cuda/FFT.h

#ifndef PRDC_CUDA_FFT_H
#define PRDC_CUDA_FFT_H
 
/*
* 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 "RField.h"
#include "CField.h"
#include "RFieldDft.h"
#include "types.h"
 
#include <pscf/math/IntVec.h>
#include <util/global.h>
 
#include <cufft.h>
 
namespace Pscf {
namespace Prdc {
namespace Cuda {
 
   using namespace Util;

   template <int D>
   class FFT 
   {
 
   public:

      FFT();

      virtual ~FFT();

      void setup(IntVec<D> const & meshDimensions);
 
      // Real <-> Complex transforms
      
      void forwardTransform(RField<D> const & rField, RFieldDft<D>& kField) 
      const;

      void inverseTransformUnsafe(RFieldDft<D>& kField, RField<D>& rField) 
      const;

      void inverseTransformSafe(RFieldDft<D> const & kField, 
                                RField<D>& rField) const;
 
      // Complex <-> Complex transforms
      
      void forwardTransform(CField<D> const & rField, CField<D>& kField) 
      const;

      void inverseTransform(CField<D> const & kField, CField<D>& rField) 
      const;

      const IntVec<D>& meshDimensions() const;

      bool isSetup() const;
 
      // Static function

      static 
      void computeKMesh(IntVec<D> const & rMeshDimensions,
                        IntVec<D> & kMeshDimensions,
                        int & kSize );

      static 
      bool hasImplicitInverse(IntVec<D> const & wavevector,
                              IntVec<D> const & meshDimensions);
 
   private:

      IntVec<D> meshDimensions_;

      mutable RFieldDft<D> kFieldCopy_;

      int rSize_;

      int kSize_;

      cufftHandle rcfPlan_;

      cufftHandle criPlan_;

      cufftHandle ccPlan_;

      bool isSetup_;

      void makePlans();
 
   };
 
   // Declarations of explicit specializations
 
   template <>
   void FFT<1>::makePlans();
 
   template <>
   void FFT<2>::makePlans();
 
   template <>
   void FFT<3>::makePlans();
 
   // Inline functions
 
   /*
   * Return the dimensions of the grid for which this was allocated.
   */
   template <int D>
   inline IntVec<D> const & FFT<D>::meshDimensions() const
   {  return meshDimensions_; }
 
   /*
   * Has this FFT object been setup? 
   */
   template <int D>
   inline bool FFT<D>::isSetup() const
   {  return isSetup_; }
 
   /*
   * Does this wavevector have an implicit inverse?
   */
   template <int D>
   inline
   bool FFT<D>::hasImplicitInverse(IntVec<D> const & wavevector,
                                   IntVec<D> const & meshDimensions)
   {
      int i = wavevector[D-1];
      int d = meshDimensions[D-1];
      if ((i != 0) && (d - i > d/2 + 1)) {
         return true;
      } else {
         return false;
      }
   }
 
   #ifndef PRDC_CUDA_FFT_TPP
   // Suppress implicit instantiation
   extern template class FFT<1>;
   extern template class FFT<2>;
   extern template class FFT<3>;
   #endif
 
} // Cuda
} // Prdc
} // Pscf
#endif