Build MPICH with CMake - cmake

Question

I need to force my Cmake to build and link my MPI code with MPICH. My MPICH is installed using the Ubuntu Package manager, in a standard location /usr/lib/mpich/. However, CMake still looks for the OpenMPI libraries, which I do not use. How can I instruct CMake to look for MPICH instead?
Below, you can see the output of some basic diagnostics:
$ whereis openmpi
openmpi:
$ whereis mpich
mpich: /usr/lib/mpich /usr/include/mpich
$ mpicc -v
mpicc for MPICH version 3.2
Below, I also provide the Cmake script and the errors I get from cmake and the mpirun.mpich. My Cmake is 3.5.1 and I run on Ubuntu Xenial 16.04.
cmake_minimum_required(VERSION 3.0)
message (STATUS "Adding mpiService")
find_package(MPI REQUIRED)
set(CMAKE_C_COMPILER mpicc)
set(CMAKE_CXX_COMPILER mpicxx)
set(MPI_GUESS_LIBRARY_NAME MPICH2)
message(STATUS ${MPI_INCLUDE_PATH})
message(STATUS ${MPI_C_LIBRARIES})
#add_definitions(-DOMPI_SKIP_MPICXX)
add_executable(mpiService main.cpp)
set(CMAKE_VERBOSE_MAKEFILE ON)
include_directories(SYSTEM ${MPI_INCLUDE_PATH})
target_link_libraries(
mpiService
PRIVATE
${MPI_C_LIBRARIES}
)
From the Cmake STATUS I get the following output:
/usr/lib/openmpi/include/openmpi/opal/mca/event/libevent2021/libevent/usr/lib/openmpi/include/openmpi/opal/mca/event/libevent2021/libevent/include/usr/lib/openmpi/include/usr/lib/openmpi/include/openmpi
/usr/lib/openmpi/lib/libmpi.so
And when I run the binary I get the following:
ubuntu#node1:~$ mpirun.mpich -np 2 --host node1,node2 mpiService
mpiService: error while loading shared libraries: libmpi.so.12: cannot open shared object file: No such file or directory
mpiService: error while loading shared libraries: libmpi.so.12: cannot open shared object file: No such file or directory

Answer 1

How can I instruct CMake to look for MPICH instead?
According to FindMPI documentation, you may set MPI_<lang>_COMPILER variable to the desired MPI compiler:
Set MPI_<lang>_COMPILER to the MPI wrapper (mpicc, etc.) of your
choice and reconfigure. FindMPI will attempt to determine all the
necessary variables using THAT compiler's compile and link flags.
set(MPI_CXX_COMPILER <path-to-mpich-compiler>)
find_package(MPI REQUIRED)
Alternatively, since CMake version 3.10, variable MPI_EXECUTABLE_SUFFIX can be set instead:
A suffix which is appended to all names that are being looked for. For instance you may set this to .mpich or .openmpi to prefer the one or the other on Debian and its derivatives.
set(MPI_EXECUTABLE_SUFFIX ".mpich")
find_package(MPI REQUIRED)

Answer 2

Herewith my current solution.
find_package(MPI REQUIRED)
# ----------------
# This is the only thing that made it work
# ----------------
set(MPI_C_LIBRARIES "/usr/lib/mpich/lib/libmpich.so")
set(MPI_INCLUDE_PATH "/usr/include/mpich")
# ----------------
add_executable(mpiService main.cpp)
include_directories(SYSTEM ${MPI_INCLUDE_PATH})
target_link_libraries(
mpiService
${MPI_C_LIBRARIES}
)
I personally do not like this solution, as I have to explicitly specify the path. Any other proposed solution was still building with OpenMPI. If I find a better alternative, I will re-post.