BurgersUpwind.c

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#include <stdlib.h>
#include <math.h>
#include <basic.h>
#include <arrayfunctions.h>
#include <mathfunctions.h>
#include <physicalmodels/burgers.h>
#include <hypar.h>

int BurgersUpwind(  double* fI,   
                    double* fL,   
                    double* fR,   
                    double* uL,   
                    double* uR,   
                    double* u,    
                    int     dir,  
                    void*   s,    
                    double  t     
                )
{
  HyPar   *solver = (HyPar*)   s;
  Burgers *param  = (Burgers*) solver->physics;
  int     done,v;

  int ndims   = solver->ndims;
  int nvars   = solver->nvars;
  int *dim    = solver->dim_local;
  int ghosts  = solver->ghosts;

  int index_outer[ndims], index_inter[ndims], bounds_outer[ndims], bounds_inter[ndims];
  _ArrayCopy1D_(dim,bounds_outer,ndims); bounds_outer[dir] =  1;
  _ArrayCopy1D_(dim,bounds_inter,ndims); bounds_inter[dir] += 1;

  done = 0; _ArraySetValue_(index_outer,ndims,0);
  while (!done) {
    _ArrayCopy1D_(index_outer,index_inter,ndims);
    for (index_inter[dir] = 0; index_inter[dir] < bounds_inter[dir]; index_inter[dir]++) {

      int p; _ArrayIndex1D_(ndims,bounds_inter,index_inter,0,p);
      int indexL[ndims]; _ArrayCopy1D_(index_inter,indexL,ndims); indexL[dir]--;
      int indexR[ndims]; _ArrayCopy1D_(index_inter,indexR,ndims);
      int pL; _ArrayIndex1D_(ndims,dim,indexL,ghosts,pL);
      int pR; _ArrayIndex1D_(ndims,dim,indexR,ghosts,pR);

      for (v = 0; v < nvars; v++) {
        double eigL = u[nvars*pL+v],
               eigR = u[nvars*pR+v];

        if ((eigL > 0) && (eigR > 0)) {
           fI[nvars*p+v] = fL[nvars*p+v];
        } else if ((eigL < 0) && (eigR < 0)) {
           fI[nvars*p+v] = fR[nvars*p+v];
        } else { 
           double alpha = max(absolute(eigL), absolute(eigR));
           fI[nvars*p+v] = 0.5 * (fL[nvars*p+v] + fR[nvars*p+v] - alpha * (uR[nvars*p+v] - uL[nvars*p+v]));
        }
      }

    }
    _ArrayIncrementIndex_(ndims,bounds_outer,index_outer,done);

  }

  return(0);
}