The STE||AR Group (pronounced as stellar) stands for “Systems Technology, Emergent Parallelism, and Algorithm Research”. We are an international group of faculty, researchers, and students working at various institutions around the world. The goal of the STE||AR Group is to promote the development of scalable parallel applications by providing a community for ideas, a framework for collaboration, and a platform for communicating these concepts to the broader community.

Our work is focused on building technologies for scalable parallel applications. HPX, our general purpose C++ runtime system for parallel and distributed applications, is no exception. We use HPX for a broad range of scientific applications, helping scientists and developers to write code which scales better and shows better performance compared to more conventional programming models such as MPI.

HPX is based on ParalleX which is a new (and still experimental) parallel execution model aiming to overcome the limitations imposed by the current hardware and the techniques we use to write applications today. Our group focuses on two types of applications - those requiring excellent strong scaling, allowing for a dramatic reduction of execution time for fixed workloads and those needing highest level of sustained performance through massive parallelism. These applications are presently unable (through conventional practices) to effectively exploit a relatively small number of cores in a multi-core system. By extension, these application will not be able to exploit high-end exascale computing systems which are likely to employ hundreds of millions of such cores by the end of this decade.

Critical bottlenecks to the effective use of new generation high performance computing (HPC) systems include:

  • Starvation: due to lack of usable application parallelism and means of managing it,

  • Overhead: reduction to permit strong scalability, improve efficiency, and enable dynamic resource management,

  • Latency: from remote access across system or to local memories,

  • Contention: due to multicore chip I/O pins, memory banks, and system interconnects.

The ParalleX model has been devised to address these challenges by enabling a new computing dynamic through the application of message-driven computation in a global address space context with lightweight synchronization. The work on HPX is centered around implementing the concepts as defined by the ParalleX model. HPX is currently targeted at conventional machines, such as classical Linux based Beowulf clusters and SMP nodes.

We fully understand that the success of HPX (and ParalleX) is very much the result of the work of many people. To see a list of who is contributing see our tables below.

HPX contributors#

Table 183 Contributors#




Hartmut Kaiser

Center for Computation and Technology (CCT), Louisiana State University (LSU)


Thomas Heller

Department of Computer Science 3 - Computer Architecture, Friedrich-Alexander University Erlangen-Nuremberg (FAU)


Agustin Berge


Mikael Simberg

Swiss National Supercomputing Centre


John Biddiscombe

Swiss National Supercomputing Centre


Anton Bikineev

Center for Computation and Technology (CCT), Louisiana State University (LSU)


Martin Stumpf

Department of Computer Science 3 - Computer Architecture, Friedrich-Alexander University Erlangen-Nuremberg (FAU)


Bryce Adelstein Lelbach


Shuangyang Yang

Center for Computation and Technology (CCT), Louisiana State University (LSU)


Jeroen Habraken


Steven Brandt

Center for Computation and Technology (CCT), Louisiana State University (LSU)


Antoine Tran Tan

Paris-Saclay University,


Adrian S. Lemoine



Maciej Brodowicz


Giannis Gonidelis

Center for Computation and Technology (CCT), Louisiana State University (LSU)


Contributors to this document#

Table 184 Documentation authors#




Hartmut Kaiser

Center for Computation and Technology (CCT), Louisiana State University (LSU)


Thomas Heller

Department of Computer Science 3 - Computer Architecture, Friedrich-Alexander University Erlangen-Nuremberg (FAU)


Bryce Adelstein Lelbach


Vinay C Amatya

Center for Computation and Technology (CCT), Louisiana State University (LSU)


Steven Brandt

Center for Computation and Technology (CCT), Louisiana State University (LSU)


Maciej Brodowicz


Adrian S. Lemoine



Rebecca Stobaugh


Dimitra Karatza

Faculty of Electrical Engineering, Mathematics & Computer Science, Delft University of Technology


Bhumit Attarde



Thanks also to the following people who contributed directly or indirectly to the project through discussions, pull requests, documentation patches, etc.

  • Panos Syskakis for benchmarking and optimizing our parallel algorithms.

  • Shreyas Atre, for contributing fixes to our implementation of senders/receivers and extending our coroutines integration with senders/receivers.

  • Alexander Neumann, for contributing fixes to the cmake build system.

  • Dimitra Karatza, for her work on refactoring the documentation and providing a new user-friendly environment during and after Google Season of Docs 2021.

  • Srinivas Yadav, for his work on SIMD support in algorithms before and during Google Summer of Code 2021.

  • Akhil Nair, for his work on adapting algorithms to C++20 before and during Google Summer of Code 2021.

  • Alexander Toktarev, for updating the parallel algorithm customization points to use tag_fallback_invoke for the default implementations.

  • Brice Goglin, for reporting and helping fix issues related to the integration of hwloc in HPX.

