[libcxx-commits] [libcxx] [libc++][PSTL] Implement std::equal (PR #72448)

Louis Dionne via libcxx-commits libcxx-commits at lists.llvm.org
Tue Nov 28 06:49:51 PST 2023


https://github.com/ldionne updated https://github.com/llvm/llvm-project/pull/72448

>From e26d027e424e2b2a9467ef6727cf8b9ff29ba759 Mon Sep 17 00:00:00 2001
From: Nikolas Klauser <nikolasklauser at berlin.de>
Date: Tue, 14 Nov 2023 23:56:49 +0100
Subject: [PATCH 1/6] [libc++][PSTL] Implement std::equal

Spies: ldionne, libcxx-commits

Differential Revision: https://reviews.llvm.org/D157131
---
 libcxx/include/CMakeLists.txt                 |   1 +
 libcxx/include/__algorithm/pstl_equal.h       | 167 ++++++++++++++++++
 libcxx/include/algorithm                      |   1 +
 libcxx/include/module.modulemap.in            |   1 +
 .../alg.equal/pstl.equal.pass.cpp             |  98 ++++++++++
 .../pstl.exception_handling.pass.cpp          |  59 +++++++
 6 files changed, 327 insertions(+)
 create mode 100644 libcxx/include/__algorithm/pstl_equal.h
 create mode 100644 libcxx/test/std/algorithms/alg.nonmodifying/alg.equal/pstl.equal.pass.cpp
 create mode 100644 libcxx/test/std/algorithms/alg.nonmodifying/alg.equal/pstl.exception_handling.pass.cpp

