[libcxx-commits] [libcxx] [libc++] Optimize {std, ranges}::distance for segmented iterators (PR #133612)
via libcxx-commits
libcxx-commits at lists.llvm.org
Mon Mar 31 07:28:08 PDT 2025
llvmbot wrote:
<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-libcxx
Author: Peng Liu (winner245)
<details>
<summary>Changes</summary>
This patch enhances the performance of `std::distance` and `std::ranges::distance` for non-random-access segmented iterators. The original implementation operates in linear time, `O(n)`, where `n` is the total number of elements. The optimized version reduces this to approximately `O(n / segment_size)` by leveraging segmented structure, where `segment_size` is the average size of each segment.
The table below summarizes the peak performance improvements observed across different segment sizes, with the total element count `n` ranging up to `1 << 20` (1,048,576 elements), based on benchmark results.
```
----------------------------------------------------------------------------
Contaier/n/segment_size std::distance std::ranges::distance
----------------------------------------------------------------------------
vector<vector<int>>/1048576/256 401.6x 422.9x
deque<deque<int>>/1048576/256 112.1x 132.6x
vector<vector<int>>/1048576/1024 1669.2x 1559.1x
deque<deque<int>>/1048576/1024 487.7x 497.4x
```
## Benchmarks
#### Segment size = 1024
```
-----------------------------------------------------------------------------------------
Benchmark Before After Speedup
-----------------------------------------------------------------------------------------
std::distance(join_view(vector<vector<int>>))/50 38.8 ns 1.01 ns 38.4x
std::distance(join_view(vector<vector<int>>))/1024 660 ns 1.02 ns 647.1x
std::distance(join_view(vector<vector<int>>))/4096 2934 ns 1.98 ns 1481.8x
std::distance(join_view(vector<vector<int>>))/8192 5751 ns 3.92 ns 1466.8x
std::distance(join_view(vector<vector<int>>))/16384 11520 ns 7.06 ns 1631.7x
std::distance(join_view(vector<vector<int>>))/65536 46367 ns 32.2 ns 1440.6x
std::distance(join_view(vector<vector<int>>))/262144 182611 ns 114 ns 1601.9x
std::distance(join_view(vector<vector<int>>))/1048576 737785 ns 442 ns 1669.2x
std::distance(join_view(deque<deque<int>>))/50 53.1 ns 6.13 ns 8.7x
std::distance(join_view(deque<deque<int>>))/1024 854 ns 7.53 ns 113.4x
std::distance(join_view(deque<deque<int>>))/4096 3507 ns 14.7 ns 238.6x
std::distance(join_view(deque<deque<int>>))/8192 7114 ns 17.6 ns 404.2x
std::distance(join_view(deque<deque<int>>))/16384 13997 ns 30.7 ns 455.9x
std::distance(join_view(deque<deque<int>>))/65536 55598 ns 114 ns 487.7x
std::distance(join_view(deque<deque<int>>))/262144 214293 ns 480 ns 446.4x
std::distance(join_view(deque<deque<int>>))/1048576 833000 ns 2183 ns 381.6x
rng::distance(join_view(vector<vector<int>>))/50 39.1 ns 1.10 ns 35.5x
rng::distance(join_view(vector<vector<int>>))/1024 689 ns 1.14 ns 604.4x
rng::distance(join_view(vector<vector<int>>))/4096 2753 ns 2.15 ns 1280.5x
rng::distance(join_view(vector<vector<int>>))/8192 5530 ns 4.61 ns 1199.6x
rng::distance(join_view(vector<vector<int>>))/16384 10968 ns 7.97 ns 1376.2x
rng::distance(join_view(vector<vector<int>>))/65536 46009 ns 35.3 ns 1303.4x
rng::distance(join_view(vector<vector<int>>))/262144 190569 ns 124 ns 1536.9x
rng::distance(join_view(vector<vector<int>>))/1048576 746724 ns 479 ns 1559.1x
rng::distance(join_view(deque<deque<int>>))/50 51.6 ns 6.57 ns 7.9x
rng::distance(join_view(deque<deque<int>>))/1024 826 ns 6.50 ns 127.1x
