add io offload prototype

Makefile.am

@@ -43,6 +43,7 @@ SUBDIRS = \
   fms2_io \
   mosaic2 \
   fms \
+  offloading \
   parser \
   string_utils \
   affinity \

configure.ac

@@ -520,6 +520,7 @@ AC_CONFIG_FILES([
   diag_integral/Makefile
   sat_vapor_pres/Makefile
   random_numbers/Makefile
+  offloading/Makefile
   libFMS/Makefile
   docs/Makefile
   parser/Makefile
@@ -554,6 +555,7 @@ AC_CONFIG_FILES([
   test_fms/random_numbers/Makefile
   test_fms/topography/Makefile
   test_fms/column_diagnostics/Makefile
+  test_fms/offloading/Makefile
   test_fms/block_control/Makefile
   FMS.pc
   ])

fms2_io/netcdf_io.F90

@@ -29,6 +29,7 @@ module netcdf_io_mod
 #endif
 use netcdf
 use mpp_mod
+use mpp_domains_mod
 use fms_io_utils_mod
 use platform_mod
 implicit none
@@ -122,6 +123,17 @@ module netcdf_io_mod
                                        !! cur_dim_len(3) : z dimensions
 endtype dimension_information
 
+type, public :: fmsOffloadingIn_type
+  !TODO should be private, need getter functions
+  integer, public :: id !< unique identifier for each type
+  integer, public, allocatable :: offloading_pes(:) !< list of pe numbers that will be used to just write
+  integer, public, allocatable :: model_pes(:) !< list of pe numbers that will be running the model
+  logical :: is_model_pe !< true if current pe is in model_pes
+  type(domain2D) :: domain_in !< domain for grid that is to be written out
+  contains
+    procedure :: init
+endtype fmsOffloadingIn_type
+
 !> @brief Netcdf file type.
 !> @ingroup netcdf_io_mod
 type, public :: FmsNetcdfFile_t
@@ -148,12 +160,13 @@ module netcdf_io_mod
   character (len=20) :: time_name
   type(dimension_information) :: bc_dimensions !<information about the current dimensions for regional
                                                !! restart variables
-  integer :: tile_comm=MPP_COMM_NULL  !< MPI communicator used for parallel reads.
-                                      !! This is deprecated. Please use open_file(..., tile_comm=...)
-  logical :: use_netcdf_mpi = .false. !< Enable parallel reads/writes via NetCDF MPI. This
-                                      !! causes the I/O domain to be ignored.
-  logical :: use_collective = .false. !< Flag indicating whether reads and writes should be performed
-                                      !! collectively rather than independently.
+  type(fmsOffloadingIn_type) :: offloading_obj_in
+  logical :: use_collective = .false. !< Flag indicating if we should open the file for collective input
+                                      !! this should be set to .true. in the user application if they want
+                                      !! collective reads (put before open_file())
+  integer :: tile_comm=MPP_COMM_NULL   !< MPI communicator used for collective reads.
+                                      !! To be replaced with a real communicator at user request
+  logical        :: use_netcdf_mpi = .false.
 
   contains
 
@@ -2417,6 +2430,25 @@ subroutine flush_file(fileobj)
   endif
 end subroutine flush_file
 
+!> Initialization routine for fmsOffloadingIn_type
+subroutine init(this, offloading_obj_id, offloading_pes, model_pes, domain)
+  class(fmsOffloadingIn_type), intent(inout) :: this !< offloading object to initialize
+  integer, intent(in) :: offloading_obj_id !< unique id number to set
+  integer, intent(in) :: offloading_pes(:) !< list of pe's from current list to offload writes to
+  integer, intent(in) :: model_pes(:) !< list of model pe's (any pes not in offloading_pes argument)
+  type(domain2D) :: domain
+
+  this%id = offloading_obj_id
+  allocate(this%offloading_pes(size(offloading_pes)))
+  this%offloading_pes = offloading_pes
+  allocate(this%model_pes(size(model_pes)))
+  this%model_pes = model_pes
+
+ this%is_model_pe = .false.
+  if (any(model_pes .eq. mpp_pe())) &
+    this%is_model_pe = .true.
+  this%domain_in = domain
+end subroutine
 !> @brief Getter for use_netcdf_mpi
 pure logical function is_file_using_netcdf_mpi(this)
   class(FmsNetcdfFile_t), intent(in) :: this !< fms2io fileobj to query

libFMS/Makefile.am

@@ -63,6 +63,7 @@ libFMS_la_LIBADD += $(top_builddir)/diag_integral/libdiag_integral.la
 libFMS_la_LIBADD += $(top_builddir)/sat_vapor_pres/libsat_vapor_pres.la
 libFMS_la_LIBADD += $(top_builddir)/parser/libparser.la
 libFMS_la_LIBADD += $(top_builddir)/string_utils/libstring_utils.la
+libFMS_la_LIBADD += $(top_builddir)/offloading/liboffload.la
 libFMS_la_LIBADD += $(top_builddir)/libFMS_mod.la
 
 libFMS_la_SOURCES =

offloading/Makefile.am

@@ -0,0 +1,46 @@
+#***********************************************************************
+#*                   GNU Lesser General Public License
+#*
+#* This file is part of the GFDL Flexible Modeling System (FMS).
+#*
+#* FMS is free software: you can redistribute it and/or modify it under
+#* the terms of the GNU Lesser General Public License as published by
+#* the Free Software Foundation, either version 3 of the License, or (at
+#* your option) any later version.
+#*
+#* FMS is distributed in the hope that it will be useful, but WITHOUT
+#* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+#* FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+#* for more details.
+#*
+#* You should have received a copy of the GNU Lesser General Public
+#* License along with FMS.  If not, see <http://www.gnu.org/licenses/>.
+#***********************************************************************
+
+# This is an automake file for the constants directory of the FMS
+# package.
+
+# Ryan Mulhall 2025
+
+# Include .h and .mod files.
+AM_CPPFLAGS = -I$(top_srcdir)/include
+AM_FCFLAGS = $(FC_MODINC). $(FC_MODOUT)$(MODDIR)
+
+# Build this uninstalled convenience library.
+noinst_LTLIBRARIES = liboffload.la
+
+# The convenience library depends on its source.
+liboffload_la_SOURCES = \
+  metadata_transfer.F90 \
+  offloading_io.F90
+
+MODFILES = \
+  metadata_transfer_mod.$(FC_MODEXT) \
+  offloading_io_mod.$(FC_MODEXT)
+
+offloading_io_mod.$(FC_MODEXT): metadata_transfer_mod.$(FC_MODEXT)
+
+BUILT_SOURCES = $(MODFILES)
+nodist_include_HEADERS = $(MODFILES)
+
+include $(top_srcdir)/mkmods.mk