diff --git a/libcxx/include/CMakeLists.txt b/libcxx/include/CMakeLists.txt
index b0bc3718576f66b..f2f052d3b61ad47 100644
--- a/libcxx/include/CMakeLists.txt
+++ b/libcxx/include/CMakeLists.txt
@@ -87,6 +87,7 @@ set(files
   __algorithm/pstl_backends/cpu_backends/transform_reduce.h
   __algorithm/pstl_copy.h
   __algorithm/pstl_count.h
+  __algorithm/pstl_equal.h
   __algorithm/pstl_fill.h
   __algorithm/pstl_find.h
   __algorithm/pstl_for_each.h
diff --git a/libcxx/include/__algorithm/pstl_equal.h b/libcxx/include/__algorithm/pstl_equal.h
new file mode 100644
index 000000000000000..9a296a37a153e9c
--- /dev/null
+++ b/libcxx/include/__algorithm/pstl_equal.h
@@ -0,0 +1,167 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP___ALGORITHM_PSTL_EQUAL_H
+#define _LIBCPP___ALGORITHM_PSTL_EQUAL_H
+
+#include <__algorithm/pstl_frontend_dispatch.h>
+#include <__config>
+#include <__functional/operations.h>
+#include <__numeric/pstl_transform_reduce.h>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#  pragma GCC system_header
+#endif
+
+#if !defined(_LIBCPP_HAS_NO_INCOMPLETE_PSTL) && _LIBCPP_STD_VER >= 17
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+template <class>
+void __pstl_equal();
+
+template <class _ExecutionPolicy,
+          class _ForwardIterator1,
+          class _ForwardIterator2,
+          class _Pred,
+          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
+          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
+[[nodiscard]] _LIBCPP_HIDE_FROM_ABI optional<bool>
+__equal(_ExecutionPolicy&& __policy,
+        _ForwardIterator1&& __first1,
+        _ForwardIterator1&& __last1,
+        _ForwardIterator2&& __first2,
+        _Pred&& __pred) noexcept {
+  return std::__pstl_frontend_dispatch(
+      _LIBCPP_PSTL_CUSTOMIZATION_POINT(__pstl_equal),
+      [&__policy](
+          _ForwardIterator1 __g_first1, _ForwardIterator1 __g_last1, _ForwardIterator2 __g_first2, _Pred __g_pred) {
+        return std::__transform_reduce(
+            __policy,
+            std::move(__g_first1),
+            std::move(__g_last1),
+            std::move(__g_first2),
+            true,
+            std::logical_and{},
+            std::move(__g_pred));
+      },
+      std::move(__first1),
+      std::move(__last1),
+      std::move(__first2),
+      std::move(__pred));
+}
+
+template <class _ExecutionPolicy,
+          class _ForwardIterator1,
+          class _ForwardIterator2,
+          class _Pred,
+          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
+          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
+_LIBCPP_HIDE_FROM_ABI bool
+equal(_ExecutionPolicy&& __policy,
+      _ForwardIterator1 __first1,
+      _ForwardIterator1 __last1,
+      _ForwardIterator2 __first2,
+      _Pred __pred) {
+  auto __res = std::__equal(__policy, std::move(__first1), std::move(__last1), std::move(__first2), std::move(__pred));
+  if (!__res)
+    std::__throw_bad_alloc();
+  return *__res;
+}
+
+template <class _ExecutionPolicy,
+          class _ForwardIterator1,
+          class _ForwardIterator2,
+          enable_if_t<is_execution_policy_v<__remove_cvref_t<_ExecutionPolicy>>, int> = 0>
+_LIBCPP_HIDE_FROM_ABI bool
+equal(_ExecutionPolicy&& __policy, _ForwardIterator1 __first1, _ForwardIterator1 __last1, _ForwardIterator2 __first2) {
+  return std::equal(__policy, std::move(__first1), std::move(__last1), std::move(__first2), std::equal_to{});
+}
+
+template <class _ExecutionPolicy,
+          class _ForwardIterator1,
+          class _ForwardIterator2,
+          class _Pred,
+          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
+          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
+[[nodiscard]] _LIBCPP_HIDE_FROM_ABI optional<bool>
+__equal(_ExecutionPolicy&& __policy,
+        _ForwardIterator1&& __first1,
+        _ForwardIterator1&& __last1,
+        _ForwardIterator2&& __first2,
+        _ForwardIterator2&& __last2,
+        _Pred&& __pred) noexcept {
+  return std::__pstl_frontend_dispatch(
+      _LIBCPP_PSTL_CUSTOMIZATION_POINT(__pstl_equal),
+      [&__policy](_ForwardIterator1 __g_first1,
+                  _ForwardIterator1 __g_last1,
+                  _ForwardIterator2 __g_first2,
+                  _ForwardIterator2 __g_last2,
+                  _Pred __g_pred) -> optional<bool> {
+        if constexpr (__has_random_access_iterator_category<_ForwardIterator1>::value &&
+                      __has_random_access_iterator_category<_ForwardIterator2>::value) {
+          if (__g_last1 - __g_first1 != __g_last2 - __g_first2)
+            return false;
+          return std::__equal(
+              __policy, std::move(__g_first1), std::move(__g_last1), std::move(__g_first2), std::move(__g_pred));
