Install opencoarrays with Homebrew, MacPorts, Nix

Project links

• Homepage
• Repository
• Upstream docs
• Package manager page

Commands and aliases

• caf
• cafrun

Project history

Coarrays entered standard Fortran as a PGAS-style parallel programming model in Fortran 2008, but free compiler support depended on a runtime that could map language-level image communication onto existing communication libraries. The OpenCoarrays project filled that role for GCC by providing an ABI between gfortran and a backend such as MPI.

A 2014 PGAS workshop paper described OpenCoarrays as a new project offering open-source transport layers for coarray Fortran compilers, including MPI and GASNet-based approaches. The 1.0.0 release was announced in July 2015 with the runtime library, compiler wrapper, and launcher, and the announcement noted that GNU Fortran 5.1.0 used OpenCoarrays to support most Fortran 2008 coarray features and some proposed Fortran 2015 TS 18508 features.

Adoption history

The project's most important adoption path was through GCC: the OpenCoarrays README says the OpenCoarrays ABI was adopted by gfortran in GCC 5.1.0. That made OpenCoarrays part of the practical route for package managers and HPC users who wanted Coarray Fortran through a free compiler toolchain rather than a vendor compiler.

Packaging spread into Unix package systems such as Homebrew, MacPorts, FreeBSD ports, Nix, and Linux distributions, usually as a science or parallel-computing package. MacPorts summarizes the project as an ABI for gfortran support of coarrays and other Fortran 2018 parallel programming features.

How it is used

Developers compile coarray programs through `caf`, which wraps the selected Fortran compiler and links the OpenCoarrays runtime consistently with the MPI stack used at build time. They launch multi-image programs with `cafrun`, avoiding direct MPI command-line details in routine Coarray Fortran workflows.

OpenCoarrays is especially relevant for scientific and HPC Fortran users who want to experiment with standard-language parallelism, compare coarray code with MPI implementations, or package Fortran applications that rely on gfortran's coarray support.

Why package nerds care

OpenCoarrays is a small package with an outsized toolchain role: it is not just another Fortran library, but the runtime side of a compiler feature. That makes ABI compatibility, MPI selection, compiler version, and wrapper behavior more important than they are for ordinary numerical libraries.

Timeline

• 2014: OpenCoarrays was described in PGAS workshop material as a new open-source transport-layer project for coarray Fortran compilers.
• 2015: GCC 5.1.0 adopted the OpenCoarrays ABI for gfortran coarray support, and OpenCoarrays 1.0.0 was announced with `libcaf_mpi`, `caf`, and `cafrun`.
• 2022: Caffeine work at Lawrence Berkeley National Laboratory pointed toward a compiler-independent Fortran runtime direction built on GASNet-EX, related to the longer-term evolution beyond the MPI-focused OpenCoarrays path.

Related projects

• OpenCoarrays sits alongside GCC/gfortran, MPI implementations, GASNet-EX, Caffeine, and the broader Fortran 2008/2018/2023 parallel-language standards work.

Sources

• https://github.com/berkeleylab/caffeine
• https://github.com/sourceryinstitute/OpenCoarrays/blob/main/README.md
• https://groups.google.com/g/comp.lang.fortran/c/Dm-KY5wivQk
• https://nic.uoregon.edu/pgas14/papers/pgas14_submission_7.pdf
• https://ports.macports.org/port/OpenCoarrays/summary/
• https://www.opencoarrays.org/