On Sun, Apr 8, 2018 at 8:56 PM, Damian Rouson <dam...@sourceryinstitute.org> wrote: > On April 4, 2018 at 1:12:25 AM, Richard Biener > (richard.guent...@gmail.com(mailto:richard.guent...@gmail.com)) wrote: > >> In that case user programs compiled with -fcoarray=lib are but gfortran >> or libgfortran itself is not linked against OpenCoarrays? > > Yes. OpenCoarrays produces the parallel runtime library libcaf_mpi using MPI. > >> So if we consider OpenCoarrays part of the gfortran runtime then >> it makes sense to build it in-tree… > > Yes. Many gfortran users and developers who will be glad to see this both > because it enables the Fortran 2008/2018 parallel features and because it > facilitates building related tests. > >> ... but building an mpi library in-tree might not? > > OpenCoarrays requires an underlying parallel programming model. MPI is the > default model because it provides the broadest coverage of the required > features. OpenCoarrays also offers alternatives to MPI, but those are > experimental and support a more restricted subset of Fortran 2008/2018. > >> I'm still lacking an idea of what it takes to enable coarrays with gfortran > > We will mimic the OpenCoarrays build system, which installs “caf" and > “cafrun" scripts analogous to MPI's "mpifort" and “mpirun,” respectively. > These are used to compile and launch parallel programs: > > $ cat hello.f90 > print *,”Hello from image “,this_image(),” of “,num_images() > end > $ caf hello.f90 > $ cafrun -n 4 ./a.out > Hello from image 2 of 4 > Hello from image 1 of 4 > Hello from image 4 of 4 > Hello from image 3 of 4
I see. So it's more like OpenCoarrays is in control of everything rather than GCC... >> since install.texi doesn't talk about this at all, neither in the >> prerequesites >> section nor in a fortran/coarray specific section. > > If there are guidelines for modifying install.texi and invoke.texi, please > send a link. It appears install.texi is written in raw TeX. I use LaTeX > regularly but haven’t touched TeX in decades. I’ll give it a shot. I also > don’t understand how those files are used There are no guidelines - simply follow surrounding code. Note this is texinfo, not tex. We generate man pages, html documentation and pdf docs from these sources. See for example https://gcc.gnu.org/install/ >> In fact the only thing I find is in invoke.texi which says >> >> @item -fcoarray=@var{} >> @opindex @code{fcoarray} >> ... >> @item @samp{lib} >> Library-based coarray parallelization; a suitable GNU Fortran coarray >> library needs to be linked. >> @end table >> >> which suggests linking to the coarray library doesn't happen automatically >> but the user is supposed to link a suitable library? > > caf invokes gfortran and links against libcaf_mpi and the MPI libraries. The > OpenCoarrays build system customizes caf to ensure a consistent tool chain > (e.g., ensuring the employed MPI was built by the employed compiler). This > allows for reusing one gfortran installation with multiple parallel > programming models. > >> I'd love to "enable" coarray support for openSUSE but as said I have a hard >> time assessing what I'd need to do here. > > Until we figure out how to get the GCC build system to build MPICH and > OpenCoarrays, enabling coarray support requires downloading and building > MPICH and OpenCoarrays separately. Please see the instructions for GCC > developers: > https://github.com/sourceryinstitute/opencoarrays/blob/master/INSTALL. Thanks - I expected to find sth in the GCC manual or on the GCC wiki ;) I'll have a look when I have some spare cycles. > Thanks for your feedback. I’m hopeful that your advice will be helpful for > Daniel in figuring out how to modify the GCC build system. As said I'm still not convinced building those libraries in-tree is the best way forward. I won't stand in the way of making that work though. Richard. > Damian > >
