add c wrapper to allow testing fortran interface w/o fortran MPI libs

unittest/fortran/CMakeLists.txt

@@ -21,20 +21,6 @@ if(CMAKE_Fortran_COMPILER)
   endif()
 
   get_filename_component(LAMMPS_FORTRAN_MODULE ${LAMMPS_SOURCE_DIR}/../fortran/lammps.f90 ABSOLUTE)
-  if(BUILD_MPI)
-    find_package(MPI REQUIRED)
-    if((NOT MPI_Fortran_FOUND) OR (NOT MPI_Fortran_HAVE_F77_HEADER))
-      message(STATUS "Skipping Tests for the LAMMPS Fortran Module: no MPI support for Fortran")
-      return()
-    endif()
-  else()
-    add_library(fmpi_stubs STATIC mpi_stubs.f90)
-    get_filename_component(_tmp_fc ${CMAKE_Fortran_COMPILER} NAME)
-    if (_tmp_fc STREQUAL "flang")
-      target_link_libraries(fmpi_stubs PUBLIC gfortran)
-    endif()
-    add_library(MPI::MPI_Fortran ALIAS fmpi_stubs)
-  endif()
 
   add_library(flammps STATIC ${LAMMPS_FORTRAN_MODULE} keepstuff.f90)
   get_filename_component(_tmp_fc ${CMAKE_Fortran_COMPILER} NAME)
@@ -42,66 +28,62 @@ if(CMAKE_Fortran_COMPILER)
     target_link_libraries(flammps PUBLIC gfortran)
   endif()
 
-  if(MPI_Fortran_HAVE_F90_MODULE)
+  add_executable(test_fortran_create wrap_create.cpp test_fortran_create.f90)
-    add_executable(test_fortran_create wrap_create.cpp test_fortran_create.f90)
+  target_link_libraries(test_fortran_create PRIVATE flammps lammps GTest::GTestMain)
-    target_link_libraries(test_fortran_create PRIVATE flammps lammps MPI::MPI_Fortran GTest::GTestMain)
+  target_include_directories(test_fortran_create PRIVATE "${LAMMPS_SOURCE_DIR}/../fortran")
-    target_include_directories(test_fortran_create PRIVATE "${LAMMPS_SOURCE_DIR}/../fortran")
+  add_test(NAME FortranOpen COMMAND test_fortran_create)
-    add_test(NAME FortranOpen COMMAND test_fortran_create)
-  else()
-    message(STATUS "Skipping FortranOpen test since no working F90 MPI module was found")
-  endif()
 
   add_executable(test_fortran_commands wrap_commands.cpp test_fortran_commands.f90)
-  target_link_libraries(test_fortran_commands PRIVATE flammps lammps MPI::MPI_Fortran GTest::GTestMain)
+  target_link_libraries(test_fortran_commands PRIVATE flammps lammps GTest::GTestMain)
   add_test(NAME FortranCommands COMMAND test_fortran_commands)
 
   add_executable(test_fortran_get_thermo wrap_get_thermo.cpp test_fortran_get_thermo.f90)
-  target_link_libraries(test_fortran_get_thermo PRIVATE flammps lammps MPI::MPI_Fortran GTest::GTestMain)
+  target_link_libraries(test_fortran_get_thermo PRIVATE flammps lammps GTest::GTestMain)
   add_test(NAME FortranGetThermo COMMAND test_fortran_get_thermo)
 
   add_executable(test_fortran_box wrap_box.cpp test_fortran_box.f90)
-  target_link_libraries(test_fortran_box PRIVATE flammps lammps MPI::MPI_Fortran GTest::GTestMain)
+  target_link_libraries(test_fortran_box PRIVATE flammps lammps GTest::GTestMain)
   add_test(NAME FortranBox COMMAND test_fortran_box)
 
   add_executable(test_fortran_properties wrap_properties.cpp test_fortran_properties.f90 test_fortran_commands.f90)
-  target_link_libraries(test_fortran_properties PRIVATE flammps lammps MPI::MPI_Fortran GTest::GMockMain)
+  target_link_libraries(test_fortran_properties PRIVATE flammps lammps GTest::GMockMain)
   add_test(NAME FortranProperties COMMAND test_fortran_properties)
 
