Problem compiling distributed memory code (MPI-MPICH)

Accelerated Computing HPC Compilers Legacy PGI Compilers
1

Hi everybody!

I’m trying to compile the model WRF-CHEM model using the PGI compiler and the dmpar option (i.e.: distributed memory option using mpich). I’ve already installed MPICH following the PGI tutorial, and set the environmental variable MPI_ROOT pointing to the MPICH installation directory.

The problem is that the software does not compile correctly complaining that:

pgf90 -w -Mfree -byteswapio   -c  -I/home/modelstation/pgnetcdf/include -I../ioapi_share diffwrf.f
diffwrf io_netcdf is being built now. 
/usr/bin/ld: cannot find -lmpi
make[2]: [diffwrf] Error 2 (ignored)

What is -lmpi? is it a compiler flag? A header to include? In the MPICH folder I cannot find any file with that string in the name.

Sorry for the probably stupid question, I’m quite new at parallel computing.

Thanks in advance for all your help!

2

Hi AZaldei,

What is -lmpi?

“-l” is a compiler/linker flag stating the “libname.a” library should be linked with the user’s compiled code.

/usr/bin/ld: cannot find -lmpi

The linker can find where “libmpi.a” is located. You’re options are to use the “-L” to tell the linker the directory where this library is located, or use the “mpif90” driver instead of “pgf90”. “mpif90” is a wrapper which will automatically add the necessary MPI libraries.

If you are using the prebuilt MPICH libraries that we ship with the compilers, a third option would be to add the “-Mmpi=mpich” flag. This flag will set the appropriate “-L” and “-l” linker flags.

Hope this helps,
Mat

3

Thanks, Mat that was very helpful!

I was able to solve the problem following your suggestions!