtual int Integrator( double Step, double Start = 0.0, ConstraintListPointer Constraints = NULL );
			 virtual int IntegratorConservationCheck( double Step );
			 virtual int TrajectoryContinuationCheck( double At, double Step, int nStep, int nSteps );
                         virtual int RunTrajectory( double Start, double Step, int nSteps, ConstraintListPointer Constraints = NULL );
                         double Gamma, KbT;
	                };
			   
/* --------------------------------------------------------- */

#endif