neumann_kernel.h

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#ifndef __BC_NEUMANN_KERNEL__
#define __BC_NEUMANN_KERNEL__
 
#include "bc_utils.h"
 
#define coef_normal_area_idx(i, j, k, l, lx, nf) \
  (((i) + (lx) * (((j) - 1) + (lx) * (((k) - 1) + (nf) * (((l) - 1))))) - 1)
 
 
template< typename T >
__global__
void neumann_apply_scalar_kernel(const int * __restrict__ msk,
                                 const int * __restrict__ facet,
                                 T * __restrict__ x,
                                 const T * __restrict__ flux,
                                 const T * __restrict__ area,
                                 const int lx,
                                 const int m) {
  int index[4];
  const int idx = blockIdx.x * blockDim.x + threadIdx.x;
  const int str = blockDim.x * gridDim.x;
 
  for (int i = (idx + 1); i < m; i += str) {
    const int k = (msk[i] - 1);
    const int f = (facet[i]);
    nonlinear_index(msk[i], lx, index);
 
    switch(f) {
    case 1:
    case 2:
      {
        const int na_idx = coef_normal_area_idx(index[1], index[2],
                                                f, index[3], lx, 6);
        x[k] += flux[i-1] * area[na_idx];
        break;
      }
    case 3:
    case 4:
      {
        const int na_idx = coef_normal_area_idx(index[0], index[2],
                                                f, index[3], lx, 6);
        x[k] += flux[i-1] * area[na_idx];
        break;
      }
    case 5:
    case 6:
      {
        const int na_idx = coef_normal_area_idx(index[0], index[1],
                                                f, index[3], lx, 6);
        x[k] += flux[i-1] * area[na_idx];
        break;
      }
    }
  }
}
 
#endif // __BC_NEUMANN_KERNEL__