rng::distance(join_view(deque<deque<int>>))/4096 3323 ns 12.5 ns 265.8x
rng::distance(join_view(deque<deque<int>>))/8192 6619 ns 19.1 ns 346.5x
rng::distance(join_view(deque<deque<int>>))/16384 13495 ns 33.2 ns 406.5x
rng::distance(join_view(deque<deque<int>>))/65536 53668 ns 114 ns 470.8x
rng::distance(join_view(deque<deque<int>>))/262144 236277 ns 475 ns 497.4x
rng::distance(join_view(deque<deque<int>>))/1048576 914177 ns 2157 ns 423.8x
-----------------------------------------------------------------------------------------
```
#### Segment size = 256
```
-----------------------------------------------------------------------------------------
Benchmark Before After Speedup
-----------------------------------------------------------------------------------------
std::distance(join_view(vector<vector<int>>))/50 38.1 ns 1.02 ns 37.4x
std::distance(join_view(vector<vector<int>>))/1024 689 ns 2.06 ns 334.5x
std::distance(join_view(vector<vector<int>>))/4096 2815 ns 7.01 ns 401.6x
std::distance(join_view(vector<vector<int>>))/8192 5507 ns 14.3 ns 385.1x
std::distance(join_view(vector<vector<int>>))/16384 11050 ns 33.7 ns 327.9x
std::distance(join_view(vector<vector<int>>))/65536 44197 ns 118 ns 374.6x
std::distance(join_view(vector<vector<int>>))/262144 175793 ns 449 ns 391.5x
std::distance(join_view(vector<vector<int>>))/1048576 703242 ns 2140 ns 328.7x
std::distance(join_view(deque<deque<int>>))/50 50.2 ns 6.12 ns 8.2x
std::distance(join_view(deque<deque<int>>))/1024 835 ns 11.4 ns 73.2x
std::distance(join_view(deque<deque<int>>))/4096 3353 ns 32.9 ns 101.9x
std::distance(join_view(deque<deque<int>>))/8192 6711 ns 64.2 ns 104.5x
std::distance(join_view(deque<deque<int>>))/16384 13231 ns 118 ns 112.1x
std::distance(join_view(deque<deque<int>>))/65536 53523 ns 556 ns 96.3x
std::distance(join_view(deque<deque<int>>))/262144 219101 ns 2166 ns 101.2x
std::distance(join_view(deque<deque<int>>))/1048576 880277 ns 15852 ns 55.5x
rng::distance(join_view(vector<vector<int>>))/50 37.7 ns 1.13 ns 33.4x
rng::distance(join_view(vector<vector<int>>))/1024 697 ns 2.14 ns 325.7x
rng::distance(join_view(vector<vector<int>>))/4096 2804 ns 7.52 ns 373.0x
rng::distance(join_view(vector<vector<int>>))/8192 5749 ns 15.2 ns 378.2x
rng::distance(join_view(vector<vector<int>>))/16384 11742 ns 34.8 ns 337.4x
rng::distance(join_view(vector<vector<int>>))/65536 47274 ns 116 ns 407.7x
rng::distance(join_view(vector<vector<int>>))/262144 187774 ns 444 ns 422.9x
rng::distance(join_view(vector<vector<int>>))/1048576 749724 ns 2109 ns 355.5x
rng::distance(join_view(deque<deque<int>>))/50 53.0 ns 6.09 ns 8.7x
rng::distance(join_view(deque<deque<int>>))/1024 895 ns 11.0 ns 81.4x
rng::distance(join_view(deque<deque<int>>))/4096 3825 ns 30.6 ns 125.0x
rng::distance(join_view(deque<deque<int>>))/8192 7550 ns 60.5 ns 124.8x
rng::distance(join_view(deque<deque<int>>))/16384 14847 ns 112 ns 132.6x
rng::distance(join_view(deque<deque<int>>))/65536 56888 ns 453 ns 125.6x
rng::distance(join_view(deque<deque<int>>))/262144 231395 ns 2034 ns 113.8x
rng::distance(join_view(deque<deque<int>>))/1048576 933093 ns 15012 ns 62.2x
-----------------------------------------------------------------------------------------
```
---
Full diff: https://github.com/llvm/llvm-project/pull/133612.diff
4 Files Affected:
- (modified) libcxx/include/__iterator/distance.h (+53-15)
- (added) libcxx/test/benchmarks/iterators/distance.bench.cpp (+71)
- (modified) libcxx/test/std/iterators/iterator.primitives/iterator.operations/distance.pass.cpp (+56-21)
