Move implementation of create_mpi_datatype from CarpetInterp2 to CarpetLib

2 files changed, 34 insertions, 0 deletions

diff --git a/Carpet/CarpetLib/src/dist.cc b/Carpet/CarpetLib/src/dist.cc
index 7ac6f73f6..c870990fb 100644
--- a/Carpet/CarpetLib/src/dist.cc
+++ b/Carpet/CarpetLib/src/dist.cc
@@ -53,6 +53,27 @@ namespace dist {
     MPI_Finalize ();
   }
   
+  
+  
+  // Create an MPI datatype from a C datatype description
+  void create_mpi_datatype (size_t const count,
+                            mpi_struct_descr_t const descr[],
+                            MPI_Datatype & newtype)
+  {
+    int blocklengths[count];
+    MPI_Aint displacements[count];
+    MPI_Datatype types[count];
+    for (size_t n=0; n<count; ++n) {
+      blocklengths [n] = descr[n].blocklength;
+      displacements[n] = descr[n].displacement;
+      types        [n] = descr[n].type;
+    }
+    MPI_Type_struct (count, blocklengths, displacements, types, &newtype);
+    MPI_Type_commit (&newtype);
+  }
+  
+  
+  
   void checkpoint (const char* file, int line) {
     DECLARE_CCTK_PARAMETERS;
     if (verbose) {
diff --git a/Carpet/CarpetLib/src/dist.hh b/Carpet/CarpetLib/src/dist.hh
index ae7953f99..cf4cbd70c 100644
--- a/Carpet/CarpetLib/src/dist.hh
+++ b/Carpet/CarpetLib/src/dist.hh
@@ -30,6 +30,19 @@ namespace dist {
   void pseudoinit (MPI_Comm const c);
   void finalize ();
   
+  // Create MPI datatypes from C structures
+  struct mpi_struct_descr_t {
+    int          blocklength;
+    MPI_Aint     displacement;
+    MPI_Datatype type;
+  };
+  
+  void create_mpi_datatype (size_t const count,
+                            mpi_struct_descr_t const descr[],
+                            MPI_Datatype & newtype);
+  
+  
+  
   // Debugging output
 #define CHECKPOINT dist::checkpoint(__FILE__, __LINE__)
   void checkpoint (const char* file, int line);