What does "::MPI_C" meant in ld: cannot find -lMPI::MPI_C?

English Install/Boot/Login
1

Hi, I am building ElmerGUI Flatpak package, https://github.com/kevinsmia1939/flathub/tree/fi.csc.Elmer
but I have some problem understanding something about building package in general.

I got error while compiling ElmerGUI. I did build Open MPI before Elmer. But Elmer does not seems to find Open MPI.

 65%] Building Fortran object fem/src/CMakeFiles/elmersolver.dir/TimeIntegrate.F90.o
 65%] Building Fortran object fem/src/CMakeFiles/elmersolver.dir/ListMatrix.F90.o
 65%] Building Fortran object fem/src/CMakeFiles/elmersolver.dir/IterativeMethods.F90.o
 65%] Linking CXX executable ElmerGUI
 65%] Building Fortran object fem/src/CMakeFiles/elmersolver.dir/IterSolve.F90.o
/usr/lib/gcc/x86_64-unknown-linux-gnu/10.2.0/../../../../x86_64-unknown-linux-gnu/bin/ld: cannot find -lMPI::MPI_C
 65%] Building Fortran object fem/src/CMakeFiles/elmersolver.dir/SParIterSolver.F90.o
collect2: error: ld returned 1 exit status
make[2]: *** [ElmerGUI/Application/CMakeFiles/ElmerGUI.dir/build.make:1352: ElmerGUI/Application/ElmerGUI] Error 1
make[1]: *** [CMakeFiles/Makefile2:24531: ElmerGUI/Application/CMakeFiles/ElmerGUI.dir/all] Error 2
make[1]: *** Waiting for unfinished jobs....

I can check where and what Open MPI ld is looking for using


ld -IMPI --verbose
ld: mode elf_x86_64 
attempt to open /usr/x86_64-unknown-linux-gnu/lib64/libMPI.so failed 
attempt to open /usr/x86_64-unknown-linux-gnu/lib64/libMPI.a failed 
attempt to open /usr/lib/x86_64-linux-gnu/libMPI.so failed 
attempt to open /usr/lib/x86_64-linux-gnu/libMPI.a failed 
attempt to open /usr/lib/libMPI.so failed 
attempt to open /usr/lib/libMPI.a failed 
attempt to open /usr/x86_64-unknown-linux-gnu/lib/libMPI.so failed 
attempt to open /usr/x86_64-unknown-linux-gnu/lib/libMPI.a failed 
ld: cannot find -lMPI 
attempt to open /usr/x86_64-unknown-linux-gnu/lib64/libMPI.so failed 
attempt to open /usr/x86_64-unknown-linux-gnu/lib64/MPI.a failed 
attempt to open /usr/lib/x86_64-linux-gnu/libMPI.so failed 
attempt to open /usr/lib/x86_64-linux-gnu/MPI.a failed 
attempt to open /usr/lib/libMPI.so failed 
attempt to open /usr/lib/MPI.a failed 
attempt to open /usr/x86_64-unknown-linux-gnu/lib/libMPI.so failed 
attempt to open /usr/x86_64-unknown-linux-gnu/lib/MPI.a failed 
Error: module test: Child process exited with code 1

Is it normal for ld to not find Open MPI in /usr because in case of Flatpak, it is installed in /app

So I use,

ld -L/app/lib -lMPI --verbose
attempt to open /app/lib/libMPI.so succeeded 
/app/lib/libMPI.so
bla bla

which it does find Open MPI.

But with


ld -L/app/lib -lMPI::MPI_C --verbose
ld: mode elf_x86_64 
attempt to open /app/lib/libMPI::MPI_C.so failed 
attempt to open /app/lib/libMPI::MPI_C.a failed 
attempt to open /usr/x86_64-unknown-linux-gnu/lib64/libMPI::MPI_C.so failed 
attempt to open /usr/x86_64-unknown-linux-gnu/lib64/libMPI::MPI_C.a failed 
attempt to open /usr/lib/x86_64-linux-gnu/libMPI::MPI_C.so failed 
attempt to open /usr/lib/x86_64-linux-gnu/libMPI::MPI_C.a failed 
attempt to open /usr/lib/libMPI::MPI_C.so failed 
attempt to open /usr/lib/libMPI::MPI_C.a failed 
attempt to open /usr/x86_64-unknown-linux-gnu/lib/libMPI::MPI_C.so failed 
attempt to open /usr/x86_64-unknown-linux-gnu/lib/libMPI::MPI_C.a failed 
ld: cannot find -lMPI::MPI_C 
attempt to open /app/lib/libMPI::MPI_C.so failed 
attempt to open /app/lib/MPI::MPI_C.a failed 
attempt to open /usr/x86_64-unknown-linux-gnu/lib64/libMPI::MPI_C.so failed 
attempt to open /usr/x86_64-unknown-linux-gnu/lib64/MPI::MPI_C.a failed 
attempt to open /usr/lib/x86_64-linux-gnu/libMPI::MPI_C.so failed 
attempt to open /usr/lib/x86_64-linux-gnu/MPI::MPI_C.a failed 
attempt to open /usr/lib/libMPI::MPI_C.so failed 
attempt to open /usr/lib/MPI::MPI_C.a failed 
attempt to open /usr/x86_64-unknown-linux-gnu/lib/libMPI::MPI_C.so failed 
attempt to open /usr/x86_64-unknown-linux-gnu/lib/MPI::MPI_C.a failed 
Error: module test: Child process exited with code 1

Failed, so…

I would like to know what the part “::MPI_C” mean. Thanks.

2

https://github.com/ResearchComputing/Documentation/blob/master/docs/programming/MPI-C.md

IMHO you need MPI for C and C++ being installed - not only Fortran part.

3

Hi,
Thanks for reply, I am not sure what am I missing. Elmer have OpenMP and MPI flag, but is it referring to mpich or OpenMPI?

4

I pass this flags to Open MPI, still same error.

       --prefix=/app
       --bindir=/app/bin
       --datadir=/app/share
       --includedir=/app/include
       --libdir=/app/lib
       --enable-mpi-fortran=all
       --enable-mpi-cxx
       --disable-static
       --enable-builtin-atomics
       --enable-mpi-thread-multiple
       --with-libmpi-name=MPI
5

https://software.opensuse.org/package/elmerfem
https://software.opensuse.org/package/elmerfem-ElmerGUI

Openmpi packages are available in openSUSE (but rather old).

6

Thanks for the help, but I still can’t figured it out. I will ask around.