[libc++][PSTL] Implement std::for_each{, _n}

[philnik]

Fix diff

[ldionne]

libcxx/include/__algorithm/for_each.h

22–24 ↗

(On Diff #517713)

I don't think these formatting changes are necessary here.

libcxx/test/std/algorithms/alg.nonmodifying/alg.foreach/pstl.for_each.pass.cpp

42

I think it does, cause it's a bit reference under the hood and so for example begin(), begin() + 1 will share the same underlying byte but can be processed in different threads. So yeah, I think vector<bool> + pstl is not a happy combination.

[philnik]

Generate files

[philnik]

Address comments

[philnik]

Rebased

[philnik]

Rebased

[philnik]

Rebased

[philnik]

Try to fix CI

[ldionne]

Could you perhaps make a quick pass over all your pstl tests to make sure you don't have copy-paste errors in those signatures?

libcxx/test/std/algorithms/alg.nonmodifying/alg.foreach/pstl.for_each_n.pass.cpp

16–18

Wrong signature!

libcxx/include/CMakeLists.txt

set(files
   __algorithm/partial_sort.h
   __algorithm/partial_sort_copy.h
   __algorithm/partition.h
   __algorithm/partition_copy.h
   __algorithm/partition_point.h
   __algorithm/pop_heap.h
   __algorithm/prev_permutation.h
   __algorithm/pstl_any_all_none_of.h
+  __algorithm/pstl_for_each.h
   __algorithm/push_heap.h
   __algorithm/ranges_adjacent_find.h
   __algorithm/ranges_all_of.h
   __algorithm/ranges_any_of.h
   __algorithm/ranges_binary_search.h
   __algorithm/ranges_clamp.h
   __algorithm/ranges_copy.h
   __algorithm/ranges_copy_backward.h

libcxx/include/__algorithm/pstl_for_each.h

+//===----------------------------------------------------------------------===//
+//
+// 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_FOR_EACH_H
+#define _LIBCPP___ALGORITHM_PSTL_FOR_EACH_H
+
+#include <__algorithm/for_each.h>
+#include <__algorithm/for_each_n.h>
+#include <__config>
+#include <__iterator/iterator_traits.h>
+#include <__pstl/internal/parallel_backend.h>
+#include <__pstl/internal/unseq_backend_simd.h>
+#include <__type_traits/is_execution_policy.h>
+#include <__utility/terminate_on_exception.h>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#  pragma GCC system_header
+#endif
+
+#if defined(_LIBCPP_HAS_PARALLEL_ALGORITHMS) && _LIBCPP_STD_VER >= 17
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+template <class _ExecutionPolicy,
+          class _ForwardIterator,
+          class _Function,
+          enable_if_t<is_execution_policy_v<__remove_cvref_t<_ExecutionPolicy>>, int> = 0>
+_LIBCPP_HIDE_FROM_ABI void
+for_each(_ExecutionPolicy&& __policy, _ForwardIterator __first, _ForwardIterator __last, _Function __func) {
+  if constexpr (__is_parallel_execution_policy_v<_ExecutionPolicy> &&
+                __is_cpp17_random_access_iterator<_ForwardIterator>::value) {
+    std::__terminate_on_exception([&] {
+      __pstl::__par_backend::__parallel_for(
+          {},
+          __policy,
+          __first,
+          __last,
+          [&__policy, __func](_ForwardIterator __brick_first, _ForwardIterator __brick_last) {
+            std::for_each(std::__remove_parallel_policy(__policy), __brick_first, __brick_last, __func);
+          });
+    });
+  } else if constexpr (__is_unsequenced_execution_policy_v<_ExecutionPolicy> &&
+                       __is_cpp17_random_access_iterator<_ForwardIterator>::value) {
+    __pstl::__unseq_backend::__simd_walk_1(__first, __last - __first, __func);
+  } else {
+    std::for_each(__first, __last, __func);
+  }
+}
+
+template <class _ExecutionPolicy,
+          class _ForwardIterator,
+          class _Size,
+          class _Function,
+          enable_if_t<is_execution_policy_v<__remove_cvref_t<_ExecutionPolicy>>, int> = 0>
+_LIBCPP_HIDE_FROM_ABI void
+for_each_n(_ExecutionPolicy&& __policy, _ForwardIterator __first, _Size __size, _Function __func) {
+  if constexpr (__is_cpp17_random_access_iterator<_ForwardIterator>::value) {
+    std::for_each(__policy, __first, __first + __size, __func);
+  } else {
+    std::for_each_n(__first, __size, __func);
+  }
+}
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // defined(_LIBCPP_HAS_PARALLEL_ALGORITHMS) && _LIBCPP_STD_VER >= 17
+
+#endif // _LIBCPP___ALGORITHM_PSTL_FOR_EACH_H

libcxx/include/__pstl/internal/glue_algorithm_defs.h

 
 #include "execution_defs.h"
 #include "pstl_config.h"
 
