From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: by sourceware.org (Postfix, from userid 2181) id 8D5EC3857C69; Fri, 26 Nov 2021 15:41:03 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 8D5EC3857C69 MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="utf-8" From: Jonathan Wakely To: gcc-cvs@gcc.gnu.org, libstdc++-cvs@gcc.gnu.org Subject: [gcc r10-10302] libstdc++: Optimize std::seed_seq construction X-Act-Checkin: gcc X-Git-Author: Antony Polukhin X-Git-Refname: refs/heads/releases/gcc-10 X-Git-Oldrev: a2139a9a95e624f99f470191335495d02254e1f1 X-Git-Newrev: 11f4502ce55b1a833ed6988e03499d06213395c4 Message-Id: <20211126154103.8D5EC3857C69@sourceware.org> Date: Fri, 26 Nov 2021 15:41:03 +0000 (GMT) X-BeenThere: libstdc++-cvs@gcc.gnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Libstdc++-cvs mailing list List-Unsubscribe: , List-Archive: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 26 Nov 2021 15:41:03 -0000 https://gcc.gnu.org/g:11f4502ce55b1a833ed6988e03499d06213395c4 commit r10-10302-g11f4502ce55b1a833ed6988e03499d06213395c4 Author: Antony Polukhin Date: Tue Aug 17 13:50:53 2021 +0100 libstdc++: Optimize std::seed_seq construction When std::seed_seq is constructed from random access iterators we can detect the internal vector size in O(1). Reserving memory for elements in such cases may avoid multiple memory allocations. Signed-off-by: Jonathan Wakely libstdc++-v3/ChangeLog: * include/bits/random.tcc (seed_seq::seed_seq): Reserve capacity if distance is O(1). * testsuite/26_numerics/random/pr60037-neg.cc: Adjust dg-error line number. Co-authored-by: Jonathan Wakely (cherry picked from commit 174f9257a75dec93221eca26c236e0a6346c9dfd) Diff: --- libstdc++-v3/include/bits/random.tcc | 4 ++++ libstdc++-v3/testsuite/26_numerics/random/pr60037-neg.cc | 2 +- 2 files changed, 5 insertions(+), 1 deletion(-) diff --git a/libstdc++-v3/include/bits/random.tcc b/libstdc++-v3/include/bits/random.tcc index d7503ee7094..74ee6ada13a 100644 --- a/libstdc++-v3/include/bits/random.tcc +++ b/libstdc++-v3/include/bits/random.tcc @@ -3200,6 +3200,7 @@ namespace __detail template seed_seq::seed_seq(std::initializer_list<_IntType> __il) { + _M_v.reserve(__il.size()); for (auto __iter = __il.begin(); __iter != __il.end(); ++__iter) _M_v.push_back(__detail::__mod::__value>(*__iter)); @@ -3208,6 +3209,9 @@ namespace __detail template seed_seq::seed_seq(_InputIterator __begin, _InputIterator __end) { + if _GLIBCXX17_CONSTEXPR (__is_random_access_iter<_InputIterator>::value) + _M_v.reserve(std::distance(__begin, __end)); + for (_InputIterator __iter = __begin; __iter != __end; ++__iter) _M_v.push_back(__detail::__mod::__value>(*__iter)); diff --git a/libstdc++-v3/testsuite/26_numerics/random/pr60037-neg.cc b/libstdc++-v3/testsuite/26_numerics/random/pr60037-neg.cc index 9cffc3d06f9..1291967b0d1 100644 --- a/libstdc++-v3/testsuite/26_numerics/random/pr60037-neg.cc +++ b/libstdc++-v3/testsuite/26_numerics/random/pr60037-neg.cc @@ -12,4 +12,4 @@ auto x = std::generate_canonical