46e8816928
Part of #102817. This patch attempts to optimize the performance of `std::generate` for segmented iterators. Below are the benchmark numbers from `libcxx\test\benchmarks\algorithms\modifying\generate.bench.cpp`. Test cases that use segmented iterators have also been added. - before ``` std::generate(deque<int>)/32 194 ns 193 ns 3733333 std::generate(deque<int>)/50 276 ns 276 ns 2488889 std::generate(deque<int>)/1024 5096 ns 5022 ns 112000 std::generate(deque<int>)/8192 40806 ns 40806 ns 17231 ``` - after ``` std::generate(deque<int>)/32 106 ns 105 ns 6400000 std::generate(deque<int>)/50 139 ns 138 ns 4977778 std::generate(deque<int>)/1024 2713 ns 2699 ns 248889 std::generate(deque<int>)/8192 18983 ns 19252 ns 37333 ``` --------- Co-authored-by: A. Jiang <de34@live.cn>
78 lines
1.8 KiB
C++
78 lines
1.8 KiB
C++
//===----------------------------------------------------------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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// <algorithm>
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// template<ForwardIterator Iter, Callable Generator>
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// requires OutputIterator<Iter, Generator::result_type>
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// && CopyConstructible<Generator>
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// constexpr void // constexpr after c++17
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// generate(Iter first, Iter last, Generator gen);
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#include <algorithm>
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#include <cassert>
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#include <deque>
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#include "test_macros.h"
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#include "test_iterators.h"
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struct gen_test
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{
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TEST_CONSTEXPR int operator()() const {return 1;}
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};
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#if TEST_STD_VER > 17
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TEST_CONSTEXPR bool test_constexpr() {
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int ia[] = {0, 1, 2, 3, 4};
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std::generate(std::begin(ia), std::end(ia), gen_test());
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return std::all_of(std::begin(ia), std::end(ia), [](int x) { return x == 1; })
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;
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}
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#endif
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template <class Iter>
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void
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test()
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{
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const unsigned n = 4;
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int ia[n] = {0};
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std::generate(Iter(ia), Iter(ia+n), gen_test());
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assert(ia[0] == 1);
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assert(ia[1] == 1);
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assert(ia[2] == 1);
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assert(ia[3] == 1);
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}
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void deque_test() {
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int sizes[] = {0, 1, 2, 1023, 1024, 1025, 2047, 2048, 2049};
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for (const int size : sizes) {
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std::deque<int> d(size);
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std::generate(d.begin(), d.end(), gen_test());
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assert(std::all_of(d.begin(), d.end(), [](int x) { return x == 1; }));
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}
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}
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int main(int, char**)
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{
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test<forward_iterator<int*> >();
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test<bidirectional_iterator<int*> >();
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test<random_access_iterator<int*> >();
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test<int*>();
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deque_test();
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#if TEST_STD_VER > 17
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static_assert(test_constexpr());
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#endif
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return 0;
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}
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