+        } else {
+          (void)__policy; // Avoid unused lambda captue warning
+          return std::equal(
+              std::move(__g_first1),
+              std::move(__g_last1),
+              std::move(__g_first2),
+              std::move(__g_last2),
+              std::move(__g_pred));
+        }
+      },
+      std::move(__first1),
+      std::move(__last1),
+      std::move(__first2),
+      std::move(__last2),
+      std::move(__pred));
+}
+
+template <class _ExecutionPolicy,
+          class _ForwardIterator1,
+          class _ForwardIterator2,
+          class _Pred,
+          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
+          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
+_LIBCPP_HIDE_FROM_ABI bool
+equal(_ExecutionPolicy&& __policy,
+      _ForwardIterator1 __first1,
+      _ForwardIterator1 __last1,
+      _ForwardIterator2 __first2,
+      _ForwardIterator2 __last2,
+      _Pred __pred) {
+  auto __res = std::__equal(
+      __policy, std::move(__first1), std::move(__last1), std::move(__first2), std::move(__last2), std::move(__pred));
+  if (!__res)
+    std::__throw_bad_alloc();
+  return *__res;
+}
+
+template <class _ExecutionPolicy,
+          class _ForwardIterator1,
+          class _ForwardIterator2,
+          enable_if_t<is_execution_policy_v<__remove_cvref_t<_ExecutionPolicy>>, int> = 0>
+_LIBCPP_HIDE_FROM_ABI bool
+equal(_ExecutionPolicy&& __policy,
+      _ForwardIterator1 __first1,
+      _ForwardIterator1 __last1,
+      _ForwardIterator2 __first2,
+      _ForwardIterator2 __last2) {
+  return std::equal(
+      __policy, std::move(__first1), std::move(__last1), std::move(__first2), std::move(__last2), std::equal_to{});
+}
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // !defined(_LIBCPP_HAS_NO_INCOMPLETE_PSTL) && _LIBCPP_STD_VER >= 17
+
+#endif // _LIBCPP___ALGORITHM_PSTL_EQUAL_H
diff --git a/libcxx/include/algorithm b/libcxx/include/algorithm
index 578de74d401dc2c..627e7d20213fe80 100644
--- a/libcxx/include/algorithm
+++ b/libcxx/include/algorithm
@@ -1826,6 +1826,7 @@ template <class BidirectionalIterator, class Compare>
 #include <__algorithm/pstl_any_all_none_of.h>
 #include <__algorithm/pstl_copy.h>
 #include <__algorithm/pstl_count.h>
+#include <__algorithm/pstl_equal.h>
 #include <__algorithm/pstl_fill.h>
 #include <__algorithm/pstl_find.h>
 #include <__algorithm/pstl_for_each.h>
diff --git a/libcxx/include/module.modulemap.in b/libcxx/include/module.modulemap.in
index 90381f4f7f720d4..cf7475b0b86af8b 100644
--- a/libcxx/include/module.modulemap.in
+++ b/libcxx/include/module.modulemap.in
@@ -748,6 +748,7 @@ module std_private_algorithm_pstl_backends_cpu_backends_transform        [system
 module std_private_algorithm_pstl_backends_cpu_backends_transform_reduce [system] { header "__algorithm/pstl_backends/cpu_backends/transform_reduce.h" }
 module std_private_algorithm_pstl_copy                                   [system] { header "__algorithm/pstl_copy.h" }
 module std_private_algorithm_pstl_count                                  [system] { header "__algorithm/pstl_count.h" }
+module std_private_algorithm_pstl_equal                                  [system] { header "__algorithm/pstl_equal.h" }
 module std_private_algorithm_pstl_fill                                   [system] { header "__algorithm/pstl_fill.h" }
 module std_private_algorithm_pstl_find                                   [system] {
   header "__algorithm/pstl_find.h"
diff --git a/libcxx/test/std/algorithms/alg.nonmodifying/alg.equal/pstl.equal.pass.cpp b/libcxx/test/std/algorithms/alg.nonmodifying/alg.equal/pstl.equal.pass.cpp
new file mode 100644
index 000000000000000..4788e564e953980
--- /dev/null
+++ b/libcxx/test/std/algorithms/alg.nonmodifying/alg.equal/pstl.equal.pass.cpp
@@ -0,0 +1,98 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+
+// UNSUPPORETD: libcpp-has-no-incomplete-pstl
+
+// <algorithm>
+
+// template<class ExecutionPolicy, class ForwardIterator1, class ForwardIterator2>
+//   bool equal(ExecutionPolicy&& exec,
+//              ForwardIterator1 first1, ForwardIterator1 last1,
+//              ForwardIterator2 first2);
+//
+// template<class ExecutionPolicy, class ForwardIterator1, class ForwardIterator2,
+//          class BinaryPredicate>
+//   bool equal(ExecutionPolicy&& exec,
+//              ForwardIterator1 first1, ForwardIterator1 last1,
+//              ForwardIterator2 first2, BinaryPredicate pred);
+//
+// template<class ExecutionPolicy, class ForwardIterator1, class ForwardIterator2>
+//   bool equal(ExecutionPolicy&& exec,
+//              ForwardIterator1 first1, ForwardIterator1 last1,
