ComputeRestraints.C

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#include "ComputeRestraints.h"
#include "Node.h"
#include "Molecule.h"
#include "SimParameters.h"
#include "Patch.h"
#include "NamdOneTools.h"

/************************************************************************/
/*                                                                      */
/*                      FUNCTION ComputeRestraints                      */
/*                                                                      */
/************************************************************************/

ComputeRestraints::ComputeRestraints(ComputeID c, PatchID pid)
  : ComputePatch(c,pid)
{
        reduction = ReductionMgr::Object()->willSubmit(REDUCTIONS_BASIC);

        SimParameters *simParams = Node::Object()->simParameters;

        //  Get parameters from the SimParameters object
        consExp = simParams->constraintExp;
        
        //****** BEGIN selective restraints (X,Y,Z) changes 
        consSelectOn = simParams->selectConstraintsOn;
        if (consSelectOn) {
          consSelectX = simParams->constrXOn;
          consSelectY = simParams->constrYOn;
          consSelectZ = simParams->constrZOn;
        }
        //****** END selective restraints (X,Y,Z) changes 
        
        //****** BEGIN moving constraints changes 
        consMoveOn = simParams->movingConstraintsOn;
        if (consMoveOn) {
          moveVel = simParams->movingConsVel;
        }
        //****** END moving constraints changes 
        //****** BEGIN rotating constraints changes 
        consRotOn = simParams->rotConstraintsOn;
        if (consRotOn) {
          rotVel = simParams->rotConsVel;
          rotAxis = simParams->rotConsAxis;
          rotPivot = simParams->rotConsPivot;
        }
        //****** END rotating constraints changes 

}
/*                      END OF FUNCTION ComputeRestraints               */

/************************************************************************/
/*                                                                      */
/*                      FUNCTION ~ComputeRestraints                     */
/*                                                                      */
/*      This is the destructor for the ComputeRestraints force object.  */
/*                                                                      */
/************************************************************************/

ComputeRestraints::~ComputeRestraints()

{
        delete reduction;
}
/*                      END OF FUNCTION ~ComputeRestraints              */

/************************************************************************/
/*                                                                      */
/*                              FUNCTION force                          */
/*                                                                      */
/************************************************************************/
void ComputeRestraints::doForce(CompAtom* p, CompAtomExt* pExt, Results* res)
{
        Molecule *molecule = Node::Object()->molecule;
        Real k;                 //  Force constant
        BigReal scaling = Node::Object()->simParameters->constraintScaling;
        Vector refPos;          //  Reference position
        BigReal r, r2;  //  r=distance between atom position and the
                        //  reference position, r2 = r^2
        Vector Rij;     //  vector between current position and reference pos
        BigReal value;  //  Current calculated value

        // aliases to work with old code
        Force *f = res->f[Results::normal];
        BigReal energy = 0;
        BigReal m[9];
        Tensor virial;
        Vector netForce = 0;

        // BEGIN moving and rotating constraint changes ******

        // This version only allows one atom to be moved 
        // and only ALL ref positions to be rotated

        int currentTime = patch->flags.step;
        if (consRotOn) {
          vec_rotation_matrix(rotVel * currentTime, rotAxis, m);
        }

        // END moving and rotating constraint changes ******

          
        if (scaling != 0.) for (int localID=0; localID<numAtoms; ++localID)
        {
          if (molecule->is_atom_constrained(pExt[localID].id))
          {
            molecule->get_cons_params(k, refPos, pExt[localID].id);

            k *= scaling;

            // BEGIN moving and rotating constraint changes ******
            
            if (consMoveOn) {
              refPos += currentTime * moveVel;
            }
            else if(consRotOn) {
              refPos = mat_multiply_vec(refPos - rotPivot, m) + rotPivot;
            }

            // END moving and rotating constraint changes *******

            Rij = patch->lattice.delta(refPos,p[localID].position);
            Vector vpos = refPos - Rij;

            //****** BEGIN selective restraints (X,Y,Z) changes 
            if (consSelectOn) { // check which components we want to restrain:
              if (!consSelectX) {Rij.x=0.0;}  // by setting the appropriate
              if (!consSelectY) {Rij.y=0.0;}  // Cartesian component to zero
              if (!consSelectZ) {Rij.z=0.0;}  // we will avoid a restoring force
            }                                 // along that component, and the
                                              // energy will also be correct
            //****** END selective restraints (X,Y,Z) changes 

            
            //  Calculate the distance and the distance squared
            r2 = Rij.length2();
            r = sqrt(r2);

            //  Only calculate the energy and the force if the distance is
            //  non-zero.   Otherwise, you could end up dividing by 0, which
            //  is bad
            if (r>0.0)
            {
              value=k;
      
              //  Loop through and multiple k by r consExp times.
              //  i.e.  calculate kr^e
              //  I know, I could use pow(), but I don't trust it.
              for (int k=0; k<consExp; ++k)
              {
                value *= r;
              }

              //  Add to the energy total
              energy += value;
      
              //  Now calculate the force, which is ekr^(e-1).  Also, divide
              //  by another factor of r to normalize the vector before we
              //  multiple it by the magnitude
              value *= consExp;
              value /= r2;
      
              Rij *= value;
              //iout << iINFO << "restraining force" << Rij        << "\n"; 

              f[localID] += Rij;
              netForce += Rij;
              virial += outer(Rij,vpos);
            }
          }
        }

        reduction->item(REDUCTION_BC_ENERGY) += energy;
        ADD_TENSOR_OBJECT(reduction,REDUCTION_VIRIAL_NORMAL,virial);
        ADD_VECTOR_OBJECT(reduction,REDUCTION_EXT_FORCE_NORMAL,netForce);
        reduction->submit();

}
/*                      END OF FUNCTION force                           */

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