#include <stdlib.h>
#include <string.h>
#include <math.h>
#include "geostat.h"


/*FAST FOURIER TRANSFORM MOVING AVERAGE METHOD */
/*Turns a Gaussian white noise vector into a   */
/*spatially correlated vector                  */
/*input:                                       */
/*variogram: structure defining the variogram  */
/*           model                             */
/*grid: structure defining the grid            */
/*n: vector with the number of cells along the */
/*   X, Y and Z axes for the underlying grid   */
/*   i = [0 1 2]                               */
/*   --> 0 0 0        : n will be computed and */
/*   updated as output                         */
/*   --> nx ny nz: these dimensions are used   */
/*realin: structure defining a realization -   */
/*        must be a Gaussian white noise       */
/*output:                                      */
/*realout: structure defining a realization -  */

void FFTMA2(struct vario_mod variogram,struct grid_mod grid,int n[3],struct realization_mod *realin,struct realization_mod *realout)
{
  int NTOT,i,j,k,NMAX,NDIM,ntot,nmax,NXYZ,nxyz,maille0,maille1;
  int solver;
  double temp;
  double *ireal,*covar,*workr,*worki,*realization;
  string variable;

  /*covariance axis normalization*/
  axes(variogram.ap,variogram.scf,variogram.Nvario);
  
  /*pseudo-grid definition*/
  cgrid(variogram,grid,n);
  
  /*constant definition*/
  NTOT = n[0]*n[1]*n[2];
  ntot = NTOT+1;
  NMAX = n[0];
  NDIM = 3;
  for (i=1;i<3;i++) {
    if (n[i] > NMAX)
      NMAX = n[i];
    if (n[i] == 1)
      NDIM--;
  }
  nmax = NMAX+1;
  NXYZ = grid.NX*grid.NY*grid.NZ;
  nxyz = NXYZ+1;
  
  /*array initialization*/
  covar = (double *) malloc(ntot * sizeof(double));
/*   testmemory(covar); */
  allouememoire(covar,'covar');




  ireal = (double *) malloc(ntot * sizeof(double));
  testmemory(ireal);

  realization = (double *) malloc(ntot * sizeof(double));
  testmemory(realization);

  workr = (double *) malloc(nmax * sizeof(double));
  testmemory(workr);

  worki = (double *) malloc(nmax * sizeof(double));
  testmemory(worki);
	
	/*covariance function creation*/
  covariance(covar,variogram,grid,n);
	
  /*power spectrum*/
  fourt(covar,ireal,n,NDIM,1,0,workr,worki);
	
  /*organization of the input Gaussian white noise*/
  solver=0;
  prebuild_gwn(grid,n,realin,realization,solver);
	
  /*forward fourier transform of the GWN*/
  fourt(realization,ireal,n,NDIM,1,0,workr,worki);

  /* build realization in spectral domain   */
  build_real(n,NTOT,covar,realization,ireal);
	
  free(covar);
	
	/*backward fourier transform*/
  fourt(realization,ireal,n,NDIM,0,1,workr,worki);
	
	
  free(ireal);
  free(workr);
  free(worki);
	
	/*output realization*/
  clean_real(realin,n,grid,realization,realout);
	
  free(realization);
	
  return;
}