+//              ForwardIterator2 first2, ForwardIterator2 last2);
+//
+// template<class ExecutionPolicy, class ForwardIterator1, class ForwardIterator2,
+//          class BinaryPredicate>
+//   bool equal(ExecutionPolicy&& exec,
+//              ForwardIterator1 first1, ForwardIterator1 last1,
+//              ForwardIterator2 first2, ForwardIterator2 last2,
+//              BinaryPredicate pred);
+
+#include <algorithm>
+#include <cassert>
+
+#include "test_execution_policies.h"
+#include "test_iterators.h"
+#include "test_macros.h"
+
+template <class Iter1, class Iter2>
+struct Test {
+  template <class Policy>
+  void operator()(Policy&& policy) {
+    { // 3 iter overloads
+      int a[] = {1, 2, 3, 4, 5, 6, 7, 8};
+      int b[] = {1, 2, 3, 5, 6, 7, 8, 9};
+
+      // simple test
+      assert(std::equal(policy, Iter1(std::begin(a)), Iter1(std::end(a)), Iter2(std::begin(a))));
+
+      // check that false is returned on different ranges
+      assert(!std::equal(policy, Iter1(std::begin(a)), Iter1(std::end(a)), Iter2(std::begin(b))));
+
+      // check that the predicate is used
+      assert(std::equal(policy, Iter1(std::begin(a)), Iter1(std::end(a)), Iter2(std::begin(b)), [](int lhs, int rhs) {
+        return lhs == rhs || lhs + 1 == rhs || rhs + 1 == lhs;
+      }));
+    }
+
+    { // 4 iter overloads
+      int a[] = {1, 2, 3, 4, 5, 6, 7, 8};
+      int b[] = {1, 2, 3, 5, 6, 7, 8, 9};
+
+      // simple test
+      assert(std::equal(policy, Iter1(std::begin(a)), Iter1(std::end(a)), Iter2(std::begin(a)), Iter2(std::end(a))));
+
+      // check that false is returned on different ranges
+      assert(!std::equal(policy, Iter1(std::begin(a)), Iter1(std::end(a)), Iter2(std::begin(b)), Iter2(std::end(b))));
+
+      // check that false is returned on different sized ranges
+      assert(
+          !std::equal(policy, Iter1(std::begin(a)), Iter1(std::end(a)), Iter2(std::begin(a)), Iter2(std::end(a) - 1)));
+
+      // check that the predicate is used
+      assert(std::equal(
+          policy,
+          Iter1(std::begin(a)),
+          Iter1(std::end(a)),
+          Iter2(std::begin(b)),
+          Iter2(std::end(b)),
+          [](int lhs, int rhs) { return lhs == rhs || lhs + 1 == rhs || rhs + 1 == lhs; }));
+    }
+  }
+};
+
+int main(int, char**) {
+  types::for_each(types::forward_iterator_list<int*>{}, types::apply_type_identity{[](auto v) {
+                    using Iter1 = typename decltype(v)::type;
+                    types::for_each(
+                        types::forward_iterator_list<int*>{},
+                        TestIteratorWithPolicies<types::partial_instantiation<Test, Iter1>::template apply>{});
+                  }});
+}
diff --git a/libcxx/test/std/algorithms/alg.nonmodifying/alg.equal/pstl.exception_handling.pass.cpp b/libcxx/test/std/algorithms/alg.nonmodifying/alg.equal/pstl.exception_handling.pass.cpp
new file mode 100644
index 000000000000000..4d93850ca96f1f3
--- /dev/null
+++ b/libcxx/test/std/algorithms/alg.nonmodifying/alg.equal/pstl.exception_handling.pass.cpp
@@ -0,0 +1,59 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+// UNSUPPORTED: no-exceptions
+
+// UNSUPPORTED: libcpp-has-no-incomplete-pstl
+
+// check that std::equal(ExecutionPolicy) terminates on user-thrown exceptions
+
+#include <algorithm>
+
+#include "check_assertion.h"
+#include "test_execution_policies.h"
+#include "test_iterators.h"
+
+struct ThrowOnCompare {};
+
+#ifndef TEST_HAS_NO_EXCEPTIONS
+bool operator==(ThrowOnCompare, ThrowOnCompare) { throw int{}; }
+#endif
+
+int main(int, char**) {
+  test_execution_policies([](auto&& policy) {
+    EXPECT_STD_TERMINATE([&] {
+      try {
+        int a[] = {1, 2};
+        int b[] = {1, 2};
+        (void)std::equal(policy,
+                         util::throw_on_move_iterator(std::begin(a), 1),
+                         util::throw_on_move_iterator(std::end(a), 1),
+                         util::throw_on_move_iterator(std::begin(b), 1));
+      } catch (const util::iterator_error&) {
+        assert(false);
+      }
+      std::terminate(); // make the test pass in case the algorithm didn't move the iterator
+    });
+    EXPECT_STD_TERMINATE([&] {
+      try {
+        int a[] = {1, 2};
+        int b[] = {1, 2};
+        (void)std::equal(
+            policy,
+            util::throw_on_move_iterator(std::begin(a), 1),
+            util::throw_on_move_iterator(std::end(a), 1),
+            util::throw_on_move_iterator(std::begin(b), 1),
+            util::throw_on_move_iterator(std::end(b), 1));
+      } catch (const util::iterator_error&) {
+        assert(false);
+      }
+      std::terminate(); // make the test pass in case the algorithm didn't move the iterator
+    });
+  });
+}

