• Complete, mathematically equivalent implementation of the GraphBLAS C API Specification (current specification http://graphblas.org).
• Use of modern, idiomatic C++ for the implementation and provide a testing ground for the GraphBLAS C++ API Specification development.
• Graph algorithm library containing examples of commonly used graph algorithms implemented with the GraphBLAS primitive operations.

This is Version 3.0 of the C++ implementation and is mathematically equivalent to Version 1.3 of the GraphBLAS C API. The API defined by this (v. 3.0) release is not backward compatible with GBTL v. 2.0. See the ChangeLog file for details.

The project also contains example implementations of many common graph algorithms using the C++ API:

• Breadth-first traversal (aka BFS)
  • level BFS
  • parent list BFS
  • batched BFS
• Single-source shortest path (SSSP)
  • Bellman-Ford
  • Filtered Bellman-Ford
  • Delta stepping
• All-pairs shortest path (APSP)
• Centrality measures
  • Vertex Betweenness Centrality (batch variant too)
  • Edge Betweenness Centrality
  • Closeness centrality
• Clustering
  • peer pressure clustering
  • Markov clustering
  • Louvain
• Triangle counting (many variants)
• K-truss enumeration
  • incidence matrix variant
  • adjacency matrix variant
• PageRank
• Maximal Independent Set (MIS)
• Minimum Spanning Tree (MST)
• Maxflow
  • Ford-Fulkerson
• Metrics
  • degree, in and out
  • graph distance
  • radius, diameter
  • vertex eccentricity

Work is underway to port some of the algorithms in LAGraph repository to GBTL.

The file structure and build system support defining multiple different 'backend' implementations (platforms), but only one of these can be configured and compiled at a time. However, if multiple different build directories are used (extending what is shown below), then each can configured for a different platform. The code for each platform can be found in an appropriately named subdirectory of src/graphblas/platforms.

1. 'sequential' platform: this platform is written for a single CPU. It is intended as a reference implementation focusing on correctness, but contains some modest (significant in some cases) performance improvements over previous releases.

2. 'optimized_sequential' platform: this is an experimental platform that is currently under development and is exploring more comprehensive performance improvements (currently only for the mxm operation).

Support for GPUs that was in version 1.0 is currently not available but can be accessed using the git tag: '1.0.0').

1. Cmake is required to build the set of makefiles. It has been successfully built with cmake 3.10.2.

2. A detailed study of which C++ compilers are required has not been carried out. The cmake configuration file is currently setup to require C++17 support. The test and demo programs have been successfully built using the GNU g++ compiler version 9.2.1 with the -std=gnu++1z option.

3. Building the unit tests also requires the "Boost Test Library: The Unit Test Framework."

This project is designed to use cmake to build and use an "out of source" style build to make it easy to clean up. The tests and demos can be built in to a "build" directory in the top-level directory by following these steps:

$ mkdir build
$ cd build
$ cmake [-DPLATFORM=<platform name>] [-DCMAKE_BUILD_TYPE={Release,Debug}] ../src
$ make

The optional PLATFORM argument to cmake specifies which platform-specific source code (also referred to as the backend) should be configured for the build and the value must correspond to a subdirectory in "gbtl/src/graphblas/platforms/" and that subdirectory must have a "backend_include.hpp" file. If this argument is omitted it defaults to configuring the "sequential" platform. The other platform currently available is "optimized_sequential" which is currently under development to improve the performance of various operations.

The optional CMAKE_BUILD_TYPE argument to cmake can be used to build debug or release (using -O3 compiler option) versions of the library. The default is Debug.

The compiler used to build the library can be changed by specifying -DCXX=<pathname_to_compiler> on the cmake commandline as well.

Once cmake is done building the Makefiles, options to make can be used. For example, using "make -i -j8" tries to build every test (ignoring all errors) and uses 8 threads to speed up the build (use a number appropriate for the number of cores/hyperthreads on your system).

There is a convenience script to do all of this from scratch called rebuild.sh that also removes all the old content from a previous build.

For CLion support in the cmake project settings "Build, Execution, Deployment > CMake > Generation path:" set it to "../build" to use the same makefiles as that created by the clean build process so that there aren't two different build trees.

The current library is set up as a header only library. To install this library, copy the graphblas directory, its subdirectories and the specific platform subdirectory (sans the platform's test directories) to a location in your include path.

Documentation can be generated using the Doxygen documentation system. To generate documentation run doxygen from the src directory:

$ cd src
$ doxygen

All documentation is built in the 'docs' subdirectory.

GraphBLAS Template Library (GBTL), Version 3.0 includes and/or can make use of certain third party software ("Third Party Software"). The Third Party Software that is used by GraphBLAS Template Library (GBTL), Version 3.0 is dependent upon your system configuration, but typically includes the software identified below. By using GraphBLAS Template Library (GBTL), Version 3.0, You agree to comply with any and all relevant Third Party Software terms and conditions contained in any such Third Party Software or separate license file distributed with such Third Party Software. The parties who own the Third Party Software ("Third Party Licensors") are intended third party beneficiaries to this License with respect to the terms applicable to their Third Party Software. Third Party Software licenses only apply to the Third Party Software and not any other portion of GraphBLAS Template Library (GBTL), Version 3.0 or GraphBLAS Template Library (GBTL), Version 3.0 as a whole.

This material is based upon work funded and supported by the United States Department of Defense under Contract No. FA8702-15-D-0002 with Carnegie Mellon University for the operation of the Software Engineering Institute, a federally funded research and development center and by the United States Department of Energy under Contract DE-AC05-76RL01830 with Battelle Memorial Institute for the Operation of the Pacific Northwest National Laboratory.

THIS MATERIAL WAS PREPARED AS AN ACCOUNT OF WORK SPONSORED BY AN AGENCY OF THE UNITED STATES GOVERNMENT. NEITHER THE UNITED STATES GOVERNMENT NOR THE UNITED STATES DEPARTMENT OF ENERGY, NOR THE UNITED STATES DEPARTMENT OF DEFENSE, NOR CARNEGIE MELLON UNIVERSITY, NOR BATTELLE, NOR ANY OF THEIR EMPLOYEES, NOR ANY JURISDICTION OR ORGANIZATION THAT HAS COOPERATED IN THE DEVELOPMENT OF THESE MATERIALS, MAKES ANY WARRANTY, EXPRESS OR IMPLIED, OR ASSUMES ANY LEGAL LIABILITY OR RESPONSIBILITY FOR THE ACCURACY, COMPLETENESS, OR USEFULNESS OR ANY INFORMATION, APPARATUS, PRODUCT, SOFTWARE, 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, or Carnegie Mellon University, or Battelle Memorial Institute. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof.

Please see “AUTHORS” file for a list of known contributors.

[DISTRIBUTION STATEMENT A] This material has been approved for public release and unlimited distribution. Please see Copyright notice for non-US Government use and distribution.

This release is an update of:

1. GraphBLAS Template Library (GBTL) (https://github.com/cmu-sei/gbtl/blob/1.0.0/LICENSE) Copyright 2015 Carnegie Mellon University and The Trustees of Indiana. DM17-0037, DM-0002659

2. GraphBLAS Template Library (GBTL) (https://github.com/cmu-sei/gbtl/blob/2.0.0/LICENSE) Copyright 2018 Carnegie Mellon University, Battelle Memorial Institute, and Authors. DM18-0559

DM20-0442