CpuNonbondedForce.h

/* Portions copyright (c) 2006-2013 Stanford University and Simbios.
 * Contributors: Pande Group
 *
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 * a copy of this software and associated documentation files (the
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 * permit persons to whom the Software is furnished to do so, subject
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 *
 * The above copyright notice and this permission notice shall be included
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 *
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#ifndef OPENMM_CPU_NONBONDED_FORCE_H__
#define OPENMM_CPU_NONBONDED_FORCE_H__

#include "ReferencePairIxn.h"
#include <set>
#include <utility>
#include <vector>
#include <smmintrin.h>
// ---------------------------------------------------------------------------------------

class CpuNonbondedForce {

   private:
       
      bool cutoff;
      bool useSwitch;
      bool periodic;
      bool ewald;
      bool pme;
      const std::vector<std::pair<int, int> >* neighborList;
      float periodicBoxSize[3];
      float cutoffDistance, switchingDistance;
      float krf, crf;
      float alphaEwald;
      int numRx, numRy, numRz;
      int meshDim[3];
      __m128 boxSize, invBoxSize, half;
      static float TWO_OVER_SQRT_PI;

   public:

      /**---------------------------------------------------------------------------------------
      
         Constructor
      
         --------------------------------------------------------------------------------------- */

       CpuNonbondedForce( );

      /**---------------------------------------------------------------------------------------
      
         Destructor
      
         --------------------------------------------------------------------------------------- */

       ~CpuNonbondedForce( );

      /**---------------------------------------------------------------------------------------
      
         Set the force to use a cutoff.
      
         @param distance            the cutoff distance
         @param neighbors           the neighbor list to use
         @param solventDielectric   the dielectric constant of the bulk solvent
      
         --------------------------------------------------------------------------------------- */
      
      void setUseCutoff( float distance, const std::vector<std::pair<int, int> >& neighbors, float solventDielectric );

      /**---------------------------------------------------------------------------------------
      
         Set the force to use a switching function on the Lennard-Jones interaction.
      
         @param distance            the switching distance
      
         --------------------------------------------------------------------------------------- */
      
      void setUseSwitchingFunction( float distance );
      
      /**---------------------------------------------------------------------------------------
      
         Set the force to use periodic boundary conditions.  This requires that a cutoff has
         already been set, and the smallest side of the periodic box is at least twice the cutoff
         distance.
      
         @param boxSize             the X, Y, and Z widths of the periodic box
      
         --------------------------------------------------------------------------------------- */
      
      void setPeriodic( float* periodicBoxSize );
       
      /**---------------------------------------------------------------------------------------
      
         Set the force to use Ewald summation.
      
         @param alpha  the Ewald separation parameter
         @param kmaxx  the largest wave vector in the x direction
         @param kmaxy  the largest wave vector in the y direction
         @param kmaxz  the largest wave vector in the z direction
      
         --------------------------------------------------------------------------------------- */
      
      void setUseEwald(float alpha, int kmaxx, int kmaxy, int kmaxz);

     
      /**---------------------------------------------------------------------------------------
      
         Set the force to use Particle-Mesh Ewald (PME) summation.
      
         @param alpha    the Ewald separation parameter
         @param gridSize the dimensions of the mesh
      
         --------------------------------------------------------------------------------------- */
      
      void setUsePME(float alpha, int meshSize[3]);

      /**---------------------------------------------------------------------------------------
      
         Calculate Ewald ixn
      
         @param numberOfAtoms    number of atoms
         @param posq             atom coordinates and charges
         @param atomCoordinates  atom coordinates (in format needed by PME)
         @param atomParameters   atom parameters (sigma/2, 2*sqrt(epsilon))
         @param exclusions       atom exclusion indices
                                 exclusions[atomIndex] contains the list of exclusions for that atom
         @param fixedParameters  non atom parameters (not currently used)
         @param forces           force array (forces added)
         @param totalEnergy      total energy
            
         --------------------------------------------------------------------------------------- */
          
      void calculateReciprocalIxn(int numberOfAtoms, float* posq, std::vector<OpenMM::RealVec>& atomCoordinates,
                            const std::vector<std::pair<float, float> >& atomParameters, const std::vector<std::set<int> >& exclusions,
                            float* fixedParameters, std::vector<OpenMM::RealVec>& forces, float* totalEnergy) const;
      
      /**---------------------------------------------------------------------------------------
      
         Calculate LJ Coulomb pair ixn
      
         @param numberOfAtoms    number of atoms
         @param posq             atom coordinates and charges
         @param atomParameters   atom parameters (sigma/2, 2*sqrt(epsilon))
         @param exclusions       atom exclusion indices
                                 exclusions[atomIndex] contains the list of exclusions for that atom
         @param fixedParameters  non atom parameters (not currently used)
         @param forces           force array (forces added)
         @param totalEnergy      total energy
      
         --------------------------------------------------------------------------------------- */
          
      void calculateDirectIxn(int numberOfAtoms, float* posq,
                            const std::vector<std::pair<float, float> >& atomParameters, const std::vector<std::set<int> >& exclusions,
                            float* fixedParameters, float* forces, float* totalEnergy) const;

private:
            
      /**---------------------------------------------------------------------------------------
      
         Calculate LJ Coulomb pair ixn between two atoms
      
         @param atom1            the index of the first atom
         @param atom2            the index of the second atom
         @param posq             atom coordinates and charges
         @param atomParameters   atom parameters (sigma/2, 2*sqrt(epsilon))
         @param forces           force array (forces added)
         @param totalEnergy      total energy
            
         --------------------------------------------------------------------------------------- */
          
      void calculateOneIxn( int atom1, int atom2, float* posq,
                            const std::vector<std::pair<float, float> >& atomParameters, float* forces,
                            double* totalEnergy ) const;
            
      /**---------------------------------------------------------------------------------------
      
         Calculate LJ Coulomb pair ixn between two atoms
      
         @param atom1            the index of the first atom
         @param atom2            the index of the second atom
         @param posq             atom coordinates and charges
         @param atomParameters   atom parameters (sigma/2, 2*sqrt(epsilon))
         @param forces           force array (forces added)
         @param totalEnergy      total energy
            
         --------------------------------------------------------------------------------------- */
          
      void calculateOneEwaldIxn( int atom1, int atom2, float* posq,
                            const std::vector<std::pair<float, float> >& atomParameters, float* forces,
                            double* totalEnergy ) const;

      
      void getDeltaR(const __m128& posI, const __m128& posJ, __m128& deltaR, float& r2, bool periodic) const;

      static float erfcApprox(float x);
};

// ---------------------------------------------------------------------------------------

#endif // OPENMM_CPU_NONBONDED_FORCE_H__