>From aa8938865209b0964266eb694968e7c9c4272040 Mon Sep 17 00:00:00 2001
From: Louis Dionne <ldionne.2 at gmail.com>
Date: Thu, 23 Nov 2023 13:44:28 -0500
Subject: [PATCH 2/6] Apply review comments

---
 libcxx/docs/Status/PSTLPaper.csv              |   2 +-
 libcxx/include/__algorithm/pstl_backend.h     |   3 +
 libcxx/include/__algorithm/pstl_equal.h       |   7 +-
 .../alg.equal/pstl.equal.pass.cpp             | 122 +++++++++++++-----
 .../pstl.exception_handling.pass.cpp          |   8 --
 5 files changed, 97 insertions(+), 45 deletions(-)

diff --git a/libcxx/docs/Status/PSTLPaper.csv b/libcxx/docs/Status/PSTLPaper.csv
index f8cf950847c62cf..3fb5adfe3ec46aa 100644
--- a/libcxx/docs/Status/PSTLPaper.csv
+++ b/libcxx/docs/Status/PSTLPaper.csv
@@ -8,7 +8,7 @@ Section,Description,Assignee,Complete
 | `[alg.copy] <https://wg21.link/alg.copy>`_,std::copy_n,Nikolas Klauser,|Complete|
 | `[alg.count] <https://wg21.link/alg.count>`_,std::count,Nikolas Klauser,|Complete|
 | `[alg.count] <https://wg21.link/alg.count>`_,std::count_if,Nikolas Klauser,|Complete|
-| `[alg.equal] <https://wg21.link/alg.equal>`_,std::equal,Nikolas Klauser,|Not Started|
+| `[alg.equal] <https://wg21.link/alg.equal>`_,std::equal,Nikolas Klauser,|Complete|
 | `[alg.exclusive.scan] <https://wg21.link/alg.exclusive.scan>`_,std::exclusive_scan,Nikolas Klauser,|Not Started|
 | `[alg.exclusive.scan] <https://wg21.link/alg.exclusive.scan>`_,std::exclusive_scan,Nikolas Klauser,|Not Started|
 | `[alg.fill] <https://wg21.link/alg.fill>`_,std::fill,Nikolas Klauser,|Complete|
diff --git a/libcxx/include/__algorithm/pstl_backend.h b/libcxx/include/__algorithm/pstl_backend.h
index a28e47dad8f399a..3af03ce2fbc8ee2 100644
--- a/libcxx/include/__algorithm/pstl_backend.h
+++ b/libcxx/include/__algorithm/pstl_backend.h
@@ -177,6 +177,9 @@ implemented, all the algorithms will eventually forward to the basis algorithms
   template <class _ExecutionPolicy, class _Iterator, class _Comp>
   optional<__empty> __pstl_sort(_Backend, _Iterator __first, _Iterator __last, _Comp __comp);
 
+  template <class _ExecutionPolicy, class _Iterator1, class _Iterator2, class _Comp>
+  optional<bool> __pstl_equal(_Backend, _Iterator1 first1, _Iterator1 last1, _Iterator2 first2, _Comp __comp);
+
 // TODO: Complete this list
 
 Exception handling
diff --git a/libcxx/include/__algorithm/pstl_equal.h b/libcxx/include/__algorithm/pstl_equal.h
index 9a296a37a153e9c..3403ee60a344654 100644
--- a/libcxx/include/__algorithm/pstl_equal.h
+++ b/libcxx/include/__algorithm/pstl_equal.h
@@ -13,6 +13,7 @@
 #include <__config>
 #include <__functional/operations.h>
 #include <__numeric/pstl_transform_reduce.h>
+#include <__utility/move.h>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
@@ -38,7 +39,7 @@ __equal(_ExecutionPolicy&& __policy,
         _ForwardIterator2&& __first2,
         _Pred&& __pred) noexcept {
   return std::__pstl_frontend_dispatch(
-      _LIBCPP_PSTL_CUSTOMIZATION_POINT(__pstl_equal),
+      _LIBCPP_PSTL_CUSTOMIZATION_POINT(__pstl_equal, _RawPolicy),
       [&__policy](
           _ForwardIterator1 __g_first1, _ForwardIterator1 __g_last1, _ForwardIterator2 __g_first2, _Pred __g_pred) {
         return std::__transform_reduce(
@@ -97,7 +98,7 @@ __equal(_ExecutionPolicy&& __policy,
         _ForwardIterator2&& __last2,
         _Pred&& __pred) noexcept {
   return std::__pstl_frontend_dispatch(
-      _LIBCPP_PSTL_CUSTOMIZATION_POINT(__pstl_equal),
+      _LIBCPP_PSTL_CUSTOMIZATION_POINT(__pstl_equal, _RawPolicy),
       [&__policy](_ForwardIterator1 __g_first1,
                   _ForwardIterator1 __g_last1,
                   _ForwardIterator2 __g_first2,
@@ -110,7 +111,7 @@ __equal(_ExecutionPolicy&& __policy,
           return std::__equal(
               __policy, std::move(__g_first1), std::move(__g_last1), std::move(__g_first2), std::move(__g_pred));
         } else {
-          (void)__policy; // Avoid unused lambda captue warning
+          (void)__policy; // Avoid unused lambda capture warning
           return std::equal(
               std::move(__g_first1),
               std::move(__g_last1),
diff --git a/libcxx/test/std/algorithms/alg.nonmodifying/alg.equal/pstl.equal.pass.cpp b/libcxx/test/std/algorithms/alg.nonmodifying/alg.equal/pstl.equal.pass.cpp
index 4788e564e953980..9583b44b17321a9 100644
--- a/libcxx/test/std/algorithms/alg.nonmodifying/alg.equal/pstl.equal.pass.cpp
+++ b/libcxx/test/std/algorithms/alg.nonmodifying/alg.equal/pstl.equal.pass.cpp
@@ -37,62 +37,118 @@
 
