Fix filling reflection-ghostzone boundary points

Reflection ghostzones are not filled on sync.

1 files changed, 6 insertions, 3 deletions

diff --git a/src/maximal_slicing_axi_mg.c b/src/maximal_slicing_axi_mg.c
index fed6ff5..3d082a3 100644
--- a/src/maximal_slicing_axi_mg.c
+++ b/src/maximal_slicing_axi_mg.c
@@ -17,6 +17,7 @@
 #include "util_Table.h"
 
 #define SQR(x) ((x) * (x))
+#define ABS(x) ((x >= 0) ? (x) : -(x))
 #define ARRAY_ELEMS(x) (sizeof(x) / sizeof(*x))
 
 #define CPINDEX(cp, i, j, k) ((k * cp->grid_size[1] + j) * cp->grid_size[0] + i)
@@ -692,14 +693,16 @@ void msa_mg_solve(CCTK_ARGUMENTS)
             }
         }
         /* if the condition above was false, then lapse_mg should be filled by
-         * prolongation from the coarser level */
+         * prolongation from the coarser level
+         * note that the reflection-boundary ghost points are not filled
+         */
 
         /* fill the solver boundary conditions */
         for (int j = 0; j < cp->solver->fd_stencil; j++) {
             MG2DBoundary *bnd = cp->solver->boundaries[MG2D_BOUNDARY_1U];
             double *dst = bnd->val + j * bnd->val_stride;
             for (ptrdiff_t i = -j; i < (ptrdiff_t)cp->solver->domain_size + j; i++) {
-                const ptrdiff_t idx = CCTK_GFINDEX3D(cctkGH, i + cp->offset_left[0], cp->y_idx, cp->offset_left[1] + cp->solver->domain_size - 1 + j);
+                const ptrdiff_t idx = CCTK_GFINDEX3D(cctkGH, ABS(i) + cp->offset_left[0], cp->y_idx, cp->offset_left[1] + cp->solver->domain_size - 1 + j);
                 dst[i] = lapse_mg[idx] - 1.0;
             }
         }
@@ -707,7 +710,7 @@ void msa_mg_solve(CCTK_ARGUMENTS)
             MG2DBoundary *bnd = cp->solver->boundaries[MG2D_BOUNDARY_0U];
             double *dst = bnd->val + j * bnd->val_stride;
             for (ptrdiff_t i = -j; i < (ptrdiff_t)cp->solver->domain_size + j; i++) {
-                const ptrdiff_t idx = CCTK_GFINDEX3D(cctkGH, cp->offset_left[1] + cp->solver->domain_size - 1 + j, cp->y_idx, cp->offset_left[1] + i);
+                const ptrdiff_t idx = CCTK_GFINDEX3D(cctkGH, cp->offset_left[1] + cp->solver->domain_size - 1 + j, cp->y_idx, cp->offset_left[1] + ABS(i));
                 dst[i] = lapse_mg[idx] - 1.0;
             }
         }