Fix neighbor indexing

ECP-copa · May 20, 2021 · 83cec77 · 83cec77
1 parent ea20f3d
commit 83cec77
Showing 1 changed file with 7 additions and 2 deletions.
diff --git a/cajita/src/Cajita_ParticleGridDistributor.hpp b/cajita/src/Cajita_ParticleGridDistributor.hpp
@@ -170,10 +170,15 @@ class ParticleGridDistributor
                         nid[d] = 2;
                 }
 
-                // Compute the destination MPI rank.
+                // Compute the destination MPI rank [ni + 3*(nj + 3*nk) in 3d].
                 int neighbor_index = nid[0];
                 for ( std::size_t d = 1; d < num_space_dim; ++d )
-                    neighbor_index += pow( 3, d ) * nid[d];
+                {
+                    int npower = 1;
+                    for ( std::size_t dp = 1; dp <= d; ++dp )
+                        npower *= 3;
+                    neighbor_index += npower * nid[d];
+                }
                 destinations( p ) = neighbor_ranks( neighbor_index );
 
                 // Shift particles through periodic boundaries.