 _PSTL_HIDE_FROM_ABI_PUSH
 
 namespace std {
 
-// [alg.foreach]
-
-template <class _ExecutionPolicy, class _ForwardIterator, class _Function>
-__pstl::__internal::__enable_if_execution_policy<_ExecutionPolicy, void>
-for_each(_ExecutionPolicy&& __exec, _ForwardIterator __first, _ForwardIterator __last, _Function __f);
-
-template <class _ExecutionPolicy, class _ForwardIterator, class _Size, class _Function>
-__pstl::__internal::__enable_if_execution_policy<_ExecutionPolicy, _ForwardIterator>
-for_each_n(_ExecutionPolicy&& __exec, _ForwardIterator __first, _Size __n, _Function __f);
-
 // [alg.find]
 
 template <class _ExecutionPolicy, class _ForwardIterator, class _Predicate>
 __pstl::__internal::__enable_if_execution_policy<_ExecutionPolicy, _ForwardIterator>
 find_if(_ExecutionPolicy&& __exec, _ForwardIterator __first, _ForwardIterator __last, _Predicate __pred);
 
 template <class _ExecutionPolicy, class _ForwardIterator, class _Predicate>
 __pstl::__internal::__enable_if_execution_policy<_ExecutionPolicy, _ForwardIterator>

libcxx/include/__pstl/internal/glue_algorithm_impl.h

 #include "utils.h"
 
 #include "execution_impl.h"
 
 _PSTL_HIDE_FROM_ABI_PUSH
 
 namespace std {
 
-// [alg.foreach]
-
-template <class _ExecutionPolicy, class _ForwardIterator, class _Function>
-__pstl::__internal::__enable_if_execution_policy<_ExecutionPolicy, void>
-for_each(_ExecutionPolicy&& __exec, _ForwardIterator __first, _ForwardIterator __last, _Function __f) {
-  auto __dispatch_tag = __pstl::__internal::__select_backend(__exec, __first);
-
-  __pstl::__internal::__pattern_walk1(__dispatch_tag, std::forward<_ExecutionPolicy>(__exec), __first, __last, __f);
-}
-
-template <class _ExecutionPolicy, class _ForwardIterator, class _Size, class _Function>
-__pstl::__internal::__enable_if_execution_policy<_ExecutionPolicy, _ForwardIterator>
-for_each_n(_ExecutionPolicy&& __exec, _ForwardIterator __first, _Size __n, _Function __f) {
-  auto __dispatch_tag = __pstl::__internal::__select_backend(__exec, __first);
-
-  return __pstl::__internal::__pattern_walk1_n(
-      __dispatch_tag, std::forward<_ExecutionPolicy>(__exec), __first, __n, __f);
-}
-
 // [alg.find]
 
 template <class _ExecutionPolicy, class _ForwardIterator, class _Predicate>
 __pstl::__internal::__enable_if_execution_policy<_ExecutionPolicy, _ForwardIterator>
 find_if(_ExecutionPolicy&& __exec, _ForwardIterator __first, _ForwardIterator __last, _Predicate __pred) {
   auto __dispatch_tag = __pstl::__internal::__select_backend(__exec, __first);
 
   return __pstl::__internal::__pattern_find_if(

libcxx/include/algorithm

 #include <__algorithm/transform.h>
 #include <__algorithm/unique.h>
 #include <__algorithm/unique_copy.h>
 #include <__algorithm/unwrap_iter.h>
 #include <__algorithm/upper_bound.h>
 
 #ifdef _LIBCPP_HAS_PARALLEL_ALGORITHMS
 #  include <__algorithm/pstl_any_all_none_of.h>
+#  include <__algorithm/pstl_for_each.h>
 #endif
 