- (modified) libcxx/test/std/iterators/iterator.primitives/range.iter.ops/range.iter.ops.distance/iterator_sentinel.pass.cpp (+65-26)
``````````diff
diff --git a/libcxx/include/__iterator/distance.h b/libcxx/include/__iterator/distance.h
index 1732aa527f64a..8d14299191e30 100644
--- a/libcxx/include/__iterator/distance.h
+++ b/libcxx/include/__iterator/distance.h
@@ -10,41 +10,82 @@
#ifndef _LIBCPP___ITERATOR_DISTANCE_H
#define _LIBCPP___ITERATOR_DISTANCE_H
+#include <__algorithm/for_each_segment.h>
#include <__config>
#include <__iterator/concepts.h>
#include <__iterator/incrementable_traits.h>
#include <__iterator/iterator_traits.h>
+#include <__iterator/segmented_iterator.h>
#include <__ranges/access.h>
#include <__ranges/concepts.h>
#include <__ranges/size.h>
#include <__type_traits/decay.h>
+#include <__type_traits/enable_if.h>
#include <__type_traits/remove_cvref.h>
+#include <__utility/move.h>
#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
# pragma GCC system_header
#endif
+_LIBCPP_PUSH_MACROS
+#include <__undef_macros>
+
_LIBCPP_BEGIN_NAMESPACE_STD
-template <class _InputIter>
-inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 typename iterator_traits<_InputIter>::difference_type
-__distance(_InputIter __first, _InputIter __last, input_iterator_tag) {
- typename iterator_traits<_InputIter>::difference_type __r(0);
+#if _LIBCPP_STD_VER >= 20
+template <class _Iter>
+using __iter_distance_t _LIBCPP_NODEBUG = std::iter_difference_t<_Iter>;
+#else
+template <class _Iter>
+using __iter_distance_t _LIBCPP_NODEBUG = typename iterator_traits<_Iter>::difference_type;
+#endif
+
+template <class _InputIter, class _Sent>
+inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 __iter_distance_t<_InputIter>
+__distance(_InputIter __first, _Sent __last) {
+ __iter_distance_t<_InputIter> __r(0);
for (; __first != __last; ++__first)
++__r;
return __r;
}
-template <class _RandIter>
-inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 typename iterator_traits<_RandIter>::difference_type
-__distance(_RandIter __first, _RandIter __last, random_access_iterator_tag) {
+template <class _RandIter, __enable_if_t<__has_random_access_iterator_category<_RandIter>::value, int> = 0>
+inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 __iter_distance_t<_RandIter>
+__distance(_RandIter __first, _RandIter __last) {
return __last - __first;
}
+template <class _SegmentedIter, class _Difference>
+struct __segment_distance {
+ using _Traits _LIBCPP_NODEBUG = __segmented_iterator_traits<_SegmentedIter>;
+
+ _Difference& __r_;
+
+ _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 explicit __segment_distance(_Difference& __r) : __r_(__r) {}
+
+ _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 void
+ operator()(typename _Traits::__local_iterator __lfirst, typename _Traits::__local_iterator __llast) {
+ __r_ += std::__distance(__lfirst, __llast);
+ }
+};
+
+template <class _SegmentedIter,
+ __enable_if_t<!__has_random_access_iterator_category<_SegmentedIter>::value &&
+ __is_segmented_iterator<_SegmentedIter>::value,
+ int> = 0>
+inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 __iter_distance_t<_SegmentedIter>
+__distance(_SegmentedIter __first, _SegmentedIter __last) {
+ using __difference_type = __iter_distance_t<_SegmentedIter>;
+ __difference_type __r(0);
+ std::__for_each_segment(__first, __last, std::__segment_distance<_SegmentedIter, __difference_type>(__r));
+ return __r;
+}
+
template <class _InputIter>
-inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 typename iterator_traits<_InputIter>::difference_type
+inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 __iter_distance_t<_InputIter>
distance(_InputIter __first, _InputIter __last) {
- return std::__distance(__first, __last, typename iterator_traits<_InputIter>::iterator_category());
+ return std::__distance(__first, __last);
}
#if _LIBCPP_STD_VER >= 20
@@ -56,12 +97,7 @@ struct __distance {
template <class _Ip, sentinel_for<_Ip> _Sp>
requires(!sized_sentinel_for<_Sp, _Ip>)
_LIBCPP_HIDE_FROM_ABI constexpr iter_difference_t<_Ip> operator()(_Ip __first, _Sp __last) const {
- iter_difference_t<_Ip> __n = 0;
- while (__first != __last) {
- ++__first;
- ++__n;
- }
- return __n;
+ return std::__distance(std::move(__first), std::move(__last));
}
template <class _Ip, sized_sentinel_for<decay_t<_Ip>> _Sp>
@@ -92,4 +128,6 @@ inline constexpr auto distance = __distance{};
_LIBCPP_END_NAMESPACE_STD
+_LIBCPP_POP_MACROS
+
#endif // _LIBCPP___ITERATOR_DISTANCE_H
diff --git a/libcxx/test/benchmarks/iterators/distance.bench.cpp b/libcxx/test/benchmarks/iterators/distance.bench.cpp
new file mode 100644
index 0000000000000..db9e6a9201658
--- /dev/null
+++ b/libcxx/test/benchmarks/iterators/distance.bench.cpp
@@ -0,0 +1,71 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+#include <cstddef>
+#include <deque>
+#include <iterator>
+#include <ranges>
+#include <vector>
+
+#include <benchmark/benchmark.h>
+
+int main(int argc, char** argv) {
+ auto std_distance = [](auto first, auto last) { return std::distance(first, last); };
+
+ // {std,ranges}::distance
+ {
+ auto bm = []<class Container>(std::string name, auto distance, std::size_t seg_size) {
+ benchmark::RegisterBenchmark(
+ name,
+ [distance, seg_size](auto& st) {
+ std::size_t const size = st.range(0);
+ std::size_t const segments = (size + seg_size - 1) / seg_size;
+ Container c(segments);
+ for (std::size_t i = 0, n = size; i < segments; ++i, n -= seg_size) {
+ c[i].resize(std::min(seg_size, n));
+ }
+
+ auto view = c | std::views::join;
+ auto first = view.begin();
+ auto last = view.end();
+
+ for ([[maybe_unused]] auto _ : st) {
+ benchmark::DoNotOptimize(c);
+ auto result = distance(first, last);
+ benchmark::DoNotOptimize(result);
+ }
+ })
+ ->Arg(50) // non power-of-two
+ ->Arg(1024)
+ ->Arg(4096)
+ ->Arg(8192)
+ ->Arg(1 << 14)
+ ->Arg(1 << 16)
+ ->Arg(1 << 18)
+ ->Arg(1 << 20);
+ };
+ bm.operator()<std::vector<std::vector<int>>>("std::distance(join_view(vector<vector<int>>))", std_distance, 256);
+ bm.operator()<std::deque<std::deque<int>>>("std::distance(join_view(deque<deque<int>>))", std_distance, 256);
+ bm.operator()<std::vector<std::vector<int>>>(
+ "rng::distance(join_view(vector<vector<int>>)", std::ranges::distance, 256);
+ bm.operator()<std::deque<std::deque<int>>>(
+ "rng::distance(join_view(deque<deque<int>>)", std::ranges::distance, 256);
+
+ // bm.operator()<std::vector<std::vector<int>>>("std::distance(join_view(vector<vector<int>>))", std_distance, 1024);
+ // bm.operator()<std::deque<std::deque<int>>>("std::distance(join_view(deque<deque<int>>))", std_distance, 1024);
+ // bm.operator()<std::vector<std::vector<int>>>("rng::distance(join_view(vector<vector<int>>)", std::ranges::distance, 1024);
+ // bm.operator()<std::deque<std::deque<int>>>("rng::distance(join_view(deque<deque<int>>)", std::ranges::distance, 1024);
+ }
+
+ benchmark::Initialize(&argc, argv);
+ benchmark::RunSpecifiedBenchmarks();
+ benchmark::Shutdown();
+ return 0;
+}
diff --git a/libcxx/test/std/iterators/iterator.primitives/iterator.operations/distance.pass.cpp b/libcxx/test/std/iterators/iterator.primitives/iterator.operations/distance.pass.cpp
