Hi, I wanted to bring some attention to this in devel, not only to openblas' maintainer (in CC), because there have been some discussions around BLAS/LAPACK in the past here.
As Dave Love pointed out in a previous discussion, generally, parallelization is made at the top level and then you simply call a single-threaded BLAS/LAPACK implementation. But as it turns out, openblas is not thread-safe in such a scenario since v0.3.7 at least. To ensure thread-safety, we need to build single-threaded openblas with USE_LOCKING=1 [1] (which we don't do now, and we should, especially if we intend to make this implementation a system-wide default [2]). Some bug reports motivated the inclusion of this new flag in v0.3.7 (see [3, 4]). And I stumbled upon this due to a question in r-sig-fedora [5] about a proper way to switch BLAS/LAPACK version in Fedora motivated by this issue in an R package. So it's clear that things are failing out there, and USE_LOCKING=1 is a sensible default that we should apply. I didn't find though what's the performance penalty of setting such a flag. But if that's noticeable, then this is another argument in favour of providing a proper mechanism for the user to switch the implementation, as e.g. Debian does. [1] https://github.com/xianyi/OpenBLAS/wiki/Faq/4bded95e8dc8aadc70ce65267d1093ca7bdefc4c#multi-threaded [2] https://fedoraproject.org/wiki/Changes/OpenBLAS_as_default_BLAS [3] https://github.com/xianyi/OpenBLAS/issues/2126 [4] https://github.com/xianyi/OpenBLAS/issues/2155 [5] https://stat.ethz.ch/pipermail/r-sig-fedora/2020-May/000616.html -- Iñaki Úcar _______________________________________________ devel mailing list -- devel@lists.fedoraproject.org To unsubscribe send an email to devel-le...@lists.fedoraproject.org Fedora Code of Conduct: https://docs.fedoraproject.org/en-US/project/code-of-conduct/ List Guidelines: https://fedoraproject.org/wiki/Mailing_list_guidelines List Archives: https://lists.fedoraproject.org/archives/list/devel@lists.fedoraproject.org