 // standard-mandated includes
 
 // [algorithm.syn]
 #include <initializer_list>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)

libcxx/test/std/algorithms/alg.nonmodifying/alg.foreach/pstl.for_each.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+// 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
+
+// REQUIRES: with-pstl
+
+// <algorithm>
+
+// template<class ExecutionPolicy, class ForwardIterator, class Function>
+//   void for_each(ExecutionPolicy&& exec,
+//                 ForwardIterator first, ForwardIterator last,
+//                 Function f);
+
+#include <algorithm>
+#include <atomic>
+#include <cassert>
+#include <vector>
+
+#include "test_macros.h"
+#include "test_execution_policies.h"
+#include "test_iterators.h"
+
+EXECUTION_POLICY_SFINAE_TEST(for_each);
+
+static_assert(sfinae_test_for_each<int, int*, int*, bool (*)(int)>);
+static_assert(!sfinae_test_for_each<std::execution::parallel_policy, int*, int*, bool (*)(int)>);
+
+template <class Iter>
+struct Test {
+  template <class Policy>
+  void operator()(Policy&& policy) {
+    int sizes[] = {0, 1, 2, 100};
+    for (auto size : sizes) {
+      std::vector<int> a(size);
+      std::vector<Bool> called(size);
+      std::for_each(policy, Iter(std::data(a)), Iter(std::data(a) + std::size(a)), [&](int& v) {
+        assert(!called[&v - a.data()]);
+        called[&v - a.data()] = true;
+      });
+      assert(std::all_of(std::begin(called), std::end(called), [](bool b) { return b; }));
+    }
+  }
+};
+
+int main(int, char**) {
+  types::for_each(types::forward_iterator_list<int*>{}, TestIteratorWithPolicies<Test>{});
+
+#ifndef TEST_HAS_NO_EXCEPTIONS
+  std::set_terminate(terminate_successful);
+  int a[] = {1, 2};
+  try {
+    std::for_each(std::execution::par, std::begin(a), std::end(a), [](int) { throw int{}; });
+  } catch (int) {
+    assert(false);
+  }
+#endif
+
+  return 0;
+}

libcxx/test/std/algorithms/alg.nonmodifying/alg.foreach/pstl.for_each_n.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+// 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
+
+// REQUIRES: with-pstl
+
+// <algorithm>
+
+// template<class ExecutionPolicy, class ForwardIterator, class Function>
+//   void for_each(ExecutionPolicy&& exec,
+//                 ForwardIterator first, ForwardIterator last,
+//                 Function f);
+
+#include <algorithm>
+#include <atomic>
+#include <cassert>
+#include <vector>
+
+#include "test_macros.h"
+#include "test_execution_policies.h"
+#include "test_iterators.h"
+
+EXECUTION_POLICY_SFINAE_TEST(for_each);
+
+static_assert(sfinae_test_for_each<int, int*, int*, bool (*)(int)>);
+static_assert(!sfinae_test_for_each<std::execution::parallel_policy, int*, int*, bool (*)(int)>);
+
+template <class Iter>
+struct Test {
+  template <class Policy>
+  void operator()(Policy&& policy) {
+    int sizes[] = {0, 1, 2, 100};
+    for (auto size : sizes) {
+      std::vector<int> a(size);
+      std::vector<Bool> called(size);
+      std::for_each_n(policy, Iter(std::data(a)), std::size(a), [&](int& v) {
+        assert(!called[&v - a.data()]);
+        called[&v - a.data()] = true;
+      });
+      assert(std::all_of(std::begin(called), std::end(called), [](bool b) { return b; }));
+    }
+  }
+};
+
+int main(int, char**) {
+  types::for_each(types::forward_iterator_list<int*>{}, TestIteratorWithPolicies<Test>{});
+
+#ifndef TEST_HAS_NO_EXCEPTIONS
+  std::set_terminate(terminate_successful);
+  int a[] = {1, 2};
+  try {
+    std::for_each_n(std::execution::par, std::data(a), std::size(a), [](int) { throw int{}; });
+  } catch (int) {
+    assert(false);
+  }
+#endif
+
+  return 0;
+}

libcxx/test/support/test_execution_policies.h

 template <template <class Iter> class TestClass>
 struct TestIteratorWithPolicies {
   template <class Iter>
   void operator()() {
     test_execution_policies(TestClass<Iter>{});
   }
 };
 
+struct Bool {
+  bool b_;
+  Bool() = default;
+  Bool(bool b) : b_(b) {}
+
+  operator bool&() {
+    return b_;
+  }
+};
+
 [[noreturn]] inline void terminate_successful() { std::exit(0); }
 
 #endif // TEST_SUPPORT_TEST_EXECUTION_POLICIES