   add_executable(test_fortran_extract_global wrap_extract_global.cpp test_fortran_extract_global.f90)
-  target_link_libraries(test_fortran_extract_global PRIVATE flammps lammps MPI::MPI_Fortran GTest::GTestMain)
+  target_link_libraries(test_fortran_extract_global PRIVATE flammps lammps GTest::GTestMain)
   add_test(NAME FortranExtractGlobal COMMAND test_fortran_extract_global)
 
   add_executable(test_fortran_extract_atom wrap_extract_atom.cpp test_fortran_extract_atom.f90)
-  target_link_libraries(test_fortran_extract_atom PRIVATE flammps lammps MPI::MPI_Fortran GTest::GTestMain)
+  target_link_libraries(test_fortran_extract_atom PRIVATE flammps lammps GTest::GTestMain)
   add_test(NAME FortranExtractAtom COMMAND test_fortran_extract_atom)
 
   add_executable(test_fortran_extract_compute wrap_extract_compute.cpp test_fortran_extract_compute.f90)
-  target_link_libraries(test_fortran_extract_compute PRIVATE flammps lammps MPI::MPI_Fortran GTest::GTestMain)
+  target_link_libraries(test_fortran_extract_compute PRIVATE flammps lammps GTest::GTestMain)
   add_test(NAME FortranExtractCompute COMMAND test_fortran_extract_compute)
 
   add_executable(test_fortran_extract_fix wrap_extract_fix.cpp test_fortran_extract_fix.f90)
-  target_link_libraries(test_fortran_extract_fix PRIVATE flammps lammps MPI::MPI_Fortran GTest::GTestMain)
+  target_link_libraries(test_fortran_extract_fix PRIVATE flammps lammps GTest::GTestMain)
   add_test(NAME FortranExtractFix COMMAND test_fortran_extract_fix)
 
   add_executable(test_fortran_extract_variable wrap_extract_variable.cpp test_fortran_extract_variable.f90)
   target_compile_definitions(test_fortran_extract_variable PRIVATE -DTEST_INPUT_FOLDER=${CMAKE_CURRENT_SOURCE_DIR})
-  target_link_libraries(test_fortran_extract_variable PRIVATE flammps lammps MPI::MPI_Fortran GTest::GTestMain)
+  target_link_libraries(test_fortran_extract_variable PRIVATE flammps lammps GTest::GTestMain)
   add_test(NAME FortranExtractVariable COMMAND test_fortran_extract_variable)
 
   add_executable(test_fortran_gather_scatter wrap_gather_scatter.cpp test_fortran_gather_scatter.f90)
-  target_link_libraries(test_fortran_gather_scatter PRIVATE flammps lammps MPI::MPI_Fortran GTest::GTestMain)
+  target_link_libraries(test_fortran_gather_scatter PRIVATE flammps lammps GTest::GTestMain)
   add_test(NAME FortranGatherScatter COMMAND test_fortran_gather_scatter)
 
   add_executable(test_fortran_create_atoms wrap_create_atoms.cpp test_fortran_create_atoms.f90)
-  target_link_libraries(test_fortran_create_atoms PRIVATE flammps lammps MPI::MPI_Fortran GTest::GTestMain)
+  target_link_libraries(test_fortran_create_atoms PRIVATE flammps lammps GTest::GTestMain)
   add_test(NAME FortranCreateAtoms COMMAND test_fortran_create_atoms)
 
   add_executable(test_fortran_configuration wrap_configuration.cpp test_fortran_configuration.f90 test_fortran_commands.f90)
-  target_link_libraries(test_fortran_configuration PRIVATE flammps lammps MPI::MPI_Fortran GTest::GMockMain)
+  target_link_libraries(test_fortran_configuration PRIVATE flammps lammps GTest::GMockMain)
   add_test(NAME FortranConfiguration COMMAND test_fortran_configuration)
 
   add_executable(test_fortran_neighlist wrap_neighlist.cpp test_fortran_neighlist.f90)
-  target_link_libraries(test_fortran_neighlist PRIVATE flammps lammps MPI::MPI_Fortran GTest::GMockMain)
+  target_link_libraries(test_fortran_neighlist PRIVATE flammps lammps GTest::GMockMain)
   add_test(NAME FortranNeighlist COMMAND test_fortran_neighlist)
 
   add_executable(test_fortran_fixexternal wrap_fixexternal.cpp test_fortran_fixexternal.f90)