 #include <algorithm>
 #include <cassert>
+#include <iterator>
 
 #include "test_execution_policies.h"
 #include "test_iterators.h"
 #include "test_macros.h"
 
-template <class Iter1, class Iter2>
+template <class It1, class It2>
 struct Test {
   template <class Policy>
   void operator()(Policy&& policy) {
     { // 3 iter overloads
-      int a[] = {1, 2, 3, 4, 5, 6, 7, 8};
-      int b[] = {1, 2, 3, 5, 6, 7, 8, 9};
-
-      // simple test
-      assert(std::equal(policy, Iter1(std::begin(a)), Iter1(std::end(a)), Iter2(std::begin(a))));
-
-      // check that false is returned on different ranges
-      assert(!std::equal(policy, Iter1(std::begin(a)), Iter1(std::end(a)), Iter2(std::begin(b))));
+      // check with equal ranges
+      {
+        int a[] = {1, 2, 3, 4};
+        int b[] = {1, 2, 3, 4};
+        assert(std::equal(policy, It1(std::begin(a)), It1(std::end(a)), It2(std::begin(b))));
+      }
+
+      // check with an empty range
+      {
+        int a[] = {999};
+        int b[] = {1, 2, 3};
+        assert(std::equal(policy, It1(std::begin(a)), It1(std::begin(a)), It2(std::begin(b))));
+      }
+
+      // check with different ranges
+      {
+        int a[] = {1, 2, 3};
+        int b[] = {3, 2, 1};
+        assert(!std::equal(policy, It1(std::begin(a)), It1(std::end(a)), It2(std::begin(b))));
+      }
 
       // check that the predicate is used
-      assert(std::equal(policy, Iter1(std::begin(a)), Iter1(std::end(a)), Iter2(std::begin(b)), [](int lhs, int rhs) {
-        return lhs == rhs || lhs + 1 == rhs || rhs + 1 == lhs;
-      }));
+      {
+        int a[] = {2, 4, 6, 8, 10};
+        int b[] = {12, 14, 16, 18, 20};
+        assert(std::equal(policy, It1(std::begin(a)), It1(std::end(a)), It2(std::begin(b)), [](int lhs, int rhs) {
+          return lhs % 2 == rhs % 2;
+        }));
+      }
     }
 
     { // 4 iter overloads
-      int a[] = {1, 2, 3, 4, 5, 6, 7, 8};
-      int b[] = {1, 2, 3, 5, 6, 7, 8, 9};
-
-      // simple test
-      assert(std::equal(policy, Iter1(std::begin(a)), Iter1(std::end(a)), Iter2(std::begin(a)), Iter2(std::end(a))));
-
-      // check that false is returned on different ranges
-      assert(!std::equal(policy, Iter1(std::begin(a)), Iter1(std::end(a)), Iter2(std::begin(b)), Iter2(std::end(b))));
-
-      // check that false is returned on different sized ranges
-      assert(
-          !std::equal(policy, Iter1(std::begin(a)), Iter1(std::end(a)), Iter2(std::begin(a)), Iter2(std::end(a) - 1)));
+      // check with equal ranges of equal size
+      {
+        int a[] = {1, 2, 3, 4};
+        int b[] = {1, 2, 3, 4};
+        assert(std::equal(policy, It1(std::begin(a)), It1(std::end(a)), It2(std::begin(b)), It2(std::end(b))));
+      }
+
+      // check with unequal ranges of equal size
+      {
+        int a[] = {1, 2, 3, 4};
+        int b[] = {4, 3, 2, 1};
+        assert(!std::equal(policy, It1(std::begin(a)), It1(std::end(a)), It2(std::begin(b)), It2(std::end(b))));
+      }
+
+      // check with equal ranges of unequal size
+      {
+        {
+          int a[] = {1, 2, 3, 4};
+          int b[] = {1, 2, 3, 4, 5};
+          assert(!std::equal(policy, It1(std::begin(a)), It1(std::end(a)), It2(std::begin(b)), It2(std::end(b))));
+        }
+        {
+          int a[] = {1, 2, 3, 4, 5};
+          int b[] = {1, 2, 3, 4};
+          assert(!std::equal(policy, It1(std::begin(a)), It1(std::end(a)), It2(std::begin(b)), It2(std::end(b))));
+        }
+      }
+
+      // check empty ranges
+      {
+        // empty/empty
+        {
+          int a[] = {888};
+          int b[] = {999};
+          assert(std::equal(policy, It1(std::begin(a)), It1(std::begin(a)), It2(std::begin(b)), It2(std::begin(b))));
+        }
+        // empty/non-empty
+        {
+          int a[] = {999};
+          int b[] = {999};
+          assert(!std::equal(policy, It1(std::begin(a)), It1(std::begin(a)), It2(std::begin(b)), It2(std::end(b))));
+        }
+        // non-empty/empty
+        {
+          int a[] = {999};
+          int b[] = {999};
+          assert(!std::equal(policy, It1(std::begin(a)), It1(std::end(a)), It2(std::begin(b)), It2(std::begin(b))));
+        }
+      }
 