  • Giannis Gonidelis, for his work on the ranges adaptation during the Google Summer of Code 2020.

  • Auriane Reverdell (Swiss National Supercomputing Centre), for her tireless work on refactoring our CMake setup and modularizing HPX.

  • Christopher Hinz, for his work on refactoring our CMake setup.

  • Weile Wei, for fixing HPX builds with CUDA on Summit.

  • Severin Strobl, for fixing our CMake setup related to linking and adding new entry points to the HPX runtime.

  • Rebecca Stobaugh, for her major documentation review and contributions during and after the 2019 Google Season of Documentation.

  • Jan Melech, for adding automatic serialization of simple structs.

  • Austin McCartney, for adding concept emulation of the Ranges TS bidirectional and random access iterator concepts.

  • Marco Diers, reporting and fixing issues related PMIx.

  • Maximilian Bremer, for reporting multiple issues and extending the component migration tests.

  • Piotr Mikolajczyk, for his improvements and fixes to the set and count algorithms.

  • Grant Rostig, for reporting several deficiencies on our web pages.

  • Jakub Golinowski, for implementing an HPX backend for OpenCV and in the process improving documentation and reporting issues.

  • Mikael Simberg (Swiss National Supercomputing Centre), for his tireless help cleaning up and maintaining HPX.

  • Tianyi Zhang, for his work on HPXMP.

  • Shahrzad Shirzad, for her contributions related to Phylanx.

  • Christopher Ogle, for his contributions to the parallel algorithms.

  • Surya Priy, for his work with statistic performance counters.

  • Anushi Maheshwari, for her work on random number generation.

  • Bruno Pitrus, for his work with parallel algorithms.

  • Nikunj Gupta, for rewriting the implementation of hpx_main.hpp and for his fixes for tests.

  • Christopher Taylor, for his interest in HPX and the fixes he provided. Chris also contributed support for RISC-V architectures.

  • Shoshana Jakobovits, for her work on the resource partitioner.

  • Denis Blank, who re-wrote our unwrapped function to accept plain values arbitrary containers, and properly deal with nested futures.

  • Ajai V. George, who implemented several of the parallel algorithms.

  • Taeguk Kwon, who worked on implementing parallel algorithms as well as adapting the parallel algorithms to the Ranges TS.

  • Zach Byerly (Louisiana State University (LSU)), who in his work developing applications on top of HPX opened tickets and contributed to the HPX examples.

  • Daniel Estermann, for his work porting HPX to the Raspberry Pi.

  • Alireza Kheirkhahan (Louisiana State University (LSU)), who built and administered our local cluster as well as his work in distributed IO.

  • Abhimanyu Rawat, who worked on stack overflow detection.

  • David Pfander, who improved signal handling in HPX, provided his optimization expertise, and worked on incorporating the Vc vectorization into HPX.

  • Denis Demidov, who contributed his insights with VexCL.

  • Khalid Hasanov, who contributed changes which allowed to run HPX on 64Bit power-pc architectures.

  • Zahra Khatami (Louisiana State University (LSU)), who contributed the prefetching iterators and the persistent auto chunking executor parameters implementation.

  • Marcin Copik, who worked on implementing GPU support for C++AMP and HCC. He also worked on implementing a HCC backend for HPX.Compute.

  • Minh-Khanh Do, who contributed the implementation of several segmented algorithms.

  • Bibek Wagle (Louisiana State University (LSU)), who worked on fixing and analyzing the performance of the parcel coalescing plugin in HPX.

  • Lukas Troska, who reported several problems and contributed various test cases allowing to reproduce the corresponding issues.

  • Andreas Schaefer, who worked on integrating his library (LibGeoDecomp) with HPX. He reported various problems and submitted several patches to fix issues allowing for a better integration with LibGeoDecomp.

  • Satyaki Upadhyay, who contributed several examples to HPX.

  • Brandon Cordes, who contributed several improvements to the inspect tool.

  • Harris Brakmic, who contributed an extensive build system description for building HPX with Visual Studio.

  • Parsa Amini (Louisiana State University (LSU)), who refactored and simplified the implementation of AGAS in HPX and who works on its implementation and optimization.

  • Luis Martinez de Bartolome who implemented a build system extension for HPX integrating it with the Conan C/C++ package manager.

  • Vinay C Amatya (Louisiana State University (LSU)), who contributed to the documentation and provided some of the HPX examples.

  • Kevin Huck and Nick Chaimov (University of Oregon), who contributed the integration of APEX (Autonomic Performance Environment for eXascale) with HPX.

  • Francisco Jose Tapia, who helped with implementing the parallel sort algorithm for HPX.

  • Patrick Diehl, who worked on implementing CUDA support for our companion library targeting GPGPUs (HPXCL).

