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Getting Started
===============
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* [The caf compiler wrapper]
* [A sample basic workflow]
* [An advanced workflow]
The caf compiler wrapper
--------------------------
The preferred method for compiling a CAF program is by invoking the `caf` bash script
that the OpenCoarrays CMake scripts install in the `bin` subdirectory of the installation
path. This is an experimental script with limited but useful capabilities that will
grow over time. Please submit bug reports and feature requests via our [Issues] page.
The `caf` script liberates the source code and workflow from explicit dependence on the
underlying compiler and communication library by passing the unmodified source code to
the compiler with the necessary arguments for building a parallel Fortran 2018 program,
embedding the paths to OpenCoarrays libraries (e.g., `libcaf_mpi.a`) installed
in the `lib` subdirectory of the OpenCoarrays installation path.
A sample basic workflow
-----------------------
The following program listing, compilation, and execution workflow exemplify
the use of OpenCoarrays with GCC in a Linux bash shell with the `bin`
directory of the chosen installation path in the user's `PATH` environment variable:
```fortran
$ cat tally.f90
program main
use iso_c_binding, only : c_int
use iso_fortran_env, only : error_unit
implicit none
integer(c_int) :: tally
tally = this_image() ! this image's contribution
call co_sum(tally)
verify: block
integer(c_int) :: image
if (tally/=sum([(image,image=1,num_images())])) then
write(error_unit,'(a,i5)') "Incorrect tally on image ",this_image()
error stop
end if
end block verify
! Wait for all images to pass the test
sync all
if (this_image()==1) print *,"Test passed"
end program
$ caf tally.f90 -o tally
$ cafrun -np 4 ./tally
Test passed
```
where "4" is the number of images to be launched at program start-up.
An advanced workflow
--------------------
If you prefer to invoke the compiler directly, first run `caf` and `cafrun` with the `--show` flag
to see the proper linking and file includes. For example, on a macOS system where OpenCoarrays
was installed via the [homebrew] package manager, the following results:
```bash
$ caf --show
/usr/local/bin/gfortran -I/usr/local/Cellar/opencoarrays/2.2.0/include/OpenCoarrays-2.2.0_GNU-8.2.0 -fcoarray=lib -Wl,-flat_namespace -Wl,-commons,use_dylibs -L/usr/local/Cellar/libevent/2.1.8/lib -L/usr/local/Cellar/open-mpi/3.1.1/lib ${@} /usr/local/Cellar/opencoarrays/2.2.0/lib/libcaf_mpi.a /usr/local/lib/libmpi_usempif08.dylib /usr/local/lib/libmpi_usempi_ignore_tkr.dylib /usr/local/lib/libmpi_mpifh.dylib /usr/local/lib/libmpi.dylib
$ cafrun --show
/usr/local/bin/mpiexec -n <number_of_images> /path/to/coarray_Fortran_program [arg4 [arg5 [...]]]
```
---
[](https://github.com/sourceryinstitute/OpenCoarrays/fork)
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[](https://github.com/sourceryinstitute/OpenCoarrays)
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[Hyperlinks]:#
[The caf compiler wrapper]: #the-caf-compiler-wrapper
[A sample basic workflow]: #a-sample-basic-workflow
[An advanced workflow]: #an-advanced-workflow
[Sourcery Store]: http://www.sourceryinstitute.org/store
[Issues]: https://github.com/sourceryinstitute/OpenCoarrays/issues
[opencoarrays module]: ./src/extensions/opencoarrays.F90
[GCC]: http://gcc.gnu.org
[TS 18508]: http://isotc.iso.org/livelink/livelink?func=ll&objId=17181227&objAction=Open
[The caf compiler wrapper]: #the-caf-compiler-wrapper
[The cafrun program launcher]: #the-cafrun-program-launcher
[pdf img]: https://img.shields.io/badge/PDF-GETTING_STARTED.md-6C2DC7.svg?style=flat-square "Download as PDF"
[homebrew]: https://brew.sh
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