       // check that the predicate is used
-      assert(std::equal(
-          policy,
-          Iter1(std::begin(a)),
-          Iter1(std::end(a)),
-          Iter2(std::begin(b)),
-          Iter2(std::end(b)),
-          [](int lhs, int rhs) { return lhs == rhs || lhs + 1 == rhs || rhs + 1 == lhs; }));
+      {
+        int a[] = {2, 4, 6, 8, 10};
+        int b[] = {12, 14, 16, 18, 20};
+        assert(std::equal(
+            policy, It1(std::begin(a)), It1(std::end(a)), It2(std::begin(b)), It2(std::end(b)), [](int lhs, int rhs) {
+              return lhs % 2 == rhs % 2;
+            }));
+      }
     }
   }
 };
 
 int main(int, char**) {
   types::for_each(types::forward_iterator_list<int*>{}, types::apply_type_identity{[](auto v) {
-                    using Iter1 = typename decltype(v)::type;
+                    using It1 = typename decltype(v)::type;
                     types::for_each(
                         types::forward_iterator_list<int*>{},
-                        TestIteratorWithPolicies<types::partial_instantiation<Test, Iter1>::template apply>{});
+                        TestIteratorWithPolicies<types::partial_instantiation<Test, It1>::template apply>{});
                   }});
+  return 0;
 }
diff --git a/libcxx/test/std/algorithms/alg.nonmodifying/alg.equal/pstl.exception_handling.pass.cpp b/libcxx/test/std/algorithms/alg.nonmodifying/alg.equal/pstl.exception_handling.pass.cpp
index 4d93850ca96f1f3..e3486b50742af14 100644
--- a/libcxx/test/std/algorithms/alg.nonmodifying/alg.equal/pstl.exception_handling.pass.cpp
+++ b/libcxx/test/std/algorithms/alg.nonmodifying/alg.equal/pstl.exception_handling.pass.cpp
@@ -19,12 +19,6 @@
 #include "test_execution_policies.h"
 #include "test_iterators.h"
 
-struct ThrowOnCompare {};
-
-#ifndef TEST_HAS_NO_EXCEPTIONS
-bool operator==(ThrowOnCompare, ThrowOnCompare) { throw int{}; }
-#endif
-
 int main(int, char**) {
   test_execution_policies([](auto&& policy) {
     EXPECT_STD_TERMINATE([&] {
@@ -38,7 +32,6 @@ int main(int, char**) {
       } catch (const util::iterator_error&) {
         assert(false);
       }
-      std::terminate(); // make the test pass in case the algorithm didn't move the iterator
     });
     EXPECT_STD_TERMINATE([&] {
       try {
@@ -53,7 +46,6 @@ int main(int, char**) {
       } catch (const util::iterator_error&) {
         assert(false);
       }
-      std::terminate(); // make the test pass in case the algorithm didn't move the iterator
     });
   });
 }

>From 7d281e9bd193aa0e9a2a7a1d82ae097ef5ae40a5 Mon Sep 17 00:00:00 2001
From: Louis Dionne <ldionne.2 at gmail.com>
Date: Thu, 23 Nov 2023 17:47:58 -0500
Subject: [PATCH 3/6] Fix modules build

