From 8b36944935610791244a0a9979f13b0d7a2db693 Mon Sep 17 00:00:00 2001
From: Martin Quinson <martin.quinson@ens-rennes.fr>
Date: Thu, 16 Nov 2023 19:18:49 +0100
Subject: [PATCH] Ease the usage of cmake for SMPI programs

---
 FindSimGrid.cmake                      | 25 +++++++++++++++++++++-
 docs/source/Start_your_own_project.rst | 29 ++++++++++++++++++++------
 2 files changed, 47 insertions(+), 7 deletions(-)

diff --git a/FindSimGrid.cmake b/FindSimGrid.cmake
index 6f9d9e19cf..eec2f92ed5 100644
--- a/FindSimGrid.cmake
+++ b/FindSimGrid.cmake
@@ -40,6 +40,18 @@
 #  Since SimGrid header files require C++17, so we set CMAKE_CXX_STANDARD to 17.
 #    Change this variable in your own file if you need a later standard.
 
+# DEVELOPPERS OF MPI PROGRAMS USING SIMGRID
+#   You should use smpi_c_target() on the targets that are intended to run in SMPI.
+#   ${SMPIRUN} is correctly set if it's installed.
+#
+#   Example:
+#     add_executable(roundtrip roundtrip.c)
+#     smpi_c_target(roundtrip)
+#
+#     enable_testing()
+#     add_test(NAME Roundtrip
+#              COMMAND ${SMPIRUN} -platform ${CMAKE_SOURCE_DIR}/../cluster_backbone.xml -np 2 ./roundtrip)
+
 #
 # IMPROVING THIS FILE
 # -------------------
@@ -48,7 +60,7 @@
 #    https://cmake.org/Wiki/CMake/Tutorials/How_to_create_a_ProjectConfig.cmake_file
 #    https://github.com/boostcon/cppnow_presentations_2017/blob/master/05-19-2017_friday/effective_cmake__daniel_pfeifer__cppnow_05-19-2017.pdf
 
-cmake_minimum_required(VERSION 2.8.12)
+cmake_minimum_required(VERSION 3.5)
 
 set(CMAKE_CXX_STANDARD 17)
 set(CMAKE_CXX_STANDARD_REQUIRED ON)
@@ -103,6 +115,17 @@ find_package_handle_standard_args(SimGrid
 )
 
 if (SimGrid_FOUND)
+
+  find_program(SMPIRUN smpirun
+               HINTS ${SimGrid_PATH}/bin /opt/simgrid/bin)
+
+  MACRO(smpi_c_target NAME)
+    target_compile_options(${NAME} PUBLIC "-include;smpi/smpi_helpers.h;-fPIC;-shared;-Wl,-z,defs")
+    target_link_options(${NAME} PUBLIC "-fPIC;-shared;-Wl,-z,defs;-lm")
+    target_link_libraries(${NAME} PUBLIC ${SimGrid_LIBRARY})
+    target_include_directories(${NAME} PUBLIC "${SimGrid_INCLUDE_DIR};${SimGrid_INCLUDE_DIR}/smpi")
+  ENDMACRO()
+
   add_library(SimGrid::SimGrid SHARED IMPORTED)
   set_target_properties(SimGrid::SimGrid PROPERTIES
     INTERFACE_SYSTEM_INCLUDE_DIRECTORIES ${SimGrid_INCLUDE_DIR}
diff --git a/docs/source/Start_your_own_project.rst b/docs/source/Start_your_own_project.rst
index c339a00c32..bb06f098db 100644
--- a/docs/source/Start_your_own_project.rst
+++ b/docs/source/Start_your_own_project.rst
@@ -58,16 +58,33 @@ manually but your project will produce relevant error messages when
 trying to compile on a machine where SimGrid is not installed. Please
 also refer to the file header for more information.
 
-MPI projects should include ``find_package (MPI)`` in CMakeLists.txt. Then, the
-variables ``MPI_C_COMPILER``, ``MPI_CXX_COMPILER``, and ``MPI_Fortran_COMPILER`` should
-point to the full path of smpicc, smpicxx, and smpiff respectively.
-It is however not advised to set these variables from the CMakeLists.txt file directly.
-In addition, you may need to set ``SMPI_PRETEND_CC=1`` to please cmake when it tests the compiler.
+MPI projects should NOT search for MPI as usual in cmake, but instead use the ``smpi_c_target()`` macro
+to declare that a given target is meant to be executed in ``smpirun`` (which path is set in ``${SMPIRUN}``).
+This macro should work for C and C++ programs. Here is a small example:
+
+.. code-block:: cmake
+
+   # Search FindSimgrid in my sources
+   set(CMAKE_MODULE_PATH ${CMAKE_MODULE_PATH} "${CMAKE_SOURCE_DIR}")
+   find_package(SimGrid)
+
+   # Declare an executable, and specify that it's meant to run within smpirun
+   add_executable(roundtrip roundtrip.c)
+   smpi_c_target(roundtrip)
+
+   # Declare a test running our executable in ${SMPIRUN}
+   enable_testing()
+   add_test(NAME RoundTrip
+            COMMAND ${SMPIRUN} -platform ${CMAKE_SOURCE_DIR}/../cluster_backbone.xml -np 2 ./roundtrip)
+
+To compile Fortran code with cmake, you must override the ``MPI_Fortran_COMPILER`` variable as follows, but it will probably
+break some configuration checks, so you should export ``SMPI_PRETEND_CC=1`` during the configuration (not during the compilation
+nor the execution).
 
 .. code-block:: console
 
    $ SMPI_PRETEND_CC=1 cmake -DMPI_C_COMPILER=/opt/simgrid/bin/smpicc -DMPI_CXX_COMPILER=/opt/simgrid/bin/smpicxx -DMPI_Fortran_COMPILER=/opt/simgrid/bin/smpiff .
-
+   $ make
 
 Building your project with Makefile
 -----------------------------------
-- 
2.20.1