c06ae43e26
Part of #102817. This is a natural follow-up to #163006. We are forwarding `std::generate_n` to `std::__for_each_n` (`std::for_each_n` needs c++17), resulting in improved performance for segmented iterators. before: ``` std::generate_n(deque<int>)/32 17.5 ns 17.3 ns 40727273 std::generate_n(deque<int>)/50 25.7 ns 25.5 ns 26352941 std::generate_n(deque<int>)/1024 490 ns 487 ns 1445161 std::generate_n(deque<int>)/8192 3908 ns 3924 ns 179200 ``` after: ``` std::generate_n(deque<int>)/32 11.1 ns 11.0 ns 64000000 std::generate_n(deque<int>)/50 16.1 ns 16.0 ns 44800000 std::generate_n(deque<int>)/1024 291 ns 292 ns 2357895 std::generate_n(deque<int>)/8192 2269 ns 2250 ns 298667 ```
98 lines
2.5 KiB
C++
98 lines
2.5 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<class Iter, IntegralLike Size, 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_n(Iter first, Size n, 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_iterators.h"
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#include "test_macros.h"
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#include "user_defined_integral.h"
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TEST_MSVC_DIAGNOSTIC_IGNORED(4244) // conversion from 'const double' to 'int', possible loss of data
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struct gen_test
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{
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TEST_CONSTEXPR int operator()() const {return 2;}
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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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const std::size_t N = 5;
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int ib[] = {0, 0, 0, 0, 0, 0}; // one bigger than N
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auto it = std::generate_n(std::begin(ib), N, gen_test());
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return it == (std::begin(ib) + N)
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&& std::all_of(std::begin(ib), it, [](int x) { return x == 2; })
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&& *it == 0 // don't overwrite the last value in the output array
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;
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}
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#endif
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template <class Iter, class Size>
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void
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test2()
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{
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const unsigned n = 4;
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int ia[n] = {0};
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assert(std::generate_n(Iter(ia), Size(n), gen_test()) == Iter(ia+n));
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assert(ia[0] == 2);
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assert(ia[1] == 2);
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assert(ia[2] == 2);
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assert(ia[3] == 2);
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}
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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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test2<Iter, int>();
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test2<Iter, unsigned int>();
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test2<Iter, long>();
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test2<Iter, unsigned long>();
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test2<Iter, UserDefinedIntegral<unsigned> >();
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test2<Iter, float>();
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test2<Iter, double>(); // this is PR#35498
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test2<Iter, long double>();
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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_n(d.begin(), size, gen_test());
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assert(std::all_of(d.begin(), d.end(), [](int x) { return x == 2; }));
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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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