---
 libcxx/include/__algorithm/pstl_equal.h | 1 +
 1 file changed, 1 insertion(+)

diff --git a/libcxx/include/__algorithm/pstl_equal.h b/libcxx/include/__algorithm/pstl_equal.h
index 3403ee60a344654..8ea9b2c3a8a53b8 100644
--- a/libcxx/include/__algorithm/pstl_equal.h
+++ b/libcxx/include/__algorithm/pstl_equal.h
@@ -12,6 +12,7 @@
 #include <__algorithm/pstl_frontend_dispatch.h>
 #include <__config>
 #include <__functional/operations.h>
+#include <__iterator/iterator_traits.h>
 #include <__numeric/pstl_transform_reduce.h>
 #include <__utility/move.h>
 

>From 5dac60cf51167473b816a23f63933294942770c2 Mon Sep 17 00:00:00 2001
From: Louis Dionne <ldionne.2 at gmail.com>
Date: Thu, 23 Nov 2023 18:32:37 -0500
Subject: [PATCH 4/6] Add another missing include

---
 libcxx/include/__algorithm/pstl_equal.h | 1 +
 1 file changed, 1 insertion(+)

diff --git a/libcxx/include/__algorithm/pstl_equal.h b/libcxx/include/__algorithm/pstl_equal.h
index 8ea9b2c3a8a53b8..b343d2675980c9c 100644
--- a/libcxx/include/__algorithm/pstl_equal.h
+++ b/libcxx/include/__algorithm/pstl_equal.h
@@ -9,6 +9,7 @@
 #ifndef _LIBCPP___ALGORITHM_PSTL_EQUAL_H
 #define _LIBCPP___ALGORITHM_PSTL_EQUAL_H
 
+#include <__algorithm/equal.h>
 #include <__algorithm/pstl_frontend_dispatch.h>
 #include <__config>
 #include <__functional/operations.h>

>From d5cb5b28ac92cfdaf847ad65bda963e4f0b55fa2 Mon Sep 17 00:00:00 2001
From: Louis Dionne <ldionne.2 at gmail.com>
Date: Mon, 27 Nov 2023 15:57:46 -0500
Subject: [PATCH 5/6] Fix typo in UNSUPPORTED annotation

---
 .../algorithms/alg.nonmodifying/alg.equal/pstl.equal.pass.cpp   | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/libcxx/test/std/algorithms/alg.nonmodifying/alg.equal/pstl.equal.pass.cpp b/libcxx/test/std/algorithms/alg.nonmodifying/alg.equal/pstl.equal.pass.cpp
index 9583b44b17321a9..e2f4dafe1a05d80 100644
--- a/libcxx/test/std/algorithms/alg.nonmodifying/alg.equal/pstl.equal.pass.cpp
+++ b/libcxx/test/std/algorithms/alg.nonmodifying/alg.equal/pstl.equal.pass.cpp
@@ -8,7 +8,7 @@
 
 // UNSUPPORTED: c++03, c++11, c++14
 
-// UNSUPPORETD: libcpp-has-no-incomplete-pstl
+// UNSUPPORTED: libcpp-has-no-incomplete-pstl
 
 // <algorithm>
 

>From c7e3b6f0b9d84e589e810859222179e0d82a04c4 Mon Sep 17 00:00:00 2001
From: Louis Dionne <ldionne.2 at gmail.com>
Date: Tue, 28 Nov 2023 09:49:32 -0500
Subject: [PATCH 6/6] Require unix headers in exception test

---
 .../alg.nonmodifying/alg.equal/pstl.exception_handling.pass.cpp  | 1 +
 1 file changed, 1 insertion(+)

diff --git a/libcxx/test/std/algorithms/alg.nonmodifying/alg.equal/pstl.exception_handling.pass.cpp b/libcxx/test/std/algorithms/alg.nonmodifying/alg.equal/pstl.exception_handling.pass.cpp
index e3486b50742af14..4c2f9946165e7a9 100644
--- a/libcxx/test/std/algorithms/alg.nonmodifying/alg.equal/pstl.exception_handling.pass.cpp
+++ b/libcxx/test/std/algorithms/alg.nonmodifying/alg.equal/pstl.exception_handling.pass.cpp
@@ -8,6 +8,7 @@
 
 // UNSUPPORTED: c++03, c++11, c++14
 // UNSUPPORTED: no-exceptions
+// REQUIRES: has-unix-headers
 
 // UNSUPPORTED: libcpp-has-no-incomplete-pstl
 



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