Caffeine

CoArray Fortran Framework of Efficient Interfaces to Network Environments

Caffeine is a parallel runtime library that aims to support Fortran compilers with a programming-model-agnostic application interface to various communication libraries. Current work is on supporting the Parallel Runtime Interface for Fortran (PRIF) with the GASNet-EX exascale-ready networking middleware. Future plans include support for an alternative Message Passing Interface (MPI) back end.

Prerequisites

Build prerequisites

The install.sh script uses the following packages:

• Fortran and C compilers
• GASNet-EX exascale networking middleware
• Fortran package manager fpm
• pkg-config
• realpath
• make

The script will invoke these if present in a user's PATH. If not present, the script will ask permission to use Homebrew to install the relevant package.

Caffeine leverages the following non-parallel features of Fortran to simplify the writing of a portable, compact runtime-library that supports Fortran's parallel features:

Feature	Introduced in
The iso_c_binding module	Fortran 2003
The contiguous attribute	Fortran 2008
Submodule support [1]	Fortran 2008
do concurrent [2]	Fortran 2008
The ISO_Fortran_binding.h C header file	Fortran 2018
Assumed-type dummy arguments: type(*)	Fortran 2018
Assumed-rank dummy arguments: array(..)	Fortran 2018

[1] This feature simplifies development but is not essential to the package

[2] This feature is used to support only co_reduce and might become optional in a future release.

Download, build, and run an example

git clone https://github.com/BerkeleyLab/caffeine.git
cd caffeine
./install.sh
export GASNET_PSHM_NODES=8
FC=<Fortran-compiler-path> CC=<C-compiler-path> CXX=<C++-compiler-path> ./build/run-fpm.sh run --example hello

Run tests

./build/run-fpm.sh test

Implementation Status

For details on the PRIF features that are implemented, please see the Implementation Status doc.

Publications

Citing Caffeine? Please use the following publication:

Damian Rouson, Dan Bonachea.
"Caffeine: CoArray Fortran Framework of Efficient Interfaces to Network Environments",
Proceedings of the Eighth Annual Workshop on the LLVM Compiler Infrastructure in HPC (LLVM-HPC2022), November 2022.
Paper: https://doi.org/10.25344/S4459B
Talk Slides

Caffeine is an implementation of the Parallel Runtime Interface for Fortran (PRIF):

Dan Bonachea, Katherine Rasmussen, Brad Richardson, Damian Rouson.
"Parallel Runtime Interface for Fortran (PRIF) Specification, Revision 0.4",
Lawrence Berkeley National Laboratory Technical Report (LBNL-2001604), July 2024.
https://doi.org/10.25344/S4WG64

Documentation

One of our continuous integration (CI) scripts generates up-to-date Caffeine documentation using ford. The CI script also deploys the generated documentation to the our GitHub Pages site. Alternatively, generate HTML documentation locally using ford as follows:

ford doc-generator.md

Open doc/html/index.html in a web browser.

Funding

The Computer Languages and Systems Software (CLaSS) Group at Berkeley Lab has developed Caffeine development on funding from the Exascale Computing Project (ECP) and the Stewardship for Programming Systems and Tools (S4PST) project.

License

See LICENSE.txt for usage terms and conditions.