ImmersedBoundaryFftInterface.cpp

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#include "ImmersedBoundaryFftInterface.hpp"
#include <assert.h>
#include "FileFinder.hpp"
#include "Warnings.hpp"
 
template<unsigned DIM>
ImmersedBoundaryFftInterface<DIM>::ImmersedBoundaryFftInterface(ImmersedBoundaryMesh<DIM,DIM>* pMesh,
                                                                double* pIn,
                                                                std::complex<double>* pComplex,
                                                                double* pOut,
                                                                bool activeSources)
    : mpMesh(pMesh),
      mpInputArray(pIn),
      mpComplexArray(pComplex),
      mpOutputArray(pOut)
{
    int num_grid_pts_x = (int)mpMesh->GetNumGridPtsX();
    int num_grid_pts_y = (int)mpMesh->GetNumGridPtsY();
 
    // We require an even number of grid points
    assert(num_grid_pts_y % 2 == 0);
 
    /*
     * Resize the grids.  All complex grids are half-sized in the y-coordinate due to redundancy inherent in the
     * fast-Fourier method for solving Navier-Stokes.
     */
    int reduced_y = 1 + (num_grid_pts_y/2);
 
    // Plan variables
    mRealDims = {(long unsigned int)num_grid_pts_x, (long unsigned int)num_grid_pts_y};   // Dimensions of each real array
    mCompDims = {(long unsigned int)num_grid_pts_x, (long unsigned int)reduced_y};       // Dimensions of each complex array
 
    mHowManyForward = 2 + (unsigned)activeSources;      // Number of forward transforms (one more if sources are active)
    mHowManyInverse = 2;                           // Number of inverse transforms (always 2)
 
    mRealSep = num_grid_pts_x * num_grid_pts_y;       // How many doubles between start of first array and start of second
    mCompSep = num_grid_pts_x * reduced_y;           // How many fftw_complex between start of first array and start of second
 
    mRealStride = sizeof(double);                                // Each real array is contiguous in memory
    mCompStride = sizeof(std::complex<double>);                                // Each complex array is contiguous in memory
 
/*
 
 multi-dimensional arrays are stored row-major
 real_dims = dimensions of matrix
 real_sep = pointer offset between matrices
 how_many_forward = number of matrices to operate on
 stride = 1 => matrices are continguously stored one after the other
 */
}
 
template<unsigned DIM>
ImmersedBoundaryFftInterface<DIM>::~ImmersedBoundaryFftInterface()
{
}
 
template<unsigned DIM>
void ImmersedBoundaryFftInterface<DIM>::FftExecuteForward()
{
    // Real to complex
    pocketfft::stride_t rStride = {mRealStride*static_cast<long int>(mRealDims[1]), mRealStride};
    pocketfft::stride_t cStride = {mCompStride*static_cast<long int>(mCompDims[1]), mCompStride};
    pocketfft::shape_t axes = {0, 1};
 
    for (unsigned i = 0; i < mHowManyForward; i++)
    {
        pocketfft::r2c<double>(mRealDims, rStride, cStride, axes, true, mpInputArray + i*mRealSep, mpComplexArray + i*mCompSep, 1.0, 1);
    }
}
 
template<unsigned DIM>
void ImmersedBoundaryFftInterface<DIM>::FftExecuteInverse()
{
    // Complex to real
    pocketfft::stride_t rStride = {mRealStride*static_cast<long int>(mRealDims[1]), mRealStride};
    pocketfft::stride_t cStride = {mCompStride*static_cast<long int>(mCompDims[1]), mCompStride};
    pocketfft::shape_t axes = {0, 1};
 
    for (unsigned i = 0; i < mHowManyInverse; i++)
    {
        // For c2r, output array dims are supplied
        pocketfft::c2r(mRealDims, cStride, rStride, axes, false, mpComplexArray + i*mCompSep, mpOutputArray + i*mRealSep, 1.0, 1);
    }
}
 
// Explicit instantiation
template class ImmersedBoundaryFftInterface<1>;
template class ImmersedBoundaryFftInterface<2>;
template class ImmersedBoundaryFftInterface<3>;