Nikolas Klauser 07b18c5e1b
[libc++] Optimize ranges::fill{,_n} for vector<bool>::iterator (#84642)
```
------------------------------------------------------
Benchmark                          old             new
------------------------------------------------------
bm_ranges_fill_n/1             1.64 ns         3.06 ns
bm_ranges_fill_n/2             3.45 ns         3.06 ns
bm_ranges_fill_n/3             4.88 ns         3.06 ns
bm_ranges_fill_n/4             6.46 ns         3.06 ns
bm_ranges_fill_n/5             8.03 ns         3.06 ns
bm_ranges_fill_n/6             9.65 ns         3.07 ns
bm_ranges_fill_n/7             11.5 ns         3.06 ns
bm_ranges_fill_n/8             13.0 ns         3.06 ns
bm_ranges_fill_n/16            25.9 ns         3.06 ns
bm_ranges_fill_n/64             103 ns         4.62 ns
bm_ranges_fill_n/512            711 ns         4.40 ns
bm_ranges_fill_n/4096          5642 ns         9.86 ns
bm_ranges_fill_n/32768        45135 ns         33.6 ns
bm_ranges_fill_n/262144      360818 ns          243 ns
bm_ranges_fill_n/1048576    1442828 ns          982 ns
bm_ranges_fill/1               1.63 ns         3.17 ns
bm_ranges_fill/2               3.43 ns         3.28 ns
bm_ranges_fill/3               4.97 ns         3.31 ns
bm_ranges_fill/4               6.53 ns         3.27 ns
bm_ranges_fill/5               8.12 ns         3.33 ns
bm_ranges_fill/6               9.76 ns         3.32 ns
bm_ranges_fill/7               11.6 ns         3.29 ns
bm_ranges_fill/8               13.2 ns         3.26 ns
bm_ranges_fill/16              26.3 ns         3.26 ns
bm_ranges_fill/64               104 ns         4.92 ns
bm_ranges_fill/512              716 ns         4.47 ns
bm_ranges_fill/4096            5772 ns         8.21 ns
bm_ranges_fill/32768          45778 ns         33.1 ns
bm_ranges_fill/262144        351422 ns          241 ns
bm_ranges_fill/1048576      1404710 ns          965 ns
```
2024-03-17 20:00:54 +01:00

64 lines
2.0 KiB
C++

//===----------------------------------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
// <algorithm>
// template<InputIterator Iter, class T>
// requires HasEqualTo<Iter::value_type, T>
// constexpr Iter::difference_type // constexpr after C++17
// count(Iter first, Iter last, const T& value);
// ADDITIONAL_COMPILE_FLAGS(has-fconstexpr-steps): -fconstexpr-steps=20000000
// ADDITIONAL_COMPILE_FLAGS(has-fconstexpr-ops-limit): -fconstexpr-ops-limit=80000000
#include <algorithm>
#include <cassert>
#include <vector>
#include "test_macros.h"
#include "test_iterators.h"
#include "type_algorithms.h"
struct Test {
template <class Iter>
TEST_CONSTEXPR_CXX20 void operator()() {
int ia[] = {0, 1, 2, 2, 0, 1, 2, 3};
const unsigned sa = sizeof(ia) / sizeof(ia[0]);
assert(std::count(Iter(ia), Iter(ia + sa), 2) == 3);
assert(std::count(Iter(ia), Iter(ia + sa), 7) == 0);
assert(std::count(Iter(ia), Iter(ia), 2) == 0);
}
};
TEST_CONSTEXPR_CXX20 bool test() {
types::for_each(types::cpp17_input_iterator_list<const int*>(), Test());
if (TEST_STD_AT_LEAST_20_OR_RUNTIME_EVALUATED) {
std::vector<bool> vec(256 + 64);
for (ptrdiff_t i = 0; i != 256; ++i) {
for (size_t offset = 0; offset != 64; ++offset) {
std::fill(vec.begin(), vec.end(), false);
std::fill(vec.begin() + offset, vec.begin() + i + offset, true);
assert(std::count(vec.begin() + offset, vec.begin() + offset + 256, true) == i);
assert(std::count(vec.begin() + offset, vec.begin() + offset + 256, false) == 256 - i);
}
}
}
return true;
}
int main(int, char**) {
test();
#if TEST_STD_VER >= 20
static_assert(test());
#endif
return 0;
}