index 13caefff92365..bcaeee14cad6d 100644
--- a/libcxx/test/std/iterators/iterator.primitives/iterator.operations/distance.pass.cpp
+++ b/libcxx/test/std/iterators/iterator.primitives/iterator.operations/distance.pass.cpp
@@ -16,38 +16,73 @@
// Iter::difference_type
// distance(Iter first, Iter last); // constexpr in C++17
-#include <iterator>
+#include <array>
#include <cassert>
+#include <deque>
+#include <iterator>
+#include <vector>
#include <type_traits>
#include "test_macros.h"
#include "test_iterators.h"
template <class It>
-TEST_CONSTEXPR_CXX17
-void check_distance(It first, It last, typename std::iterator_traits<It>::difference_type dist)
-{
- typedef typename std::iterator_traits<It>::difference_type Difference;
- static_assert(std::is_same<decltype(std::distance(first, last)), Difference>::value, "");
- assert(std::distance(first, last) == dist);
+TEST_CONSTEXPR_CXX17 void check_distance(It first, It last, typename std::iterator_traits<It>::difference_type dist) {
+ typedef typename std::iterator_traits<It>::difference_type Difference;
+ static_assert(std::is_same<decltype(std::distance(first, last)), Difference>::value, "");
+ assert(std::distance(first, last) == dist);
}
-TEST_CONSTEXPR_CXX17 bool tests()
-{
- const char* s = "1234567890";
- check_distance(cpp17_input_iterator<const char*>(s), cpp17_input_iterator<const char*>(s+10), 10);
- check_distance(forward_iterator<const char*>(s), forward_iterator<const char*>(s+10), 10);
- check_distance(bidirectional_iterator<const char*>(s), bidirectional_iterator<const char*>(s+10), 10);
- check_distance(random_access_iterator<const char*>(s), random_access_iterator<const char*>(s+10), 10);
- check_distance(s, s+10, 10);
- return true;
+#if TEST_STD_VER >= 20
+void test_deque() {
+ using Container = std::deque<std::deque<double>>;
+ Container c;
+ auto view = c | std::views::join;
+ Container::difference_type n = 0;
+ for (std::size_t i = 0; i < 10; ++i) {
+ n += i;
+ c.push_back(Container::value_type(i));
+ }
+ assert(std::distance(view.begin(), view.end()) == n);
+}
+#endif
+
+TEST_CONSTEXPR_CXX17 bool tests() {
+ const char* s = "1234567890";
+ check_distance(cpp17_input_iterator<const char*>(s), cpp17_input_iterator<const char*>(s + 10), 10);
+ check_distance(forward_iterator<const char*>(s), forward_iterator<const char*>(s + 10), 10);
+ check_distance(bidirectional_iterator<const char*>(s), bidirectional_iterator<const char*>(s + 10), 10);
+ check_distance(random_access_iterator<const char*>(s), random_access_iterator<const char*>(s + 10), 10);
+ check_distance(s, s + 10, 10);
+
+#if TEST_STD_VER >= 20
+ {
+ using Container = std::vector<std::vector<int>>;
+ Container c;
+ auto view = c | std::views::join;
+ Container::difference_type n = 0;
+ for (std::size_t i = 0; i < 10; ++i) {
+ n += i;
+ c.push_back(Container::value_type(i));
+ }
+ assert(std::distance(view.begin(), view.end()) == n);
+ }
+ {
+ using Container = std::array<std::array<char, 3>, 10>;
+ Container c;
+ auto view = c | std::views::join;
+ assert(std::distance(view.begin(), view.end()) == 30);
+ }
+ if (!TEST_IS_CONSTANT_EVALUATED)
+ test_deque();
+#endif
+ return true;
}
-int main(int, char**)
-{
- tests();
+int main(int, char**) {
+ tests();
#if TEST_STD_VER >= 17
- static_assert(tests(), "");
+ static_assert(tests(), "");
#endif
- return 0;
+ return 0;
}
diff --git a/libcxx/test/std/iterators/iterator.primitives/range.iter.ops/range.iter.ops.distance/iterator_sentinel.pass.cpp b/libcxx/test/std/iterators/iterator.primitives/range.iter.ops/range.iter.ops.distance/iterator_sentinel.pass.cpp
