Move MPI initialisation into cable_driver_init

src/offline/cable_driver_init.F90

@@ -1,6 +1,10 @@
 MODULE cable_driver_init_mod
   !! Module for containing routines for CABLE offline driver initialisation
   USE cable_namelist_util, ONLY : get_namelist_file_name
+#ifdef __MPI__
+  USE mpi
+  USE cable_mpicommon, ONLY : comm, rank
+#endif
   IMPLICIT NONE
   PRIVATE
 
@@ -10,6 +14,9 @@ MODULE cable_driver_init_mod
 
   SUBROUTINE cable_driver_init()
     !! Model initialisation routine for the CABLE offline driver.
+#ifdef __MPI__
+    INTEGER :: np, ierr
+#endif
 
     !check to see if first argument passed to cable is
     !the name of the namelist file
@@ -18,6 +25,16 @@ SUBROUTINE cable_driver_init()
 
 #ifdef __MPI__
     ! MPI specific initialisation
+    CALL MPI_Init(ierr)
+    CALL MPI_Comm_dup(MPI_COMM_WORLD, comm, ierr)
+    CALL MPI_Comm_size(comm, np, ierr)
+
+    IF (np < 2) THEN
+      WRITE (*,*) 'This program needs at least 2 processes to run!'
+      CALL MPI_Abort(comm, 0, ierr)
+    END IF
+
+    CALL MPI_Comm_rank(comm, rank, ierr)
 #else
     ! Serial specific initialisation
 #endif

src/offline/cable_mpicommon.F90

@@ -27,6 +27,13 @@ MODULE cable_mpicommon
 
   PUBLIC
 
+  ! MPI commicator and rank are declared as global variables (see
+  ! cable_driver_init_mod for their initialisation). This is done so that the comm
+  ! and rank variables are only accessible in cable_driver_init_mod when MPI
+  ! compilation is enabled.
+  ! TODO(Sean): revise which module to declare these variables in
+  INTEGER :: comm, rank
+
   ! base number of input fields: must correspond to CALLS to 
   ! MPI_address (field ) in *_mpimaster/ *_mpiworker
   INTEGER, PARAMETER :: nparam = 330

src/offline/cable_mpidrv.F90

@@ -22,28 +22,17 @@ PROGRAM mpi_driver
   USE mpi
   USE cable_driver_init_mod
 
-  USE cable_mpicommon
+  USE cable_mpicommon, ONLY : comm, rank
   USE cable_mpimaster
   USE cable_mpiworker
 
   IMPLICIT NONE
 
-  INTEGER :: comm, np, rank, ierr
+  INTEGER :: ierr
   REAL    :: etime ! Declare the type of etime()
 
   CALL cable_driver_init()
 
-  CALL MPI_Init (ierr)
-  CALL MPI_Comm_dup (MPI_COMM_WORLD, comm, ierr)
-  CALL MPI_Comm_size (comm, np, ierr)
-
-  IF (np < 2) THEN
-     WRITE (*,*) 'This program needs at least 2 processes to run!'
-     CALL MPI_Abort (comm, 0, ierr)
-  END IF
-
-  CALL MPI_Comm_rank (comm, rank, ierr)
-
   IF (rank == 0) THEN
      CALL mpidrv_master (comm)
   ELSE