FirstDerivativeSecondOrderNoGhosts.c

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#include <stdio.h>
#include <stdlib.h>
#include <basic.h>
#include <arrayfunctions.h>
#include <firstderivative.h>

#include <mpivars.h>
typedef MPIVariables  MPIContext;

#undef  _MINIMUM_GHOSTS_

#define _MINIMUM_GHOSTS_ 1

#ifdef with_omp
#include <omp.h>
#endif

int FirstDerivativeSecondOrderCentralNoGhosts(  double  *Df,    
                                                double  *f,     
                                                int     dir,    
                                                int     bias,   
                                                int     ndims,  
                                                int     *dim,   
                                                int     ghosts, 
                                                int     nvars,  
                                                void*   m        )
{
  MPIContext* mpi = (MPIContext*) m;
  int  i, j, v;

  if ((!Df) || (!f)) {
    fprintf(stderr, "Error in FirstDerivativeSecondOrder(): input arrays not allocated.\n");
    return(1);
  }
  if (ghosts < _MINIMUM_GHOSTS_) {
    fprintf(stderr, "Error in FirstDerivativeSecondOrderCentralNoGhosts(): insufficient number of ghosts.\n");
    return(1);
  }

  /* create index and bounds for the outer loop, i.e., to loop over all 1D lines along
     dimension "dir"                                                                    */
  int indexC[ndims], index_outer[ndims], bounds_outer[ndims];
  _ArrayCopy1D_(dim,bounds_outer,ndims); bounds_outer[dir] =  1;
  int N_outer;  _ArrayProduct1D_(bounds_outer,ndims,N_outer);

#pragma omp parallel for schedule(auto) default(shared) private(i,j,v,index_outer,indexC)
  for (j=0; j<N_outer; j++) {
    _ArrayIndexnD_(ndims,j,bounds_outer,index_outer,0);
    _ArrayCopy1D_(index_outer,indexC,ndims);
    for (i = 0; i < dim[dir]; i++) {
      int qC, qL, qR;
      indexC[dir] = i-1; _ArrayIndex1D_(ndims,dim,indexC,ghosts,qL);
      indexC[dir] = i  ; _ArrayIndex1D_(ndims,dim,indexC,ghosts,qC );
      indexC[dir] = i+1; _ArrayIndex1D_(ndims,dim,indexC,ghosts,qR);
      for (v=0; v<nvars; v++)  Df[qC*nvars+v] = 0.5 * (f[qR*nvars+v]-f[qL*nvars+v]);
    }
  }

  if (mpi->ip[dir] == 0) {
    /* left physical boundary: overwrite the leftmost value with biased finite-difference */
#pragma omp parallel for schedule(auto) default(shared) private(i,j,v,index_outer,indexC)
    for (j=0; j<N_outer; j++) {
      _ArrayIndexnD_(ndims,j,bounds_outer,index_outer,0);
      _ArrayCopy1D_(index_outer,indexC,ndims);
      i = 0;
      int qC, qR, qR2;
      indexC[dir] = i  ; _ArrayIndex1D_(ndims,dim,indexC,ghosts,qC );
      indexC[dir] = i+1; _ArrayIndex1D_(ndims,dim,indexC,ghosts,qR);
      indexC[dir] = i+2; _ArrayIndex1D_(ndims,dim,indexC,ghosts,qR2);
      for (v=0; v<nvars; v++)  Df[qC*nvars+v] = (-0.5*f[qR2*nvars+v]+2*f[qR*nvars+v]-1.5*f[qC*nvars+v]);
    }
  }

  if (mpi->ip[dir] == (mpi->iproc[dir]-1)) {
    /* right physical boundary: overwrite the rightmost value with biased finite-difference */
#pragma omp parallel for schedule(auto) default(shared) private(i,j,v,index_outer,indexC)
    for (j=0; j<N_outer; j++) {
      _ArrayIndexnD_(ndims,j,bounds_outer,index_outer,0);
      _ArrayCopy1D_(index_outer,indexC,ndims);
      i = dim[dir] - 1;
      int qC, qL, qL2;
      indexC[dir] = i-2; _ArrayIndex1D_(ndims,dim,indexC,ghosts,qL2);
      indexC[dir] = i-1; _ArrayIndex1D_(ndims,dim,indexC,ghosts,qL);
      indexC[dir] = i  ; _ArrayIndex1D_(ndims,dim,indexC,ghosts,qC );
      for (v=0; v<nvars; v++)  Df[qC*nvars+v] = (0.5*f[qL2*nvars+v]-2*f[qL*nvars+v]+1.5*f[qC*nvars+v]);
    }
  }

  return 0;
}