/* -*- c++ -*- ----------------------------------------------------------
   LAMMPS - Large-scale Atomic/Molecular Massively Parallel Simulator
   https://www.lammps.org/, Sandia National Laboratories
   Steve Plimpton, sjplimp@sandia.gov

   Copyright (2003) Sandia Corporation.  Under the terms of Contract
   DE-AC04-94AL85000 with Sandia Corporation, the U.S. Government retains
   certain rights in this software.  This software is distributed under
   the GNU General Public License.

   See the README file in the top-level LAMMPS directory.
------------------------------------------------------------------------- */

#include <mpi.h>

// User-settable FFT precision

// FFT_PRECISION = 1 is single-precision complex (4-byte real, 4-byte imag)
// FFT_PRECISION = 2 is double-precision complex (8-byte real, 8-byte imag)

#ifdef FFT_SINGLE
#define FFT_PRECISION 1
typedef float FFT_SCALAR;
#else
#define FFT_PRECISION 2
typedef double FFT_SCALAR;
#endif

// if user set FFTW, it means FFTW3

#ifdef FFT_FFTW
#define FFT_FFTW3
#endif

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

// Data types for single-precision complex

#if FFT_PRECISION == 1

#if defined(FFT_MKL)
#include "mkl_dfti.h"
typedef float _Complex FFT_DATA;
#define FFT_MKL_PREC DFTI_SINGLE

#elif defined(FFT_FFTW3)
#include "fftw3.h"
typedef fftwf_complex FFT_DATA;
#define FFTW_API(function) fftwf_##function

#else

/* use a stripped down version of kiss fft as default fft */

#ifndef FFT_KISS
#define FFT_KISS
#endif
#define kiss_fft_scalar float
typedef struct {
  kiss_fft_scalar re;
  kiss_fft_scalar im;
} FFT_DATA;

struct kiss_fft_state;
typedef struct kiss_fft_state *kiss_fft_cfg;
#endif

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

// Data types for double-precision complex

#elif FFT_PRECISION == 2

#if defined(FFT_MKL)
#include "mkl_dfti.h"
typedef double _Complex FFT_DATA;
#define FFT_MKL_PREC DFTI_DOUBLE

#elif defined(FFT_FFTW3)
#include "fftw3.h"
typedef fftw_complex FFT_DATA;
#define FFTW_API(function) fftw_##function

#else

/* use a stripped down version of kiss fft as default fft */
#ifndef FFT_KISS
#define FFT_KISS
#endif
#define kiss_fft_scalar double
typedef struct {
  kiss_fft_scalar re;
  kiss_fft_scalar im;
} FFT_DATA;

struct kiss_fft_state;
typedef struct kiss_fft_state *kiss_fft_cfg;
#endif

#else
#error "FFT_PRECISION needs to be either 1 (=single) or 2 (=double)"
#endif

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

// details of how to do a 3d FFT

struct fft_plan_3d {
  struct remap_plan_3d *pre_plan;     // remap from input -> 1st FFTs
  struct remap_plan_3d *mid1_plan;    // remap from 1st -> 2nd FFTs
  struct remap_plan_3d *mid2_plan;    // remap from 2nd -> 3rd FFTs
  struct remap_plan_3d *post_plan;    // remap from 3rd FFTs -> output
  FFT_DATA *copy;                     // memory for remap results (if needed)
  FFT_DATA *scratch;                  // scratch space for remaps
  int total1, total2, total3;         // # of 1st,2nd,3rd FFTs (times length)
  int length1, length2, length3;      // length of 1st,2nd,3rd FFTs
  int pre_target;                     // where to put remap results
  int mid1_target, mid2_target;
  int scaled;     // whether to scale FFT results
  int normnum;    // # of values to rescale
  double norm;    // normalization factor for rescaling

  // system specific 1d FFT info
#if defined(FFT_MKL)
  DFTI_DESCRIPTOR *handle_fast;
  DFTI_DESCRIPTOR *handle_mid;
  DFTI_DESCRIPTOR *handle_slow;
#elif defined(FFT_FFTW3)
  FFTW_API(plan) plan_fast_forward;
  FFTW_API(plan) plan_fast_backward;
  FFTW_API(plan) plan_mid_forward;
  FFTW_API(plan) plan_mid_backward;
  FFTW_API(plan) plan_slow_forward;
  FFTW_API(plan) plan_slow_backward;
#elif defined(FFT_KISS)
  kiss_fft_cfg cfg_fast_forward;
  kiss_fft_cfg cfg_fast_backward;
  kiss_fft_cfg cfg_mid_forward;
  kiss_fft_cfg cfg_mid_backward;
  kiss_fft_cfg cfg_slow_forward;
  kiss_fft_cfg cfg_slow_backward;
#endif
};

// function prototypes

extern "C" {
void fft_3d(FFT_DATA *, FFT_DATA *, int, struct fft_plan_3d *);
struct fft_plan_3d *fft_3d_create_plan(MPI_Comm, int, int, int, int, int, int, int, int, int, int,
                                       int, int, int, int, int, int, int, int *, int);
void fft_3d_destroy_plan(struct fft_plan_3d *);
void factor(int, int *, int *);
void bifactor(int, int *, int *);
void fft_1d_only(FFT_DATA *, int, int, struct fft_plan_3d *);
}

/* ERROR/WARNING messages:

*/
