rpc/field/Mask.tpp

#ifndef RPC_MASK_TPP
#define RPC_MASK_TPP
 
/*
* PSCF - Polymer Self-Consistent Field
*
* Copyright 2015 - 2025, The Regents of the University of Minnesota
* Distributed under the terms of the GNU General Public License.
*/
 
#include "Mask.h"
 
namespace Pscf {
namespace Rpc
{
 
   using namespace Util;
   using namespace Pscf::Prdc;
   using namespace Pscf::Prdc::Cpu;
 
   /*
   * Return volume fraction of the unit cell occupied by the 
   * polymers/solvents.
   */
   template <int D>
   double Mask<D>::rGridAverage() const
   {
      RField<D> const & rg = MaskReal< D, RField<D>, FieldIo<D> >::rgrid();
 
      // Sum up elements of r-grid mask field.
      // Use Kahan summation to reduce accumulation of error
      double sum(0.0), err(0.0), tempVal, tempSum;
      int n = rg.capacity();
      for (int i = 0; i < n; ++i) {
         tempVal = rg[i] - err;
         tempSum = sum + tempVal;
         err = tempSum - sum - tempVal;
         sum = tempSum;
      }
 
      return (sum / ((double)rg.capacity()));
   }
 
} // namespace Rpc
} // namespace Pscf
#endif