Skip to navigation Skip to content
Careers | Phone Book | A - Z Index
Computer Languages & Systems Software

Damian Rouson

20170722 103 3 orig
Damian Rouson
Computer Languages and Systems Software Group
Lawrence Berkeley National Laboratory

Damian Rouson is the Group Lead for the Computer Languages and Systems Software (CLaSS) Group at Berkeley Lab. He is a mechanical engineer with experience in simulating turbulent flows in multiphase, quantum, and magnetohydrodynamic media. He leads the development of the OpenCoarrays parallel runtime library and the Morfeus partial differential equation solver framework. His work at Berkeley Lab involves researching ways to accelerate predictions of climate change's regional impacts, teaching UPC++, and contributing to the LLVM flang Fortran compiler. 

He co-authored the textbook Scientific Software Design: The Object-Oriented Way (Cambridge University Press, 2011) and has taught related university courses and tutorials on Fortran 2018 and agile software development. He is an alternate member of the Fortran standards committee. He has held academic staff and faculty positions at the City University of New York, the University of Maryland, the University of Cyprus, the University of Bergen, and Stanford University.  He has held technical staff and leadership positions at the U.S. Naval Research Laboratory and Sandia National Laboratories. He received a 2003-'04 NASA Summer Faculty Fellowship and a 2020-'21 Department of Energy Better Scientific Software Fellowship. He has been a (co-)principal investigator on research grants and research software engineering contracts funded by the National Institute of Standards and Technology, the National Science Foundation, the Office of Naval Research, the U.S. Nuclear Regulatory Commission and the National Aeronautics and Space Administration.

He founded Archaeologic Inc. and Sourcery Institute.  He holds a B.S. from Howard University and a M.S. and Ph.D. from Stanford University, all in mechanical engineering. He is also a licensed Professional Engineer (P.E.) in the State of California.

Dr. Rouson's Curriculum Vitae (PDF)

Recent Publications

Conference Papers

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), Dallas, Texas, USA, IEEE, November 2022, doi: 10.25344/S4459B

This paper provides an introduction to the CoArray Fortran Framework of Efficient Interfaces to Network Environments (Caffeine), a parallel runtime library built atop the GASNet-EX exascale networking library. Caffeine leverages several non-parallel Fortran features to write type- and rank-agnostic interfaces and corresponding procedure definitions that support parallel Fortran 2018 features, including communication, collective operations, and related services. One major goal is to develop a runtime library that can eventually be considered for adoption by LLVM Flang, enabling that compiler to support the parallel features of Fortran. The paper describes the motivations behind Caffeine's design and implementation decisions, details the current state of Caffeine's development, and previews future work. We explain how the design and implementation offer benefits related to software sustainability by lowering the barrier to user contributions, reducing complexity through the use of Fortran 2018 C-interoperability features, and high performance through the use of a lightweight communication substrate.


Katherine A. Yelick, Amir Kamil, Damian Rouson, Dan Bonachea, Paul H. Hargrove, UPC++: An Asynchronous RMA/RPC Library for Distributed C++ Applications (SC21), Tutorial at the International Conference for High Performance Computing, Networking, Storage, and Analysis (SC21), November 15, 2021,

UPC++ is a C++ library supporting Partitioned Global Address Space (PGAS) programming. UPC++ offers low-overhead one-sided Remote Memory Access (RMA) and Remote Procedure Calls (RPC), along with future/promise-based asynchrony to express dependencies between computation and asynchronous data movement. UPC++ supports simple/regular data structures as well as more elaborate distributed applications where communication is fine-grained and/or irregular. UPC++ provides a uniform abstraction for one-sided RMA between host and GPU/accelerator memories anywhere in the system. UPC++'s support for aggressive asynchrony enables applications to effectively overlap communication and reduce latency stalls, while the underlying GASNet-EX communication library delivers efficient low-overhead RMA/RPC on HPC networks.

This tutorial introduces UPC++, covering the memory and execution models and basic algorithm implementations. Participants gain hands-on experience incorporating UPC++ features into application proxy examples. We examine a few UPC++ applications with irregular communication (metagenomic assembler and COVID-19 simulation) and describe how they utilize UPC++ to optimize communication performance.


Katherine Rasmussen, Damian Rouson, Naje George, Dan Bonachea, Hussain Kadhem, Brian Friesen, "Agile Acceleration of LLVM Flang Support for Fortran 2018 Parallel Programming", Research Poster at the International Conference for High Performance Computing, Networking, Storage, and Analysis (SC22), November 2022, doi: 10.25344/S4CP4S

The LLVM Flang compiler ("Flang") is currently Fortran 95 compliant, and the frontend can parse Fortran 2018. However, Flang does not have a comprehensive 2018 test suite and does not fully implement the static semantics of the 2018 standard. We are investigating whether agile software development techniques, such as pair programming and test-driven development (TDD), can help Flang to rapidly progress to Fortran 2018 compliance. Because of the paramount importance of parallelism in high-performance computing, we are focusing on Fortran’s parallel features, commonly denoted “Coarray Fortran.” We are developing what we believe are the first exhaustive, open-source tests for the static semantics of Fortran 2018 parallel features, and contributing them to the LLVM project. A related effort involves writing runtime tests for parallel 2018 features and supporting those tests by developing a new parallel runtime library: the CoArray Fortran Framework of Efficient Interfaces to Network Environments (Caffeine).

Paul H. Hargrove, Dan Bonachea, Amir Kamil, Colin A. MacLean, Damian Rouson, Daniel Waters, "UPC++ and GASNet: PGAS Support for Exascale Apps and Runtimes (ECP'22)", Poster at Exascale Computing Project (ECP) Annual Meeting 2022, May 5, 2022,

We present UPC++ and GASNet-EX, distributed libraries which together enable one-sided, lightweight communication such as arises in irregular applications, libraries and frameworks running on exascale systems.

UPC++ is a C++ PGAS library, featuring APIs for Remote Procedure Call (RPC) and for Remote Memory Access (RMA) to host and GPU memories.  The combination of these two features yields performant, scalable solutions to problems of interest within ECP.

GASNet-EX is PGAS communication middleware, providing the foundation for UPC++ and Legion, plus numerous non-ECP clients.  GASNet-EX RMA interfaces match or exceed the performance of MPI-RMA across a variety of pre-exascale systems.