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.


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

  • 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.
  • 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 C++11/14.
  • 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.
  • Praveen Velliengiri, Jean-Loup Tastet, Michael Levine, Aalekh Nigam, HadrienG2, Prayag Verma, 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, and Matthew Anderson who contributed to the general improvement of HPX

In addition to the people who worked directly with HPX development we would like to acknowledge the NSF, DoE, DARPA, Center for Computation and Technology (CCT), Department of Computer Science 3 - Computer Architecture, and Swiss National Supercomputing Centre who fund and support our work. We would also like to thank the following organizations for granting us allocations of their compute resources: LSU HPC, LONI, XSEDE, NERSC, and the Gauss Center for Supercomputing.

HPX is currently funded by the following grants:

  • The National Science Foundation through awards 1240655 (STAR), 1339782 (STORM), and 1737785 (Phylanx). Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.
  • The Department of Energy (DoE) through the awards DE-AC52-06NA25396 (FLeCSI) and DE-NA0003525 (Resilience). Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof.
  • The Defense Technical Information Center (DTIC) under contract FA8075-14-D-0002/0007. Neither the United States Government nor any agency thereof, nor any of their employees makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights.
  • The Bavarian Research Foundation (Bayerische Forschungsstfitung) through the grant AZ-987-11.
  • The European Commission’s Horizon 2020 programme through the grant H2020-EU.1.2.2. 671603 (AllScale).