index b4199b73ad76a..a5fcf337387c2 100644
--- a/libcxx/test/std/iterators/iterator.primitives/range.iter.ops/range.iter.ops.distance/iterator_sentinel.pass.cpp
+++ b/libcxx/test/std/iterators/iterator.primitives/range.iter.ops/range.iter.ops.distance/iterator_sentinel.pass.cpp
@@ -15,18 +15,21 @@
// template<class I, sized_sentinel_for<decay_t<I>> S>
// constexpr iter_difference_t<I> ranges::distance(I&& first, S last); // TODO: update when LWG3664 is resolved
-#include <iterator>
+#include <array>
#include <cassert>
+#include <deque>
+#include <iterator>
+#include <vector>
#include "test_iterators.h"
#include "test_macros.h"
-template<class It, class Sent>
+template <class It, class Sent>
constexpr void test_unsized() {
static_assert(std::sentinel_for<Sent, It> && !std::sized_sentinel_for<Sent, It>);
- int a[3] = {1,2,3};
+ int a[3] = {1, 2, 3};
{
- It first = It(a);
+ It first = It(a);
auto last = Sent(It(a));
assert(std::ranges::distance(first, last) == 0);
assert(std::ranges::distance(It(a), last) == 0);
@@ -36,7 +39,7 @@ constexpr void test_unsized() {
}
{
auto check = [&a]<class ItQual, class SentQual> {
- It first = It(a);
+ It first = It(a);
Sent last = Sent(It(a + 3));
assert(std::ranges::distance(static_cast<ItQual>(first), static_cast<SentQual>(last)) == 3);
};
@@ -61,13 +64,13 @@ constexpr void test_unsized() {
}
}
-template<class It, class Sent>
+template <class It, class Sent>
constexpr void test_sized() {
static_assert(std::sized_sentinel_for<Sent, It>);
- int a[] = {1,2,3};
+ int a[] = {1, 2, 3};
{
auto check = [&a]<class ItQual, class SentQual> {
- It first = It(a + 3);
+ It first = It(a + 3);
Sent last = Sent(It(a));
assert(std::ranges::distance(static_cast<ItQual>(first), static_cast<SentQual>(last)) == -3);
};
@@ -91,7 +94,7 @@ constexpr void test_sized() {
check.template operator()<const It&&, const Sent&&>();
}
{
- It first = It(a);
+ It first = It(a);
auto last = Sent(It(a));
assert(std::ranges::distance(first, last) == 0);
assert(std::ranges::distance(It(a), last) == 0);
@@ -100,7 +103,7 @@ constexpr void test_sized() {
ASSERT_SAME_TYPE(decltype(std::ranges::distance(It(a), Sent(It(a)))), std::iter_difference_t<It>);
}
{
- It first = It(a);
+ It first = It(a);
auto last = Sent(It(a + 3));
assert(std::ranges::distance(first, last) == 3);
assert(std::ranges::distance(It(a), last) == 3);
@@ -110,13 +113,17 @@ constexpr void test_sized() {
}
struct StrideCounter {
- int *it_;
- int *inc_;
- using value_type = int;
+ int* it_;
+ int* inc_;
+ using value_type = int;
using difference_type = int;
explicit StrideCounter();
- constexpr explicit StrideCounter(int *it, int *inc) : it_(it), inc_(inc) {}
- constexpr auto& operator++() { ++it_; *inc_ += 1; return *this; }
+ constexpr explicit StrideCounter(int* it, int* inc) : it_(it), inc_(inc) {}
+ constexpr auto& operator++() {
+ ++it_;
+ *inc_ += 1;
+ return *this;
+ }
StrideCounter operator++(int);
int& operator*() const;
bool operator==(StrideCounter) const;
@@ -125,11 +132,11 @@ static_assert(std::forward_iterator<StrideCounter>);
static_assert(!std::sized_sentinel_for<StrideCounter, StrideCounter>);
struct SizedStrideCounter {
- int *it_;
- int *minus_;
+ int* it_;
+ int* minus_;
using value_type = int;
explicit SizedStrideCounter();
- constexpr explicit SizedStrideCounter(int *it, int *minus) : it_(it), minus_(minus) {}
+ constexpr explicit SizedStrideCounter(int* it, int* minus) : it_(it), minus_(minus) {}