  • Eric Lemanissier contributed fixes to allow compilation using the MingW toolchain.

  • Nidhi Makhijani who helped cleaning up some enum consistencies in HPX and contributed to the resource manager used in the thread scheduling subsystem. She also worked on HPX in the context of the Google Summer of Code 2015.

  • Larry Xiao, Devang Bacharwar, Marcin Copik, and Konstantin Kronfeldner who worked on HPX in the context of the Google Summer of Code program 2015.

  • Daniel Bourgeois (Center for Computation and Technology (CCT)) who contributed to HPX the implementation of several parallel algorithms (as proposed by N4313).

  • Anuj Sharma and Christopher Bross (Department of Computer Science 3 - Computer Architecture), who worked on HPX in the context of the Google Summer of Code program 2014.

  • Martin Stumpf (Department of Computer Science 3 - Computer Architecture), who rebuilt our contiguous testing infrastructure (see the HPX Buildbot Website). Martin is also working on HPXCL (mainly all work related to OpenCL) and implementing an HPX backend for POCL, a portable computing language solution based on OpenCL.

  • Grant Mercer (University of Nevada, Las Vegas), who helped creating many of the parallel algorithms (as proposed by N4313).

  • Damond Howard (Louisiana State University (LSU)), who works on HPXCL (mainly all work related to CUDA).

  • Christoph Junghans (Los Alamos National Lab), who helped making our buildsystem more portable.

  • Antoine Tran Tan (Laboratoire de Recherche en Informatique, Paris), who worked on integrating HPX as a backend for NT2. He also contributed an implementation of an API similar to Fortran co-arrays on top of HPX.

  • John Biddiscombe (Swiss National Supercomputing Centre), who helped with the BlueGene/Q port of HPX, implemented the parallel sort algorithm, and made several other contributions.

  • Erik Schnetter (Perimeter Institute for Theoretical Physics), who greatly helped to make HPX more robust by submitting a large amount of problem reports, feature requests, and made several direct contributions.

  • Mathias Gaunard (Metascale), who contributed several patches to reduce compile time warnings generated while compiling HPX.

  • Andreas Buhr, who helped with improving our documentation, especially by suggesting some fixes for inconsistencies.

  • Patricia Grubel (New Mexico State University), who contributed the description of the different HPX thread scheduler policies and is working on the performance analysis of our thread scheduling subsystem.

  • Lars Viklund, whose wit, passion for testing, and love of odd architectures has been an amazing contribution to our team. He has also contributed platform specific patches for FreeBSD and MSVC12.

  • Agustin Berge, who contributed patches fixing some very nasty hidden template meta-programming issues. He rewrote large parts of the API elements ensuring strict conformance with the C++ ISO Standard.

  • Anton Bikineev for contributing changes to make using boost::lexical_cast safer, he also contributed a thread safety fix to the iostreams module. He also contributed a complete rewrite of the serialization infrastructure replacing Boost.Serialization inside HPX.

  • Pyry Jahkola, who contributed the Mac OS build system and build documentation on how to build HPX using Clang and libc++.

  • Mario Mulansky, who created an HPX backend for his Boost.Odeint library, and who submitted several test cases allowing us to reproduce and fix problems in HPX.

  • Rekha Raj, who contributed changes to the description of the Windows build instructions.

  • Jeremy Kemp how worked on an HPX OpenMP backend and added regression tests.

  • Alex Nagelberg for his work on implementing a C wrapper API for HPX.

  • Chen Guo, helvihartmann, Nicholas Pezolano, and John West who added and improved examples in HPX.

  • Joseph Kleinhenz, Markus Elfring, Kirill Kropivyansky, Alexander Neundorf, Bryant Lam, and Alex Hirsch who improved our CMake.

  • Tapasweni Pathak, Praveen Velliengiri, Jean-Loup Tastet, Michael Levine, Aalekh Nigam, HadrienG2, Prayag Verma, lslada, Alex Myczko, and Avyav Kumar who improved the documentation.

  • Jayesh Badwaik, J. F. Bastien, Christoph Garth, Christopher Hinz, Brandon Kohn, Mario Lang, Maikel Nadolski, pierrele, hendrx, Dekken, woodmeister123, xaguilar, Andrew Kemp, Dylan Stark, Matthew Anderson, Jeremy Wilke, Jiazheng Yuan, CyberDrudge, david8dixon, Maxwell Reeser, Raffaele Solca, Marco Ippolito, Jules Penuchot, Weile Wei, Severin Strobl, Kor de Jong, albestro, Jeff Trull, Yuri Victorovich, and Gregor Daiß who contributed to the general improvement of HPX.

HPX Funding Acknowledgements lists current and past funding sources for HPX. Special thanks to Google Summer of Code and Google Season of Docs for the continuous support they provide which helps us enhance both our code and our documentation.