Issues with Compiling MPI Program

[Bernardo Pacini]

Hello, I am trying to update my code wrapped in f90wrap to be MPI parallel instead of OpenMP. From your paper and linked code packages it seems this is possible, but I am struggling to get it to work.

Following the f2py documentation, I am trying to wrap the example code:

! file: helloworld.f90
subroutine sayhello(comm)
  use mpi
  implicit none
  integer :: comm, rank, size, ierr
  call MPI_Comm_size(comm, size, ierr)
  call MPI_Comm_rank(comm, rank, ierr)
  print *, 'Hello, World! I am process ',rank,' of ',size,'.'
end subroutine sayhello

It can be called from Python with:

from mpi4py import MPI
import helloworld
fcomm = MPI.COMM_WORLD.py2f()
helloworld.sayhello(fcomm)

For f2py, this compiles and runs using the command:

f2py -c --f90exec=mpif90 helloworld.f90 -m helloworld

With f90wrap, I tried to use the commands:

f90wrap -m test helloworld.f90 -P -v
f2py-f90wrap --fcompiler=mpif90 --build-dir . -c -m _test -L. -lsrc f90wrap*.f90 

But it results in the error:

.
.
.
running build_ext
customize UnixCCompiler
customize UnixCCompiler using build_ext
don't know how to compile Fortran code on platform 'posix' with 'ompi_fc' compiler. Supported compilers are: gnu,gnu95,compaq,intel,intelv,intele,intelev,intelvem,intelem,none,nag,nagfor,pg,flang,ibm,sun,nv,lahey,g95,mips,hpux,pathf95,fujitsu,absoft,vast)
warning: build_ext: f77_compiler=mpif90 is not available.

building '_test' extension
error: extension '_test' has Fortran sources but no Fortran compiler found
.
.

Do you have any guidance or instructions on how to compile this code correctly?

Thanks in advance!

[James Kermode]

Looks like f2py can't find your MPI Fortran compiler. Try f2py-f90wrap -c --help-fcompiler to see what is auto-detected, and then try setting the F90 environment variable to the correct compiler, or pass additional options to f2py-f90wrap.

[James Kermode]

Maybe you need

f2py-f90wrap --build-dir . -c --f90exec=mpif90 -m _test -L. -lsrc f90wrap*.f90 

to be equivalent to your working f2py example? Note that f2py-f90wrap is only a very thin wrapper over f2py, so it shouldn't change how compiler arguments are handled.

[Bernardo Pacini]

Thank you for the guidance! As you suggest, I ended up having it work with the following call:

f90wrap -m $(PYTHON_MODN) $(wrap_files) --only $(wrap_subroutines) -k $(KIND_MAP) -P -v --py-max-line-length 120
f2py-f90wrap --f90exec=mpif90 --build-dir . -c -m _${PYTHON_MODN} -L. -lsrc f90wrap*.f90 $(INCLUDES) -lgfortran

This works without issue on Ubuntu 20.04, but on Mac I get the error:

ld: file not found: /System/Library/Frameworks/Foundation.framework/Versions/C/Foundation for architecture x86_64
collect2: error: ld returned 1 exit status

This may be due to my environment though, I have not been keeping up to date with the latest Mac changes.