BLIS 0.8.1 now available

[Field Van Zee]

Friends of BLIS,

BLIS 0.8.1 is now available.

This release contains mostly minor updates and bugfixes. However, it does have some noteworthy improvements, including preliminary support for low-precision gemm on the POWER10 microarchitecture, authored by Nicholai Tukanov.

A complete list of improvements present in 0.8.1 follows.

Framework:
- Implemented an automatic reduction in the number of threads when the user requests parallelism via a single number (ie: the automatic way) and (a) that number of threads is prime, and (b) that number exceeds a minimum threshold defined by the macro BLIS_NT_MAX_PRIME, which defaults to 11. If prime numbers are really desired, this feature may be suppressed by defining the macro BLIS_ENABLE_AUTO_PRIME_NUM_THREADS in the appropriate configuration family's bli_family_*.h. (Jeff Diamond)
- Changed default value of BLIS_THREAD_RATIO_M from 2 to 1, which leads to slightly different automatic thread factorizations.
- Enable the 1m method only if the real domain microkernel is not a reference kernel. BLIS now forgoes use of 1m if both the real and complex domain kernels are reference implementations.
- Relocated the general stride handling for gemmsup. This fixed an issue whereby gemm would fail to trigger to conventional code path for cases that use general stride even after gemmsup rejected the problem. (RuQing Xu)
- Disabled AMD's small matrix handling entry points for syrk and trsm due to lack of testing on our side.
- Fixed an incorrect function signature (and prototype) of bli_?gemmt(). (RuQing Xu)
- Redefined BLIS_NUM_ARCHS to be part of the arch_t enum, which means it will be updated automatically when defining future subconfigs.
- Minor code consolidation in all level-3 _front() functions.
- Reorganized Windows cpp branch of bli_pthreads.c.
- Implemented bli_pthread_self() and _equals(), but left them commented out (via cpp guards) due to issues with getting the Windows versions working. Thankfully, these functions aren't yet needed by BLIS.

Kernels:
- Added low-precision POWER10 gemm kernels via a 'power10' sandbox. This sandbox also provides an API for implementations that use these kernels. See the sandbox/power10/POWER10.md document for more info. (Nicholai Tukanov)
- Added assembly packm kernels for the 'haswell' kernel set and registered to 'haswell', 'zen', and 'zen2' subconfigs accordingly. The s, c, and z kernels were modeled on the d kernel, which was contributed by AMD.
- Reduced KC in the 'skx' subconfig from 384 to 256. (Tze Meng Low)
- Fixed bugs in two 'haswell' dgemmsup kernels, which involved extraneous assembly instructions left over from when the kernels were first written. (Kiran Varaganti, Bhaskar Nallani)
- Minor updates to all of the gemmtrsm kernels to allow division by diagonal elements rather that scaling by pre-inverted elements. This change was applied to 'haswell' and 'penryn' kernel sets as well as reference kernels, 1m kernels, and the pre-broadcast B (bb) format kernels used by the 'power9' subconfig. (Bhaskar Nallani)
- Fixed incorrect return type on bli_diag_offset_with_trans(). (Devin Matthews)

Build system:
- Output a pkgconfig file so that CMake users that use BLIS can find and incorporate BLIS build products. (Ajay Panyala)
- Fixed an issue in the the configure script's kernel-to-config map that caused 'skx' kernel flags to be used when compiling kernels from the 'zen' kernel set. This issue wasn't really fixed, but rather tweaked in such a way that it happens to now work. A more proper fix would require a serious rethinking of the configuration system. (Devin Matthews)
- Fixed the shared library build rule in top-level Makefile. The previous rule was incorrectly only linking prerequisites that were newer than the target ($?) rather than correctly linking all prerequisites ($^). (Devin Matthews)
- Fixed cc_vendor for crosstool-ng toolchains. (Isuru Fernando)
- Allow disabling of trsm diagonal pre-inversion at compile time via --disable-trsm-preinversion.

Testing:
- Fixed obscure testsuite bug for the gemmt test module that relates to its dependency on gemv.
- Allow the amaxv testsuite module to run with a dimension of 0. (Meghana Vankadari)

Documentation:
- Documented auto-reduction for prime numbers of threads in docs/Multithreading.md.
- Fixed a missing trans_t argument in the API documentation for her2k/syr2k in BLISTypedAPI.md. (RuQing Xu)
- Removed an extra call to free() in the level-1v tapi example code. (Ilknur Mustafazade)

Special thanks to Devin Matthews, Nicholai Tukanov, Jeff Diamond, RuQing Xu, Tze Meng Low, Kiran Varaganti, Bhaskar Nallani, Ajay Panyala, Isuru Fernando, Meghana Vankadari, Ilknur Mustafazade, and the CPU libraries group at AMD for their numerous helpful bug reports, suggestions, contributions, and help in tracking down issues. (And please forgive me if I inadvertently left out your name.) Please continue to give us feedback--it is always appreciated!

As always, a full list of changes is available in the CHANGELOG [1].

Please let us know if you have any questions.

Field

[1] https://github.com/flame/blis/blob/master/CHANGELOG