Particle-grid periodic communication

core/src/CMakeLists.txt

@@ -32,6 +32,12 @@ if(Cabana_ENABLE_MPI)
     )
 endif()
 
+if(Cabana_ENABLE_CAJITA)
+  list(APPEND HEADERS_PUBLIC
+    Cabana_ParticleGridCommunication.hpp
+    )
+endif()
+
 set(HEADERS_IMPL
   impl/Cabana_CartesianGrid.hpp
   impl/Cabana_Index.hpp
@@ -54,6 +60,10 @@ if(Cabana_ENABLE_MPI)
   target_link_libraries(cabanacore MPI::MPI_CXX)
 endif()
 
+if(Cabana_ENABLE_CAJITA)
+  target_link_libraries(cabanacore Cajita)
+endif()
+
 target_include_directories(cabanacore
   PUBLIC
   $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}>

core/src/Cabana_CommunicationPlan.hpp

@@ -30,6 +30,7 @@ namespace Cabana
 {
 namespace Impl
 {
+
 //---------------------------------------------------------------------------//
 // Count sends and create steering algorithm tags.
 struct CountSendsAndCreateSteeringDuplicated
@@ -246,6 +247,29 @@ auto countSendsAndCreateSteering( const ExportRankView element_export_ranks,
     return std::make_pair( neighbor_counts, neighbor_ids );
 }
 
+//---------------------------------------------------------------------------//
+// Return unique neighbor ranks, with the current rank first.
+std::vector<int> getUniqueTopology( std::vector<int> topology )
+{
+    auto remove_end = std::remove( topology.begin(), topology.end(), -1 );
+    std::sort( topology.begin(), remove_end );
+    auto unique_end = std::unique( topology.begin(), remove_end );
+    topology.resize( std::distance( topology.begin(), unique_end ) );
+
+    // Put this rank first.
+    int my_rank = -1;
+    MPI_Comm_rank( MPI_COMM_WORLD, &my_rank );
+    for ( auto& n : topology )
+    {
+        if ( n == my_rank )
+        {
+            std::swap( n, topology[0] );
+            break;
+        }
+    }
+    return topology;
+}
+
 //---------------------------------------------------------------------------//
 
 } // end namespace Impl
@@ -464,11 +488,8 @@ class CommunicationPlan
         // Store the number of export elements.
         _num_export_element = element_export_ranks.size();
 
-        // Store the unique neighbors.
-        _neighbors = neighbor_ranks;
-        std::sort( _neighbors.begin(), _neighbors.end() );
-        auto unique_end = std::unique( _neighbors.begin(), _neighbors.end() );
-        _neighbors.resize( std::distance( _neighbors.begin(), unique_end ) );
+        // Store the unique neighbors (this rank first).
+        _neighbors = Impl::getUniqueTopology( neighbor_ranks );
         int num_n = _neighbors.size();
 
         // Get the size of this communicator.
@@ -483,15 +504,6 @@ class CommunicationPlan
         // communication space so any mpi tag will do.
         const int mpi_tag = 1221;
 
-        // If we are sending to ourself put that one first in the neighbor
-        // list.
-        for ( auto& n : _neighbors )
-            if ( n == my_rank )
-            {
-                std::swap( n, _neighbors[0] );
-                break;
-            }
-
         // Initialize import/export sizes.
         _num_export.assign( num_n, 0 );
         _num_import.assign( num_n, 0 );

core/src/Cabana_Core.hpp

@@ -33,6 +33,10 @@
 #include <Cabana_Halo.hpp>
 #endif
 
+#ifdef Cabana_ENABLE_CAJITA
+#include <Cabana_ParticleGridCommunication.hpp>
+#endif
+
 #ifdef Cabana_ENABLE_ARBORX
 #include <Cabana_Experimental_NeighborList.hpp>
 #endif