The master branch has been updated by Jonathan Wakely <r...@gcc.gnu.org>:
https://gcc.gnu.org/g:c5fd1a483858c0e85b40149aef88be00f94980a7 commit r15-3650-gc5fd1a483858c0e85b40149aef88be00f94980a7 Author: Jonathan Wakely <jwak...@redhat.com> Date: Tue Jan 9 23:39:14 2024 +0000 libstdc++: Make PSTL algorithms accept C++20 iterators [PR110512] This is a step towards implementing the C++23 change P2408R5, "Ranges iterators as inputs to non-Ranges algorithms". C++20 random access iterators which do not meet the Cpp17RandomAccessIterator requirements will now be recognized by the PSTL algorithms. As noted by Patrick, P2408R5 only relaxes the requirements for non-mutating algorithms, but this relaxes them for all parallel algorithms. I believe that's OK. A call with a type which previously didn't compile at all was undefined, so we're allowed to start accepting those calls if the type satisfies std::random_access_iterator. However, this also causes a change in behaviour for calls with arguments which satisfy std::random_access_iterator and meet the Cpp17ForwardIterator requirements but not the Cpp17RandomAccessIterator requirements. The algorithms will dispatch to a different implementation now. I believe that's also OK. The algorithms should give the same results whether acting on forward iterators or random access iterators, just more efficiently for the latter. Additionally, we can optimize the C++17 implementation by using std::__and_, and use std::__remove_cvref_t and std::__iter_category_t for readability. This diverges from the upstream PSTL, but since libc++ is no longer using that upstream (so we're the only consumer of this code) I think it's reasonable to use libstdc++ extensions in localized places like this. Rebasing this small header on upstream should not be difficult. libstdc++-v3/ChangeLog: PR libstdc++/110512 * include/pstl/execution_impl.h (__are_random_access_iterators): Recognize C++20 random access iterators, and use more efficient implementations. * testsuite/25_algorithms/pstl/110512.cc: New test. -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/2030797 Title: Parallel C++ algorithms run sequentially To manage notifications about this bug go to: https://bugs.launchpad.net/gcc/+bug/2030797/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
