[Bug libstdc++/94971] [10/11 Regression] Parallel Mode cannot be used in C++20
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94971 Jonathan Wakely changed: What|Removed |Added Status|ASSIGNED|RESOLVED Resolution|--- |WONTFIX --- Comment #6 from Jonathan Wakely --- (In reply to Jonathan Wakely from comment #0) > This fails to compile in C++20 mode: > > #define _GLIBCXX_PARALLEL 1 > #include > > The new std::lexicographical_compare_three_way algo I added is in the wrong > namespace. This is fixed. (In reply to Jonathan Wakely from comment #2) > All the tests for C++20 constexpr algorithms fail, because the > std::__parallel versions are not constexpr: [...] > I think that could be fixed by adding _GLIBCXX20_CONSTEXPR to them and then > at the beginning of each function: > > #if __cpp_lib_is_constant_evaluated > if (std::is_constant_evaluated()) > return _GLIBCXX_STD_A::replace_if(...); > #endif I don't plan to do that. > These fail to compile because the parallel algos don't support move > semantics: > FAIL: 25_algorithms/stable_sort/49559.cc (test for excess errors) > FAIL: 25_algorithms/stable_sort/moveable.cc (test for excess errors) > FAIL: 25_algorithms/stable_sort/moveable2.cc (test for excess errors) > FAIL: 25_algorithms/partial_sort/moveable.cc (test for excess errors) > FAIL: 25_algorithms/nth_element/moveable.cc (test for excess errors) > FAIL: 25_algorithms/for_each/1.cc (test for excess errors) > FAIL: 25_algorithms/for_each/for_each_n.cc (test for excess errors) This has been broken for years. > This fails because the new overload of std::search that takes a searcher > isn't declared in std::__parallel: > > FAIL: 25_algorithms/search/searcher.cc (test for excess errors) > Excess errors: > /home/jwakely/src/gcc/libstdc++-v3/testsuite/25_algorithms/search/searcher. > cc:39: error: no matching function for call to 'search(int [2], int*, > nocopy)' Fixed. > These fail at runtime, because the parallel algos copy instead of moving: > > FAIL: 26_numerics/accumulate/lwg2055.cc execution test > FAIL: 26_numerics/inner_product/lwg2055.cc execution test Not going to be fixed. I'm going to close this as WONTFIX. Parallel Mode should be considered legacy code in maintenance mode only.
[Bug libstdc++/94971] [10/11 Regression] Parallel Mode cannot be used in C++20
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94971 --- Comment #5 from CVS Commits --- The master branch has been updated by Jonathan Wakely : https://gcc.gnu.org/g:e0af865ab9d9d5b6b3ac7fdde26cf9bbf635b6b4 commit r11-4722-ge0af865ab9d9d5b6b3ac7fdde26cf9bbf635b6b4 Author: Jonathan Wakely Date: Wed Nov 4 13:36:32 2020 + libstdc++: Define new C++17 std::search overload for Parallel Mode [PR 94971] libstdc++-v3/ChangeLog: PR libstdc++/94971 * include/bits/stl_algo.h (search(FIter, FIter, const Searcher): Adjust #if condition. * include/parallel/algo.h (search(FIter, FIter, const Searcher&): Define new overload for C++17.
[Bug libstdc++/94971] [10/11 Regression] Parallel Mode cannot be used in C++20
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94971 Richard Biener changed: What|Removed |Added Target Milestone|10.2|10.3 --- Comment #4 from Richard Biener --- GCC 10.2 is released, adjusting target milestone.
