bc_utils.h

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#ifndef __BC_UTILS__
#define __BC_UTILS__
 
__inline__ __device__
void nonlinear_index(const int idx, const int lx, int *index) {
  const int idx2 = idx -1;
  index[3] = idx2/(lx * lx * lx) ;
  index[2] = (idx2 - (lx*lx*lx)*index[3])/(lx * lx);
  index[1] = (idx2 - (lx*lx*lx)*index[3] - (lx*lx) * index[2]) / lx;
  index[0] = (idx2 - (lx*lx*lx)*index[3] - (lx*lx) * index[2]) - lx*index[1];
  index[0]++;
  index[1]++;
  index[2]++;
  index[3]++;
}
 
#endif