unittest/fortran/mpi_stubs.f90

@@ -1,20 +0,0 @@
-MODULE MPI
-  IMPLICIT NONE
-  PRIVATE
-
-  INTEGER, PARAMETER :: MPI_COMM_WORLD=0
-  INTEGER, PARAMETER :: MPI_SUCCESS=0
-
-  PUBLIC :: MPI_COMM_WORLD, MPI_SUCCESS, &
-      mpi_comm_split
-
-CONTAINS
-
-  SUBROUTINE mpi_comm_split(comm,color,key,newcomm,ierr)
-    INTEGER, INTENT(in)  :: comm,color,key
-    INTEGER, INTENT(out) :: newcomm,ierr
-
-    newcomm = comm + 1
-    ierr = 0
-  END SUBROUTINE mpi_comm_split
-END MODULE MPI

unittest/fortran/test_fortran_create.f90

@@ -1,3 +1,20 @@
+MODULE MYMPI
+  USE, INTRINSIC :: ISO_C_BINDING, ONLY: c_int
+
+  IMPLICIT NONE
+  PRIVATE
+  PUBLIC :: lmp_comm_split
+
+  INTERFACE
+      FUNCTION lmp_comm_split(color, key) BIND(C,name='create_mpi_comm_split')
+        IMPORT :: c_int
+        IMPLICIT NONE
+        INTEGER(c_int), VALUE, INTENT(IN) :: color, key
+        INTEGER(c_int)                    :: lmp_comm_split
+      END FUNCTION lmp_comm_split
+  END INTERFACE
+END MODULE MYMPI
+
 FUNCTION f_lammps_no_mpi_no_args() BIND(C, name="f_lammps_no_mpi_no_args")
   USE ISO_C_BINDING, ONLY: c_ptr
   USE liblammps
@@ -25,35 +42,35 @@ END FUNCTION f_lammps_no_mpi_with_args
 
 FUNCTION f_lammps_open_no_args() BIND(C, name="f_lammps_open_no_args")
   USE ISO_C_BINDING, ONLY: c_ptr
-  USE MPI,           ONLY: MPI_COMM_WORLD, mpi_comm_split
+  USE MYMPI,           ONLY: lmp_comm_split
   USE liblammps
   USE keepstuff,      ONLY: lmp,mycomm
   IMPLICIT NONE
   TYPE(c_ptr) :: f_lammps_open_no_args
-  INTEGER     :: color, key, ierr
+  INTEGER     :: color, key
 
   color = 1
   key = 1
-  CALL mpi_comm_split(MPI_COMM_WORLD, color, key, mycomm, ierr)
+  mycomm = lmp_comm_split(color, key)
   lmp = lammps(comm=mycomm)
   f_lammps_open_no_args = lmp%handle
 END FUNCTION f_lammps_open_no_args
 
 FUNCTION f_lammps_open_with_args() BIND(C, name="f_lammps_open_with_args")
   USE ISO_C_BINDING, ONLY: c_ptr
-  USE MPI,           ONLY: MPI_COMM_WORLD, mpi_comm_split
+  USE MYMPI,         ONLY: lmp_comm_split
   USE liblammps
   USE keepstuff,      ONLY: lmp,mycomm
   IMPLICIT NONE
   TYPE(c_ptr) :: f_lammps_open_with_args
-  INTEGER     :: color, key, ierr
+  INTEGER     :: color, key
 
   CHARACTER(len=12), DIMENSION(4), PARAMETER :: args = &
       [ CHARACTER(len=12) :: 'liblammps', '-log', 'none', '-nocite' ]
 
   color = 2
   key = 1
-  CALL mpi_comm_split(MPI_COMM_WORLD, color, key, mycomm, ierr)
+  mycomm = lmp_comm_split(color, key)
   lmp = lammps(args,mycomm)
   f_lammps_open_with_args = lmp%handle
 END FUNCTION f_lammps_open_with_args

unittest/fortran/wrap_create.cpp

@@ -17,6 +17,14 @@ void f_lammps_close();
 int f_lammps_get_comm();
 }
 
+// C wrapper to split MPI communicator w/o requiring a Fortran MPI lib
+extern "C" int create_mpi_comm_split(int color, int key)
+{
+    MPI_Comm c_newcomm = MPI_COMM_NULL;
+    MPI_Comm_split(MPI_COMM_WORLD, color, key, &c_newcomm);
+    return MPI_Comm_c2f(c_newcomm);
+}
+
 TEST(open_no_mpi, no_args)
 {
     ::testing::internal::CaptureStdout();