[Bug libstdc++/94971] [10/11 Regression] Parallel Mode cannot be used in C++20
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94971 --- Comment #3 from CVS Commits --- The master branch has been updated by Jonathan Wakely : https://gcc.gnu.org/g:9c24e97a97aaad4ad0500170cbae4f387d82ddd6 commit r11-180-g9c24e97a97aaad4ad0500170cbae4f387d82ddd6 Author: Jonathan Wakely Date: Thu May 7 21:43:49 2020 +0100 libstdc++: Fix some C++20 algorithms to work in parallel mode Some new algorithms need to use _GLIBCXX_STD_A to refer to the "normal" version of the algorithm, to workaround the namespace dance done for parallel mode. PR libstdc++/94971 (partial) * include/bits/ranges_algo.h (ranges::__sample_fn): Qualify std::sample using macro to work in parallel mode. (__sort_fn): Likewise for std::sort. (ranges::__nth_element_fn): Likewise for std::nth_element. * include/bits/stl_algobase.h (lexicographical_compare_three_way): Likewise for std::__min_cmp. * include/parallel/algobase.h (lexicographical_compare_three_way): Add to namespace std::__parallel.
[Bug libstdc++/94971] [10/11 Regression] Parallel Mode cannot be used in C++20
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94971 --- Comment #2 from Jonathan Wakely --- Parallel mode is basically broken for any new C++ standard. All the tests for C++20 constexpr algorithms fail, because the std::__parallel versions are not constexpr: FAIL: 25_algorithms/replace_if/constexpr.cc (test for excess errors) Excess errors: /home/jwakely/src/gcc/libstdc++-v3/testsuite/25_algorithms/replace_if/constexpr.cc:29: error: call to non-'constexpr' function 'void std::__parallel::replace_if(_FIter, _FIter, _Predicate, const _Tp&) [with _FIter = int*; _Predicate = test()::; _Tp = int]' /home/jwakely/src/gcc/libstdc++-v3/testsuite/25_algorithms/replace_if/constexpr.cc:34: error: non-constant condition for static assertion /home/jwakely/src/gcc/libstdc++-v3/testsuite/25_algorithms/replace_if/constexpr.cc:34: error: 'constexpr bool test()' called in a constant expression I think that could be fixed by adding _GLIBCXX20_CONSTEXPR to them and then at the beginning of each function: #if __cpp_lib_is_constant_evaluated if (std::is_constant_evaluated()) return _GLIBCXX_STD_A::replace_if(...); #endif These fail to compile because the parallel algos don't support move semantics: FAIL: 25_algorithms/stable_sort/49559.cc (test for excess errors) FAIL: 25_algorithms/stable_sort/moveable.cc (test for excess errors) FAIL: 25_algorithms/stable_sort/moveable2.cc (test for excess errors) FAIL: 25_algorithms/partial_sort/moveable.cc (test for excess errors) FAIL: 25_algorithms/nth_element/moveable.cc (test for excess errors) FAIL: 25_algorithms/for_each/1.cc (test for excess errors) FAIL: 25_algorithms/for_each/for_each_n.cc (test for excess errors) These time out, I didn't check why: FAIL: 25_algorithms/move/deque_iterators/1.cc execution test FAIL: 25_algorithms/move_backward/deque_iterators/1.cc execution test FAIL: 25_algorithms/copy_backward/deque_iterators/1.cc execution test This fails because the new overload of std::search that takes a searcher isn't declared in std::__parallel: FAIL: 25_algorithms/search/searcher.cc (test for excess errors) Excess errors: /home/jwakely/src/gcc/libstdc++-v3/testsuite/25_algorithms/search/searcher.cc:39: error: no matching function for call to 'search(int [2], int*, nocopy)' These fail at runtime, because the parallel algos copy instead of moving: FAIL: 26_numerics/accumulate/lwg2055.cc execution test FAIL: 26_numerics/inner_product/lwg2055.cc execution test
[Bug libstdc++/94971] [10/11 Regression] Parallel Mode cannot be used in C++20
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94971 Jonathan Wakely changed: What|Removed |Added Status|UNCONFIRMED |ASSIGNED Last reconfirmed||2020-05-06 Target Milestone|--- |10.2 Assignee|unassigned at gcc dot gnu.org |redi at gcc dot gnu.org Ever confirmed|0 |1 --- Comment #1 from Jonathan Wakely --- I'm not going to fix this for 10.1, I doubt anybody is using our non-standard parallel mode with C++20 (they should be using the standard parallel algos added in C++17 instead).
