ESMF_FieldRegridGetIwts Subroutine

      subroutine ESMF_FieldRegridGetIwts(Field, Iwts, MaskValues, rc)
!
! !RETURN VALUE:
!      
! !ARGUMENTS:
      type(ESMF_Field), intent(inout)                    :: Field
      type(ESMF_Field), intent(inout)                 :: Iwts
      integer(ESMF_KIND_I4), intent(in), optional     :: MaskValues(:)
      integer, intent(out), optional                  :: rc 
!
! !DESCRIPTION:
!
!     The arguments are:
!     \begin{description}
!     \item [Field]
!           The Field.
!     \item [{[rc]}]
!           Return code; equals {\tt ESMF\_SUCCESS} if there are no errors.
!     \end{description}
!
!EOPI
        integer :: localrc
        integer              :: isSphere
        type(ESMF_GeomType_Flag)  :: geomtype

        type(ESMF_Grid)      :: Grid
        type(ESMF_Array)     :: Array
        type(ESMF_VM)        :: vm
        type(ESMF_Mesh)      :: Mesh
        type(ESMF_StaggerLoc) :: staggerLoc

        ! Initialize return code; assume failure until success is certain
        localrc = ESMF_SUCCESS
        if (present(rc)) rc = ESMF_RC_NOT_IMPL

        ! global vm for now
        call ESMF_VMGetGlobal(vm, rc=localrc)
        if (ESMF_LogFoundError(localrc, ESMF_ERR_PASSTHRU, &
          ESMF_CONTEXT, rcToReturn=rc)) return

  !  check Field and Iwts to make sure they are from the same grid

        ! Now we go through the painful process of extracting the data members
        ! that we need.
        call ESMF_FieldGet(Iwts, geomtype=geomtype, array=Array, rc=localrc)
        if (ESMF_LogFoundError(localrc, ESMF_ERR_PASSTHRU, &
          ESMF_CONTEXT, rcToReturn=rc)) return


        ! If grids, then convert to a mesh to do the regridding
        if (geomtype .eq. ESMF_GEOMTYPE_GRID) then
          call ESMF_FieldGet(Iwts, grid=Grid, &
                 staggerloc=staggerLoc, rc=localrc)
          if (ESMF_LogFoundError(localrc, ESMF_ERR_PASSTHRU, &
            ESMF_CONTEXT, rcToReturn=rc)) return

          ! check grid
          call checkGrid(Grid,staggerloc,rc=localrc)
          if (ESMF_LogFoundError(localrc, ESMF_ERR_PASSTHRU, &
            ESMF_CONTEXT, rcToReturn=rc)) return

          ! Convert Grid to Mesh
          Mesh = ESMF_GridToMesh(Grid, staggerLoc, isSphere, &
                      maskValues=MaskValues, regridConserve=ESMF_REGRID_CONSERVE_ON, rc=localrc)
          if (ESMF_LogFoundError(localrc, ESMF_ERR_PASSTHRU, &
            ESMF_CONTEXT, rcToReturn=rc)) return

        else
          call ESMF_FieldGet(Iwts, mesh=Mesh, rc=localrc)
          if (ESMF_LogFoundError(localrc, ESMF_ERR_PASSTHRU, &
            ESMF_CONTEXT, rcToReturn=rc)) return
        endif

        ! call into the Regrid GetIwts interface
        call ESMF_RegridGetIwts(Grid, Mesh, Array, staggerLoc, rc=localrc)
        if (ESMF_LogFoundError(localrc, &
          ESMF_ERR_PASSTHRU, &
          ESMF_CONTEXT, rcToReturn=rc)) return

        ! destroy Mesh, if they were created here
        if (geomtype .ne. ESMF_GEOMTYPE_MESH) then
        call ESMF_MeshDestroy(Mesh, noGarbage=.true., rc=localrc)
          if (ESMF_LogFoundError(localrc, &
            ESMF_ERR_PASSTHRU, &
            ESMF_CONTEXT, rcToReturn=rc)) return
        endif

        if(present(rc)) rc = ESMF_SUCCESS

    end subroutine ESMF_FieldRegridGetIwts