How to compile MPI with gcc?

Question

Does anyone know if it is possible to compile MPI with gcc?. I need to use gcc, no mpicc.

Answer 1

mpicc -compile_info for MPICH.

Answer 2

mpicc is just a wrapper around certain set of compilers. Most implementations have their mpicc wrappers understand a special option like -showme (Open MPI) or -show (Open MPI, MPICH and derivates) that gives the full list of options that the wrapper passes on to the backend compiler.

For example, in Open MPI, wrappers are C++ programs that read plain text configuration files and build command line options that are further passed on to the compiler. mpicc -showme shows the full list of such options:

$ mpicc -showme icc -I/opt/MPI/openmpi-1.5.3/linux/intel/include -I/opt/MPI/openmpi-1.5.3/linux/intel/include/openmpi -fexceptions -pthread -I/opt/MPI/openmpi-1.5.3/linux/intel/lib -Wl,-rpath,/opt/MPI/openmpi-1.5.3/linux/intel/lib -I/opt/MPI/openmpi-1.5.3/linux/intel/lib -L/opt/MPI/openmpi-1.5.3/linux/intel/lib -lmpi -ldl -Wl,--export-dynamic -lnsl -lutil 

(it's really a single line that I have split here to improve readability)

It that particular case Intel C Compiler icc is used as the backend compiler but we also have variants that use GCC. You can also get the list of options needed for the comple phase (usually known as CFLAGS) with mpicc -showme:compile:

$ mpicc -showme:compile -I/opt/MPI/openmpi-1.5.3/linux/intel/include -I/opt/MPI/openmpi-1.5.3/linux/intel/include/openmpi -fexceptions -pthread -I/opt/MPI/openmpi-1.5.3/linux/intel/lib 

as well as the list of options that you need to pass to the linker (known as LDFLAGS) with mpicc -showme:link:

$ mpicc -showme:link -fexceptions -pthread -I/opt/MPI/openmpi-1.5.3/linux/intel/lib -Wl,-rpath,/opt/MPI/openmpi-1.5.3/linux/intel/lib -I/opt/MPI/openmpi-1.5.3/linux/intel/lib -L/opt/MPI/openmpi-1.5.3/linux/intel/lib -lmpi -ldl -Wl,--export-dynamic -lnsl -lutil 

These could be used, e.g. in a Makefile, like this:

... CFLAGS += $(shell mpicc -showme:compile) LDFLAGS += $(shell mpicc -showme:link) ... 

As far as I know -showme:compile and -showme:link are specific to Open MPI and other implementations only give the full list of options when called with -show.

I still think it's better to use mpicc directly because if it happens that something in the MPI setup is changed, it will be immediately reflected in the wrapper while you would have to change your build script / Makefile manually (unless you use -showme:compile and -showme:link to obtain the options automatically).