SizedStrideCounter& operator++();
SizedStrideCounter operator++(int);
int& operator*() const;
@@ -147,22 +154,34 @@ constexpr void test_stride_counting() {
int a[] = {1, 2, 3};
int inc = 0;
StrideCounter first(a, &inc);
- StrideCounter last(a+3, nullptr);
+ StrideCounter last(a + 3, nullptr);
std::same_as<int> auto result = std::ranges::distance(first, last);
assert(result == 3);
assert(inc == 3);
}
{
- int a[] = {1, 2, 3};
+ int a[] = {1, 2, 3};
int minus = 0;
SizedStrideCounter first(a, &minus);
- SizedStrideCounter last(a+3, nullptr);
+ SizedStrideCounter last(a + 3, nullptr);
std::same_as<int> auto result = std::ranges::distance(first, last);
assert(result == 3);
assert(minus == 1);
}
}
+void test_deque() {
+ using Container = std::deque<std::deque<double>>;
+ Container c;
+ auto view = c | std::views::join;
+ Container::difference_type n = 0;
+ for (std::size_t i = 0; i < 10; ++i) {
+ n += i;
+ c.push_back(Container::value_type(i));
+ }
+ assert(std::ranges::distance(view.begin(), view.end()) == n);
+}
+
constexpr bool test() {
{
int a[] = {1, 2, 3};
@@ -197,7 +216,7 @@ constexpr bool test() {
test_sized<contiguous_iterator<int*>, contiguous_iterator<int*>>();
{
- using It = cpp20_input_iterator<int*>; // non-copyable, thus not a sentinel for itself
+ using It = cpp20_input_iterator<int*>; // non-copyable, thus not a sentinel for itself
static_assert(!std::is_copy_constructible_v<It>);
static_assert(!std::sentinel_for<It, It>);
static_assert(!std::is_invocable_v<decltype(std::ranges::distance), It&, It&>);
@@ -206,10 +225,10 @@ constexpr bool test() {
static_assert(!std::is_invocable_v<decltype(std::ranges::distance), It&&, It&&>);
}
{
- using It = cpp20_input_iterator<int*>; // non-copyable
- using Sent = sentinel_wrapper<It>; // not a sized sentinel
+ using It = cpp20_input_iterator<int*>; // non-copyable
+ using Sent = sentinel_wrapper<It>; // not a sized sentinel
static_assert(std::sentinel_for<Sent, It> && !std::sized_sentinel_for<Sent, It>);
- int a[] = {1,2,3};
+ int a[] = {1, 2, 3};
Sent last = Sent(It(a + 3));
static_assert(!std::is_invocable_v<decltype(std::ranges::distance), It&, Sent&>);
static_assert(!std::is_invocable_v<decltype(std::ranges::distance), It&, Sent&&>);
@@ -217,7 +236,7 @@ constexpr bool test() {
assert(std::ranges::distance(It(a), Sent(It(a + 3))) == 3);
}
{
- using It = cpp17_input_iterator<int*>; // not a sentinel for itself
+ using It = cpp17_input_iterator<int*>; // not a sentinel for itself
static_assert(!std::sentinel_for<It, It>);
static_assert(!std::is_invocable_v<decltype(std::ranges::distance), It&, It&>);
static_assert(!std::is_invocable_v<decltype(std::ranges::distance), It&, It&&>);
@@ -231,6 +250,26 @@ constexpr bool test() {
static_assert(!std::is_invocable_v<decltype(std::ranges::distance), int, int*>);
static_assert(!std::is_invocable_v<decltype(std::ranges::distance), int*, char*>);
+ {
+ using Container = std::vector<std::vector<int>>;
+ Container c;
+ auto view = c | std::views::join;
+ Container::difference_type n = 0;
+ for (std::size_t i = 0; i < 10; ++i) {
+ n += i;
+ c.push_back(Container::value_type(i));
+ }
+ assert(std::ranges::distance(view.begin(), view.end()) == n);
+ }
+ {
+ using Container = std::array<std::array<char, 3>, 10>;
+ Container c;
+ auto view = c | std::views::join;
+ assert(std::ranges::distance(view.begin(), view.end()) == 30);
+ }
+ if (!TEST_IS_CONSTANT_EVALUATED)
+ test_deque();
+
return true;
}
``````````
</details>
https://github.com/llvm/llvm-project/pull/133612
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