Improve handling of MPI CMake option

CMakeLists.txt

@@ -4,8 +4,8 @@ cmake_minimum_required(VERSION 3.7)
 option(MDI_CXX "Build with CXX suport - ON (DEFAULT) or OFF)" ON)
 option(MDI_Fortran "Build with Fortran support - ON (DEFAULT) or OFF)" ON)
 option(MDI_Python "Build with Python support - ON (DEFAULT) or OFF)" ON)
+set(MDI_USE_MPI "" CACHE STRING "Flag to use MPI - ON (DEFAULT) or OFF")
 
-option(mpi "on or off" ON)
 option(python_package "on or off" OFF)
 option(plugins "on or off" ON)
 option(python_plugins "on or off" ${plugins})
@@ -18,6 +18,7 @@ option(debug "on or off" OFF)
 # Deprecated Options
 option(language "Deprecated; use MDI_CXX, MDI_Fortran, and/or MDI_Python instead.")
 option(libtype "Deprecated; use BUILD_SHARED_LIBS instead.")
+set(mpi ${MDI_USE_MPI} CACHE STRING "Deprecated; use MDI_USE_MPI instead.")
 
 set(use_C "")
 set(use_CXX "")
@@ -55,7 +56,19 @@ project(mdi
         VERSION 1.4.31
         LANGUAGES ${use_C} ${use_CXX} ${use_Fortran})
 
-# set a definition to enable MDI debug mode
+# Check for MPI
+if ( mpi STREQUAL "ON" )
+   find_package(MPI REQUIRED)
+elseif( NOT ( mpi STREQUAL "OFF") )
+   find_package(MPI)
+   if ( MPI_FOUND )
+      set( mpi "ON" )
+   else()
+      set( mpi "OFF" )
+   endif()
+endif()
+
+# Set a definition to enable MDI debug mode
 if( ${debug} )
   add_definitions(-D_MDI_DEBUG=1)
 else()

MDI_Library/CMakeLists.txt

@@ -7,17 +7,6 @@ endmacro(string_to_list _VAR _STR)
 include(GNUInstallDirs)
 include(CMakePackageConfigHelpers)
 
-# Check for MPI
-if ( NOT ( mpi STREQUAL "OFF") )
-   find_package(MPI)
-endif()
-if( NOT MPI_FOUND )
-   if( mpi STREQUAL "ON" )
-      message( WARNING "Could not find MPI.  Compiling without MPI support." )
-   endif()
-   set(mpi "OFF")
-endif()
-
 # Confirm that "language" is a valid value
 if( language AND (NOT language STREQUAL "C") AND (NOT language STREQUAL "CXX") AND (NOT language STREQUAL "Fortran") AND (NOT language STREQUAL "Python") )
    message( FATAL_ERROR "Value of language not recognized. Accepted values are: C; CXX; Fortran; Python." )
@@ -122,7 +111,7 @@ elseif( mpi STREQUAL "OFF" )
 
 else()
 
-   message( FATAL_ERROR "Value of mpi not recognized. Accepted values are: ON; OFF." )
+   message( FATAL_ERROR "Value of mpi (${mpi}) not recognized. Accepted values are: ON; OFF." )
 
 endif()
 

tests/MDI_Test_Codes/CMakeLists.txt

@@ -1,20 +1,9 @@
-# Check for MPI
-
-if ( NOT ( mpi STREQUAL "OFF") )
-   find_package(MPI)
-endif()
-if( NOT MPI_FOUND )
-   if( mpi STREQUAL "ON" )
-      message( WARNING "Could not find MPI.  Compiling without MPI support." )
-   endif()
+# Include MPI stubs, if needed
+if( mpi STREQUAL "OFF" )
    configure_file(${CMAKE_CURRENT_SOURCE_DIR}/STUBS_MPI/mpi.h ${CMAKE_CURRENT_BINARY_DIR}/STUBS_MPI/mpi.h COPYONLY)
-   set(mpi "OFF")
 endif()
 
-
-
 # Macro to link target to MPI
-
 macro(link_against_mpi _TAR)
    if( mpi STREQUAL "ON" )