Version 0.7

Highlights:

1. This release re-implements the nonblocking ALP/GraphBLAS backend by Mastoras
   et al. (GrAPL/IPDPSW '22, TACO '23) on the latest ALP code base. The use of
   the nonblocking backend for some algorithms results in multiple-factor
   speedups versus standard blocking execution as well as versus external
   industry-standard frameworks. This includes Eigen, which, like nonblocking
   ALP/GraphBLAS, perform cross-operation fusion. Simply compile your ALP
   programs using grbcxx -b nonblocking, and enjoy the speedups!

2. We also introduce a new programming interface to the ALP software stack that
   allows vertex-centric programming in addition to programming using
   generalised sparse linear algebra. This new interface, ALP/Pregel,
   translates vertex-centric programs to standard ALP/GraphBLAS primitives
   during compilation, and thus benefits of all automatic optimisations
   included with the ALP software stack.

3. Support for software prefetching during vxm and mxv has been added to
   the reference and reference_omp backends. Since optimal prefetch
   settings and its overall effectiveness relies strongly on 1) the structure
   of the sparse matrices and graphs considered as well as on 2) the algorithms
   used on those data, this new feature is turned off by default. To use it,
   please enable it via include/graphblas/reference/config.hpp and tune the
   there-defined prefetch distances.

4. Finally, this release includes another new backend, the hyperdags backend.
   A program compiled with this backend will, after execution, dump a HyperDAG
   representation of the ALP computations that the program executed.

More detailed changes since v0.6 are noted in the changelog.

This release has been thoroughly tested using various combinations of:

• OS: Fedora 31, CentOS Stream, Ubuntu 20.04 LTS;
• GCC: 8.5.0, 9.3.1, 9.4.0, and 12.2.0;
• MPI: MPICH 3.3.2, MPICH 3.4.2, and OpenMPI 4.1.1;
• Linux kernels: 4.18.0, 5.4.0, and 5.8.18;
• Architectures: x86_64 and ARMv8.2.

Version 0.6

Highlights and changes to the specification:

• Deprecated grb::init and grb::finalize in favour of grb::Launcher.
  Existing code should migrate to using the Launcher as any later release may
  remove the now-deprecated primitives.
• If you wish to rely on ALP/GraphBLAS for more standard sparse linear
  algebra but if you cannot, or do not wish to, adapt your existing sources
  to the C++ ALP/GraphBLAS API, then v0.6 onwards generates libraries that
  implement a subset of the standard C/C++ SparseBLAS and SpBLAS interfaces.
  After installation, these libraries are found in
  • <install path>/lib/sequential/libsparseblas.a (sequential) and
  • <install path>/lib/sequential/libsparseblas_omp.a (shared-memory
    parallel).
    The headers are found in
  • <install path>/include/transition/sparseblas.h and
  • <install path>/include/transition/spblas.h.
• Input iterators passed to grb::buildMatrixUnique that happen to be random
  access will now lead to shared-memory parallel ingestion when using the
  reference_omp or hybrid backends.
• grb::Phase is now only accepted for primitives with non-scalar
  ALP/GraphBLAS output containers.

Algorithms:

• Feature: the CG algorithm has been adapted to work with complex-valued
  matrices making use of the standard std::complex type. A corresponding
  smoke test is added.
• Bugfix: BiCGstab erroneously relied on grb::utils::equals, and could
  (rarely) lead to false orthogonality detection and an unnecessary abort.

Utilities:

• The parser that reads MatrixMarket files, grb::utils::MatrixFileReader, now
  can parse complex values and load Hermitian matrices.
• What constitutes an ALP/GraphBLAS sparse matrix iterator has been formalised
  with a novel type trait, grb::utils::is_alp_matrix_iterator. ALP/GraphBLAS
  matrix output iterators now also adhere to these requirements.
• A grb::utils::is_complex type trait has been added, and is used by the CG
  algorithm so as to not materialise unnecessary buffers and code paths.
• Bugfixes to the grb::utils::equals routine, as well as better
  documentation. A unit test has been added for it.

Testing, development, and documentation:

• Documentation has been adapted to include GitHub for reporting issues.
• Documentation of various ALP/GraphBLAS primitives and concepts have been
  improved.
• Documentation detailing the compiler warning suppressions and their rationale
  have been moved to the code repository at docs/Suppressions.md.
• Add basic CI tests (build, install, and smoke tests) for GitHub.
• More thorough testing of output matrix iterators, input iterators, and of
  grb::buildMatrixUnique.
• The dense_spmv.cpp smoke test did not correctly verify output, and could
  fail for SpMV multiplications that yield very small nonzero values.
• Improvements to various tests and scripts.

Reference and reference_omp backends:

• Bugfix: matrix output iterators failed if all nonzeroes were on the last row
  and no nonzeroes existed anywhere else.
• Bugfix: copying and immediately dereferencing a matrix output iterator led to
  use of uninitialised values.
• Bugfix: grb::foldl with a dense descriptor would accept sparse inputs while
  it should return ILLEGAL. This behaviour, as well as for other error codes,
  are now also (unit) tested for, including with masks and inverted masks.
• Bugfix: grb::set was moved from reference/blas1.hpp to
  reference/io.hpp, but the macros that guard parallelisation were not
  properly updated.
• Bugfix: the OpenMP schedule( static, chunk_size ) has a dynamic (run-time)
  component that was not intended.
• Bugifx: some OpenMP schedule( dynamic, chunk_size ) operate on regular
  loops and should employ a static schedule instead.

BSP1D backend:

• Bugfix: too thorough sanity checking disallowed building dense matrices.
• Bugfix: grb::set on vectors with non-fundamental value types would not
  compile (due to code handling the use_index descriptor).
• Bugfix: grb::clear could leave the vector in an undefined state if it
  immediately followed an operation that left said vector dense.
• Code improvement: PinnedVector constructors now throws exceptions on errors.

All backends:

• Bugfix: an input-masked variant of grb::foldr was missing. These are now
  also added to the unit test suite.
• Bugfix: matrix constructors that throw an exception could segfault on
  destruction.
• Bugfix: use of PinnedVectors that pin sparse or empty vectors could segfault.
• Code improvements: noexcept additions, const-correctness, code style fixes,
  removal of compiler warnings (on some compiler versions), dead code removal,
  improved _DEBUG tracing, additional debug-mode sanity checks, and reduced
  code duplication.