Merge pull request #2972 from GEOS-ESM/release/v2.46

Hotfix: Fix support for external MPI

CHANGELOG.md

@@ -17,6 +17,12 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Deprecated
 
+## [2.47.2] - 2024-08-16
+
+### Fixed
+
+- Fix bug in supporting externally initialized MPI
+
 ## [2.47.1] - 2024-07-17
 
 ### Fixed

CMakeLists.txt

@@ -8,7 +8,7 @@ endif ()
 
 project (
   MAPL
-  VERSION 2.47.1
+  VERSION 2.47.2
   LANGUAGES Fortran CXX C)  # Note - CXX is required for ESMF
 
 # Set the possible values of build type for cmake-gui

gridcomps/Cap/MAPL_Cap.F90

@@ -447,17 +447,19 @@ subroutine initialize_mpi(this, unusable, rc)
 
       _UNUSED_DUMMY(unusable)
 
-      !call MPI_Initialized(this%mpi_already_initialized, ierror)
-      !_VERIFY(ierror)
-      call  ESMF_InitializePreMPI(_RC)
+      call MPI_Initialized(this%mpi_already_initialized, ierror)
+      _VERIFY(ierror)
 
       if (.not. this%mpi_already_initialized) then
+         call ESMF_InitializePreMPI(_RC)
          call MPI_Init_thread(MPI_THREAD_MULTIPLE, provided, ierror)
-         _ASSERT(provided == MPI_THREAD_MULTIPLE, 'MPI_THREAD_MULTIPLE not supported by this MPI.')
-!         call MPI_Init_thread(MPI_THREAD_SINGLE, provided, ierror)
-!         _VERIFY(ierror)
-!         _ASSERT(provided == MPI_THREAD_SINGLE, "MPI_THREAD_SINGLE not supported by this MPI.")
+      else
+         ! If we are here, then MPI has already been initialized by the user
+         ! and we are just using it. But we need to make sure that the user
+         ! has initialized MPI with the correct threading level.
+         call MPI_Query_thread(provided, ierror)
       end if
+      _ASSERT(provided == MPI_THREAD_MULTIPLE, 'MPI_THREAD_MULTIPLE not supported by this MPI.')
 
       call MPI_Comm_rank(this%comm_world, this%rank, ierror); _VERIFY(ierror)
       call MPI_Comm_size(this%comm_world, npes_world, ierror); _VERIFY(ierror)